The ecology of estuarine channels of the Pacific Northwest coast: A ...
The ecology of estuarine channels of the Pacific Northwest coast: A ...
The ecology of estuarine channels of the Pacific Northwest coast: A ...
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. ~ -~c-~*-ii"~.:~vT~FISH h VI:LT~L':": -.A December FWS/OBS-83/05 1983w~I..~-'stH- Sfidell CompYLe. COD"V~*~1010 cause f4auIev~rdSlidell, LA 70458NMATHE ECOLOGY OF ESTUARINE CHANNELSOF THE PACIFIC NORTHWEST COAST:A COMMUNITY PROFILEChar1 es A. SirnenstadFisheries Research InstituteColl ege <strong>of</strong> Ocean and Fishery SciencesUniversity <strong>of</strong> WashingtonSeattle, WA 98195Project OfficerJay F. WatsonU.S. Fish and Wildlife Service500 N.E. Mu1 tnomah StreetPortland, OR 97232Prepared forU.S.Department o
PREFACEThis pr<strong>of</strong>ile <strong>of</strong> <strong>the</strong> <strong>estuarine</strong> channel habitats or subecosystems, considerabl ehabitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> is one effort was dedicated to detailing hydro-in d series <strong>of</strong> conmuni ty pr<strong>of</strong>iles syn<strong>the</strong>- 1 ogical , geonorphological , and chemicalsizing information pertinent to specific components and processes <strong>of</strong> <strong>the</strong> systems ashdbitats <strong>of</strong> particular interest to envi- well as <strong>the</strong> biological. <strong>The</strong>se factors inronmental managers. <strong>The</strong> intent <strong>of</strong> <strong>the</strong> concert with <strong>the</strong> biota dictate both <strong>the</strong>series is to provide scientific infor- short- and long-term ecological structureoation in a format that is useful to a and function <strong>of</strong> <strong>the</strong>se habitats. <strong>The</strong> finalbroad spectruin <strong>of</strong> users including envi- chapter integrates <strong>the</strong> information in <strong>the</strong>rormentdl managers, col 1 ege educators, and preceding chapters by detail ing considerinterestedlaypersons. This specificpr<strong>of</strong>ile focuses or1 <strong>the</strong> cornpl ex network <strong>of</strong>ations for management.<strong>channels</strong> <strong>of</strong> various origins in <strong>the</strong> estu- Any questions or comments about orarine reaches <strong>of</strong> <strong>the</strong> <strong>coast</strong>al waters <strong>of</strong> <strong>the</strong> requests for pub1 ications shor~ld bePacif i c Pbrthwest. <strong>The</strong> geographic scope di rected to:or study area is primarily that region <strong>of</strong><strong>the</strong> <strong>coast</strong> from Strait <strong>of</strong> Juan de Fuca onInformation Transfer Special ist<strong>the</strong> north to Cape Plendoci no, Cal ifornia, National Coastal Ecosystems Teamon <strong>the</strong> south. U.S. Fish and Wildlife ServiceNASA/Sl idel 1 Computer Conpl exIn order to explain <strong>the</strong> <strong>ecology</strong> with-1010 Gause Boul evardin <strong>the</strong>se channel systetns and <strong>the</strong>ir Sl i dell , LA 70458ec1~1 ogical re1 ationships to <strong>the</strong> adjacenti i i
COr4VERSI ON FACTORSMetric to U.S.CustomaryTo Obtainmil 1 imeters (m)centimeters (cm)meters (m)ki1 ometers (km)2square meters (m )square ki 1 ometers (km )hectares (ha)liters (1)cubic meters (m3)cubic meters (m )milligrams (mg)grarns (g)kilograms (kg)metric tons (rat)metric tons (mt)ki l ocal ori es (kcal )Cel s ius degrees1.8(C0) t 32inchesinchesfeetmil essquare feetsquare milesacresgal 1 onscubic feetacre-feetouncesouncespoundspoundsshort tonsBTUFahrenheit degreesinchesinchesfeet (ft)fa thomsmiles (mi)nautical miles (mi)2square feet (ft )acres 2square miles (mi )gallons (gal)cubic feet (ft )acre- feetounces (oz)pounds (Ib)short tons (ton)BTUU.S.Customary to Metricmil 1 imeterscentimetersmetersmeterskilometerskil meterssquare metershectaressquare ki 1 ometers1 i terscubic meterscubic metersgramskil ogramsmetric tonski 1 ocal ori esCelsius degrees
CONTENTSPagePREFACE ............................. i iiCOPNERSION FACTORS ........................ ivLIST UF FIGURES ......................... viiiLIST OF TABLES .......................... xiACKNOWLEDGMENTS ......................... xiiCHAPTER 1 . 1NTRODUCTI.ON ..................... 11.1 Objectives ......................* 11.2 Scope ......................... 21.3 Methods ........................ 2CHAPTER 2 . PHYSICAL DESCRIPTION OF ESTUARINE CHANNELS ...... 42.1 DefinitionandDescription ............... 42.2 Geomorphol ogy ..................... 42.3 Circulation ...................... 102.4 Water Mass Characteristics ............... 122.4.1 Physical .................... 122.4.2 Chemi cal .................... 142.5 Substrate Characteristics ............... 182.5.1 Physical .................... 182.5.2 Chemical .................... 212.6 Itemization and Classification <strong>of</strong> EstuarineChannel Habitats in Region .............. 25CHAPTER 3 . PRIMARY PRODUCTION IN ESTUARINE CHANNELS ....... 323.1 Benthic Mi cr<strong>of</strong> lora ................... 323.2 Macroalgae ....................... 323.3 Angiosperms ...................... 333.4 Phytoplankton ..................... 333.5 Estimates <strong>of</strong> Standing Crop and PrimaryProduction Rates ................... 343.6 Driving and Limiting Variables to PrirflaryProduction ...................... 35CHAPTER 4 . UETRITUS PROCESSING IN ESTUARINE CHANNELS ...... 384.1 Detritus Sources .................... 384.2 Distribution <strong>of</strong> Detritus ................ 414.3 Fungi and Bacteria Colonization ............ 424.4 Physical. Chemical. and Biological Conditioning .... 42
CHAPTER 5 . INVERTEBRATE ASSEMBLAGES OF ESTUARINE CHANNELS .... 465.1 Bentni c Infauna and Sessi 1 e €pi fauna .......... 465.2 Motile Epifauna .................... 525.3 Epibenthic Zooplankton ................. 545.4 Pel ayi c Zoopl ankton and Neuston ............ 62CHAPTER 6 . FISH ASSEMBLAGES OF ESTUARINE CHANNELS ........ 686.1 Demersal Fishes .................... 686.2 Pelagic Fishes ..................... 716.2.1 Resident Pelagic Fishes ............. 736.2.2 Anadromous Pelagic Fi shes ............ 786.2.3 Ichthyopl ankton ................. 86CHAPTER 7 . BIRD ASSEMBLAGES OF ESTUARINE CHANNELS ........ 877.1 Shallow-Probing and Surface-Searching Shorebirds .... 877.2 Waders ......................... 937.3 Surface and Diving Waterbirds ............. 947.4 Aerial -Searching Birds ................. 95CHAPTER 8 . MAMMALS OF ESTUARINE CHANNELS ............ 978.1 Terrestrial Mammal s .................. 998.2 Aquatic Mammals .................... 998.3 Marine Mammals ..................... 100CHAPTEK 9 . TRUPHIC AND COMMUNITY ECOLOGY OF ESTUARINECHANNELS ............................ 1039.1 Principal Pathways <strong>of</strong> Energy Flow throughInternal Food Webs .................. 1039.2 Roles <strong>of</strong> Predation and Competition Interactionsin Structuring Communities and Food Webs ....... 1129.3 Estuarine Channels as Critical Reproductive.Nursery. Foraging. and Refugia Habitats ....... 1139.4 Interrelationships among Estuarine ChannelHabitats and Riverine. Wetland. Oceanic. andO<strong>the</strong>r Estuarine Habitats ............... 115........10.1 Sources and Mechanisms <strong>of</strong> Impact ............ 11910.2 Utilization <strong>of</strong> and Dependence on Channels by Economicaily-and Ecolopically-Important Species .... 124CHAPTEK 10 . SUMMARY . THE RULE OF CHANNEL HABITATS INESTUARINE ECUSYSTEMS AND MANAGEMENT IMPLICATIONS 117.......................10.3 Rates and Pathways <strong>of</strong> Recovery from Short-termImpacts 125v i
Page10.4 Methods <strong>of</strong> Channel Restoration andRehabilitation . . . . . . . . . . . . . . . . . . . . 12610.5 Research Gaps and Priorities . . . . . . . . . . . . . . 12710.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . 129LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . 130APPENDICES: A. Glossary <strong>of</strong> Terms . . . . . . . . . . . . . . . . 1598. Sediment Classification Schemes . . . . . . . , . 165C. Tidal Channel Characteristics f.leasurements. . . . 167D. Summary <strong>of</strong> Current Research andResearch Groups/Centers AddressingEstuarine Channel Ecology orEffects <strong>of</strong> Alteration <strong>of</strong> Channel Habitats . . . 175vii
Fi g.LIST OF FIGURESPage1.1 Location <strong>of</strong> estuaries in Oregon and Washington ....... 22.1 Kepresentati ve <strong>estuarine</strong> channel classesand geomorphologi es and associated estuari nefeatures and regions 5....................2.2 Example <strong>of</strong> <strong>estuarine</strong> channel habitats in <strong>Pacific</strong>krthwest; (A) braided mainsten <strong>channels</strong> <strong>of</strong> main arm<strong>of</strong> Fraser River are separated by saltmarsh habitat,and (B) closer view <strong>of</strong> bl ind <strong>channels</strong> in sal trnarshhabitat on Woodward Is1 and. ................. 62.3 Estuarine channel mouth depositional patternsassociated with macrotidal systems in <strong>the</strong> absence(A) and presence (6) <strong>of</strong> strong wave action ......... 82.4 Estuarine channel dimensional characteristics ........ 92.5 Estuarine classification diaorami 11 us tra ti ng seven types <strong>of</strong><strong>estuarine</strong> circulation .................... 112.6 Sediment size fraction (% wet weight) distributedat seven channel bottom and slope locations inGrays Harbor 20........................2.7 Volatile solids (% <strong>of</strong> total dcy weight) in sedimentsat seven channel bottom and slope locationsin Grays Harbor ....................... 232.8 Distribution <strong>of</strong> organic matter (volatile solids,chemi cal oxygen demand, and tota 1 organic carbon )in sediments at fourteen channel bottom and slope/bank locations in Grays Harbor 24...............3.1 Primary production compartments and driving variablesand limiting factors i nf fuenci ng distri bution,standing crop, and rate <strong>of</strong> production 36 .........tuarine channel habitats <strong>of</strong> <strong>the</strong>s t *.....................39e mechanisms and flowsmical, and biological................ 43
Fig.Page4.3 Terrestrial (wood chips, tree bark, and leaves)detritus <strong>of</strong> varying particle sizes deposited onlittoral flats <strong>of</strong> Duckabush River estuary, HoodCanal, Washington 43......................5.1 Representative illustration <strong>of</strong> common benthic infaunaand sessile epifauna assemblages <strong>of</strong> <strong>estuarine</strong>channel habitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> 49..........5.2 Representative illustration <strong>of</strong> common motile epifaunaassemblages <strong>of</strong> <strong>estuarine</strong> <strong>channels</strong> <strong>of</strong> <strong>the</strong>Paci f i c <strong>Northwest</strong> ...................... 555.3 Representative illustration <strong>of</strong> common epibenthiczooplankton assemblages <strong>of</strong> <strong>estuarine</strong> channel habitats<strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> 57..................5.4 Representative illustration <strong>of</strong> common pelagic zoopranktonand neuston assemblages <strong>of</strong> <strong>estuarine</strong> <strong>channels</strong><strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> .................. 64....6.1 Kepresentative illustration <strong>of</strong> common fish assemblayes<strong>of</strong> <strong>estuarine</strong> <strong>channels</strong> <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> 726.2 Mean Shannon-Weaver diversity index <strong>of</strong> demersalfishes in <strong>the</strong> Columbia River estuary as a function<strong>of</strong> location along <strong>the</strong> longitudinal axis (A)and over <strong>the</strong> 18-month sampling period (B) .......... 726.3 Mean Shannon-Weaver diversity index <strong>of</strong> pel agicfishes in <strong>the</strong> Columbia River estuary as a function<strong>of</strong> location along <strong>the</strong> longitudinal axis (A)and over <strong>the</strong> 18-month sampling period (B) 77..........6.4 Tidal channel trap net set in blind channel <strong>of</strong> FraserRiver estuary to sample juvenile salmon utilizingsal tmarsh habitat 82..........................7.1 Representative illustration <strong>of</strong> common bird assemblages<strong>of</strong> <strong>estuarine</strong> <strong>channels</strong> <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> 917.2 Representative avi fauna <strong>of</strong> <strong>estuarine</strong> channel habitatsin <strong>the</strong>pacific <strong>Northwest</strong> ................7.3 Seabird (primarily rhinoceros auklets, commarbled murrelets, and pigeon gui 1 lemots)ti on in Grays Harbor, Washington, OctoberSeptember 1975..............8.1 Representative illustration <strong>of</strong> commonblages <strong>of</strong> <strong>estuarine</strong> <strong>channels</strong> <strong>of</strong> <strong>the</strong> Pi x
Fig. -8.2 <strong>Pacific</strong> harbor seal haulout site along channel inWillapa Bay, Washington, June 1980 ............. 1018.3 Maximum total abundance <strong>of</strong> <strong>Pacific</strong> harbor sealsat haulout sites in three <strong>of</strong> Washington's <strong>coast</strong>alestuaries in 1980 and in 1981 ............... 1029.1 Representative food web <strong>of</strong> <strong>estuarine</strong> channel habitats<strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>. 111..................10.1 Configuration <strong>of</strong> channel habitats in <strong>the</strong> Cot umbiaRiver estuary in 1868-1875 (A) and recent time (B). ..... 11810.2 Late 1800's dredging <strong>of</strong> Uuwamish River <strong>channels</strong> andlittoral flats in Elliott Bay, Seattle, Washington ..... 12010.3 Example <strong>of</strong> where diking and filling have removed(blind or tidal) channel habitat in Fraser Riverestuary: {A) i 1 lustrates diking <strong>of</strong> subsidiary(entering from lower right) channel and blind<strong>channels</strong> in sal tmarsh and (B) shows historicalchannel patterns still evident in existing fields ...... 122
This syn<strong>the</strong>sis <strong>of</strong> infomation on<strong>estuarine</strong> channel s <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>woul d have been virtual ly impossibl ewithout <strong>the</strong> aid and assistance <strong>of</strong> manyindividuals, to whom I extend my utrnostgratitude. John Cooper, Jay Watson,Nancy Nelson, and <strong>the</strong>ir coll eagues in <strong>the</strong>U.S. Fish and Wildlife Service were responsiblefor initiating and sustaining<strong>the</strong> effort, providing reference material,and generating critical reviews. Robertdolton and Duane Higley (Oregon StateUniversity, Corvall is), David Levy (WestwaterResearch Centre, Vancouver, B. C. ),Colin Levings (Department <strong>of</strong> <strong>the</strong> Environment,Vancouver, B.C.), Ed Roy (University<strong>of</strong> Washington, Seattle), DennisPaul son (Uni vers i ty <strong>of</strong> Washington,Seattle), and Rocky Beach (Oregon Department<strong>of</strong> Fish and Wild1 ife, Astoria) allcontributed data, reports, ideas, andreview comments which were <strong>the</strong> crux <strong>of</strong>this syn<strong>the</strong>sis. Independent reviewerswho a1 so provided extremely constructivecomr~ents included A1 yn Duxbury (University <strong>of</strong> 'rlashington, Seattle), Tom Gamer{Oregon Department <strong>of</strong> Fish and W i l dl ife,Hewport), and Char1 es Mil 1 er (OregonState University, Corvall is). <strong>The</strong> incrediblyfine it 1 ustrations were preparedby Cathy Eaton Walker <strong>of</strong> Friday Harbor,Washington. Appreciation is extended toDr. Dennis Yillows, Director <strong>of</strong> <strong>the</strong> University <strong>of</strong> Washington's Friday HarborLaboratories, for <strong>the</strong> opportunity to obtainoriginal aerial photographs <strong>of</strong><strong>estuarine</strong> channel s in Puget Sound. I arla1 so grateful for <strong>the</strong> photographs providedby Rocky Reach, Dave Levy, andDenni s Paul son.
This document has been prepared with<strong>the</strong> objective <strong>of</strong> providing <strong>estuarine</strong> resourcemanagers with a synopsis <strong>of</strong> <strong>the</strong>exi sting knowledge about <strong>the</strong> <strong>ecology</strong> <strong>of</strong><strong>estuarine</strong> <strong>channels</strong> in <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.Incorporated into this pr<strong>of</strong>ile isa summary <strong>of</strong> <strong>the</strong> principal physical, chemicalenvironments and biological features<strong>of</strong> channel communities, as we1 1 as an interpretivesyn<strong>the</strong>sis <strong>of</strong> <strong>the</strong> internal dynamics<strong>of</strong> <strong>the</strong> community and its relationshipswith o<strong>the</strong>r communities in <strong>the</strong>aggregate <strong>estuarine</strong> ecosystem.And, while this community pr<strong>of</strong>ile hasbeen specifically prepared to provideinformation for <strong>the</strong> assessment, planningand permitting activities <strong>of</strong> <strong>the</strong> U.S. Fishand Wildlife Service, it w i l l nopefullyconstitute an educational source documentfor all those interested in <strong>the</strong> ecologicalvalue <strong>of</strong> estuaries.STRAIT OFJUAN DE FUCASTRAIT OF GEORGIAQUINAULT RlVERGRAYS HARBORWILLAPA BAYCOLUMBIA RlVERNECANICUM RlVERNEHALEM BAYNETARTS BAYSAND LAKENESTUCCA BAYSALMON RlVERSILETZ BAYPORT MOODY ARMPUYALLUP RlVER1.2 SCOPEYAQUlNA BAY<strong>The</strong> reg ion <strong>of</strong> geographic coverage SIUSLAW RlVER(Fig. 1.1) is <strong>the</strong> Columbian Province(Cowardin et al. 1979), including <strong>the</strong> UMPQUA RIVER<strong>Northwest</strong> <strong>Pacific</strong> Coast from Cape Hendocino,California, to <strong>the</strong> Strait <strong>of</strong> Juan deFuca on <strong>the</strong> Washington-Canada border. COQUILLERIVERThis embraces <strong>coast</strong>al estuaries as wellas <strong>the</strong> continuum <strong>of</strong> estuaries forming <strong>the</strong>inland seas <strong>of</strong> Puyet Sound and <strong>the</strong> south- ROGUE RIVERern Strait <strong>of</strong> Georgia, with <strong>the</strong> latter PlsToLRIVERterminating between Vancouver on <strong>the</strong>main1 and and Nanaimo on Vancouver Is1 and.PT ST GEORGE -Ir/CALIFORNIAEstuarine channel habitats are definedas incised subtidal <strong>estuarine</strong> bot-TRINIDAD HEADtoms or depressions which contain saline(> 0.05~/,,) water masses freely exchangedt5rough tidal and riverine currents. Thisdefinition is intended to encompass both<strong>the</strong> principal corridor <strong>of</strong> water movement Fig. 1.1. Location <strong>of</strong> estuaries in Oregonthrough <strong>the</strong> estuary, typically along its and Washington.main longitudinal axis, as well as <strong>the</strong>cornplex dendritic or anaStomosin9 drain- resident or transitional, in or on <strong>the</strong>ayes which dissect tidefl atS and Salt- water column or subtidal substrate.marshes.<strong>The</strong> biotic community characterizing1.3 METHODS<strong>estuarine</strong> <strong>channels</strong> involves <strong>the</strong> micro- This community pr<strong>of</strong> i 1 e was constructandmacr<strong>of</strong>lora and fauna found, whe<strong>the</strong>r ed through a syn<strong>the</strong>sis <strong>of</strong> <strong>the</strong> physioyra,-,2
phy, biota, ecoloyical interactions, andeffects ot human nlanipul ations in channelnabi tats <strong>of</strong> <strong>Pacific</strong> <strong>Northwest</strong> estuaries.Material was ga<strong>the</strong>red from published aswell as unpublished reports and o<strong>the</strong>r"gray" literature, some <strong>of</strong> which are citedas examples <strong>of</strong> <strong>the</strong> processes being described.Unless 0<strong>the</strong>rwi se cited, interpretationsand conclusions based upon unpublisneddata are sole11 those <strong>of</strong> <strong>the</strong>author.Reference sources <strong>of</strong> particular usein this syn<strong>the</strong>sis included <strong>the</strong> U.S. Fishand Wi ldi 1 fe Service, Biological ServicesProgram's Ecological Characterization <strong>of</strong><strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> Region (Proctor etal. 1980) and <strong>Pacific</strong> Coast EcologicalInventory (Beccasio et dl. 1981).
2.1 DEFINITION AND DESCRIPTIONCYAPTER 2PHYSICAL DESCRIPTION OF ESTUARINE CHANNELSA1 though a diverse array <strong>of</strong> mor- occurs <strong>the</strong> principal transport <strong>of</strong> waterphol ogies characterize <strong>Pacific</strong> <strong>Northwest</strong> into and out <strong>of</strong> <strong>the</strong> estuary; subsidiarestuaries, a1 1 basi cdl ly meet <strong>the</strong> gener- (stream) <strong>channels</strong> through which mino;ally-accepted definition <strong>of</strong> Pritchard water transport occurs; and bl ind or tidal(1967), "An estuary is a semi-enclosed <strong>channels</strong> which primarily drain flats <strong>of</strong><strong>coast</strong>al body <strong>of</strong> water which has a free tidally or flood-introduced water ra<strong>the</strong>rconnection with <strong>the</strong> open sea and withinwhich sea water is measurably diluted withthan run<strong>of</strong>f from associated wet1 ands anduplands. Examples <strong>of</strong> several <strong>of</strong> <strong>the</strong>sefreshwater derived from land drainage." classes <strong>of</strong> <strong>channels</strong> are found in <strong>the</strong>By this definition we exclude <strong>coast</strong>al Fraser River estuary (Fig. 2.2).lagoons, brackish seas, and sal ine lakeswhich have nei<strong>the</strong>r <strong>the</strong> dynamic tidal 2.2 GEOMORPHOLOGYexchange <strong>of</strong> sea water nor riverine input<strong>of</strong> freshwater characterized by true es tu- Pri tchard (1967) and Russel 1 (1967)aries and where riverine input is typical- also classified four types <strong>of</strong> estuariesly exceeded by evaporation. In <strong>the</strong> <strong>Pacific</strong><strong>Northwest</strong>, however, <strong>estuarine</strong> "systems"based upon <strong>the</strong>ir geological origin anddevel opnent: 1) drowned river vall eys,such as Puget Sound and <strong>the</strong> Strait <strong>of</strong> which were produced by rises in sea levelGeorgia also meet this definition <strong>of</strong> an or subsidence <strong>of</strong> land; 2) fjords, whereinestuary, but which, because <strong>of</strong> <strong>the</strong>ir deep, U-shaped estuaries were formed bypredominantlymarine nature, we will also glacial action; 3) bar-built estuaries,exclude in favor <strong>of</strong> addressing <strong>the</strong> srnallerestuaries found within <strong>the</strong>m.created by accumulation <strong>of</strong> sedimentsacross an open rivermouth or <strong>coast</strong>albight; and 4) estuaries resulting fromWithin an estuary, <strong>channels</strong> are tectonic processes such as faulting.defined as, "an open conduit ei<strong>the</strong>r naturallyor artificially created which peri-<strong>The</strong>re is also at least one case in <strong>the</strong><strong>Pacific</strong> <strong>Northwest</strong> <strong>of</strong> a fifth type <strong>of</strong>odi cally or continuously contains moving estuary, that created by man-made mani puwater,or which forms a connecting link lations <strong>of</strong> river course and shorelinebetween two bodies <strong>of</strong> standing water" rnorphol ogy.(Langbein and Iseri 1960). As such,<strong>channels</strong> constitute critical interfaces Configurations <strong>of</strong> tidally influencedwithin <strong>the</strong> estuary itself, linking litto- deltas ~hich form intersections betweenral and sublittoral, riverine and marinehabitats. <strong>The</strong> wl ationship between estu<strong>estuarine</strong><strong>channels</strong> and <strong>the</strong> ocean aregoverned by sediment dispersal and accumuarine<strong>channels</strong> and o<strong>the</strong>r components <strong>of</strong> <strong>the</strong> lation patterns. Wright and Colemanestuary are illustrated in Figure 2.1. (1973), Coleman and Wright (1975), andWithin this definition fall three basic Wright (1977) have suggested that <strong>the</strong>secl asses <strong>of</strong> <strong>channels</strong>: mains tem channel s patterns are determined by <strong>the</strong> i nteraction(thalwegs <strong>of</strong> Proctor et a1 . 1980) wherein between outfl ow dispersion (including4
Fig. 2.2. Example <strong>of</strong> <strong>estuarine</strong> cb,annel habitats in <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>; A) braidedmainstem <strong>channels</strong> <strong>of</strong> main arm <strong>of</strong> Fraser River are separated by sal tmarsh habitat, andB) a closer view <strong>of</strong> blind <strong>channels</strong> in saitmarsh habitat on Woodward Island (Photographscourtesy <strong>of</strong> David Levy, Westwater Research Centre, University <strong>of</strong> British Columbia, Canada).
envi roniiients) , bidirectional currentscreate sand-fil led, funnel-shaped di stri b-utaries in which 1 inear tidal ridges haverep1 aced <strong>the</strong> distributary mouth bar (Fig.2.3A) ; where strong wave action i ntercepts<strong>the</strong> river mouth, constricted or deflectedchannel s develop (Fig. 2.3B). Swift(1976) a1 so developed categories <strong>of</strong> "tidalinlet" tnorphologi es, including (1) overlap,(2) <strong>of</strong>fset, and (3) symmetrical,which could be applied to <strong>Pacific</strong> <strong>Northwest</strong>estuaries. See Elliott (1978a and b)and Reineck and Singh (1980) for fur<strong>the</strong>rdiscussion <strong>of</strong> delta and inlet structure.<strong>The</strong> structure <strong>of</strong> <strong>estuarine</strong> <strong>channels</strong>reflects, in part, <strong>the</strong> origins and development<strong>of</strong> <strong>the</strong> estuary as governed by <strong>the</strong>dynariiic forces <strong>of</strong> riverine and tidalcomponents. Morphologies <strong>of</strong> channel susually ref1 ect <strong>the</strong> original riverbedshape and pattern in drowned river valleyswhile <strong>channels</strong> in bar-bui 1 t estuaries are<strong>of</strong>ten ephemeral in location and form.Given <strong>the</strong> glacial formation <strong>of</strong> fjords,<strong>channels</strong> in <strong>the</strong>se estuaries tend to bestable and re1 atively permanent. Thisvariation in stability is reflected infour basic channel configurations: 1)fixed <strong>channels</strong>, which were erosionallycreated, usually remain in <strong>the</strong> same locationand <strong>the</strong> bed is deepened over time; 2)braided <strong>channels</strong>, which are characterizedby many divisions into smaller branchesaround lenticular bars or is1 ands, with<strong>the</strong> branches uniting at various downstreamlocations; 3) meandering <strong>channels</strong>, whichhave a simple, winding course that changessystematically over time; and 4) dendri tic<strong>channels</strong>, which have irregular branches1 eading to a common channel.<strong>The</strong> principal characteristics <strong>of</strong> <strong>the</strong>channel bank are its slope and substrate,which are not only correlated but are alsoaffected by <strong>the</strong> orientation and veloci ties<strong>of</strong> <strong>the</strong> river and tidal currents at thatpoint. Bank slope can be classified int<strong>of</strong>our gradient c,l asses: 1) vertical ,90"-45"; 2) steep, 45"-30"; 3) moderate,30"-5"; and 4) shallow, 5"-0".Substrate can be defined as ei<strong>the</strong>rconsolidated (combined or firm rock orsoil ) or unconsol idated (loose and di sas-sociated particles). Unconsol idatedsedinents can be classified on <strong>the</strong> basis<strong>of</strong> particle diameter as: 1) silt or clay,2) sand, 3) gravel, 4) cobble, and 5)boulder and [nay be fur<strong>the</strong>r divided within<strong>the</strong>se categories (Appendix B) . Fur<strong>the</strong>rdiscussion <strong>of</strong> <strong>the</strong> sediment characteristics<strong>of</strong> <strong>estuarine</strong> <strong>channels</strong> is presented inSection 2.5.One <strong>of</strong> <strong>the</strong> few detailed studies <strong>of</strong><strong>estuarine</strong> channel morphology was Levy andNorthcote's (1981) documentation <strong>of</strong> tidal(bl ind) channel characteristics in <strong>the</strong>Fraser Ri ver Estuary. Twenty-two habitatcharacteristics were measured at 15 separateblind <strong>channels</strong>, most <strong>of</strong> which weredendri tic in character. <strong>The</strong> <strong>channels</strong> werefur<strong>the</strong>r classified into four orders: 1)<strong>channels</strong> <strong>of</strong> large subtidal sloughs orreaches which never dewater at low tide;2) large <strong>channels</strong> which experience highvelocity tidal flows and usually do notdewater at low tide; 3) intertidal <strong>channels</strong>which branch <strong>of</strong>f second order <strong>channels</strong>or sloughs and usually dewater completelyat low tide; and 4) small intertidal<strong>channels</strong> which branch <strong>of</strong>f second orthird order <strong>channels</strong> and always dewater atlow tide. <strong>The</strong>se and several o<strong>the</strong>r characteristicsmay be utilized to define mostbl i nd and subsi dary <strong>estuarine</strong> <strong>channels</strong> andsome may be applied to <strong>the</strong> characteristics<strong>of</strong> mainstem <strong>channels</strong> (Fig. 2.4). AppendixC lists <strong>the</strong> measurements and <strong>the</strong> valueswhich Levy and Northcote (1981) obtainedfrom <strong>the</strong>ir characterization <strong>of</strong> tidalchannel habitats in <strong>the</strong> Fraser RiverEstuary; <strong>the</strong> major descriptors <strong>of</strong> channel~norphology indicated predominantly thirdorder <strong>channels</strong> with relatively uniformtotal depths (Dc; 2 = 1.75 +- 0.33 m),trough depths (Dt; 8.69 + 5.63 cm), andinouth widths (W 1 -t W ; 13.2 + 6.0 in) butmore variable total ?engths L ; 579.6 ?505.3 m), total area (At; 5,370.3 i5,143.1 mz), and refugia area (357.9 2648.4 m2). <strong>The</strong>ir analyses <strong>of</strong> <strong>the</strong> relationshipbetween channel characteristicsand fish assemblage cornposi tion ii lustratedsome significant associations betweenparticular assemblages and channelcharacteristics, including channel morphology (see Section 6.2.2).
Fig, 2.3. Estuarine channel mouth depositional patterns associated with macrotidal systemsin <strong>the</strong> absence (A) and presence (5) <strong>of</strong> strong wave action (from Wright 1977).
TRANSVERSE SECTIONMeasurements: W1+W2 = width between tops <strong>of</strong> banks perpendicularto axis <strong>of</strong> channel (m)Ac = transverse area (m2)u and u; balk angles as measured by tan-l Dc/W1At= total area, typically meaz~.-ed byand tan-1 D,/WE. respectively; (')planimetry frm charts (m2)Channel Characteristics:Dc = total depth (m) total length = length <strong>of</strong> main axis channel (LC)and sub<strong>channels</strong> (1 (m)Dt = depth <strong>of</strong> trough in bottom <strong>of</strong> channelwhich usually carries residual tidalperimeter = wetted perimeter (P) <strong>of</strong> main axisflow (cm)channel and subchannel s; (m)Ei = elevation <strong>of</strong> channel bottm at gradient = drop in elevation (€?-El ) betweenmouth (m)mouth and end <strong>of</strong> channel, divided byE2= elevation <strong>of</strong> end <strong>of</strong> blind channel (m)axis length (LC); (m/m)E3 = elevation <strong>of</strong> surrounding bank (m)orientation = orientation <strong>of</strong> main axis from truenorth; (")H = height <strong>of</strong> surrounding vegetation;varies seasonally but typical lY meaaveragebank angle = mean <strong>of</strong> a and a ,; (")sured at peak production period; (m)angular deflection = angular deflection to pre-LC = axis length from mouth to fur<strong>the</strong>st vailing flowing tide or river current;("1point on principal axis <strong>of</strong> channel (m)'1-5= lennth <strong>of</strong> sub<strong>channels</strong> (m)refugia area = area <strong>of</strong> watered pools remaining inchannel at low tide; (m2)Fig. 2.4. ~stuarine channel dimensional characteristics (adapted from Levy and Northcote1981).9
2.3 CIRCULATION mixed estuary; and 0 1 indicates awell-mixed estuary.Estuarine ci rculation is usuallydescribed in tenns <strong>of</strong> <strong>the</strong> role played by A fur<strong>the</strong>r classification <strong>of</strong> estuariestidal currents relative to that <strong>of</strong> river proposed by Hansen (1965) and Hansen andflow and invol ves characterization <strong>of</strong> Rattray (1966) incorporates two dimension-water movements, mixing processes, and <strong>the</strong> 1 ess para~neters to describe <strong>the</strong> developdistribution<strong>of</strong> sal ini ty and temperature ment <strong>of</strong> stratification and gravitationalresul ting from <strong>the</strong>se dynamic physical convection in estuaries. This approachprocesses. <strong>The</strong> nature <strong>of</strong> tidal cycles can utilizes stratification-ci rculation diaalsoinfluence <strong>estuarine</strong> circulation. In grams (Fig. 2.5) to describe a continuum<strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>, tides are purely <strong>of</strong> <strong>estuarine</strong> conditions where <strong>the</strong> ordinatediurnal or se~nidirunal for only a few days <strong>of</strong> <strong>the</strong> figure is <strong>the</strong> ratio <strong>of</strong> <strong>the</strong> tidalpermonth and are generally classified as averaged salinity difference between <strong>the</strong>mixed (Thornson 1981). A traditional bottom and surface, 6s = sb-Ss, to <strong>the</strong>scheme <strong>of</strong> classification (Stommel and depth- and tidal-averaged sal ini ty (so) atFarmer 1952; Cameron and Pri tchard 1963; a given 'location, and <strong>the</strong> abscissa repre-Review by Bowden 1967) involves variations sents <strong>the</strong> ratio <strong>of</strong> <strong>the</strong> tidal-averaged netabout <strong>the</strong> simplest relationship between circulation velocity at <strong>the</strong> surface, US,river water and salt water, i.e., in <strong>the</strong> to <strong>the</strong> averaged, cross-sectional net riverabsence <strong>of</strong> o<strong>the</strong>r influences, <strong>the</strong> lower run<strong>of</strong>f flow velocity, Uf. This classifi-density river water will flow as a dis- cation scheme distinguishes seven types <strong>of</strong>tinct layer, separated by a discernibleinterface, over salt water. <strong>The</strong> principalestuaries:factors influencing this relationship Well-mixed estuaries;include fresh water flow, tidal currentsand resulting turbulence, <strong>the</strong> physical (11 type la, where <strong>the</strong> net flow is seadimensions<strong>of</strong> <strong>the</strong> estuary, <strong>the</strong> Coriol is ward at all depths and upstreameffect. As a result, four types <strong>of</strong> estu- transfer <strong>of</strong> seawater is controlled byaries have been described around <strong>the</strong>se diffusion and sal ini ty stratificationvariations: 1) salt wedge, which is is slight, andriver-flow dominated; 2) two-layer flow (2) type lb, <strong>the</strong> variation <strong>of</strong> type 1with entrainment, which is ri ver-flow where <strong>the</strong>re is appreciable stratifi-dominated as modified by tidal currents;cation;3) two-layer flow with vertical mixing,which is a combined effect <strong>of</strong> river flow Partially-mixed estuaries;and tidal !nixing; and 4) verticallyhomogeneous, where tidal currents are <strong>the</strong> (3) type 2a, where net flow reverses atdominant physical process affecting circu-depth and both advection and diffulationand where <strong>the</strong> degree <strong>of</strong> mixing may sion are important determinants <strong>of</strong>vary laterally. A number <strong>of</strong> cases excep- <strong>the</strong> flux <strong>of</strong> salt water upstream andstratification is slight, and(4) type 2b, <strong>the</strong> variant to type 2 wherestratification is prominent;Fjord estuaries;(5) type 3a, where advection dominates byaccounting for over 99% <strong>of</strong> <strong>the</strong> upstreamseawater transfer with 1 i ttlestratification, and<strong>the</strong> mixing (6) type 3b, where <strong>the</strong> lower layer isdeep that <strong>the</strong> salinity gradient aassociated circulation are effectivly surface phenomenon; and,10
Sal t-wedge estuary;(7) where <strong>the</strong> archetypical stratificationis well developed.But as a result 3f extremes in stratificationin <strong>the</strong> upper vs. lower reaches <strong>of</strong>dn estuary and in river discharge, <strong>the</strong>estuaries can actual Iy span several cl assifications,as indicated by <strong>the</strong> linesconnecti rly or extendi ng <strong>the</strong> various sarnpl epoitits in Fig. 2.5. Using this scheme,Harisen and Rattray (1966) compared <strong>the</strong>Columbia River estuary (drowned rivervalley) with <strong>the</strong> Strait <strong>of</strong> Juan de Fuca(fjord). <strong>The</strong>y illustrated that <strong>the</strong> ColumbiaZiver estuary actually shifted from atype lh to a type 2b in response to decreasirigriver flow while <strong>the</strong> Strait <strong>of</strong>Juari de Fuca fell into a type 3a estuary.<strong>The</strong>y also included four o<strong>the</strong>r estuariesfor coinparison (Fig. 2.5). CH2M-Hi1 1(1931) also indicated that five sites inW i l lapa Harbor (also included in Fig. 2.5)sar~iple during June fell within or betweentype 3a and 3b. Classifications <strong>of</strong> some<strong>of</strong> <strong>the</strong> laryer estuaries have been assignedit1 Section 2.6.<strong>The</strong> configuration <strong>of</strong> <strong>the</strong> mouth <strong>of</strong> <strong>the</strong>estuary can have a marked effect on <strong>the</strong>dynarnics <strong>of</strong> tidal circulation through <strong>the</strong>estuary. Goodwin et al.'s (1970) tidalarialysi s <strong>of</strong> three Oregon coas ta1 estuariesindicated that <strong>the</strong> Inore constrictedentrances to A1 sea and Siletz Bays produced"choking" <strong>of</strong> tidal amplitude andtrurlcation <strong>of</strong> tidal amplification at <strong>the</strong>entrance to <strong>the</strong> estuary ~hich was notevident in Yaquina Bay. Tidal cq~rrentsalso tended to reach 9igher maxima in <strong>the</strong>cor\stricted, "choked" estuaries (over 2 msec-1 in Si letz Bay, 1 rn sec-' in A1 seaBay, and 0.6 rn sec-I in Yaquina Bay).Phase shifts between tidal elevations andtidal currents <strong>of</strong> 90" to 100' and <strong>the</strong>temporal distribution <strong>of</strong> tidal amp1 ificationthrough <strong>the</strong> three estuaries alsoindicated <strong>the</strong> presence <strong>of</strong> (progressive)ref1 ected or resonating waves.One diinensi ona1 , vertical ly-i ntegratedmodels <strong>of</strong> circulation in <strong>the</strong> FraserRiver estuary (Crookshank 1971; Ages 1979)have been utilized to document <strong>the</strong> inter-active effect <strong>of</strong> tides and river dischargeupon water surface elevations. <strong>The</strong>yi 1 lustrate that river discharge contributesprogressively lrlore to <strong>the</strong> rise andfall <strong>of</strong> water surface elevation at pointsfur<strong>the</strong>r up (upriver) <strong>the</strong> estuary and that,as discharge increases, <strong>the</strong> point where<strong>the</strong> daily tidal fluctuations (rise andfa11 <strong>of</strong> water) cease to exist moves down<strong>the</strong> estuary. One <strong>of</strong> <strong>the</strong> more interestingsimulated characteristics <strong>of</strong> that estuarywas a significant time lag between <strong>the</strong>upriver propagation <strong>of</strong> <strong>the</strong> flood and ebbtides (e.g., ebb tide taking two hours tomove <strong>the</strong> same distance that <strong>the</strong> floodmoved in one hour).Few studies have compared or classifiedcirculation among different classes<strong>of</strong> <strong>estuarine</strong> <strong>channels</strong> or within <strong>channels</strong>ystems. Officer (1976) provides <strong>the</strong> mostdetdiled and quantitative information todate. While many <strong>of</strong> <strong>the</strong> above schemes canbe applied broadly to <strong>estuarine</strong> <strong>channels</strong>,<strong>the</strong>re are a nu~nber <strong>of</strong> factors, such as~inds, basin (bottom) and channel bathyinetry,and <strong>coast</strong>al storm surges, each <strong>of</strong>which may become more important in affectingcirculation patterns on <strong>the</strong> smallscale. For exainple, Pethick (1980) indicatedthat shallow water asyrninetric tidesare respons i bl e for vel oci ty asymnietry anddendritic channel ~norphology is responsiblefor <strong>the</strong> position and strength <strong>of</strong>velocity surges within tidal <strong>channels</strong>.2.4 WATER MASS CHARACTER1 ST1 CS2.4.1 PhysicalPhysical characteristics <strong>of</strong> <strong>the</strong> watermasses occupying <strong>estuarine</strong> <strong>channels</strong> exh ibitbroad spatial and temporal variationdue to <strong>the</strong> flux and rnixing <strong>of</strong> differentwater masses over short-term (i.e.,tidal),intervediate (i.e.,storm event), andlong-term (i.e.,seasonal cycles) . Whilesome features <strong>of</strong> any one water mass may berelatively predictable, e.g., tidal volume,<strong>the</strong> synergistic interactions amongriverine, marine, and ambient <strong>estuarine</strong>water masses and meteorologi cal eventscredte basically stochastic (random)patterns <strong>of</strong> water volume, velocity, ternperature,sediment content (turbidity),
and density over time. <strong>The</strong> variation <strong>of</strong><strong>the</strong>se parameters also changss kvith physicallocation in <strong>the</strong> estuary in response to<strong>the</strong> proportional representation <strong>of</strong> <strong>the</strong>three basic water masses and basin configuration.Total water volume <strong>of</strong> an estuarygenerally depends upon riverine run<strong>of</strong>f andtidal influx. Run<strong>of</strong>f volume depends uponprecipitation regimes and <strong>the</strong> drainagebasin <strong>of</strong> <strong>the</strong> rivers and tributaries to <strong>the</strong>estuary. Given <strong>the</strong> range in size <strong>of</strong>dra.inage bas ins contributing to <strong>Pacific</strong><strong>Northwest</strong> estuaries, from 6.68 x 105 km2for <strong>the</strong> Columbia River to less than 20 km2for Inany small estuaries along <strong>the</strong> <strong>coast</strong>,<strong>the</strong> range in average annual dischargevolume is correspondingly high; from over7,600 m3 sec-1 for <strong>the</strong> Columbia River toless than 20 m3 sec-1 for small streams,respectively. Short-term fluctuations,however, may be very dra~nati c, especiallyduring winter storm events. For example,short duration winter stom freshets in<strong>the</strong> Columbia River can actually exceed <strong>the</strong>annual sustained summer freshet <strong>of</strong> over14,000 m3 sec-1 (Fox 1981). Flushingtirnes, in terms <strong>of</strong> <strong>the</strong> number <strong>of</strong> tidalcycles requi red to rep1 ace <strong>the</strong> estuary'svolume, vary as a function <strong>of</strong> river dischargeand <strong>coast</strong>al upwelling (Duxbury1979). Sum:ner flushing times for seven<strong>coast</strong>al estuaries, summari zed by Johnsonand Gonor (1982), vary between 4 to 5tidal cycles (Salmon and Netarts Riversestuaries) compared to 63-68 tidal cycles(Coos Bay). Neal (1965) estimated flushingtimes for <strong>the</strong> Columbia River estuaryto be between two and ten tidal cycles.Pearson and Gotaas (1951), Call away(1965), and Stein and Denison (1965)estimated average flushing times for GraysHarbor <strong>of</strong> between 5 and 48 days ( 10 and 96tidal cycles) depending upon river flowvalues. Using a water mass budgetapproach, Duxbury (1979) estimated monthlyreplacement rates <strong>of</strong> between 20% (June)and 16G% (January) day-1 and correspondingresidence tirnes <strong>of</strong> 5.0 and 0.60 days,respectively, for inner (upper) GraysHarbor estuary. Flushing tirnes <strong>of</strong> coas ta1estuaries in <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>, however,may be highly variable dependingupon nearshore ocean conditions. InWillapa Bay a strong northwesterly windduring <strong>the</strong> summer can bring upwelled waterinto <strong>the</strong> bay from <strong>the</strong> ocean, promotingrapid flushing. At o<strong>the</strong>r times <strong>the</strong> ColumbiaRiver plume nay essentially block <strong>the</strong>turnover <strong>of</strong> bay and ocean water :nasses,and complete flushing at such tirnes couldtake more than 20 days (U.S. Army Corps <strong>of</strong>Engineers 1976). Flushing times <strong>of</strong>within-channel water masses have not beenaddressed, but, given <strong>the</strong> fact that most<strong>of</strong> <strong>the</strong> transport occurs through <strong>the</strong>se<strong>channels</strong>, we might safely assume that <strong>the</strong>yare somewhat shorter than those <strong>of</strong> <strong>the</strong>estuary as a who1 e.Temperature reg iines in es tua ri ne<strong>channels</strong> reflect <strong>the</strong> influence <strong>of</strong> bo<strong>the</strong>xogenous riveri ne and mari ne water massesas well as endogenous <strong>estuarine</strong> waternasses transported <strong>of</strong>f subl i ttoral and1 ittoral flats. Mixing <strong>of</strong> <strong>the</strong>se threewater masses vi thin <strong>the</strong> channel habitatcreates a temperature structure whichvaries in a conservative manner accordingto <strong>the</strong> relative contribution <strong>of</strong> each waterInass. Marine waters represent <strong>the</strong> leastvariable temperature source. <strong>The</strong>re isonly a narrow seasonal range between 3°Cand approxinately 17.0°C depending upon<strong>the</strong> presence and extent <strong>of</strong> codstal upwelling(FlcGary 1971; Oregon State University1971; Proctor et al. 1980) and <strong>the</strong> influence<strong>of</strong> riverine plumes from major sourcessuch as <strong>the</strong> Columbid (McGary 1971), Fraser(Waldichuck 1957; Tabata 1972), and Skagi tRivers (Cannon 1978). River temperaturestend to exhibit a greater temperaturerange over time, ranging from 0°C to over25°C depending upon air temperature, precipitation,solar incidence and snow/glacia1run<strong>of</strong>f. <strong>The</strong> waters in an estuary's<strong>channels</strong> are derived ul timately fromexogenous sources which are entrained over1 ittoral and upper subl i ttoral flat habitatsduring flood tide cycles and riverineflood events. Heating or caoling <strong>of</strong> <strong>the</strong>flats prior to and during <strong>the</strong> period <strong>of</strong>inundation can result in rapid and extremeelevation or depression <strong>of</strong> ambient watermass temperatures .<strong>The</strong> result <strong>of</strong> <strong>the</strong> dynamic mixing <strong>of</strong><strong>the</strong>se water masses within <strong>the</strong> <strong>channels</strong>reduces <strong>the</strong> temperature extremes but sti 11
allows cons i derable short-term (within 2.4-2 .wedtidal cycles) variation. Temperatures inchannel Qabi tats in <strong>the</strong> Columbia River Estuarine mixing <strong>of</strong> <strong>the</strong> highly variestuaryrange between 5°C and 25°C (Park able coricentrations <strong>of</strong> dissolved salts andet al. 1972); 5°C and 20°C in Grays Harbor compositions <strong>of</strong> dissolved material charac-(Loehr and Co'llias 1981); and 4°C and 23°C teristic <strong>of</strong> river waters with <strong>the</strong> relain<strong>the</strong> Duwamish giver estuary (Lenarz tively uniform chemical co~nposition <strong>of</strong>1969). Tidal effects caused temperatures <strong>coast</strong>al sea water produces a characteri s-in <strong>the</strong> Salnlon River estuary to fluctuate tic (nixing series between dilute andfrom 7.3"C due to <strong>the</strong> presence <strong>of</strong> rnarine saline end-members (~urton and Liss 1976).water on incoming spring tides to 18.Z°C Composition <strong>of</strong> river waters is influencedon outgoing tides \<strong>the</strong>n river water was by precipitation and rock and soil weathpresent(Johnson and Gonor 1982). Fine- ering. As a result, considerable variaresolutionsalnpl ing <strong>of</strong> t~nperature and tion occurs as a result <strong>of</strong> <strong>the</strong> geologicalsalinity at one station in <strong>the</strong> Salmon character <strong>of</strong> <strong>the</strong> drainage area and differ-River estuary through a c01nplet.e tidal ences in <strong>the</strong> proportional contribution <strong>of</strong>cycle (Johnson and Gonor 1982) illustrated ground water flow and surface run<strong>of</strong>fthdt <strong>the</strong> temperature <strong>of</strong> <strong>the</strong> water mass (Livingstone 1963; Gibbs 1970). In genermeasuredlate in <strong>the</strong> ebb tide originated al, calcium, bicarbonate, and silicate arein d low salinity water mass frorn at least usually <strong>the</strong> major dissolved constituents3 la;) up <strong>the</strong> es tuary. in river waters, while sodium, magnesium,chloride and sul fate predominate in seawater. In that sea water salts compriseSedilnent is transported into or ap;~roxirnately 282 <strong>of</strong> <strong>the</strong> dissolved materithrough<strong>the</strong> estuary in suspension or in a1 at 5°/,0 salinity, <strong>the</strong> chemical compoboundarylayer flow along <strong>the</strong> bottom as sition <strong>of</strong> seawater predominates early inbed load. Accordingly, sirdilrient load and <strong>estuarine</strong> mixing processes (Burton and<strong>the</strong> sources <strong>of</strong> <strong>the</strong> scdi~nent within <strong>the</strong> Liss 1976).<strong>estuarine</strong> channel vary seasonal ly withrjver discharge arid tidal flux (Boggs and This relationship was best illus-Jones 1976; Scheidegyer and PhippS 1976). trated for <strong>the</strong> Columbia River estuary(Park et a1 . 1972) , where Si02 (250-0 u ?I),02 (6.5-0.5 ml L-1) and winter NO3 (35-0Suspended sediitlent is; composed prin- I~M) could be attributed to river sourcescipally <strong>of</strong> sand and finer particles and r~hile PO4 (2.0-0 EM), total CO (2.0-1.0varies with water depth and velocity. uM), alkalinity (2.0-1.0 meq $-1 ), andSuspended sedi~llents in <strong>the</strong> Columbia River surmner NO3 values (20-0 uM) originatedabove <strong>the</strong> estuary consist <strong>of</strong> particles ~ 6 3 principally from oceanic water masses. AIn in diameter and <strong>the</strong> total suspended load recent review <strong>of</strong> historical water qua1 i tyinto <strong>the</strong> estuary, which can vary three- datd in <strong>the</strong> Columbia River estuary (Paciffoldfro111 year to year was estimated to ic <strong>Northwest</strong> River Basins Commission 1980)be 9.5 x 106 tons yr-I (Haushild et al. indicated considerable seasonal variation1966). suspended sedi:nent concentrations in nutrient concentrations a1 though nutri -can vary from 13-0 to 38.5 m L - ~ at <strong>the</strong> ent patterns had changed little over <strong>the</strong>surface, 12.5 to 69.6 mg L' 9 within <strong>the</strong> last 20 years. Representative surnlnersalt wedge and 12.5 to 59.9 m~ L-l 1 m nutrient values were 0.002 rng L-1 PO4-P,above <strong>the</strong> bottom, depending upon location undetectable nitrate, and 4.0 mg L-1in <strong>the</strong> estuary, tidal stage, and current Si02 in riverine portions <strong>of</strong> <strong>the</strong> estuaryvelocity (university <strong>of</strong> Washinqton Depart- and 0.070 mg L-1 p04-P, 0.20 mg L-1 NO3-Nnlent <strong>of</strong> oceanography 1980). Total mean and 2.0 mg L-1 sio2 in marine regions; <strong>the</strong>sediment flux in drainage <strong>channels</strong> in <strong>the</strong> data suggested nitrate and phosphatelower estuary in February 1980 ranged depletion occurs within <strong>the</strong> estuary duringbetween 0.2 and 1.0 mg an-2 set-1 at late sulnlner a1 though <strong>coast</strong>al upwelling mayChinook and Sand Island and between 0.1 increase nutrient levels (NOg, PO4) in <strong>the</strong>and 0.7 mg tin-2 S~C-1 at f lwaco,lower estuary during <strong>the</strong> summer (Haertel14
et al. 1969; Oregon State Univ. School <strong>of</strong>Oceanography 1980b). In coinpari son,spring and surnlner values <strong>of</strong> NO3-N andtotal PO4-P in <strong>the</strong> Grays Harbor estuaryranged between 0.018 arid 0.055 mg L-I and0.003 and 0.060 mg L-1, respectively(Herman 1975).A1 though it is probable that nutrientinputs i nto es tuari ne channel habitats areartificially elevated during periods <strong>of</strong>high river discharge due to run<strong>of</strong>f <strong>of</strong>nitrogen and phosphorus from agricultureand silvicul ture-appl ied fertil izers in<strong>the</strong> watershed, no causal data is avail ablefor <strong>Pacific</strong> <strong>Northwest</strong> estuaries. Coll iasand Lincoln (1977), however, calculatedthat <strong>the</strong> average inflow <strong>of</strong> phosphate into<strong>the</strong> main basin <strong>of</strong> Puget Sourid was 1,223metric tons and <strong>the</strong> contribution <strong>of</strong> phosphatefrom all sewers was 12.6 rlletrictons, co~npared to 18,400 inetric tons <strong>of</strong>phosphate in <strong>the</strong> main basin at any giver1time.Sa1 ini ty has traditionally beer1employed as an index <strong>of</strong> mixing, a1 thouglithis has been criticized because <strong>the</strong>definition <strong>of</strong> sal i ni ty depends upon <strong>the</strong>essenti a1 constancy <strong>of</strong> <strong>the</strong> re1 ati ve proportions<strong>of</strong> <strong>the</strong> dissolved ions in seawater and <strong>the</strong> introduction <strong>of</strong> river watercauses departures frorn <strong>the</strong> nearly constantionic ratios <strong>of</strong> oceanic waters (Burton andLiss 1976). As indices <strong>of</strong> mixing, chlorinity, chlorosi ty or isotopic oxygenratio (180/169) values have also beensuyges ted as sui tab1 e paraineters (Boy1 e etal. 1974), but <strong>of</strong> <strong>the</strong>se only chlorinityhas been r~easured frequently in <strong>estuarine</strong><strong>channels</strong> <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>. Consideringthat our primary concern in thissyn<strong>the</strong>sis is <strong>the</strong> biological structure anddynamics <strong>of</strong> <strong>estuarine</strong> channel communities,<strong>the</strong> spatial and temporal distribution <strong>of</strong>salinity structure in <strong>the</strong> estuary is anappropriate indication <strong>of</strong> <strong>the</strong> major chemi -cal factors structuring <strong>the</strong>se com~nuni ties(Caspers 1967).Saline oceanic water is transportedinto an estuary by both advection anddiffusion (Bowden 1967). Advected oceanicwater masses are general ly referred to as<strong>the</strong> " sal t wedge" a1 though diffusion pro-cesses can cause <strong>the</strong> intrusion <strong>of</strong> salinewater beyond <strong>the</strong> upstrearn 1 i~ni t <strong>of</strong> <strong>the</strong>salt wedge. In such estuaries as <strong>the</strong>Columbia River, it appears that longi tuditialsalt transport via diffusion may besignificant (Hansen 1965; Hughes 1968;Dyer 1973; Hughes and Rattray 1980; Fox1981). 5al ini ty gradients can be distinctand sharp in situations where fresh andsaline water masses are stratified, orbroad and variable where vertical mixingpredoininates. Thus, tfie degree <strong>of</strong> bothsalinity intrusion and stratification isdependent upon es tuary inorphol ogy, riverdischarge, seni-diurnal and spri ng-neaptidal cycles, and short-term, stochasticevents such as storms; in terins <strong>of</strong> estuarymorphology, <strong>the</strong> rate <strong>of</strong> change <strong>of</strong> crosssectionalarea through <strong>the</strong> estuary and <strong>the</strong>bed topography are important factorsdetermining sal ini ty distribution (Prandl e1951).A1 though most silnul ation models <strong>of</strong><strong>estuarine</strong> circulation, such as thoseproduced for <strong>the</strong> Fraser River estuary(Crookshank 1971; Ages and Wool lard 1976),are vertically integrated (or, at best,integrate over two depth sectors), accuratedescriptions <strong>of</strong> current flow musttake into account <strong>the</strong> dynamic effect <strong>of</strong>sal ini ty intrusion upon currents. Detailedempirical studies are requiredbefore more complex models can be assembled.Such field documentation in <strong>the</strong>Fraser (Ages 1975) has illustrated <strong>the</strong>role <strong>of</strong> <strong>the</strong> salt wedye in modifying <strong>the</strong>tidal effect upon surface outflow. Inthis instance, <strong>the</strong> sa1 t wedge continuesits upstrearr) rrlotion after flood slack,<strong>the</strong>n retreats down <strong>the</strong> estuary but maintainsits shape until it is finally carried out as a homogeneous water mass. In<strong>the</strong> Columbia Ri ver estuary, sal ine watercan be detected as far as 42 km upriverunder <strong>the</strong> combination <strong>of</strong> extremely lowriver discharge and neap flood tides, butonly as far as 10 km under high riverdischarge, with stratification more pronouncedduring neap tidal cycles thanspring tidal cycle (Hansen 1965; Dyer1973; McConnell et a1 . 1979; Jay 1981; Fox1981). It should be noted, however, that<strong>the</strong> archetypical salt wedge is not yenerallyfound in <strong>the</strong> Columbia River estuary
(D. Jay, Univ. Wash., pers. comm.).Loehr and Coll ias (1981) indicatedthat <strong>the</strong> extent <strong>of</strong> salinity intrusioti inGrays Harbor in June and July 1966 (riverflows, 49.1 m3s-1 and 68.4 m3s-1, respectively)varied according to <strong>the</strong> range <strong>of</strong>tidal cycle (i.e., neap vs. spring). <strong>The</strong>extent <strong>of</strong> intrlrsion shifted four milesover <strong>the</strong> tidal cycle during a neap andless than a mile during a- spring tidalcycle. Simenstad and Egyers (1981) indicated that sal ini ties in channel habitatsbetween March and October 1980 were relativelyuniform (well mixed) in <strong>the</strong> centralportion <strong>of</strong> <strong>the</strong> estuary (Cow Point, +loonIsland), but typically stratified at <strong>the</strong>upper (Cosmo?ol is) and 1 ower (Stearn'sBluff) extremes <strong>of</strong> mixing zone. Sal initiesat <strong>the</strong> latter two sites ranged widelybetween 5"/,, and 25"/,, but covered anarrower range hetween 25"/,, and 36O/,,at tile site (Wes tport) near <strong>the</strong> mouth <strong>of</strong><strong>the</strong> estuary.Salinity ranges at three <strong>channels</strong>ites (RM 1.0, 2.2 and 3.7) in Yaquina Baybetwwen 1960 and 1973 were 11.7°/00 (34.1-22.4'/,,; ~i = 29.7"/,,) at <strong>the</strong> lower end<strong>of</strong> <strong>the</strong> estuary, and 16.3"/,, (34.1-17.8"/,,; S; = 28.2"/,,) and 24.1°/,,(33.5-9.4"/,,; Si = 27.3"/,,) fur<strong>the</strong>r up<strong>the</strong> estuary (U.S. Army Corps <strong>of</strong> Engineers1975).Levy and Levings (1978) documentation<strong>of</strong> surface salinity at a channel in <strong>the</strong>Squamish River estuary a1 so indicated <strong>the</strong>brodd seasonal fluctuations which canexist at one site. <strong>The</strong> maxima <strong>of</strong> 26-27"/,, occurred in <strong>the</strong> winter and lessthan 4O/,, sustained during <strong>the</strong> spring andsumrner ~nonths . This seasonal effect wasalso illustrated for a blind, dendriticchannel habitat in <strong>the</strong> Fraser River estuary(Kistritz and Yesaki 1979), wherewater flooding <strong>the</strong> channel and :narsh wasbrackish (3-8°/0,) only during high wintertides, despite <strong>the</strong> greater tidal rangedurin <strong>the</strong> summer (%5 m) than <strong>the</strong> winter(1.3 m3.River waters are typically moreacidic than sea water but pH gradients in<strong>estuarine</strong> channel s are a1 so affectedsignificantly by variations in <strong>the</strong> chemi -cal composition <strong>of</strong> <strong>the</strong> mixing watermasses. pH values in <strong>the</strong> Columbia Riverestuary range from 5.8 to 8.3 but usuallyfall between 7.6 and 7.9 within <strong>the</strong> mixingzone; tributary channel waters in <strong>the</strong> area<strong>of</strong> Youngs Bay have been reported to beslightly more acidic than main channelwater in <strong>the</strong> adjacent estuary (Park et al.1980; <strong>Pacific</strong> <strong>Northwest</strong> River BasinsC<strong>of</strong>l~nission 1980). Herrman (1975) documentedspring-summer pH values between6.94 and 7.25 in <strong>the</strong> upper Grays iiarhorestuary, with <strong>the</strong> surface waters usudlly0.08 pH units less than <strong>the</strong> more salinebottom waters. A 13-year water qua1 itydata base for Yaquina Bay (U.S. Army Corps<strong>of</strong> Engineers 1975), however, illustratedquite uniform pH values at three locationsthrough <strong>the</strong> estuary (at river miles 1.0,2.2 and 3.7), with ranges between 7.6 and8.6 (pH ji = 3.1 at all three locations).Dissolved oxygen (DO), in addition tobeing <strong>the</strong> essenti a1 el ernent in aerobicinetabolism by aquatic organisms, is involvedin <strong>the</strong> biochemical breakdown <strong>of</strong>organic matter in marine environments. Inessence, aquatic organism are constantlycompeting for free dissolved oxygen andwill incur physiological limitations whendissolved oxygen 1 eve1 s decrease be1 owapproxirnately 5 pprn; <strong>the</strong> tolerance todepressed dissolved oxygen is highlyvariabl e among aqua tic organi sas, however,and many natural ly divergent structures <strong>of</strong>marine water colurnn and benthic communitiesare due to different dissolvedoxygen regimes.Due to [nixing <strong>of</strong> ri verine and marinewater masses and <strong>the</strong>ir typical rapid fluxthrough <strong>the</strong> habitat, <strong>estuarine</strong> <strong>channels</strong>typical ly do not experience dissolvedoxygen depletion except during situations<strong>of</strong> seasonal minima in water exchange ordue to increased organic loadings byorganic pollutants.Dissolved oxygen is considered to beprincipal ty regulated by: 1) <strong>the</strong> rate <strong>of</strong>addition <strong>of</strong> biological oxygen demand(BOD); 2) <strong>the</strong> net rate <strong>of</strong> addition orremoval <strong>of</strong> oxygen by benthic oxygendemand, photosyn<strong>the</strong>sis, and respiration;
3) <strong>the</strong> rate <strong>of</strong> reaeration; and 4) <strong>the</strong> rate<strong>of</strong> removal <strong>of</strong> BOD by sedi:nentation orabsorption (Dobbins 1954). Longi tudi naldispersion, <strong>the</strong> rate at which a materialis dispersed by eddies and diffusion, isnot usually a significant factor in lacustrineand strea~n systems but is thought tobe riiore important in <strong>estuarine</strong> channel s .Gunnerson (1966, 1967) and Thornann (1957)provide evidence that patterns <strong>of</strong> dissolvedoxygen concentration in estuariesmay be highly periodic, potentially exhibiting annual, 14-day, 24-hour, and 12-hourcycles with <strong>the</strong> low frequency effectsbeing re1 atively more irnportant than thoseattributable to high-frequency phenomena.<strong>The</strong>se cycles could be reasonably correlatedto daily and spring-neap tide variations,solar radiation intensity, andphotosyn<strong>the</strong>sis.Lenarz's (1969) detailed analysis <strong>of</strong>water quality data from <strong>the</strong> Duwamish Riverestuary indicated that <strong>the</strong> 1 owes t concentration<strong>of</strong> dissolved oxygen in <strong>the</strong> channelprobably was associated wit:? <strong>the</strong> upstreamedge <strong>of</strong> <strong>the</strong> salt wedge. Streamflow waspos i tively correlated to dissolved oxygenconcentration and this relationship wasattributed to increased turbulence (diffusion),lower retention time, and greaterdilution <strong>of</strong> BOD with increased streamflow.<strong>The</strong> timing <strong>of</strong> algal blooms, which <strong>of</strong>tenincreased dissolved oxygen concentrationsdramati call y, were a1 so determined to berelated to strearnflow and tidal prism.Dissolved oxygen level s in <strong>estuarine</strong>channel s <strong>of</strong> <strong>the</strong> Paci fic <strong>Northwest</strong> arenaturally high, being at or near saturation,except in a few highly developedestuaries with high BOD loadings. <strong>The</strong>Columbi a River estuary represents <strong>the</strong><strong>Pacific</strong> <strong>Northwest</strong> <strong>coast</strong>' s largest systemre1 ative to natural dissolved oxygenconcentration. Most <strong>estuarine</strong> waters areusual ly supersaturated (8-6 mg duringspring and summer inonths- and slightlyundersaturated (
several periods in <strong>the</strong> summer; <strong>the</strong> lowestvalues, 3 to 4 el!, L-I, were associatedwith <strong>the</strong> upstream edge (bottom) <strong>of</strong> <strong>the</strong>salt wedye.Bi ocherni cal oxygen demand has notbeen as widely reported as dissolved oxygen.Five-day BOD levels in Yaquina Bayaveraged 1.2 mg L-1 tnrouyhout <strong>the</strong> estuaryand a maxima ot 6.6 my L-1 was recordedw~thin two miles <strong>of</strong> <strong>the</strong> trlouth (U.S.Army Corps ot Enyineers 1975). Surriinervalues in tirays Harbor ranyed between1.45 to 5.13 my L - ~ (Herrman 1975).2.5 SUBSTKATE CHARACTERISTICS2.5.1 PhysicalChannelsubstrates reflect both his-toric and extant conditions. <strong>The</strong> yeoloyi -cdl history <strong>of</strong> <strong>the</strong> estuary and its watersheddetermines <strong>the</strong> characteristics <strong>of</strong><strong>the</strong> material tnrouyh which <strong>the</strong> channel 1sbeiny cut and <strong>of</strong> <strong>the</strong> sediment load borneby riverine currents. Uynarrlic hydroloyi -cal , tidal, and meteroloyical forces,however, affect <strong>the</strong> coinplex eroslon anddeposi t ion processes which are constantlystructuriny <strong>the</strong> channel. <strong>The</strong> reader isreferred to Elliott (1978a & b) and Keineckand Sinyh (1980) for rriore detaileddiscussions <strong>of</strong> sedimentation processes.trosiori can occur throuyh corrosion(chemical ) , corrasion (mechanical ), andcavitation (Morisawa 1968), aided by <strong>the</strong>suckiny, liftiny forces <strong>of</strong> vortex action(Mat<strong>the</strong>s 1947). Under vortex action loosenedmaterials are sucked upward and downstreasiwith tne vortex current. Localdiscontinuities or separations <strong>of</strong> flow occurwhere <strong>the</strong>re is a change in current directionand velocity caused by obstaclesor impingeelent on channel walls. <strong>The</strong>result is a nonunifor111 distribution <strong>of</strong>energy at that point, which produces aveering and overturniny <strong>of</strong> water rnassesas spiral flow. Water velocity, size otobstructions, spacing and size <strong>of</strong> obstaclesand <strong>the</strong> sharpness <strong>of</strong> channel bendsdictate <strong>the</strong> amount <strong>of</strong> separation, turbulence,and vortex action.Besides yrowing deeper or cuttinynew beds, <strong>channels</strong> a1 so widen by lateralcorrasion and wea<strong>the</strong>ring <strong>of</strong> <strong>the</strong> wall sduriny hiyh water flow, which includestidal influxes. 80th channel cutting andwidening are inediated by <strong>the</strong> resistance<strong>of</strong> <strong>the</strong> bed material. <strong>The</strong> critical erosionvelocity <strong>of</strong> unconsol idated materi a1varies as a function <strong>of</strong> <strong>the</strong> grain size.Hjul strom (1935) indicated velocity decreasedfrom ~200-500 cm sec-1 (~4-1Uknots) for particles 1 pm dia. to ~20-50cm sec-1 (Q0.4-1.0 knots) for particlesbetween 100 pm and 1 mm, and increased to500 cm sec-I ( Q:O knots) for particlesas large as 100 iilm dia. As a result,erosion <strong>of</strong> sand requires lower velocitiesthan <strong>of</strong> ei<strong>the</strong>r silt or gravel. Sternbery(1967) estimated that <strong>the</strong> critical drayvelocity required to initiate generalsediment motion in a Puget Sound channelwas 2.2 cm sec-1 for sediment yrain sizesbetween 0.3 to 1.1 riim dia.Particles entrained and transportedby a water mass are deposited when <strong>the</strong>current is no longer sufficient to carry<strong>the</strong>m ei<strong>the</strong>r as suspended particles (sedimentload) or as bottom transported (bedload) particles. Deposition <strong>of</strong> <strong>the</strong> sedimentload occurs with loss <strong>of</strong> competencecaused by a decline in gradient, a reductionin velocity or a decrease in volume.Settliny velocities range trom 0.1 cmsec-I (0.~02 knot) for particles Q 20-30Dm dia. to Q100-3UU cm sec-1 (~1-6 knots)for particles 2-10 cm dia. (Hjulstrom1935; Sundborg 1956). <strong>The</strong>se re1 ationshipsvary as a function ot <strong>the</strong> characteristics<strong>of</strong> <strong>the</strong> particle (e.y., specific gravity)and water lrlass (e.y., salinity).Thus, <strong>the</strong> dynamic changes in velocity,direction, sediment load and densityot water rnasses moving throuyh <strong>estuarine</strong><strong>channels</strong> results in spatially and temporally variable sediment structure throuyh<strong>the</strong> estuary, and with considerable variabi1 i ty arnong estuaries. A particularlyprominent feature to most estuaries is azone <strong>of</strong> minimum sediment particle sizewhich typically occurs within <strong>the</strong> "mix-i ny ," "entrapment ," "turbidity maximum,"or "null" zone where upstream bottom tidalcurrents approximately balance down-
stream river currerits (Arthur and tiall1979; Ll oern 1979). Maxin1u111 settl iny <strong>of</strong>suspended particles occurs within tniszone duriny slack water, but 111uch isresuspended duriny tl ood or ebb currents.<strong>The</strong> rrlixiny <strong>of</strong> riverirle arla sa i ine watermasses also results in <strong>the</strong> tlocculationot fine particles, both sediment (clay)and orydnic detritus, and <strong>the</strong>se aggreyatessettle within this entrdpl~~ent zone.Hubl~el 1 and Cil enn (1973) docu~llentedtnat <strong>the</strong> mean size <strong>of</strong> channel sedilllent in<strong>the</strong> Col urribia River estuary became proyressively finer downstrearrl tlirouyh <strong>the</strong>fl uvial and transitional regions, only tobecorne coarser in <strong>the</strong> marine reyion <strong>of</strong><strong>the</strong> estuary. This relationship was verifiedin <strong>the</strong> rirore detailed CREDDP~ studies<strong>of</strong> <strong>the</strong> Columbia Kiver estuary. <strong>The</strong> sedimentparticles in <strong>the</strong> rlrai n channel wereshown to decrease in modal size fro111 500-3UU 1,111 (1.01)-1.754) <strong>of</strong>t Grays Uay to 3UO-175 1 rn (1.75- 2.5114) <strong>of</strong>t Baker Uay (Royet al. 1979; University ot Washinyton Uepartrrlent<strong>of</strong> Oceanoyrapny 1980). Variationin channel sedi~nent structure, however, iswidely apparent and can be related to <strong>the</strong>current speed and <strong>the</strong> extent <strong>of</strong> cornmunicationwith riverine or tidal flow (University<strong>of</strong> Washinyton Uepartment <strong>of</strong> Uceanography1980). Sedin~ents in <strong>channels</strong> witnopen corr~munication with <strong>the</strong> ColurribiaKiver, one <strong>of</strong> <strong>the</strong> estuary's rllajor tributaries,or <strong>the</strong> density-driven flow from<strong>the</strong> ocean, tend to be coarser than sedimentson adjacent sub1 ittoral or 1 ittoralflats. Where water flow is restricted toonly one end <strong>of</strong> <strong>the</strong> channel <strong>the</strong> sedimentyrain size is usual ly finer than on <strong>the</strong>adjacent flats. Channel bathymetrj !naya1 so affect <strong>the</strong>se relationships, as finegrainedsedin~er~ts may also be found indeep segments <strong>of</strong> larye <strong>channels</strong> where<strong>the</strong>re are low velocity water areas belowchannel sill depths.<strong>The</strong>se re1 ationshi ps between sedirrlerltstructure and chanr?el ~norph<strong>of</strong> oyy have alsobeen i l 1 ustrated within Coos Bay, whereHancock et al. (1980) il lustrated thatsedi~lient yrain size remained relativelyconstant (250 v111) w itni n <strong>the</strong> Coos navi yationchdnnel but was an order <strong>of</strong> ~naynitudetiner (b2 ~111) in Isthmus Slouyh,which does not have significant freshwater current flow through <strong>the</strong> channel.[)ifferential distribution <strong>of</strong> sedimentcori~position is a1 so we1 1 ill ustratedin Phipps and ~cnernrer's (1980) data tor<strong>the</strong> hottorr~s drld slopes <strong>of</strong> <strong>the</strong> Grays tiarbornavi yation chdnnel (Fi g . 2.6). Gravel andcoarse particles tronl ri verine sourcestended to be distributed in <strong>the</strong> hiyhestand lowest reaches <strong>of</strong> <strong>the</strong> estuary, indicatinyboth riverine arid marine sources.Silts and clays accumulated within <strong>the</strong>rnixiny zone, probably lrlore <strong>the</strong> result <strong>of</strong>flocculation processes than <strong>of</strong> settl iny.Fines (predori~i nantly sand) con~posed rnost<strong>of</strong> sedin~ents in <strong>the</strong> lower estuary andprobably represented sett 1 i ny f ronl bothriverine and <strong>estuarine</strong> water nlasses. <strong>The</strong>principal di tference between bottom andslope habitats was <strong>the</strong> lonyitudinal position<strong>of</strong> <strong>the</strong> peak occurrence <strong>of</strong> yravel,which was lower in <strong>the</strong> estuary in <strong>the</strong>channel bottom sediments. This probablyreflected <strong>the</strong> niyher current velocitiesalony <strong>the</strong> bottom ot <strong>the</strong> channel.Sediments in <strong>the</strong> mainstem channel <strong>of</strong>Yaquina Bay tal l into three realnls <strong>of</strong>deposition (Kulm and Byrne 1967). <strong>The</strong>Iliarine redlm, extending 3 k~rl into tileestuary from its mouth, contains well-sorted, subangular to subrounded, fine tomedium sana. Tne marine-tluviati lerealrr~, occurring between 3 k~rr dnd 1U ~IIIfrorn <strong>the</strong> mouth <strong>of</strong> <strong>the</strong> estuary, has sedirr~entswith a wide ranye In texture, tromwell- to poorly-sorted, anyular to sub-rounded silt to isediurn Sdnd. Tne tluviatilerealm in <strong>the</strong> upper reaches <strong>of</strong> <strong>the</strong>estuary tur<strong>the</strong>r than 10 kln frorn <strong>the</strong> rnouttlis characterized by sedirl~ents which arepoorly sorted, anyul ar to subdnyu l aryrains 9f S i l t to codrse sand. Lrainsize in <strong>the</strong> lower 10 kt11 ot <strong>the</strong> estuaryaverayes 217 bm (150-291 urn) and 279 Llrnin <strong>the</strong> channel above 10 krn.Tne only comprehensive study <strong>of</strong> sub-2 ~ ~ , ~j~~~ ~ ~ ~ b i ~ ~ Oata t Develop- ~ ~ sidiary ~ and y blind <strong>estuarine</strong> <strong>channels</strong> inment Program.<strong>the</strong> region, that <strong>of</strong> <strong>the</strong> Westwater Research
CHANNEL BOTTOMC)CHANNEL SLOPEII,I/p GRAVELSTATION LOCATION(X wet wein Grays Hadistributed at seven
Centre, University <strong>of</strong> British Columbiastudies in <strong>the</strong> t-raser River estuary, describedsediments trom <strong>the</strong> center trouyhs<strong>of</strong> dendritic <strong>channels</strong> at Woodward andBarber Islands and Ladner Marsh as beingsandy, with <strong>the</strong> yrain size ranging between75 m and 192 In (Levy and Northcote1981). Sn~ith's (1980a) studies innor<strong>the</strong>rn Puyet Sound indicated sedimentsfrom a dendritic channel alony <strong>the</strong> delta<strong>of</strong> <strong>the</strong> North Fork Skagit Kiver were cornposedpredominantly <strong>of</strong> sand (81.13% byweiyht) and silt (lk1.322)~ with mednyrain size <strong>of</strong> 97.4 urn (3.36 @ ). Sedimentsfroin <strong>the</strong> bank (t 1.0 m elevationMLLW) <strong>of</strong> a principal tidal channel awayfro~rl <strong>the</strong> delta were coarser (229.2 urnC2.13 $1) and sandier (89.88%)) and had ayreater sand to mud ratio (8.88) than did<strong>the</strong> sample from <strong>the</strong> dendritic channel on<strong>the</strong> face <strong>of</strong> <strong>the</strong> delta (3.36).Bed load transport <strong>of</strong> sediment hasnot been well documented except in <strong>the</strong>Columbia Kiver estuary where, a1 though<strong>the</strong>re is considerable annual variation(Jay and Good 1977), <strong>the</strong> direction <strong>of</strong>transport has been identified by <strong>the</strong>orientation <strong>of</strong> bedforms (University <strong>of</strong>Wasninyton Department <strong>of</strong> Uceanoyraphy1980). <strong>The</strong>se studies have indicated that<strong>the</strong>re is net downstream transport in most<strong>channels</strong> above Tonyue Point, below whichbed load transport reverses direction inresponse to tidal flow. <strong>The</strong> mixing reyion<strong>of</strong> <strong>the</strong> estuary represents d trdnsitionzone for bed load within <strong>the</strong> channel andhas extremely compl ex bedform patterns.Tagged sediments released at <strong>the</strong> mouth <strong>of</strong><strong>the</strong> estuary duriny <strong>the</strong> 1980 summer lowflowperiod indicated a yreater (longitudinaldistance) transport out ot <strong>the</strong> estuaryduriny low tidal ranye than into <strong>the</strong>estuary duriny high tidal ranye.2.5.2 ChemicalEstuarine sediment chemistry can oecharacterized by <strong>the</strong> mineralogical andcherni ca I composition <strong>of</strong> <strong>the</strong> sediment particlesand associated interstitial detrituswhich, in yeneral, can be related to<strong>the</strong> yrain size structure (Burton and Liss1976). Mineralogical composi tion <strong>of</strong> <strong>estuarine</strong>channel sedirnents is quite variabledue to <strong>the</strong> different physiographic provinces(e.g., Co1 ulnbia Kiver Basin, OreyonCoast Range, Olympic Mountains, CascadeMountains) contributing sediments to <strong>Pacific</strong><strong>Northwest</strong> estuaries. For example,in <strong>the</strong> Colu~nbia Kiver, quartz, feldsparand volcanic minerals are <strong>the</strong> dominantconstituents in sand particles; quartz,feldspar and mica comprise <strong>the</strong> major mineralsin silt; and nrontmori 11 inite, chlorite,and kaolinite are <strong>the</strong> principal cornponents<strong>of</strong> clay (Forster 1972). However,<strong>the</strong>se constituents chanye dramaticallyalong <strong>the</strong> course <strong>of</strong> <strong>the</strong> river, such that<strong>the</strong> contribution <strong>of</strong> quartz, hornblendeand auyi te decrease downri ver and volcanicrock frayinents and hypers<strong>the</strong>ne becomemore prominent below <strong>the</strong> Bonneville Dam(Whetten et al . 1969). Thus, hypers<strong>the</strong>ne,cl i nopyroxene cauyi te, and hornblendecharacterize <strong>the</strong> sediment rnineraloyy <strong>of</strong><strong>the</strong> estuary (Venkatarathnam dnd McManus1973; Ni ttrouer 1978), a1 thouyh cl inopyroxeneat <strong>the</strong> mouth <strong>of</strong> <strong>the</strong> estuary isprobably <strong>coast</strong>al-derived sediment (University<strong>of</strong> Washington Department <strong>of</strong> Oceanography1980). Cl i nopyroxene a1 so characterizes Grays Harbor sediments (Scheideggerand Phipps 1976). Kulm and 8yrne(1967) recognized three distinctivesuites <strong>of</strong> heavy minerals in <strong>the</strong> <strong>channels</strong>ediments <strong>of</strong> Yaquina bay--marine, rnarinefluviatile,and fluviatile. Marine sediments,characterized Dy pyroxenes such asdiopside, and nypers<strong>the</strong>ne, extend approximately3 k111 into <strong>the</strong> estuary; <strong>the</strong> marinefluviatesuite occurs over approxi~nately6 km and is characterized bd micas, nluscovite, and biotite, with reduced contributionsby metarnorphic minerals such askyanite, staurolite, and si 1 lirnanite; and<strong>the</strong> fluviati le suite, characterized by<strong>the</strong> micas, hematite, and limonite, occursin <strong>the</strong> upper reyion <strong>of</strong> <strong>the</strong> estuary.Oryanic matter in <strong>estuarine</strong> <strong>channels</strong>ediments, principally particulate oryanicmatter (POM), oriyinates from <strong>the</strong>excretion by animals and decomposition <strong>of</strong>plants and animals and oryanic particlestransported into <strong>the</strong> estuary which havesettled in association with inorganic(mineral) particles. A variety <strong>of</strong> measureshave been utii ized to quantify organicmatter. Each evaluates a different
spectrum <strong>of</strong> <strong>the</strong> total organic or itsrelative chemical or oiological reactability.<strong>The</strong>se lnclude, but dre not ll~llitedto: I) volatile solids; 2) biochemicaloxyyen denland; 3) chernlcal oxyyen demand;and, 4) total oryan.rc carbon.because settl iny ot oryarlic particles,including those resulttny from flocculat~onprocesses, involves ~as~cdl lytne sdirle processes whlch determine inoryanlcsedlnrentdtlon, tne dlstrlbutlon otoryanic ~i~dtter tllrough an estuary isusudl ly closely i nteyrdted with sedimentsl ze dl strlbutlon. f xceptlons to tni syenerdl ization occur when point sourcesot orydnic matter (e.y., oryanlc pol lutdnts)wltnrn tne estuary dolmnate localscdl~entdtl~n part1 cles. Accord i ng 1 y ,~t~axintua oryanic content <strong>of</strong> <strong>estuarine</strong>chdnnel sediments 1s usually correlatedwltti <strong>the</strong> cllstributiun <strong>of</strong> tine sedimentpdrtlclcs assocl ated wl th <strong>the</strong> mlxlny zoneot ttie estudry, wi th vdriation due to( hdnrirl bdthynretry , 11115 correlation i sBrst I 1 lustrated by <strong>the</strong> dlstrlbutlon otsrdlll~rnt oryarlic ~natter tnrouyh <strong>the</strong> ~nai n-ste~n channel ot Grays Harbor (Flgs. 2.1dnd L.k$). In yenera 1, pedk concentrations<strong>of</strong> setfltlrent organics occur In <strong>the</strong> innertlarbor dnd central m~xiny zone portion <strong>of</strong>tltta estudry, particvldrly in associationwittl silt drld cldy tractions (see Fig.2 . Hecause tnu trldnnel slopes andbdnks trave lower (~nte~rated) water veloclt1c2s thin do <strong>the</strong> chdnnel bottonis, tineorgdnic particles nave a lonyer period ottlti~e clurlng which to scrtle <strong>the</strong>re. As aresult, <strong>the</strong> channel bank and slope habit.dt5Ot GrdJs HdTDOr t ~ ~ l ~ 11 d1ustrdt-led higher levels <strong>of</strong> orranics which startedOccurrlny fur<strong>the</strong>r up <strong>the</strong> estuary (inland)than did tnose <strong>of</strong> <strong>the</strong> cnannel bottonrs.!-or colrtparison, dredge sanlples otrstuarlne channel seairnents In <strong>the</strong> CnetcoKiver, Coos @ay, Loquil ie Bay, KoyueKiver, Siuslaw say, Umuqua gay, and'r'aqu~nd Bay estuarres nave Rad totalvoidtile sol~ds values ranginy between1 .t33-4.1)4%+ 0.38-8.7 7X, 0.44-0.50%, 1.19-1.34%, O.Zb- 0.61%, 0.91-3.272, and 0.49-tf.78x, resyectivety (Percy et 51. 1974).Estuaries niay act as yeocnemicaltraps for dissolved irraterial throuyh flocculationand sedimentaion processes. Thisresults in a net transter <strong>of</strong> trace elementsand oryanic matter to sediments(and benthic organi sins), particularly inanoxic habitats where <strong>the</strong> ptiysi co-chemicalconditions (e. y., redox potential )are conducive to <strong>the</strong> fixing <strong>of</strong> trace elementsin <strong>estuarine</strong> sediments (Burton andLiss 1976). In general, Ni, Co, Cr, V,Ha, Sr, Pb, Ln and Y concentrations aresimilar in 50th drroxic and oxidizing sedirlrentsbut irln, Cu, Se, Zr and Mo, alonywith <strong>the</strong> major elements <strong>of</strong> phosphorus,CdrbOn, and sul fur, are colnpatively enrichedin anoxic sedirilents. AM Test, Inc,(1981) reported Cu in sedilrlent elutriatefront (;rays Hdrbor as high as 1.2 my L-1;zinc as nibh as 1.85 "19 L-1; and Pt, ashiyh as 0.12 my L-1. Organic pollutants,incl udi nt, getrol cum hydrocarbons, pesti -cides, PCBs (polychlorinated biphenols),and pu 1 pnri 11contaari ndnt s , a1 so tended tobe more concentrated in <strong>the</strong> finer sedinrentsadjacent to <strong>the</strong> channel. Overall,petroleum hydrocarbon concentrations ashigh as ti mg L-1, PCB's as hiyh as 8.4ppb, and pesticides (primarily aldrin andBHC corrtyounds) as high as 4.3 ppb occurredin <strong>the</strong> elutriates trorlr channel andadjacent sediments in <strong>the</strong> industrializedreyions <strong>of</strong> <strong>the</strong> estuary.Salinities <strong>of</strong> interstitial water in<strong>the</strong> top 6 cln <strong>of</strong> ttle channel sediment in<strong>the</strong> t'raser Kiver estuary were describedby Chapnlan (1981) as having a definiteyradierit structure, garticularly in tnenresohaline region <strong>of</strong> <strong>the</strong> estuary, and that<strong>the</strong> rllayni tude <strong>of</strong> <strong>the</strong> gradients changedseasonally. Maxi~l~uiri salinity graaationwithin <strong>the</strong> sedinrent 1 ayers was ooservedto coincide with <strong>the</strong> spriny freshet. Thissuygests that sedilrlent chemi stry and infaunacoln~irunity structure rnay 5e inf liiencedby this yradient structure overannual time scales, althouyh this has notbeen investigated.
CHANNEL BOTTOM$ 201CHANNEL SLOPEO SOUTH BUOY WHITCOMB CROSSOVER MOON COW POINT COSMOPOLISJETTY 13 FLATS CHANNEL ISLANOFig. 2.7. Volatile solids (% <strong>of</strong> total dry weight) in sediments atseven channel bottom and slope locations in Grays Harbor.
7 -6 - 8,5 - 1 \4 -I3 - ICHANNEL/O---0SLOPEIBANK\ /1 o---o---od'0 - MID-CHANNEL2 -I , ,_SLOPEiBANKMID-CHANNELz 2-aMIDCHANNELa~ - SLOPEIBANKufK0 0Fig. 2.8. Distribution <strong>of</strong> organic matter (volatileygen demand, and total organic carbon) in sedimentsbottom and slope/bank 1 ocations in Grays Harbor.solids, chemical oxatfourteen channel24
2.6 ITEMILATIUN AND CLASSIFICATION dF cl assi fied dccordi ny to <strong>the</strong>ir dorni nantESTlJARINE CHANNEL HABITATS IN channel nabi tat characteri stics. Tab1 eREGION 2.1 lists <strong>the</strong> estuaries, <strong>the</strong>ir extent,type, morptIology , slope, and substrateA total <strong>of</strong> 116 estuaries in <strong>the</strong> Pa- characteristics for those where suchcific <strong>Northwest</strong> have been identi tied and information is known.
Table 2.1. Locations, characteristics, and classification <strong>of</strong> principal <strong>estuarine</strong> channel habitats in <strong>the</strong> <strong>Pacific</strong>fiorthwest. See text at end <strong>of</strong> table for fur<strong>the</strong>r explanation <strong>of</strong> classification categories. Data sourcesincluded USGS (1978, '1980); Uilliams et al. (1975); Smith et al. (1977); U.S. Army Corps <strong>of</strong> Engineers (1976);Proctor et al. (1980)); and Johnson and Gonor (1982); British Columbia data for 1981 only (Environment Canada1982) .Totalkverage Annuat €GentDrainage Annual Mxinu EstuarineArea Ui srhar Area Estuary Channel Bar@Estuary Wdterfheds (kd)Type1 lbrpholo& slope3 substrate4(Cal rfornia)Eel River Eel River 8,9M 7,322 21,776Salt River - -Humboldt 8ay Elk River -Jaco~eCreek - -62Salmn Creek - -Fresnwater Creek - - -Mad Kiver Ebd River 1,256 1,336 2.290ORLittle River1'2 Kedwood Creek01Klamath RiverSmith HiverLittle KiverRedwood CreekKlamath RiverSmith Hiver(Oregon)Winchuck Hi verChetco BayPistol RiverRoyue RiverElk RiverSixes KiverCojuil le BayCoos BayUmpqua Hi verSiuslaw RiverWi nchuck Hi verChetco KiverPistol RiverRogue RiverElk RiverSixes RiverCoquille RiverCoos Riverlstnmus SlouyhSouth SlouyhUmpqua RiverSiuslaw River
.r .-P: rL LLmL L Y ma, LaJY Y LU a, Y L5 5 a,L >L L w w m u > L L > W a ,m L.-.r >La, LL.?a .rL w aJ . r w > - Y a, ~ a , $ F,:: L w w w a> La, > W L.- a,w .- >u > u a m Y > w .- .-r >L Y .- .r a, Y.7 >Y xZ.~>U U ~ E E > E ~ > > L wXL x c m z w 0 CL .-v, Z" m a, .r U L 0 r v , ,:$ .-Y X m , r w Z Z P I X 4 C L K >CL-CE-4-1 c c N C 3 UO, u E c .-n v, m- m n .r - m m a- m E U m 3~ch.r L W C , @ ' - ~ - + I ~ csc =aU m ~ D -5 - m m ~ , c --m- c 2% - c 3 m 3 m m 3 L - m - L O x s w m w Em U m .rU m a, W.- a .-.-.-.- 01 m a 000 L a, ~ m 0 0 mSc.r 0 a, 0s.r 0 3m m m .- CJO mo.-c - c m ~ m m m v , -SSX.-~GL P:~~Y.-+I=- 4 W > WW wl Z Z L WJ I-XLY L ZZ U3S3-2 P Z m Z a Z 3 Z U W 3 U 3 1 1Lh.F w o n m P: - m'Y h 9 .r .r a , m ~ 10m Y x m Y" 5 m Em n m .,-u m m o E U C , m+.' C N c z u 2 - w . r 0 J, Q* m . r e 0 0 3 L 5 - C mw E x + o m m 5.5 U v , 0-7 - # A * c u - S U 8 -YLa, h '?! kwL L a , ? 'r >> 4 z w L m h 10 h Y 'Cm - m . - a Y o .-< zwl m 2 2 ; Z z z u m 223-
Quinaul t River Qujnaul t River 1,124 2.520 l,4M BB FBB H? M G-S08 F? M GOueets R3ver Queets R~ver 1,153 3.690 3,bW Bl3 F M GKalalocn Creek Kalalocn Creek BB n n ti- SHoh Rtver Hoh River 774 2,240 1.3W BB F M I;-S(ioodtnan Creek Goodman Creek 82Vui llayute R~ver mi 1 layute River 1,629 F M G- SOzette River Ozette Hiver 229 45 BI F M tiMukkaw Bay Waatch River 33 35-a3 Sooes River 105 95Sai 1 Rf ver Sai 1 River 14 - 20HGSekiu RiverHoko KiverClallam BayPysht KiverLyre RiverFresnwater BayNew Uunyeness layUi scovery BayPort Townsend SaySekiu RiverHoko RiverClallam RiverPysht RiverLyre RiverEfwna RiverUunqeness HiverSnow CreekDean CreekCnimacum CreekPort Ludlow Ludlow Creek - FSquami sh Harbor Snine Creek - - FThorndyke Bdy Tnorndyke Creek 31 F
Taraoo Bay Tarboo Creek 32Jackson CoveMarple CreekSpencer CreekQui 1 cene Bay 0i y Qui 1 cene RiverLittle yuilcene Riv.Dosewall ips River Dosewall ips Hi ver -Duckabush River Duckabush River 172G-Sti-sG-SHamma Harnma Ki ver Harnma Ki ver 219Li 11 iwaup Bay Lilliwaup Creek -Annas Bay Skokonlish River 622Big Mission CreekRig Mission CreekLynch Cove Union Hiver 6 1Tahuya RiverTahuya RiverOewatto Bay Dewattor Ki ver 48Anderson Cove Anderson Creek -Stavis BayStavis Creekti-Sti-sti- sSeabeck BaySeabeck CreekLittle Beef Harbor Little Beef CreekBig Beef Harbor Big Beef Creek 36Port GambleAppl etree CoveMiller BayGamble CreekMiller LakeAppl etree CreekGrovers CreekLiberty BayDogfish CreekDyes InletClear CreekStrawberry Creek -Chico CreekSinclair Inlet- Gorst Creek -(continued)
Table 2.1.Concluded.TotalAveraye Annual ExtentDrainage Annual Maximum EstuarineWatershedsArea Dischar e Dischar e Area Estuary Channel Bank(km2) m 3 y ) (m3 e (kin2) Typel ~orpho1oy.y~ Sl ope3 substrate4Olalla BayGig HarborBurley LagoonCase InletHammersley InletOakland BaySkookum InletOyster BayEld InletCapitol LakeHenderson In1 etNi squal ly ReachChambers BayComnencement BayShilshole Baytverett HarborPort SusanSkagit BaySamish BayBe1 linyhd~l~ bayDrayton HarborOlalla CreekCrescent CreekBurl ey CreekRockey CreekCoul ter CreekSherwood CreekMil 1 CreekGo1 dsborough CreekSkookum CreekKennedy CreekDeschutes KiverWoodard CreekNi squal ly RiverMcAllister CreekChambers CreekPuyallup HiverCedar KiverLake WasningtonSammamish LakeSnohomi sh Hi verStillayuamish HiverSkayit KiverSamish KiverNooksack KiverDakota CreekCalifornia Creek
LwL > w L CwL2 0 1 Cw :'a .- C P C . r . Y > Y . -c 2 a m a e m m w . w E - ' ]o o r m m L O *V) E . . - r u u c '2 .- v,.r m U .- w m La m - ' 2 4 , . ,3 c0 m rs L U UW n C,z s s z gI
CHAPTEK 3PR IMAHY PRODUCTION IN ESTUARINE CHANNELS<strong>The</strong> production <strong>of</strong> plant biomass and Stockner (1976) listed five speciesthrough <strong>the</strong> photosyn<strong>the</strong>tic. fixation <strong>of</strong> Ot diatoms - Melosira 111onil ifor~nis, M.mCarbon occurs at several phyloyenetic cf . n ~lnm~l~ides, Navicula cancel lata, - N.levels in <strong>estuarine</strong> channel habitats. grevi I lei, and Pleurosi nia zestuarii - asThis primary production is yenerated by dominant in <strong>the</strong> ----?centra det ta region <strong>of</strong>both algae and true flowering plants or <strong>the</strong> Squarnish Kiver estuary; N. ~revilleianyiosyern~s. Estuarine a1 gae, however, was <strong>the</strong> one species noted to occur partiarea taxonomical ly and ~norpholoyically cularly in 1 ittoral flat (tidal) channeldiverse yroup <strong>of</strong> flora, includiny epiphy- habitats from January to May.tic single-cel led nli~rophytobenthos andpelayic phytoplankton (i l , diatoms, 3.2 MACKOAL(;AEdin<strong>of</strong>lagel lates), epi benthic filamentousforms, and sessile ~~racroalgae (i.e., sea- As with tne rnicrophytobenthos, sesweeds,kelps). Estuarine anyiosperms are si le macroalyae does not characteristicusuallylimited to seayrasses, principal- ally occur in <strong>estuarine</strong> <strong>channels</strong> due toly Zostera spp., but can also include 0th- <strong>the</strong> usual water depths and unstable, fineersubmerged dquatic plants such as pond- textured substrates. Similarly, <strong>the</strong> not-Zannichell ia able exceptions would include shal low- lum spp., and --- Elodea spp,Cerabophyl- <strong>channels</strong> with low current velocities,i .e., blind dendritic <strong>channels</strong> on 1 ittora1flats, and channel banks with natural3.1 UENTHIC MICKOFCUKA or artificial cobble to sol id rock substrate.Macroalyae are also found at-Estuarine micr<strong>of</strong>lora (microscopic tached to artificial substrates such asplants) typically includes benthic microalyac such as diatoms (Uaci 1 lariophyceae)pi 1 inys, buoys and bulkheads.which occur on or in <strong>the</strong> upper 1 cm <strong>of</strong> A1 though not as diverse and robustbottom sediinents, a1 thouyh I iving diatoms an assemblage as <strong>the</strong> marine seaweeds andcan be found as deep as 18 cm as a result kelps, <strong>the</strong>re are a number <strong>of</strong> <strong>estuarine</strong><strong>of</strong> die1 vertical nliyration within <strong>the</strong> macroalyae which are widely distributedsediment (McLusky 1981 ).and highly productive within <strong>the</strong> narrowsalinity and substrate conditions <strong>the</strong>yA1 though microphytobenthos <strong>of</strong>ten con- are adapted to. <strong>The</strong>se generally includetribute <strong>the</strong> major portion <strong>of</strong> <strong>the</strong> primary+various blue-green algae and species <strong>of</strong>production in littoral flat habitats <strong>of</strong> Enteromor ha spp, and Fucus sp.; in <strong>the</strong><strong>Pacific</strong> <strong>Northwest</strong> estuaries, <strong>the</strong> unstable Pact rc <strong>Northwest</strong> <strong>the</strong> specific taxa arebenthic environs <strong>of</strong> <strong>estuarine</strong> channel hab- E. clathrata var, crinita, E. intestinalitatswould suyyest that; lnlcr<strong>of</strong>lora assm- -is, E. 1 inea and E. distichus. O t h e r sblayes are relatively 1 imi ted in <strong>the</strong>se d~miiiantr~haline mat- gae includehabitats. Notable exceptions might be in Monostroma arcticum, E.<strong>the</strong> case sf shallow bl ind or subsidiary ma, Ulvaf lexuosa, E. mini<strong>channels</strong>wherein bottom sediments are morestable; unforunately, practically no infannationexists relative to species corn-position or Structure <strong>of</strong> micr<strong>of</strong>lora in es- eroy and Stockner (-indicated that L.tuarint <strong>channels</strong> <strong>of</strong> thi s region. Pomeroy riparium and V. dichotoma are macroalgae-32
epresentative <strong>of</strong> 1 ittoral channel habi- in estuaries, nannopl anktonic diatoms aptatsin <strong>the</strong> Squamisn Kiver estuary.pear to be <strong>the</strong> ~rlost abundant forms duriny<strong>the</strong> summer and fall periods <strong>of</strong> peak phyto-3.3 ANGIOSPERMSplankton production (Stockner and Cliff<strong>The</strong> principal taxon <strong>of</strong> angiosperms or1979).true flowering plants common to <strong>Pacific</strong>Proctor et al. (1980) identified 34<strong>Northwest</strong> estuaries is eel yrass, Lostera taxa <strong>of</strong> diatoms as characteristic <strong>of</strong> estuspp;this includes <strong>the</strong> principal indigen- arine channel habitats; ot <strong>the</strong>se, Chaetooussuecies. -- Z. marina. as we1 1 as a rarer ceros spp., Melosi ra spy., and Skeletonemaspecies, Z. noltii (= Z. arnericana). costatum were considered abundant, andWhile L. natii-rs in only in littoral Achna<strong>the</strong>s spp. and Lauderia spp. werezones l~itchock and Cronuuist 1973). Z. considered common constituents. Karentzmarina ' occurs in sub1 itt'oral zones ad, and McIntire (1977) listed <strong>the</strong> 42 ntostas with <strong>the</strong> benthic alyae, may be found abundant diatorn taxa in Yaquina Bay, <strong>of</strong>in shall ow, non-mai nstem <strong>channels</strong>. Sub- which Cvlindroutvrxis so.. Chaetocerosstrate structure, in addition to tidal subti 1 is; ~elos'ir"a sulcat'a,. Thalassiosiraelevation and current or wave action, ap- decipiens, - C. socialis, - C. debilis, Amphipearsto be a principal determinant <strong>of</strong> prora paludosa, and Surinel la ovata corneelyrass distribution and abundance. Al- pri sed more than five percent <strong>of</strong> <strong>the</strong> totalthouyh eelyrass can be found growing in cell count. Anderson (1972) described disubstratesranyiny trom s<strong>of</strong>t mud to grav- atoms <strong>of</strong> <strong>the</strong> inshore reyion <strong>of</strong> <strong>the</strong> Columelmixed with coarse sand, its optimum bia Kiver plume as originating in partsubstrate composition appears to be muddy from <strong>the</strong> estuary. This assemblaye wasor silty sand with median yrain diameters dominated by Asterionel la formosa, Melo<strong>of</strong>-250 pm (2 4 ) and sortiny below 500 pm sira islandica, and Thalassionerna nitz-(1.0 4) (Phillips 1974). Eelgrass beds schioides durinu <strong>the</strong> winter and bv a richin Grays Harbor persist in habitats where flora <strong>of</strong> predo~n~nantl~ Asterionel la japonfinesand (62-500 m) predominates (J.L. - ica, Chaetoceros comyressus, C. radicans,Smi th et a1 . 1976) . Eel grass occurrence Rhizosolenia alata, R. alata-graci 11 ima,in Coos Bay was related to <strong>the</strong> organic - K. delicatul'a, and: frmssima durinycontent and turnover rate <strong>of</strong> sediments <strong>the</strong> summer. <strong>The</strong> diatom assemblaye in <strong>the</strong>(Oregon State University 1977). A Columbia Kiver estuary in April and Maydetailed syn<strong>the</strong>sis <strong>of</strong> information on eel- 1980 was found to be dominated by a relasrass"ecosvstem" anpears in Proctor et tively few freshwater species, includinyal. (1980; Skction 3.211.3, Vol. 2).primari ly Asterionel la formosa, Melosirai slandica, M. distans, Stephanodiscus3.4 PHYTOPLANKTONhantzschii, iid S. astraca var. minutulaIOreuon State ~nfiersity School oi' Ocean-Although perhaps not developed to<strong>the</strong> extent that phytoplankton populations?n rnore stable, less turbid marine (e.g.,oceanic) or <strong>estuarine</strong> (e.g., fjord) habitatsare, phytoplankton <strong>of</strong> <strong>estuarine</strong> <strong>channels</strong>undoubtedly constitute <strong>the</strong> principalsource ot autotrophi c production in <strong>the</strong>sehabitats. Three functional size groupscan be said to typi ty phytoplankton: 1)ultraplankton, (2 pm, consisting <strong>of</strong> principally bacteria; 2) nannopl ankton, 2-20unl, consisting <strong>of</strong> sinall diatoms and micr<strong>of</strong>1 ayel lates; and 3) microplankton, 20-2UUput, consisting <strong>of</strong> larye diatoms and din<strong>of</strong>1 aye1 1 ates. A1 thouyh din<strong>of</strong> lagel latesare occasional ly abundant (McMurray 1977)ograihy 1980b). <strong>The</strong> <strong>of</strong> uniquelymarine, <strong>estuarine</strong>, or riverine phytoplanktonor a combination <strong>of</strong> <strong>the</strong>se assemblageswithin one channel location in an estuarywi ll depend upon circulation transport andnlixiny <strong>of</strong> water masses, which are highlyvariable over short-term (tidal) andlong-term (seasonal) time scales (seeSection 2.3).Dominant phytoplankton taxa durinyspring blooms in Burrard Inlet (SeymourRiver estuary with some influence fromFraser Ri ver) i ncl uded Skel etonema costa-- tum, Certaul ina beryonii , and Thalassiosiraspp. in <strong>the</strong> outer inlet; - S, costaturn-7
ana Coscinodiscus spp. in <strong>the</strong> inner inlet;and S. costatum and Thalassiosira spp. in~ndiiin and Port Moody Arms (Stockner andC l i f f 1979). Dominants during fall bloomswere somewhat different: C. beryonii in<strong>the</strong> outer inlet; S. costatiim, Thalassio-thrix sp,. and c.-beryonii in <strong>the</strong> inner-inlet; and C. costatum, nitzshcia spp.and Exuviell? sp. in Indian and PortMoody Arms.3.5 ESTIMATES OF STANDING CROP ANDPR IMAKY PRODUCTION RATESTwo aspects are generally consideredin evaluating autotroyhic production: 1)<strong>the</strong> distribution <strong>of</strong> <strong>the</strong> producer biomass(standing crop) and, 2) <strong>the</strong> rate <strong>of</strong> photosyn<strong>the</strong>sis.Measurements <strong>of</strong> physical andchemical parameters influencing <strong>the</strong>se twoOariables are a1 so documented simul taneouslyin order to determine <strong>the</strong> environmentalfactors control l iny <strong>the</strong> fixation<strong>of</strong> plant carbon. Micr<strong>of</strong>lora and phytoplankton standing stock are typical 1yassessed by: 1) chlorophyll a concentrationi., y cm-3 or my-m-3); 2)particulate carbon and nitro en (C/N); or3) gravimetric i.. , my L-7 or my m-3)analyses, Macroalyae and anyiospermstanding stock is commonly ex ressed inyravimetric terms (i.e., y m- B ). Rates<strong>of</strong> primary production <strong>of</strong> micr<strong>of</strong>lora andphytoplankton are yenerally estimatedthrough ei<strong>the</strong>r 1) measurin labeled carbonuptake ( e . mg C - hr-1) duringincubation at representative 1 ight 1 eve1 sor, 2) measuring oxygen evolution or uptakeover an incubation period, whichyields both production (i.e., mg C m-3hr-1, mg C nl-2 hr-1) and respiration rateinformation.A1 though estimates <strong>of</strong> mean primaryproduction <strong>of</strong> micro hytobenthos as hi yhas 108 mg C IR-2 hr- Y have been documentedfor a 1 ittoral flat habitat in <strong>the</strong> ColumbiaHiver estuary (Mclntire and Amspoker1981), most gross l~rimary production rateestimates in lower 1 ittoral habitats <strong>of</strong>that estuary and in Grays Harbor (Thom,unpublished) average 0.5 my C m-2 hr-1.Given <strong>the</strong> increased water depths, lowertemperatures and unstable benthic conditions<strong>of</strong> <strong>estuarine</strong> channel substrates, itis likely that production rates in <strong>the</strong>senabi tats are significantly lower and morevariable than are those <strong>of</strong> littoral flats.Pomeroy and Stockner (1976) described production<strong>of</strong> channel -type diatom asse~nbl ayeson <strong>the</strong> Squamish River estuary as ranyinbetween approximately 0.5 and 1.0 g C m- !day-1, although tnese were not obtainedfrom cnannel habitats per se.--Gross primary production <strong>of</strong> <strong>estuarine</strong>macroal gae on I ittoral flats in GraysHarbor was found to ran e between approximately1.5-2.5 g C m-2 hr-1 for Enteromorphaclathrata var. cri ni ta (A-,1.0-1.5 g h r - 1for E.intestinalis(Auyust), 0-0.3 y C m-2 hr'=l for E. linza(June) and 0.5-1.0 y C m-2 hr-l for Fucusdi stichus (June, August) (Thom, unpub-Pomeroy and Stockner (1976) indicatedthat strongly euryhal ine macroalgaeassemblages were generally less productive(mean production <strong>of</strong> 0.6 g C m-2day-1) than weakly euryhal ine assemblages(2.2 y C m-2 day-1) on <strong>the</strong> Squamish Kiverestuary delta. <strong>The</strong>se production valuesare pr0baDly also representative <strong>of</strong> <strong>estuarine</strong>channel macroalgae which are distributedin high sublittoral elevations.Production <strong>of</strong> epiphytic macroal gae on Zos-- tera blades has not been estimated butepiphytes on Thalassia have been estirnatedto equal 20% <strong>of</strong> <strong>the</strong> estimated averagenet production <strong>of</strong> that seagrass inFlorida (Jones 1968).Rates <strong>of</strong> primary production by eelgrassvary considerably over <strong>the</strong> temperatedistribution (circumpolar) <strong>of</strong> Losteramarina, in part a function <strong>of</strong> <strong>the</strong> widerange in turion densities within eelyrassbeds (Proctor et al. 1980) and in standingstock, which varies between 6 and 5157 g(dry) m-2 (McKoy and McMillan 1977).Production estimates within <strong>the</strong> <strong>Pacific</strong><strong>Northwest</strong> region exist only for PuyetSound and range between 0.16 and 1.9 y Cm-2 hr-1 (Phi 11 ips 1969, 1972).Phytoplankton biomass and productionhas been systematically measured in <strong>estuarine</strong>channel habitats <strong>of</strong> only YaquinaBay (McMurray 1977; Johnson 1981), <strong>the</strong>Columbia River (Haertel et al. 1969;Oregon State Uni v. School <strong>of</strong> Oceanography
138Ub), and <strong>the</strong> Eraser Kiver estuaries(Takatlastli et a]. 1973; Stockner and Cliff1979). McMurrdy (1977) found standinystock duriny <strong>the</strong> spring phytoplanktonblooril in Yaquina Bay to range betweer171.1 and 1.1 x 108 y ~ n and - ~ productionto range between 4.7 and 172 my C m-3nr-1 over <strong>the</strong> same period. Johnson's(1981) studies <strong>of</strong> upper Yaquina Bay betweenJuly and November 1973 and 1974 documentedan average phytop I ankton standinystock <strong>of</strong> 5-6 my m-3, while ri~aximum production<strong>of</strong> 78 to 104 ing c ma3 hr-1 occurredin July and Auyust. Chlorophyll a measureinents<strong>of</strong> phytoplankton biomass-i n <strong>the</strong>Col urrlbia River estuary between April andNovember 1980 varied between approximately1 and 18 my m-3, with <strong>the</strong> hiyhest valuesoccurriny froin May throuyh July (OreyonState Univ., School <strong>of</strong> 0cea.nography1 J80b). Higher biomass concentrationstended to occur in <strong>the</strong> upper, riverineregion <strong>of</strong> <strong>the</strong> estuary and lower values in<strong>the</strong> downstream, marine region. Spatialvariation indicated rriore hornoyeneityabove <strong>the</strong> estuary's lr~ixiny zone regionand extreme variation in or near subsidiary<strong>channels</strong> (i.e., Younys and Lewis andClark Rivers). Primary production measuredas carbon uptake peaked at between25 and 35 mg U in-3 hr-1 duriny July.A1 thouyh sirni 1 arly high production wouldhave also beer7 expected in May because <strong>of</strong><strong>the</strong> hiyh chlorophyll a values at thattime, <strong>the</strong> eruption <strong>of</strong> Rt. St. Helens and<strong>the</strong> resulting increased inorganic suspendedsediment raised <strong>the</strong> level <strong>of</strong> liyht extinction<strong>of</strong> pnytosyn<strong>the</strong>sis (see Section3.6). Phytoplankton cells less than 101!1i1, which predominate near <strong>the</strong> mouth <strong>of</strong><strong>the</strong> estuary, and greater than 33 prrl,which predominate in <strong>the</strong> upper estuary,accounted for most <strong>of</strong> <strong>the</strong> production.Stockner and Cliff (1979) indicatedthat chl orophyl 1 a yeneral ly decreasedfrom a maximum <strong>of</strong>-approximately 800 mym-2 in <strong>the</strong> poorly flushed, upper reach(Port Moody Arm) <strong>of</strong> <strong>the</strong> estuary to lessthan 150 my in-2 in <strong>the</strong> more seawardstations in outer Burrard Inlet. <strong>The</strong>fjord-type <strong>estuarine</strong> habitats <strong>of</strong> innerBurrard Inlet and Indian and Port MoodyArms showed peak primary product ion rates<strong>of</strong> between 4 and 6.6 y C m-2 day-1 durinyspring and autumn bloOinS, 1-2 y C lr2day-1 in <strong>the</strong> sulllmertially neyliribleinterim, and essenproductionDetweenNovember and Mdrch (Stockner and Cliff1979).A number <strong>of</strong> abiotic and biotic fdctorscontrol or inf 1 uence <strong>the</strong> [~roduction,distribution, and abundance <strong>of</strong> autotrophically-produced carDon, and <strong>the</strong> fate <strong>of</strong>tne different siicro- and macrophytic producers.1 hese re1 at i onships are conceptuallyillustrated in Fiy. 3.1. A11 producersutilize l iyht and nutrients as <strong>the</strong>basic ingredients in assembliny oryanicn~olecules, initial ly carbohydrates (glucose)which are transferred and transformedinto amino acids, protein, ando<strong>the</strong>r complex nlo1 ecul es essential fororydni sins' survival , growth, and reproduction.As <strong>the</strong> universal element involvedin <strong>the</strong>se biological reactions, carbonis yeneral ly regarded as <strong>the</strong> most appropriatecociunodity to map energy flowthrouyh <strong>the</strong> ecosystem.In addition to tne photosyn<strong>the</strong>ticinyredients <strong>of</strong> 1 iyht and nutrients, o<strong>the</strong>rphysical parameters such as temperatureand salinity control <strong>the</strong> yross rate <strong>of</strong>bi oloyical reactions. U<strong>the</strong>r envi ronmentalvariables such as vertical mixinythrough <strong>the</strong> water co'lumn, liyht attenuation,substrate structure and stabi 1 ity,and shading regulate <strong>the</strong> magnitude andextent ot solar radiation available toproducers and thus ul tirnately affect bothbiomass and <strong>the</strong> rate <strong>of</strong> production by<strong>the</strong>se oryanisms. Toye<strong>the</strong>r, <strong>the</strong>se variablesare considered driving variables(inyredients or conditions 1 imi ting photosyn<strong>the</strong>sis)and control liny factors (affecting<strong>the</strong> distribution <strong>of</strong> producers,prirnari ly through physical or rnetaboi iceffects).RIntire and hspoker (1981) indicatedthat structural properties (meanyrain size, skewness, sortiny coefticient)<strong>of</strong> mudflat Sediments in <strong>the</strong> Columbia Kiver estuary were highly correlated
Fig. 3.1. Primary production compartments and driving variables and 1 imiting factorsinfluencing distribution, standing crop, and rate <strong>of</strong> production in <strong>estuarine</strong> channelhabitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.with <strong>the</strong> biological variables <strong>of</strong> microafgalbiomass and production. <strong>The</strong> lack <strong>of</strong>any significant correlations with 1 iyhtintensity and temperature suggests that<strong>the</strong> microphytobenthos is hiyhly adaptedto achieve <strong>the</strong>ir maximum photosyn<strong>the</strong>ticrate at relatively low light intensitiesand temperatures. Thus, substrate characteristicsmay be <strong>the</strong> more critical factorinfluenciny standing crop and grossproduction, by regulating <strong>the</strong> ability <strong>of</strong>microalgae to colonize and persist inhabitat. Welch et al. (1972) found <strong>the</strong>chlorophyll 5 concentrations <strong>of</strong> periphytonon submerged artifici a1 substrates in<strong>the</strong> Duwami sh Ri ver estuary di rectly corre-1 ated with light intensity, includingthat caused by increased water turbidityresulting from a rainy period. Temperaturewas relatively not as important afactor. <strong>The</strong> spatial distribution <strong>of</strong>periphyton, however, in <strong>the</strong> UuwamishRiver estuary appeared to be regulated bysalinity structure.Phytoplankton biomass distributionand production are even more affected byhydro1 oyical conditions within <strong>estuarine</strong>channel habitats due to <strong>the</strong> influences <strong>of</strong>
vertical mixing <strong>of</strong> <strong>the</strong> water column. ~ 1 -though inorganic nutrients, particularlynitrogen, were found to be potentiallylimiting in late spring and Summer in <strong>the</strong>Columbia River estuary, 1 ight attenuationin <strong>the</strong> water column was Considerd to be<strong>of</strong> primary importance in controlliny <strong>the</strong>amount <strong>of</strong> photosyn<strong>the</strong>sis per unit phytoplanktonbiomass throuyhout <strong>the</strong> year(Oregon State University School <strong>of</strong> Ocean-ography 1980b) - A simulation model <strong>of</strong>phytoplankton photos~n<strong>the</strong>sis and growth in<strong>the</strong> outer reaches <strong>of</strong> <strong>the</strong> Fraser River estuaryindicated that nitrate levels were1 imiting duri ng <strong>the</strong> summer, that temperaturewas limiting production near <strong>the</strong> surfaceduring <strong>the</strong> winter and spring, andthat light was <strong>the</strong> Principal limiting factorat <strong>the</strong> surface <strong>the</strong> rest <strong>of</strong> <strong>the</strong> year,and at depth throughout <strong>the</strong> year.
UETKITUS PKUCESSING IN ES'TUAKINE CHANNELSIn addition to <strong>the</strong> various primaryproducers characterizing <strong>estuarine</strong> channelhabitats, described in Chdpter 3, <strong>the</strong> role<strong>of</strong> oryanic detritus as potential sources<strong>of</strong> trophic carbon transported into andmade avai 1 able within <strong>the</strong> channel habitatmust be considered. Recent evidence tlasi 1 lustrated that, directly throuyh detritivoryor indirectly through heterocrophicprocesses, detritus may constitute <strong>the</strong>dominant pathway <strong>of</strong> trophic carbon into<strong>estuarine</strong> food webs (Darnel1 1961; Odum1970; Qasim and Sankaranarayanan 1972;Shubnikov 1977; Correll 1978). Detritusmay also have a valuable role in stabiliziny<strong>estuarine</strong> systems by leveling outtne seasonal variations in primary production(McLusky 1981).Darnel l (1967) has aefined oryanicdetritus as "all types <strong>of</strong> bioyenic materialin various stages <strong>of</strong> microbial decornposition which represent potential eneryysources tor consumer species." Uetritusincludes both particulate and "subparticulate"matter. 8y <strong>the</strong> reference tomicrobial decomposition and utilizationby consumers, this definition appears tobe 1 i~nited to what is commonly referredto as fine particulate oryanic carbon(FPOC). Since much <strong>of</strong> this material hasoriyinated trom much laryer organic particleswhich were inechanically or biochemicallyreduced to FPUC, this definitionshould be expanded to include any free(non-attached) particles <strong>of</strong> organic matterwhich no longer, if ever, produce carbonthrouyn photosyn<strong>the</strong>sis. Included in thisexpanded definition, <strong>the</strong>refore, are biogenicparticles <strong>of</strong> both plant and animalorigin as we1 1 as free-formed (throughchemical or geological processes) partic1es, and includiny associated sorbed dissolvedsubstances an5 <strong>the</strong> residing microbes(Christian and Wetzel 1978).4.1 DETRITUS SOURCESUnfortunately, <strong>the</strong>re is scant i nformationto indicate <strong>the</strong> sources <strong>of</strong> detritusthat are produced within or transportedinto <strong>estuarine</strong> channel habitats <strong>of</strong> <strong>the</strong>region. Thus, only speculative inferencescan be made <strong>of</strong> <strong>the</strong> relative contribution<strong>of</strong> potential detritus sources.Detritus which is usable by <strong>estuarine</strong> channel detritivores, considered tobe primarily FPOC, is derived from threeorigins: 1) that entering <strong>the</strong> estuary alreadyin FPUC form, previously colonizedor immediately colonized by microbes oncein <strong>the</strong> estuary; 2) that enteriny <strong>the</strong> estuaryas laryer particles (LPOC) and,through mechanical and microbial action,beiny reduced to FPOC within <strong>the</strong> estuary;and 3) that formed by <strong>the</strong> creation <strong>of</strong> organicparticles (Darnell's [I9671 subparticulatedetritus) throuyh <strong>the</strong> process <strong>of</strong>flocculation <strong>of</strong> dissolved oryanic carbonwhich has been ei<strong>the</strong>r transported into orgenerated within <strong>the</strong> estuary (Fig. 4.1).Both particulate and dissolved carbon canenter via riverine or marine inflows orcan be derived froin autochthonous productionwithin <strong>the</strong> channel or in associated<strong>estuarine</strong> habitats.Organic particles deposited into riverscan include tree leaves and needlesfroin forested watersheds as well as treebrancnes and whole tree trunks. Detritalparticles indigenous to <strong>the</strong> river includephytopl ankton, o<strong>the</strong>r (periphyton) a1 yalcell s , zooplankton exuvi ae and feces, andfish and o<strong>the</strong>r freshwater animal feces.Marine detritus includes detached macroalgae,phytoplankton cell s, zooplankton exuviaeand feces, and fish and o<strong>the</strong>r animalfeces. In addition to similar macrophyteand animal sources, detritus particles
RlVERlNE SOURCESMARINE SOURCESFig. 4.1. Potential sources and pathways contributing to detritus in <strong>estuarine</strong> channelhabitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.produced uniquely within <strong>the</strong> estuaryinclude abscised eel grass blades and rhi -zomes and <strong>estuarine</strong> marsh plants. Inaddition to <strong>the</strong> influx <strong>of</strong> sinking phytoplanktoncells, mats <strong>of</strong> benthic micr<strong>of</strong>loraestablished on littora flats arefloated <strong>of</strong>f <strong>the</strong> flats and into channelhabitats during hiyh tide cycles (C. O.McIntire and M. C. Anispoker, Oreyon StateUniv., unpubl. information).Dissolved oryanic carbon (DOC) in riversis considered to be primari ly al lochthonous,derived from <strong>the</strong> leachiny <strong>of</strong> terrestrial1 itter, 1 iving vegetation, andsoils (Fisher and Likens 1973; McDowelland Fisher 1976; Mu1 hol land 1981) ; however,<strong>the</strong> contribution <strong>of</strong> autochthonousfreshwater sources such as leachates fromaquatic macrophytes and phytoplankton andexcreta from aquatic animals has not Deenfully evaluated. Marine DUC, on <strong>the</strong>o<strong>the</strong>r hand, is essentially autochthonous,ori yinating from leaching by zooplanktonand from animal excreta; some leachatesfrom nearshore marine a1 yae and a1 yal detritusmay also constitute an unknown portion<strong>of</strong> marine DOC. <strong>The</strong> generation <strong>of</strong> DUCwithin <strong>the</strong> estuary, however, may surpassthat <strong>of</strong> both riverine and marine sourcesdue to accelerated leaching <strong>of</strong> extracellularDOC from <strong>the</strong> extensive 1 ittoral algaeand saltmarsh rnacropnyte assemblayescommon to <strong>Pacific</strong> <strong>Northwest</strong> estuaries.Leaching or excretion <strong>of</strong> DOC has alsoheen tound to be appreciable in phytoplanktonand periphyton (Anitd et al.1963; Hellebust 1965, 1374; Fogg 1366,1977) and in marine and <strong>estuarine</strong> macrophytes(Cragie and McLachlan 1964;Sieburtn and Jensen 1969; Sieburth 1969;Vel imi rov 1980). Mann (1972) suyyestedthat over 90% <strong>of</strong> <strong>the</strong> production <strong>of</strong> marinemacroyhytes enters <strong>the</strong> <strong>coast</strong>al marinefood web as dissolved organic matter.
Sieburth (1969) calculated that 30% <strong>of</strong><strong>the</strong> totdl carbon or 401 ot <strong>the</strong> net carbonfixed daily by <strong>the</strong> littoral fucoid, Fucusvesiculosus, is exuded as DOC. Muc3i-Xthis exuded DOC is apparently comprised<strong>of</strong> dissolved carbohydrates, which Burneyand Sieburth (1977) estimated to accountfor 10 to 20% <strong>of</strong> <strong>the</strong> total DOC in NarrayansettBay, Rhode Is1 and.Formation <strong>of</strong> FPOC from UUC through<strong>the</strong> formation <strong>of</strong> molecule masses calledaggregates has been postulated as a majorsource <strong>of</strong> detritus in estuaries. Increasedparticle sedimentation resultsfrorn formation <strong>of</strong> larger, denser agyregates.Ayyreyates from suspensions <strong>of</strong>clay and phytopl ankton particles form in<strong>the</strong> presence <strong>of</strong> electrolytes such as wouldbe encountered in <strong>estuarine</strong> mixing zones(Anvimelech et al. 1982). Although <strong>the</strong>exact mecnani s~n <strong>of</strong> aggregate formationfrom DOC is not well defined, <strong>the</strong> action<strong>of</strong> bubbles risiny to <strong>the</strong> water surfaceand bubble forrndtion at <strong>the</strong> air-sea interfacewhere oryanics tend to De highly concentrated(Harvey 1966; Goering and Wallen1967 ; W i l l ia~ns 1967 ; Ni shi zawa 1971) appearto be important processes in creating<strong>the</strong> surface required for d particle nucleus(Ka~nsey 1962; ilaylor and Sutcl iffe1963; Ki ley 1963, 1970; Sutclitte et al.1963; Kiley et al. 1964, 1965; Krone1978; Wallace dnd Duce 1978). i3arber(1966) concl Uded that microoryani sms wererequired in aygregate tormation but <strong>the</strong>current evidence suyyests that bacteria,oryanic, or inorganic particles can allact as <strong>the</strong> nuclei for initiatingayyreyation,Tne formation <strong>of</strong> detrital ayyregatesis accelerated in <strong>estuarine</strong> channel nabitatsas a result <strong>of</strong> several physical andctlemical processes that occur with <strong>the</strong>mixing <strong>of</strong> saline and fresh water. <strong>The</strong>seprocesses in consort account for "saltf 1 occul ati on," wherein even extremely 1 owsalinities promote <strong>the</strong> precipitation,f 1 occu t ation, and agyreyat ion <strong>of</strong> di ssol vedoryanics into organic detritus particlesprone to higher settling rates (Siebruthand Jensen 1968; Gardner and Menzel 1974;Sholkowi tz 1976). While it is apparentthat both chemical (i.e., ionic attrac-tion) and physical (i.e., increased particle~0lli~i0nS alony salinity yradients)mechani srns are interrel ated in fl occul a-tion (Krone 1978), no definitive work hasbeen performed to isolate and define <strong>the</strong>functional processes <strong>of</strong> FPOC for~nationf ro~n DOC.Avnimel ech et a1 .Is (1982) experimentson <strong>the</strong> flocculation and sedimentation<strong>of</strong> algae-clay ayyregates in <strong>the</strong>presence <strong>of</strong> an electrolyte suyyested thatincreased clay concentration would prornoteincreased flocculation and sedirnentai ton<strong>of</strong> a1 yae if <strong>the</strong> availabi 1 ity <strong>of</strong> aygreyatenuclei is a 1 imiting factor. This impliesthat flocculation <strong>of</strong> a1 yal detritus in<strong>Pacific</strong> <strong>Northwest</strong> estuaries would be enhancedgreatly duriny spriny freshets whensuspended sediment 1 oads entering <strong>the</strong>estuaries are at a rnaxin~urn.<strong>The</strong>refore, sources <strong>of</strong> oryanic detri -tus to <strong>estuarine</strong> <strong>channels</strong>, whe<strong>the</strong>r dissolvedor particulate, depend upon associatedterrestrial, marine, and <strong>estuarine</strong>habitats, and within <strong>the</strong> channel are <strong>the</strong>product <strong>of</strong> d number <strong>of</strong> complex and interrelated<strong>estuarine</strong> circulation and chelnicalprocesses which have not yet been successfullysorted out. Nairnan and Sibert( 1978) presented a seasonal ly-st ructuredernpi rical budget <strong>of</strong> organic carbon andnutrient inputs trom <strong>the</strong> Nanaimo Kiver to<strong>the</strong> estuary and concl uded that, comparedto in situ primary production in <strong>the</strong> rnudflatlhabitats,fluvial DOC (estimated tobe 2 x lo3 g C m-2 yr-l) imported into <strong>the</strong>estuary via <strong>the</strong> river may be <strong>the</strong> yreatestsource <strong>of</strong> carbon to that system. Hiverineinput <strong>of</strong> allochthonous FPOC was estimatedto equal 56 y C m-2 yr-1 and to be atleast half derived from <strong>the</strong> river's periphytoncommunity. Uahm et al. (1981) estimatedthat in 1974 <strong>the</strong> Columbia Riverexported approximately 5YU.4 x 1U3 metrictons <strong>of</strong> total organic carbon (TOC) <strong>of</strong>which 891 was DUC and 11% was POC; overhalf <strong>of</strong> <strong>the</strong> annual TUC entered <strong>the</strong> estuarybetween April and July, 16% <strong>of</strong> it in June.While <strong>the</strong> TOC and DOC levels were mosthiyhly correlated with river di scharye,POC was correlated with primary productivity upriver.
In addition to C:N ratios (Mann1972), liynin degradation products(Gardner and Plenzel 1974; Hedyes and Mann1979; MacCubbin and Hodson 1980), andvarious chelnical isotope characteristicsused to t ingerprint sources <strong>of</strong> detritalmatter (Peters et al. 1978; Sweeney andKaplan 1980; Estep and Dabrowski 1980),<strong>the</strong> ratio <strong>of</strong> two stable carbon isotopes,c13/~12 (abbreviated as 613~), has recentlybeen utilized to identify <strong>the</strong> yossibleorigins <strong>of</strong> oryanic carbon present in consumeroryanisrns. This is possible oecause<strong>the</strong> 1 3 values ~ <strong>of</strong> an animal 's tissues areusually unaltered trom those <strong>of</strong> <strong>the</strong> Carbonin its food source (DeNiro and Epstein1978; Teeri and Schoel let- 1979). This approachhas been used, apparently successfully , in documenting <strong>the</strong> importance <strong>of</strong>vdrious carbon sources to <strong>estuarine</strong> andmarine detritivores (Thayer et al. 1978;Hai nes dnd Montayue 1979; McConnauyheyand McKoy 1979; Frj 1981). Using liyninoxidation products in conjunction wi th613~, Hedges and Mann (1979) indicatedthat <strong>the</strong> POC from <strong>the</strong> Columbia River depositedin <strong>of</strong>fshore sediments was dominatedby yymnosperm woods and non-woodyangiosperm tissues.Usiny 14c-label ling techniques,Sibert et al. (1977b) amassed evidencethat <strong>the</strong> production <strong>of</strong> detri t ivorous harpacticoidcopepods in <strong>the</strong> Nanaimo Riverestuary (see Section 5.3) was supportedpredomi naniy by <strong>the</strong> bacteri a1 f 1 ora associatedwith oryanic detritus which waspresumed to originate from several exogenousand endogenous sources, including:(1) meadows form <strong>the</strong> seaward areas (2)alyae from intertidal areas; (3) sdltinarshplants from landward areas; and (4) downstreamtransport from <strong>the</strong> upland areas <strong>of</strong><strong>the</strong> estuary's watershed. In <strong>the</strong>ir v?cent613c studies <strong>of</strong> detritus-based food websin Hood Canal, Wissmar and Si~nenstad(Fish. Kes. Inst., univ. Wash., unpubl.data) have found <strong>the</strong> detritus Sources tovary seasonal 11, with shi ftiny contributions<strong>of</strong> riverine, marine and endemic<strong>estuarine</strong>-produced carbon. At <strong>the</strong> Sametime, a considerable recycling <strong>of</strong> autoch-thonous carbon within <strong>the</strong> estuary was aprominent characteristic <strong>of</strong> <strong>the</strong> detritivorecomponent <strong>of</strong> <strong>the</strong> <strong>estuarine</strong> foodweb.41Very little inforrrlation exists on<strong>the</strong> deposition, distribution and flux <strong>of</strong>detritus in <strong>estuarine</strong> <strong>channels</strong>, and ~irtuallynone exists for <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.Pickral and Odum (1976) found that<strong>the</strong> non-uniform distribution <strong>of</strong> detritusin a Viryinia saltrnarsh tidal creek relatedto <strong>the</strong> morpholoyy and hydrdul ic regime<strong>of</strong> <strong>the</strong> creek. <strong>The</strong>y deduced that detritusparticles, hydrodynalllical ly equivalent totine sand and silt particles, tended toaccumulate in low velocity zones insidemeanders and behind si 11 s ; storlri events,however, were responsible for periodical -ly flushing detritus accumulations frorn<strong>the</strong> tidal creek.<strong>The</strong> flux ot detrital particles within<strong>channels</strong> probably occurs in conjunctionwith <strong>the</strong> sediment bedload and 1s lnfluencedoy similar tactors (hection 2.5.1).Accordinyly, variations in boundary layervelocities determine <strong>the</strong> size distribution,flux, and accumulatior~ <strong>of</strong> detritusparticles through <strong>channels</strong>, Uepositiondlreyions, where current vel ocities arelowest, would be expected regions <strong>of</strong>detritus accumul ation. Thi s is observedin blind or subsidiary <strong>channels</strong> with lowervel oci ty reyiines which tend to accumuldtemore detritus tnan do mainsten1<strong>channels</strong>.But, as with suspended inoryanicparticles, <strong>the</strong> inainstern <strong>channels</strong> in !nixinyor entrapment zones <strong>of</strong> estudries alsoprobably constitute locations <strong>of</strong> maximumsettl ing <strong>of</strong> organic partic 1 es and inoryanic-oryanicparticle agyregates. A1 though<strong>the</strong> lony-term net transport is probablyseawdrd, detritus particles may rernai nwithin this zone for periods lony enouynto be extensively uti 1 i zed by detritivores.Naiman and Sibert (1978) pointedout <strong>the</strong> importance <strong>of</strong> "retention structures"as traps <strong>of</strong> oryanic detritus, andidentified oyster beds, macroalyae, andspaces around coobles as FPOC retentionstructures and logs and eelyrass as LPOCretention structures. To this list snoul aalso be added <strong>the</strong> eineryent plant assemblayes<strong>of</strong> <strong>estuarine</strong> salt marshes. <strong>The</strong>yconc I uded that fjord and drowned river
valley estuaries, with 1 ittle oceanic ly 10-11% as only iparticulate carbon wasexchange, l arye areas, and nunlerous types utilized.<strong>of</strong> retention structures may be <strong>the</strong> mostefficient retainers <strong>of</strong> a1 ~ O C ~ ~ ~ O ~ O U S We generally know very 1 ittle aboutdetritus.<strong>the</strong> microbi a1 assemblages characteri zi ny<strong>Pacific</strong> <strong>Northwest</strong> <strong>estuarine</strong> <strong>channels</strong>, al-4.3 FUNGI AND UACTEKIA COLUNIZATIONthough Wiebe and Liston (1972) included<strong>estuarine</strong> channel sampl es in <strong>the</strong>i r analyses<strong>of</strong> aerobic, nonexactiny , heterotrophicbenthic bacteria <strong>of</strong> <strong>the</strong> Wasninbton andOreyon qoasts. <strong>The</strong> highest individualcounts (x = 55,925.9 + 23.7 viable counts~icrooryanisms, primari ly bacteria,fun5i, and protozoa, rapidly co1 onizefresh detritus particles and are laryelyresponsible for conditioning detritus to<strong>the</strong> stage where it is pnysically and nutritionally viable for consumption bydetriti vores and o<strong>the</strong>r primary consumers(Fenchel and Jdrgensen 1977). Harrisonand Harrison (1380) indicated that inmi crocosrn experiments, fresh Losteramarina blades supported a two-week bloomdfspended bacteria. <strong>The</strong>y also foundthat fresh detritus had 100 x 103 bacteriacel 1s mm-2 wnile ayed detritus nadonly 20-40 x 103 cells mm-2. Colonizationby microalyae (pennate diatoms, tldyel1 ated prasi nophytes, and f i 1 amentousblue-greens), however, tended to be inverselyre1 ated to bacteria density wheninorganic nutrients were limiting, suygestinythat ei<strong>the</strong>r tne two yroups werecompeting tor <strong>the</strong> available nutrients orthat one or <strong>the</strong> o<strong>the</strong>r was producing inhibitory substances (Del ucca and McCracken1977).Stuart et al. (1981) conductedcontrol led experiments <strong>of</strong> heterotrophicutil ization <strong>of</strong> particulate (43-63 vm)kelp debris and found that ~t~dximuli~ bacteriabiomass (%4 my 1-1) occurred withinten days; <strong>the</strong>reafter, phayotrophic fl ayel-1 ates , ci 1 i ates, amoebae, and choan<strong>of</strong> 1 agellates successively domindted <strong>the</strong> microbialco~ru~lunity. During <strong>the</strong> initial twodays <strong>of</strong> <strong>the</strong> experiment diSS01 ved organicst'ronl <strong>the</strong> particles were used by free-livinybacteria. Over <strong>the</strong> next four days<strong>the</strong>re was rapid growth <strong>of</strong> <strong>the</strong> bacteriapopulation attacned to <strong>the</strong> particles,with substrate carbon converted to Dacterialbiomass at a conversion efficiencyot about 33%. <strong>The</strong> following four days,unti 1 yrazi ng flagellates appeared, werecharacterized by a rapid decl ine in tnerate <strong>of</strong> bacterial yrowth, with a drop in<strong>the</strong> conversion efticiency <strong>of</strong> approximate-bacteria ml-I <strong>of</strong> mud-water slurry) weredocumented from <strong>the</strong> sandy sediments atHarrington Point in <strong>the</strong> Columbia Kiverestuary but were much more variable thanthose in sediments beyond <strong>the</strong> influenceot <strong>the</strong> Columbia Kiver. Uudl itatively,three groups <strong>of</strong> Pseudomonas strains, a1 1nonpi ymented carbohydrate uti l i zers(Shewan 1963), comprised 85% <strong>of</strong> <strong>the</strong> bacteriaisolates identified in <strong>the</strong> estuary;<strong>the</strong> only si yni ficant non-Pseudomonasstrain found was Achromobacter, a nonpiyn~ented,nonnlotile-rod forrn. Cellulosedigestinybacteria were re1 atively uniqueto <strong>estuarine</strong> and continental shelfsediments.4.4 PHYSICAL, CHEMICAL, AND BIOLOGICALCONDITIUNINGUndoubtedly one <strong>of</strong> <strong>the</strong> most criticalrate-control 1 iny processes in <strong>the</strong> detrituspathway <strong>of</strong> an <strong>estuarine</strong> food web is <strong>the</strong>conversion <strong>of</strong> detritus to particles <strong>of</strong>physical dilnensi ons and nutritional characterwhich can be utilized by detritivores.Tnl s process, termed "conditioning"<strong>of</strong> <strong>the</strong> detritus, involves physical,chemical, and biological mechanisn~s (Fi y.4.2). Physical and chemical decay are dueprimarily to <strong>the</strong> wea<strong>the</strong>riny <strong>of</strong> <strong>the</strong> largercomponent <strong>of</strong> LPN particles through leachingand autolysis <strong>of</strong> soluble or volatilematerial. Physical conditioning a1 soincl udes <strong>the</strong> mechanical breakdown <strong>of</strong> cellwalls by wind, wave, and current action,which increases <strong>the</strong> rate <strong>of</strong> chemical decay.This is particularly evident inexposed, coarse substrate (e. y., cobble)1 i ttoral habitats, where continued sedimentmovement acts to break loose macrophytematerial into proyressively finerparticles (Fig. 4.3).
Fig. 4.2. Conceptual illustration <strong>of</strong> <strong>the</strong> mechanisnls and flows involved in <strong>the</strong> physical,chemical, and biological conditioning <strong>of</strong> detritus.Fig. 4.3. Terrestrial (wood chips, tree bark, and leaves) detritus <strong>of</strong> varying particlesizes deposited on 1 ittoral flats <strong>of</strong> Duckabush River estuary, Hood Canal, Washington;once degraded into finer particulate matter by physical Processes, <strong>the</strong> fine particulatedetritus is transported into blind Or subsidiary <strong>channels</strong> where fur<strong>the</strong>r biological andchemical degradation and, ultimately, util i ration take PI ace (photo by author).43
Li tterbay experiments, wherein fresh( l i ve) macropnytes are pl aced in mesh baysand secured in littoral or marsh habitatsfor temporal monitoring <strong>of</strong> decomposition,have <strong>of</strong>ten been used to docunient <strong>the</strong>breakdown <strong>of</strong> large detritus. Kistritzand Yesaki (1979) fol lowed <strong>the</strong> disappearance<strong>of</strong> tne sedge, Carex lynybyei, in <strong>the</strong>Fraser Kiver estuary. <strong>The</strong>y found that 40%<strong>of</strong> <strong>the</strong> asn-free dry weight remained afterapproximately nine months (September-June)and that decay was most precipitous duringFebruary due to increased physicaldeterioration and tidal removal. ScienceApvl ications , Inc. and Woodward-ClydeConsultants (1981) conducted 1 itterbayexperi~nents using seven emergent plantsuecies (Carex lvnubvei . potenti1 la uacif-- i ;a, ~ ~ r i s t i s balticus,' - Sci r-pus validus, cespi tosa, Tri<strong>of</strong><strong>the</strong>m a Kiver estuary. <strong>The</strong>y found varyiny rates <strong>of</strong> decomposition with pl dnt species,locations in <strong>the</strong> estuary, and tidalelevations, with rates varyiny from 6% to51% over five rnonths. Rates were typicallyhigher in <strong>the</strong> riverine portion <strong>of</strong> <strong>the</strong>estuary and succulent marsh plants yenera1ly decomposed lrlore rapidly than didyrasses.As much as 89% <strong>of</strong> <strong>the</strong> biomass <strong>of</strong>particulate kelp detritus incubated inStuart et al.'s (1981) experiments waslost in 30 days and <strong>the</strong> maximum lossoccurred in <strong>the</strong> initial 14-18 days. Thisexperiment was conducted in <strong>the</strong> absence<strong>of</strong> any herbivorous oryani sms, which by<strong>the</strong>ir own fragmentation and ingestion <strong>of</strong>detri tal particles accelerate <strong>the</strong> decornpositionby increasing <strong>the</strong> surface areaavai lable for microbial colonization.Herbivores also increase <strong>the</strong> nutritionalquality <strong>of</strong> <strong>the</strong> detritus pool throuyh <strong>the</strong>addition <strong>of</strong> nitroyen in <strong>the</strong>ir feces particles(Fig. 4.2).Most consumers require food sourceswith an average ratio <strong>of</strong> carbon to nitrogen
~nicrobes, and <strong>the</strong>ir consul~lers in estuaries lnaynitude and pdthways <strong>of</strong> nutrient andare more co~nplex than realized initially carbon recycliny within <strong>the</strong> deco~nposer-(Christian and Wetzel 1978). AS such, detritivore phase <strong>of</strong> <strong>the</strong> <strong>estuarine</strong> food<strong>the</strong> relative importacce <strong>of</strong> energy and web must be tur<strong>the</strong>r defined for differentnutrient requirements <strong>of</strong> i~iicr~bes dnd detritus sources as well as within <strong>the</strong>consumers, <strong>the</strong> heteroyeneity <strong>of</strong> rljicrobe vdrious estudrine lldbitdts such dScolonization in time and space, and <strong>the</strong> <strong>channels</strong>.
INVEKTEBKATE ASStMBLAtiES UF t-:STUUgINE CHANNELSlnverteorate animals chardcteri stic<strong>of</strong> <strong>estuarine</strong> channel habitats are typical -1s' cateyorized by size. mi crohabitat, and1 i te hi story characteristics. Sl ze categoriesinc lude:1. Mei<strong>of</strong>auna; animals 1UU to SUU p ni, includingprimari ly foramini teraris,nematodes, kinorhynchs, ostracods,harpacticoid copepods, turbellarians,01 i yocndetes, halacarids, gastrotichs,and cephalocarideans ; and2. Macro- or meyafauna; animals largerthan 500 1~ in, including primarly polychaetes,cal anoid and cyclopoid copepods,leptost racans, mysi ds, cumaceans,tarlaids, isopods, amphipods,euphausiids, decapods, gastropods,pelecypods, and echinoderms (Mare1942; Carriker 1967).Microhabitat categories include:1. Benthic infauna; animals inhabiting<strong>the</strong> sediment, ei<strong>the</strong>r beneath or in<strong>the</strong> surface <strong>of</strong> <strong>the</strong> bottom substrate;2. Sessile epifauna; animals relativelypermanently attached to <strong>the</strong> substrate;3. Motile epifauna; animals which activelymove about on <strong>the</strong> bottom;4. Epi benthic zooplankton; semiplanktonicanimals inhabiting <strong>the</strong> interfacebetween <strong>the</strong> substrate and water column,ei<strong>the</strong>r passively or actively movingbetween <strong>the</strong> very surface layer <strong>of</strong><strong>the</strong> substrate and <strong>the</strong> boundary layer<strong>of</strong> <strong>the</strong> water column; because <strong>of</strong> <strong>the</strong>emergence <strong>of</strong> many motile infaunal organismsfrom <strong>the</strong> benthos, <strong>the</strong>re <strong>of</strong>tenis overlap between <strong>the</strong> benthic infaunaand epibenthic zooplankton assemblages;5. Pelagic zooplankton; planktonic ani -mals inhabiting <strong>the</strong> water column;and,6. Neuston; animals driftiny upon or immediatelyassociated with <strong>the</strong> surfacelayer <strong>of</strong> <strong>the</strong> water column.Life history categories refer primarilyto planktonic animals and include:1. Meroplankton; ternporari ly planktonicanimals, usual ly eggs and larvae <strong>of</strong>benthic and nektonic adults; and,2. Holoplankton; permanently planktonicanimals which live in <strong>the</strong> water columnthroughout <strong>the</strong>ir complete 1 i fe cycle(Sverdrup et a1 . 1942).While <strong>the</strong> following description <strong>of</strong><strong>estuarine</strong> channel invertebrate assembl ag -es is organized along microhabitat categories,<strong>the</strong>se o<strong>the</strong>r descriptors wi 11 fur<strong>the</strong>rcategorize invertebrate fauna within<strong>the</strong>ir microhabi tats. Inclusion <strong>of</strong> characteristicorganisms in unique mi crohabi tatcategories, fur<strong>the</strong>rmore, is <strong>of</strong>ten compl i -cated by <strong>the</strong> behavior <strong>of</strong> animals and <strong>of</strong><strong>the</strong> scientific apparatuses used to sample<strong>the</strong>m. <strong>The</strong>refore, <strong>the</strong> foll owi ng descriptions<strong>of</strong> invertebrate assemblages are- functional, in that animals are includedaccording to <strong>the</strong>ir occurrence in <strong>the</strong> reportedcollections, even though <strong>the</strong>i rmicrohabi tat distribution may be poorlyrepresented and considerable overlap isevident.5.1 BENTHIC INFHUNA AND SESSILE EPIFAUNADue to <strong>the</strong>ir permanency within orupon <strong>estuarine</strong> channel substrates, benthicinfauna and sessile epifauna are <strong>the</strong> assemblagesmost structured by variations
and yradients in physical and chetliicalcharacteristics <strong>of</strong> <strong>the</strong> benthic envi ro~s<strong>of</strong> <strong>the</strong> estuary. But, on <strong>the</strong> o<strong>the</strong>r hand,<strong>the</strong>y exhibit <strong>the</strong> most stable structuresover time due to <strong>the</strong> assembla$e's adaptationto hiyhly variable conditions.<strong>The</strong> two factors most <strong>of</strong>ten cited asstructuriny <strong>the</strong> distribution <strong>of</strong> <strong>estuarine</strong>benthic infauna are salinity and sedimentstructure (Wieser 1959; tiunter 1961,Carri ker 1967 ; Gray 1974), especial lygi ven <strong>the</strong>i r typical lonyi tudi nal yradi entstructure through most estuaries. Associatedphysical and chemical factors suchas sediment stabi 1 i ty and organic contentconstitute re1 ated influences whi ch cannotnecessari ly be separated from sedimentgrain size and texture (Sanders 1959). <strong>The</strong>sarne holds for biological factors such ascompetition, predation, and life historycycles (Peterson 1979). But in general,and especially in <strong>the</strong> nlore dynamic channelhabitats, <strong>estuarine</strong> hydrology is <strong>the</strong>underlyi ng, composite factor deter~itini ny<strong>the</strong> distribution <strong>of</strong> benthic infaunathrough <strong>the</strong> structuring <strong>of</strong> salinity,sediment, velocity , and oryani c matter.<strong>The</strong> role <strong>of</strong> salinity in mainstem sa~npl i ng in closely adjacent sampl iny<strong>channels</strong> has not <strong>of</strong>ten been correlated to sites suggest that nemerteans, nematodes,<strong>the</strong> distribution <strong>of</strong> benthic infauna in oliuochaetes. uolvchaete annelids (Macle-<strong>Pacific</strong> <strong>Northwest</strong> estuaries. Marriaye Ion; spp., ~a~iteila capitata, ~drao3"Ta.(1954) and Burt and McAl ister (1958) i l-platysvanchl a, ---. Eteone spp., - Nephthys cal i-lustrated that <strong>the</strong> gaper clam, 1 f - e ~ ~ forniensis. ~Hauloscolo~~os SDU.. Sviocapax, and s<strong>of</strong>tshell clam, Mya arenarig, 7-7nE; ---- -- ~enidae -m, ydt;lmarid-2~zwere distributed in sal i ni ty?nes great- phi pods (Phoxoceptial idae spp., includinger than 25°/00 between 20°/00 and OOI'~O, - Araphoxus -- -- --- . rrii -- 11 eri , and - P. stenodes,respectively.Eohaustories estuarius, E. washingtonianuC-Sj;Ebmd i urn s hoenla ker i ~ - > i i T f j ~ i eBenthic infaunal assemblages <strong>of</strong> <strong>the</strong> rnol I ;cs-b x t n m r e <strong>the</strong> dotni nan tColumbia River estuary have been sampledextensively (Columbia River Estuary DataDevelopment Program [CUEDDP] 1980), particularlyin reference to <strong>the</strong> effects <strong>of</strong>dredging and dredge-materi a1 disposalwithin and immediately adjacent to <strong>the</strong>estuary (Sanborn 1975; ~igley et al.1976; Ourkin et a]. 1979; Higley andHal ton 1978; Bl ahm 1979). It wasnot until <strong>the</strong> initiation <strong>of</strong> <strong>the</strong> CKEODPstudies that detailed synoptic and ecol0yical investiyations <strong>of</strong> benthic infaunalassemblages were conducted throughout<strong>the</strong> estuary (Oregon State UniversitySchool <strong>of</strong> Oceanography 1930a). At <strong>the</strong>initiation ot <strong>the</strong> CKEDUP studies, a compositespecies checklist <strong>of</strong> <strong>the</strong> estuary'sinfauna included 212 taxa; 23-f whict)were polychaete annelids; 14"/,amnlaridatllphipods; 9% bivalve molluscs; and 8%eacti, gastropod rriol luscs and isopods(VTN, unpublished, cited in Oreyon StateUniversity School <strong>of</strong> Ocednography 1980a).Unfortunately, only a few <strong>of</strong> <strong>the</strong>CKEDllP benthic i nfauna sa~npl iny stationsare located in channel habitats and infor-Illation from <strong>the</strong>se stations is as yet incomplete.However, <strong>the</strong> combined studies<strong>of</strong> <strong>the</strong> Columbia Kiver estuary, culminatingwl th <strong>the</strong> on-going CHE[)DP research, sti 11present <strong>the</strong> niost comprehensi ve i 11 ustrationot bentnic infauna in <strong>estuarine</strong> channelhabitats <strong>of</strong> <strong>the</strong> region (Fox 1981).H diverse, low standing stock, intaunalassenibl aye typifies tne region atand immediately within <strong>the</strong> mouth <strong>of</strong> <strong>the</strong>Columbia Kiver estuary in a benthic environ~~lent characterized by l arye-yrained,unstable sand substrate <strong>of</strong> low organlccontent and high salinities. While notrue channel habitats have been sampled,intauna w~Tiii?i-TnK'I~- total derlsity <strong>of</strong><strong>the</strong> assemblage ranges between 200 to 1000individuals m-2 (Hiyley and Holton 1978;Oregon State University Scf~ool <strong>of</strong> Oceanoyraphy1980a; K. Holton and D. Hiyley,Oregon State Ilniversi ty , unpuol ishedCgEUDP data).Uentnic infauna in <strong>the</strong> central reyionand principal mlxing zone <strong>of</strong> <strong>the</strong>Columbia Hi ver estuary i 1 lustrate extre~~~espatial and tetr~poral variability, evenwl thin distlnyuishable habitats such as<strong>the</strong> <strong>channels</strong>. As described in Chapter 2,
salinities are highly variable (5"/,,-25O/,,) and <strong>the</strong> sediment (medi um sand)prone to resuspensi on and di f ferenti a1 ,active transport. Gammarid amphi pods(Corophium salmoni s , Eoyammarus confer-vi cot us, E. estuarius) , 01 i yochaetes,m e t e -annelids yci nde armi gera,Magel ona sacculata, Polydora s;. , Paraone1- 1 a pl atybranchi a, Hobsonia florida,~eant nessp.),andcuma~~emil~nm o m i n a t e <strong>the</strong> infaunal assemblagewithin or closely adjacent to <strong>channels</strong>,and <strong>the</strong> total assemblage can sustain hiyhdensities (20,000-70,000 m-2; Higley etal. 1976; K. Holton and U. Hiyley, UregonState Univ., unpublished CREDDP data).<strong>The</strong> benthic infauna assemblage <strong>of</strong><strong>the</strong> subsidiary channel enteriny <strong>the</strong> mixing zone region from <strong>the</strong> Lewis and Clarkand <strong>the</strong> Youngs Rivers through Youngs Baybest illustrates <strong>the</strong> synergistic influence<strong>of</strong> <strong>the</strong> fine sediments (fine sand tocoarse silt) and high sediment organics,despite relatively high current velocityregimes (Uoley et a1. 1975). Tube-buildinygamrnarid amphi pods (C. salmonis),polychaete annelids (ti. florida, Nean<strong>the</strong>slimnicola), bivalve m s l u m balthica,Carbicula manilensis), olig<strong>of</strong>iaetes, and--chi ronimid 1 arvae dominated <strong>the</strong> finer sub-strates. 01 i gochaetes dominated numeri -cal ly over Corophium in <strong>the</strong> very fine,hi yhly-organ? c sediments and o<strong>the</strong>r amphipods(E. estuari s, Ani sogammarus marussp. , xraphoxus sp. ) replaced Corophiumin <strong>the</strong> coarser, less organic sedimentscloser to <strong>the</strong> mainstem channel in <strong>the</strong> centralportion <strong>of</strong> <strong>the</strong> estuary (Higley andHolton 1975). Total densities <strong>of</strong> benthicinfauna in <strong>the</strong> inner-bay <strong>channels</strong> exceeded30,000 m-2 but were only 323 m-2 intne outer-bay portion <strong>of</strong> <strong>the</strong> channel (Higleyand Holton 1975). Specifically, C.salmonis occurred in densities between--19,000 and 29,000 nr2- 01 i gochaetes, indensities between 5,006 and 33,000 m-2-and polychaetes, between 600 and 2,200 m-2in <strong>the</strong> fine sediment channel bottomhabitats.Channels in <strong>the</strong> upper <strong>estuarine</strong> andriverine regions <strong>of</strong> <strong>the</strong> estuary includeboth <strong>the</strong> mainstem, navigation channel andsubsidiary <strong>channels</strong> in <strong>the</strong> complex is1 and-tidal marsh habitats where salinities arelow to absent and sediments are typicallycoarse (medi um sand). Gammarid amphi pods(C. salinoni s, Monoculodes spi nipes,PTioxocepnal idae spp:), polychaete annelids(N. limnicola), ol igochaetes, bivalvemolluscs(C.manilensis), and chironomid1 arvae are-representati ve benthic oryanismsin this region. Total densities tendto be low,
Fig. 5.1. Representative illustration <strong>of</strong> common benthic infauna and sessile epifaunaassembl ages <strong>of</strong> <strong>estuarine</strong> channel habitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.frequently dredyed <strong>channels</strong> in <strong>the</strong> up- or 1971). <strong>The</strong> polychaete annel~d, Q-stream portion <strong>of</strong> <strong>the</strong> estuary. Elsewhere, cinde armiyera, and gaper clam, Tresuschannel habitats have been studied on a capax, were <strong>the</strong> predominant infaunalmore 1 imi ted oasis. Mai nstem <strong>channels</strong> in macroinvertebrates in <strong>the</strong> less-scoured<strong>the</strong> lower, marine-influenced region <strong>of</strong> channel bottom ot <strong>the</strong> South Slough por-Coos Bay, Oregon are characterized by tion ot Coos Bay (Hancock et al. 1977).coarse-yrai ned, ocean-deri ved sand in <strong>the</strong>bottom sediments and steep, mudstone wallsUndoubtedly <strong>the</strong> most complete quanwherea navigation channel was created. titative characterization ot benthic in-<strong>The</strong> unconsolidated bottom sediments are fauna in dendri tic channe Is <strong>of</strong> <strong>estuarine</strong>characterized by <strong>the</strong> polychaete annelidssalt marshes (tidal creeks) in <strong>the</strong> regionOphelia limiena, Nephthys spp., and is that <strong>of</strong> Siletz and Netarts Bays,Typosyll is fasciata, while <strong>the</strong> consolidat- Oregon by Hi gley and Holton (1981). <strong>The</strong>yed mudstone walls harbor burrowing pelecy- found that 01 igochaetes numerical ly domi -pods or piddocks, Pholadidea (Penitella) nated <strong>the</strong> macroinvertebrate assemblage,Penita (Jefferts 1977; Hancock et al. accounting for approximately 50% and 70%197f),' Sessile organisms on <strong>the</strong> channel in mature hiyh marsh and sedye marshwall include <strong>the</strong> mussels Myti lus edulis tidal <strong>channels</strong>, respectively; polychaeteand Modiolus modiolus; encrusting sponges, annelids and amphi pods <strong>of</strong>ten accountedHal iclona spp. ; bryzoans, Bowerbankia for over lo%, and nematodes, dipteransp. ; hydroids, Tubularia marina; and <strong>the</strong> 1 arvae, cumaceans, and harpacticoidanemone, M e t r i d i m ~ . S . ~ . Interi- coyepods were somewhat less abundant.49
Table 5.1. Itemization and characteristics <strong>of</strong> benthic infauna and sessile epifaunacomnon to <strong>estuarine</strong> channel habitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.~ aiiii l ty Sediment Re1 evant Li f
_I_llll__l_______l_____l_l_l____-I_------I-TaxaUIVALVE MOLLUSCS - cont 'd.-- Modiolus modiolusMacanla - - - .... bal . thi ca-- Crobicula manilensisProtothaca -- stanli neaSaxidonlus yi yanteus --- Tresus - capaxPhol adidea peni taZ i r f a eaTjislETi-Tab1 e 5.1 Concl u.fetl.-~ ainlty l Sediment Relevant Li feCtrannel Associ - ASSOC~ - Hi story Char-~abi tats1 ations2 ations3 ------------- acteri sticsME, PM, S ,U t,Ps, 6 K-UM,Sk,PM,SE,PM,SE,PM,SE,DI4 k ,PSH-ETHNAIDSTanais sp.UM-PGAMMAK ID AMPH I PODSAlnphi thoe spp.Corophiurn spp.-- Ani souralrlnlarus su.~o~amiarus confervi col US ---- Eohaustorius estuarius- ~onoculodesspi nipesPhoxocephalidaeParaphoxus spp.S, U K-PS ,UH-PSM-PM,SPM, S M-ESU-MTubedwellersDIPTERAN INSECTSChi ronomidae U R-P Sc Larvae,pupae1~ = mainstem; S = subsidiary; U = blind.2~ = riverine; O = oligohaline; M = mesohaline; P = polyhaline; E =euhaljne.~ S C = silt/clay; S = sand; 6 = yravel; C = cobble; B = boulder; Cn =consolidated.Amony <strong>the</strong> arnphipods, Corophlum spp. SIJ~J.) were corrllnon but not abundant in <strong>the</strong>comprised about YO"/,f <strong>the</strong> total number nlature hlyh marsh channel. <strong>The</strong> small telinboth marshes, with Anisogammarus -linid, --- Macoma -- balthica, was also relat~ve-- confervicolus contributing up to 10% in ly colllmon In <strong>the</strong> seGe channel but not in<strong>the</strong> sedye marsh and taiitrids and Amphi- <strong>the</strong> mature high nlarsh channel. rota1 denthoespp. also occurring in <strong>the</strong> mature sities were also appreciably hiyher7-h~yh marsh. Capitellids accounted for (202,205 W2) in <strong>the</strong> sedye marsh channelmost (59%-75%) <strong>of</strong> <strong>the</strong> numbers <strong>of</strong> poly- than in <strong>the</strong> mature high ~narsh (38,238chaetes in both marsh habitats, hut Hob- Ine2), a density disparity which could besonia florida was also prevalent (>20"/.1 n <strong>the</strong> sedye marsh channel, and ampharetprimarily attrlbuted to a nine-told higherdensity ot polychaetes in <strong>the</strong> sedge marshids, spi robids, and spionids (Streblospio channel. While <strong>the</strong> mei<strong>of</strong>aunal component5 1
<strong>of</strong> <strong>the</strong>se dendritic marsh <strong>channels</strong> has not Uurkin (1Y73), and Kujala (1975) qualitabeenwell documented, it would appear tively described <strong>the</strong> riverine distributionthat in general <strong>the</strong> infaunal invertebrate <strong>of</strong> <strong>the</strong> crayfish Paci fastacus leniusculus,assemblages in <strong>the</strong>se high-elevation chan- <strong>the</strong> oligohal ine-euhal ine distribution <strong>of</strong>nel s are <strong>of</strong> significantly lower diversity immature sand shrimp, Crangon franciscorthan<strong>the</strong>y are in lower-el evation, subsidi- - um f ranciscorum, <strong>the</strong> mesohaline-euhal ineary and mainstem <strong>channels</strong> even though <strong>the</strong> distribution <strong>of</strong> Ounyeness crab, Cancerstanding stock may not be significantly magister, and <strong>the</strong> euhal ine distributiondifferent. o fcauda.t C. franciscorum and C. nigri-Det2i led bio-1 basen ne stud-Altnouyh considerable variability ies by Higley and Holton (1975) and Higley[nay exist between assemblages character- et al. (1979) in <strong>the</strong> Youngs Bay (mesohalizing <strong>coast</strong>al and "inland" estuary com- ine-polyhal i ne) reyion <strong>of</strong> <strong>the</strong> estuary docylexesot Puget Sound and <strong>the</strong> Straits <strong>of</strong> umented <strong>the</strong> seasonal variation in <strong>the</strong>Georgia and Juan de Fuca, comprehensive abundance <strong>of</strong> C. tranciscorum. Mo reintonnation on channel infauna in <strong>the</strong> detailed tempor4 and spatial documentalatterestuaries is generally lacking. tion <strong>of</strong> <strong>the</strong> standing stock <strong>of</strong> C. francis-Benthic organisms dominating sandy sedi- - corum and C. magister has since been~ilents <strong>of</strong> a blind channel in a Scirpus proauted by -<strong>the</strong> CKEDDP studies (tioughtonmarsh in Puget Sound included t h e m et al. 1980; Fox 1981).chaete Manayunkia aestuari na (maximummean density %4 x 10-1igOchaetes( ~ 2 x 105 m-2), <strong>the</strong> gammarid amphi pod Cons01 idated, <strong>the</strong>se studies repre-Corophiuln salmonis ($1 x 1u5 W2), <strong>the</strong> sent a relatively cohesive picture <strong>of</strong> <strong>the</strong>tanaid ~ana-sp.1 x lo5 w2), and <strong>the</strong> cot~lposition <strong>of</strong> <strong>the</strong> motile epifauna in <strong>the</strong>b1vdlveMacorna balthica ( sp. 2 x 103 me2) Columbia Kiver estuary. Althouyh sampl iny(J.E. Srnitll98Ome <strong>the</strong>se densities for P. leniusenlus has been nei<strong>the</strong>r efappearnigher than those reported in <strong>the</strong> fective nor extensive, subsidiary <strong>channels</strong>otner studies, <strong>the</strong> ditteriny sieve mesh in <strong>the</strong> riverine and upper oligohaline resizesutilized in <strong>the</strong>se studies preclude gions <strong>of</strong> <strong>the</strong> estuary appear to harbor modanydirect comparisons.erate densities <strong>of</strong> this crayfish; occurrencesand densities in mai nstern channel s5.2 MOTILE EPIFAUNA and channel slopes is low, however, andsuggests that <strong>the</strong> principal location <strong>of</strong>Motile epifauna, due to <strong>the</strong>ir con- <strong>the</strong>se populations is in <strong>the</strong> littoral orspicuousness or commercial importance, shallow sub1 i ttoral habitats. At <strong>the</strong>tend to be more extensively documented marine end <strong>of</strong> <strong>the</strong> estuary, juvenile Dunthanei<strong>the</strong>r infauna or zooplankton. All geness crab and adult C. niyricauda andare essentially macroinvertebrates which - C. alaskaensi s appear 30 be 1 imi ted tohave <strong>the</strong> ability to control <strong>the</strong>ir move- euhaline water masses in <strong>the</strong> <strong>channels</strong>, almentalong <strong>the</strong> bottom. Some actually en- though Dunyeness crab were reported withter<strong>the</strong> water column during some periods in <strong>the</strong> lower (seaward) polyhaline reyion(e.g., at night) and, as such, constitute duriny summer low-flow periods. Few<strong>the</strong> macroinvertebrate component <strong>of</strong> <strong>the</strong> mature or gravid Dungeness crab are foundestuary's nekton assemblages at <strong>the</strong>se within <strong>the</strong> estuary, suggesting that <strong>the</strong>setimes.moti 1 e macroinvertebrates are moving into<strong>the</strong> estuary from spawning populationsAs in <strong>the</strong> case <strong>of</strong> benthic infauna, located outside tne mouth <strong>of</strong> <strong>the</strong> estuary.information from <strong>the</strong> Columbia River estu- Crangon franciscorum represents <strong>the</strong> trulyary provides one <strong>of</strong> <strong>the</strong> most comprehen- endemic <strong>estuarine</strong> macroinvertebrate, parsivepictures <strong>of</strong> motile epifauna in chan- ticularly during <strong>the</strong> early stanzas <strong>of</strong> itsnel habitats <strong>of</strong> <strong>coast</strong>al estuaries life history. Adult sand shrimp appear(Columbia River Estuary Data Develo~ment to reproduce in <strong>the</strong> euhal ine regionsPrograrll 1980; Houyhton et al, 1980; Fox during winter and depart <strong>the</strong> estuary by1981). Haertel and Osterbery (1967), mid-spri ng. Juveni le sand shrimp remain52
and rear within tne estuary, predominantlyin rnudflat, sandflat and slope habitatsbut also in <strong>channels</strong>. <strong>The</strong> distribution<strong>of</strong> <strong>the</strong>se populations gradually expands up<strong>the</strong> estuary with <strong>the</strong> intrusion <strong>of</strong> niesoandpolyhaline waters duriny low freshwaterflow through <strong>the</strong> summer months.Similar distributions and life historypatterns <strong>of</strong> Crangon have been describedfor o<strong>the</strong>r <strong>coast</strong>al estuaries in Ureyon(Kryyier and Horton 1975).In 1971) tne mean total density andstandiny crop <strong>of</strong> <strong>the</strong> motile epi faunalassemblage in <strong>the</strong> <strong>channels</strong> <strong>of</strong> <strong>the</strong> ColumbiaRiver estuary ranged between 0.03 and0.26 individuals m-2 and 0.03 and 1.21 gm-2, respectively.Earl ier quantitative investi yations<strong>of</strong> Uungeness crab in Humboldt Bay (Gotsnall1978) indicated that densities <strong>of</strong>crab in that large <strong>coast</strong>al estuary aresignificantly higher than in <strong>the</strong> ColumbiaRiver or Grays Harbor, which may be relatedto <strong>the</strong> more euhal ine-polyhal ine conditionsin an estuary with such low riverineoutflow. Demersal trawl catchesindicated maxima as high as 0.5 m-2 inwinter, 73% <strong>of</strong> which were O t year age recruits;<strong>the</strong> annual mean averaye crabdensity from trawl catches was estimatedat 0.09 m-2 (actual density estimates byArmstrong et al. 1982). Underwater SCUBAsurveys, however, indicated that crabswere actually more dense, averaging 0.11m-2, in August and September. Given <strong>the</strong>behavior <strong>of</strong> Dungeness crabs to burrow intosediment (MacKay 1942), seasonal andshort-term variability in density estimatesbased upon net catches may be attributableto <strong>the</strong> various factors influencing <strong>the</strong> proportion <strong>of</strong> <strong>the</strong> popul ationwhich is buried (i.e., mating, spawniny,feeding, exposure during low tides, lowsalinities).Extensive investigations <strong>of</strong> Dungenesscrab and crangonid shrimp in GraysHarbor have been recently compl eted(Armstrong et al. 1982) and provide <strong>the</strong>most detailed information available oncrab and shrimp abundances, movenients,population dynamics and food web relationsnipsin <strong>estuarine</strong> channel habitats.Meyalops larvae <strong>of</strong> Dunyeness crab appearedto have entered Grays Harbor fromoceanic habitats in spring and began tometamorphose and settle in benthic habitatsin <strong>the</strong> outer (euhaline-polyhaline)regions <strong>of</strong> <strong>the</strong> estuary. Juvenile crabs<strong>of</strong> <strong>the</strong> 0+ year age yroup (recruits) wereconcentrated in mudfl at and adjacentchannel habitats. <strong>The</strong> 1+ year age yroupwas more abundant and distributed throughout<strong>the</strong> estuary. <strong>The</strong> 2+ year age groupwere less abundant than <strong>the</strong> 1t year agegroup but more abundant than <strong>the</strong> 0t yearage group and were distributed predominantlyin <strong>the</strong> outer region <strong>of</strong> <strong>the</strong> estuary.<strong>The</strong> 3+ year-old crabs were relativelyrare and occurred only at stations closeto <strong>the</strong> mouth <strong>of</strong> <strong>the</strong> estuary. Mean crabdensity ranged from 0.076 crabs rn-2 to0.012 m-2 and general ly decreased withincreasing distance up (upriver) <strong>the</strong>estuary in response to decreasing bottomsalinity. Densities in <strong>the</strong> outer estuary(0.051 m-2) were significantly yreaterthan densities in <strong>the</strong> upper region <strong>of</strong> <strong>the</strong>estuary (0.030 m-2) and <strong>the</strong> same was truefor <strong>the</strong> period <strong>of</strong> March-Auyust (0.048 m-2)compared to <strong>the</strong> period <strong>of</strong> September-February(0.021 m-2). Considerable movementbetween channel and shal lower habitatsalso occurred as a possible result <strong>of</strong> tidalinundation and dewateriny <strong>of</strong> littoralhabitats and as a result <strong>of</strong> die1 foragingbehavior. <strong>The</strong> consequence <strong>of</strong> <strong>the</strong>se activitypatterns was that <strong>the</strong> crabs were foundrelatively congregated in channel habitatsduriny day1 i yht low tide periods. Fur<strong>the</strong>rconcentration <strong>of</strong> crabs in channel habitatswas also attributed to <strong>the</strong> effects <strong>of</strong> reducedsalinities in <strong>the</strong> shallower habitatsduring periods <strong>of</strong> high riveroutflow.Qua1 i tati ve summaries <strong>of</strong> motile epifaunain o<strong>the</strong>r <strong>coast</strong>al estuaries (Monroeet al. 1974; Percy et al. 1974; Kreag1979a, b, c; Ratti 1979a, b; Roye 1979;Starr 1979a, b) fur<strong>the</strong>r indicate thatDunyeness crab uti 1 i ze <strong>estuarine</strong> <strong>channels</strong>to varyi ny degrees, principally dependingupon <strong>the</strong> volume and spatial extent <strong>of</strong>euhaline and polyhaline water masses in<strong>the</strong> estuary. While most estuaries appearto resemble <strong>the</strong> Columbia River estuary in<strong>the</strong> limited distribution <strong>of</strong> juvenile
crabs and scarsity <strong>of</strong> adult crabs, Coosand Tillamook Bays, with <strong>the</strong>ir greaterproportional extent <strong>of</strong> euhal ine and polyhalineregions appear to maintain adultpopulations in <strong>the</strong> lower reaches and havejuvenile crab populations distributedfur<strong>the</strong>r up <strong>the</strong> estuary than <strong>the</strong> o<strong>the</strong>rs.Simil arly , Dungeness crab populations in<strong>the</strong> "i nl and" estuaries <strong>of</strong> Puget Sound and<strong>the</strong> Straits <strong>of</strong> Georgia and Juan de Fucaare endemic throughout <strong>the</strong> year, although<strong>the</strong> moved lower in <strong>the</strong> estuary's <strong>channels</strong>duriny spring and o<strong>the</strong>r high freshwaterflow periods.Three species <strong>of</strong> crangonid shrimps,Cranqon f ranciscorum franciscorurn. C.nigricauda, and C. stylirostris, * werefound to predominate in Grays Harbor(Armstrong et al. 1982). C. franciscorumwas prevalent throughout -<strong>the</strong> estuary,while C. nigricauda and C, stylirostriswere c-on only in outerreaches <strong>of</strong> <strong>the</strong>estuary; <strong>the</strong> differential distribution <strong>of</strong>- C. nigricauda and C, stylirostris wasattributed to lower filerance to low bottomsalinities and some form <strong>of</strong> competitionwith C. franciscorurn. <strong>The</strong> densitydistribution <strong>of</strong> C. franci scorum showedstrong seasonal pFtterns, with peak densitiesas high as 5 individuals m-2 occurring<strong>the</strong> @per reaches <strong>of</strong> <strong>the</strong> estuaryin spring through summer. Shrimp densitiesin <strong>the</strong> outer reaches <strong>of</strong> <strong>the</strong> estuarywere siyni ticantly lower (0.3-0.9 rn-2)and typically illustrated earlier seasonalmaxima than occurred in <strong>the</strong> upperestuary. Observed die1 fluctuations inshrimp density in a littoral flat habitatin <strong>the</strong> outer estuary was interpreted as anight-time habitation <strong>of</strong> shallow habitatsfor <strong>the</strong> purpose <strong>of</strong> teeding and movementinto channel habitats during day1 i yht inorder to decrease vul nerabi 1 i ty topredation.In one <strong>of</strong> <strong>the</strong> few studies includingmoti 1 e macroinvertebrates in channel habi -tats <strong>of</strong> estuaries inside <strong>the</strong> Strait <strong>of</strong>Juan de Fuca, Northcote et al. (1976)described <strong>the</strong> distribution and standi ngcrop <strong>of</strong> Cran90n franciscorum through 150km <strong>of</strong> t h e m ~ r a s e River r and its estuary.Unlike its occurrence in <strong>the</strong> <strong>coast</strong>alestuaries, however, C. f-ranciscorum wasnot found beyond <strong>the</strong> polyhal ine region <strong>of</strong><strong>the</strong> estuary which is restricted to <strong>the</strong>lower 10 km <strong>of</strong> <strong>the</strong> North and Main ArmsChannel s.A generalized i 1 lustration and characterization<strong>of</strong> moti le epi fauna common to<strong>estuarine</strong> channel habitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong><strong>Northwest</strong> are presented in Fig. 5.2 andTable 5.2.5.3 EP IBENTHIC ZOOPLANKTON<strong>The</strong> least understood component <strong>of</strong><strong>estuarine</strong> communities, particul arly withinchannel habitats, is that <strong>of</strong> <strong>the</strong> epibenthic zoopl ankters which occupy <strong>the</strong>boundary zone between <strong>the</strong> bottom substrateand <strong>the</strong> water column. Increasedappreciation <strong>of</strong> <strong>the</strong>ir role in transferringdetrital carbon to higher trophiclevels (Kaczynski et al. 1973; Chang andParsons 1975; Sibert 1979; Simenstad etal. 1979a). however, has recently sponsoredinvestigations focused upon <strong>the</strong>structure, standing stock, behavior, andfood web relationships <strong>of</strong> <strong>the</strong>se assemblagesor component taxa.Initially, studies <strong>of</strong> epibenthic zooplanktontended to be ei<strong>the</strong>r specifical lyoriented toward prominent macr<strong>of</strong>aunaltaxa such as amphipods and mysids (Chang1975; Davis and Holton 1976; Davis 1978;Levinys 1980a; Pomeroy and Levings 1980)or, if assembl age-oriented, have by vi r-tue <strong>of</strong> <strong>the</strong> collecting apparatuses beenefficient only with macr<strong>of</strong>auna (Haerteland Osterberg 1967). Consequently, documentation<strong>of</strong> epibenthic meiotauna, especially f rorn quantitative or assemblageorientedstudies, has appeared relativelyrecently (Crandell 1967; Higley and Hol ton1975; Kask and Sibert 1976; Sibert et al.1977b; Simenstad et al. 1979a, 1980;Houghton et al. 1980; Sibert 1981). Of<strong>the</strong>se studies, however, only <strong>the</strong> CREDDPstudies in <strong>the</strong> Columbia River estuary(Houghton et al. 1980) have provided aholistic, quantitative description <strong>of</strong> epibenthicmei<strong>of</strong>auna assemblages in <strong>estuarine</strong>channel habitats. A generalized il lustrationand characterization <strong>of</strong> epibenthiczoopl ankton common to <strong>estuarine</strong> habitats
--Pisaster ochraceousFig. 5.2. Representative i 11 ustration <strong>of</strong> comr;ion motile epifauna assemblages <strong>of</strong> <strong>estuarine</strong><strong>channels</strong> <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.<strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> are presented inFig. 5.3 and Table 5.3.In conjunction with pump sampling <strong>of</strong>epi benthic zooplankton at eleven littoraland shallow sublittoral sites in <strong>the</strong>Columbia River estuary, Houyhton et al.(1980) and Simenstad (Fish. Res. Inst.,Univ. Wash., unpubl. data) documented <strong>the</strong>results <strong>of</strong> epibenthic sled sampling infour channel sites distributed within <strong>the</strong>estuary between Apri 1 1980 and February1981. Over that period, epibenthic zooplanktondensity estimates in <strong>the</strong> <strong>channels</strong>averaged 6.7 x 104 organisms m-3 (definedas 0.5 m over <strong>the</strong> bottom) and ranged be-tween 615 m-3 and 6.7 x 105 m-3; standingcrop averayed 1.02 g but ranged ashigh as 11.5 g m-3. Almost two hundredseparate taxonomi c/l i fe hi story stagecateyories were identified from <strong>the</strong> assemblage. <strong>The</strong> cal anoid copepod Eurytemoraaffinis and undifferentiated coyepodnaupl i dominated <strong>the</strong> composition basedon density, comprising 30.5% and 17.8% <strong>of</strong><strong>the</strong> total number <strong>of</strong> organisms, respectively.<strong>The</strong>re is a major question, however,whe<strong>the</strong>r ei<strong>the</strong>r Eurytemora or copepodnaupl ii should be considered as epibenthicorganisms since <strong>the</strong>y may occur closeto <strong>the</strong> bottom merely as a result <strong>of</strong> entrainmentin <strong>the</strong> deeper, more saline watermasses. Of <strong>the</strong> true epibenthic fauna,ectinosomatid harpacticoids (13.7%), and<strong>the</strong> cannel lid harpacticoid Scottol anacanddens i s (9.5%) predominated nmerical~ly. Eurytemora a1 so dominated (31.9%) <strong>the</strong>stand% crop, followed by Crangon franciscorum(18.4%); among <strong>the</strong> true epibenthiczoopl ankton, Neomysis mercedis(6.7%), Scottol ana canadensi s (5.-Corophium sal moni s (4.6%) predominated<strong>the</strong> composi tion gravimetrical ly. Standingstock <strong>of</strong> epibenthic organisms as measured
Table 5.2. Itemization and characteristics <strong>of</strong> motile epifauna common to <strong>estuarine</strong>channel habitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.---Re1 evantLifeSal ini ty Sediment Hi storyChannel Associ- Associ- Character-Taxa ~abitatl ations2 at ions3 istics4ECHI NODEKMSPi saster ochraceousPycnopodia he1 ianthoidesDECAPODSPacifi castacus 1 eni uscul us s,B R SC F-EDCrangon a1 askensi s M P-E s,G 0-MCC . c i scorum- -- M,S,B 0- E S,G 0-MC; onlyjuveni 1 esextend into01 i gohal i neM E S, ti 0-MCM Cn ,B F-EDM,S M-E S,G F-BC ;Appearprincipal 1 yas juveniles- C . y roductus- ---- M,S M-E SC ,S F-BC1~ = mainstem; S = subsidiary; B = blind.2~ = riverine; 0 = oligohaline; M = mesohaline; P = polyhaline; E =euhal ine.3~~ = siltlclay; S = sand; ti = gravel; C = cobble; B = Boulder; Cn =consolidated.40- = obligate; F- = facultative; BC = benthic carnivore; ED = epibenthicdetritivore; MC = mei<strong>of</strong>auna carnivore.by <strong>the</strong> sled in 1980 generally increasedbetween Apri 1 and May, declined in ~une,3increased again in July and August, anddecl ined between October and February1981. Peak mean standing stock typicallyoccurred in <strong>the</strong> <strong>estuarine</strong> mixing (mesohaline)region <strong>of</strong> <strong>the</strong> estuary. This phenomenoncould be attributed to ei<strong>the</strong>r physicalentrainment <strong>of</strong> <strong>the</strong> zooplankters within<strong>the</strong> nu1 1 zone or increased production anddiversity <strong>of</strong> zooplankton assemblages due3~ampl ing immediately fol lowed <strong>the</strong>May 18 eruption <strong>of</strong> Mount St, Helens and<strong>the</strong> resulting influx <strong>of</strong> turbid freshwaterinto <strong>the</strong> estuary.to <strong>the</strong> accumulation <strong>of</strong> detrital food resourcesby settl ing and flocculation (seeSection 4.2). Houghton et a1 . (1980) concludedthat epibenthic zooplankton assemblagesin <strong>the</strong> Columbia River estuary couldbe partitioned into <strong>the</strong> three basic assemblagesdescribed by Haertel and Osterberg(1967): 1) a riverine assemblage whichis primarily a product <strong>of</strong> <strong>the</strong> freshwaterColumbia River ecosystem above <strong>the</strong> estuary,2) a euryhaline, mixing zone assemblage <strong>of</strong> indi genous <strong>estuarine</strong> species,and 3) a marine assemblage, much <strong>of</strong> whichis contributed by <strong>the</strong> tidal intrusion <strong>of</strong>oceanic water through <strong>the</strong> mouth <strong>of</strong> <strong>the</strong>estuary. Some prominent taxa such as <strong>the</strong>5 6
HBIBcflnosoma spp' ' AcanlhMnys~s spp . 'ArChaeOmySlS grebnifakrl'Fig. 5.3. Representative ill ustration <strong>of</strong> common epibenthic zooplankton assemblages <strong>of</strong>-.-L ..-.- :- -L---.-_T L _ L _ . ~ _ ~ - -.E n--:z:- rt,....ch ., +ectinosomatids and Scottolana canadensis,however, are distributed ubiquitouslythroughout <strong>the</strong> estuary, even upstream in<strong>the</strong> riverine region.Crandell (1967) also employed an epibenthicsled (Cl ark-Bumpus) and describedthi rty-two taxa <strong>of</strong> epibenthic harpacticoidand cyclopoid copepods in <strong>the</strong> channelhabitats <strong>of</strong> Yaqui na Bay, Oregon. A1 though<strong>the</strong> sled samples were not considered quantitative, based simply on occurrence, <strong>the</strong>prominent harpacticoid taxa included Tis--.be furcata, Microarthridion 1 i ttorale,x-phiascel la &bil i s, Canuel la (= Scots1 ana : Coul 1 m a n a d e n s i s , parathalestris.- sp. and ~chizopera sp., and <strong>the</strong> cyclopoidcopepod Ascomyzon latum. Crandellconcluded that <strong>the</strong> epibenthic fauna in <strong>the</strong><strong>channels</strong> during <strong>the</strong> winter were derivedprimarily from mudflat assemblages butthat an endemic channel assemblage domi-nated by Tisbe furcata had developed byfa1 1 ; thi s x e - pattern was re1 atedto lower water temperatures in <strong>the</strong>fall and an extended period <strong>of</strong> relativelyhigh bottom sal ini ties which enabled moremarine forms to enter <strong>the</strong> bay via <strong>the</strong>channel s.While <strong>the</strong> structure and standingstock <strong>of</strong> <strong>the</strong> channel assemblages <strong>of</strong> epibenthiczooplankton in <strong>the</strong> Columbia Riverand Yaquina Bay estuaries i 1 lustrated considerabletemporal and spatial variation,no effort was expended to quantitativelyestablish <strong>the</strong> relative role <strong>of</strong> biotic (reproduction,recruitment, growth, selectivepredation) and abiotic (salinity,temperature, current velocities, sedimentsize, structure, and organic content) factorsin accounting for <strong>the</strong> direction ormagnitude <strong>of</strong> <strong>the</strong> variation. Williams(1983) step-wise mu1 tiple regression
Table 5.3. Itemization and characteristics <strong>of</strong> epibenthic zooplankton common to <strong>estuarine</strong>channel habitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.TaxaRe1 evant Li feChannel~abi tats1Salinity Sediment~ssociations ~ssoci at ions3History CharacteristicsROTIFEKABrachionus spp.Asplanchna spp.CRUSTACEACLADOCERADiaphanosoma brachyururn?- spp*id%2$%as!ip.Bosmina sp.Evadne nordmanniPodon spp.Alona spp.Chydorus spp.Leydi gia spp.R-0R-MRR-0R-0P-ER-UR-EH-0ROSTRACOUALimnocy<strong>the</strong>re sp.COPEPODACALANOIDAEurytemora affinisDi aotomus - soo.-rr-Acartia spp.HARPACTICO IDAScottolana canadensi sEctinosornatidaeMi croarthridion 1 ittoraleTachidius spp.Laophont i daeParaleptastacus sp,Nitocra SD.~untemann; a jadensisBryocamptus sp.BUI bam~hizcus sp.Ha 1 ect i nosoma s p.R-ER-E0-EM, S R-EM,SR-EM,SK-EM7SMK-ER-EMEMM-EM 0-EM -EMR-PM,SM-ESYBP-ES 9 BM-BP-E0-ESM-ESM-EMPSM-EM ,SM-E(continued)58SC-GNNSSSC-SSSSSSSSS-GSCSCSC-SSSSS
I___---Table 5.3. Concluded.Relevant LifeTaxaChannel~abitatslSalinity Sediment History Char-~ssociations ~sso~i~tions3 acteristicsCYCLOPOIDACorycaeus spp.Cyclops spp.Oithona spp.Cycl opi na spp.MY S I DACEAAcanthomysis spp.Neomvs i s mercedi s- N. integerArchaeomysis grebnitakiiHolmsiel 1 a anomal aM R-E NM R-E NM M- E NM ,S P-E SCM-SM-SM- SM-SSP-ER -EP-EP-EP-ESC-GSC-GSC-GSC-GS CCUMACEALamprops spp.Leucon sp.Leptostyl is pacificaCumel 1 a vul garisSM-SS5-BP-EEP-ESC-SAMPHIPODACorophium salmonis M- B 0-P SC-SC. spinicorne M- i3 0-P SC-SAnisogammarus sp. M- B 0-P SC-Gconfervicolus M-B 0-E SC-G- M- S 0- E SC-GEohaustorius sp. M-S 0-E SI SOPODAGnorimosphaeroma oreyonensi s M- B 0- E S-BMunna spp. S ESC-S------1~ = mainstem; S = subsidiary; B = blind.2~ = riverine; 0 = oligohaline; M = mesohaline; P = polyhaline; E = euhaline.~ S C = silt/clay; S = sand; G = gravel; C = cobble; B = boulder; Cn = consolidated;N = no definitive sediment as~ociation.analyses <strong>of</strong> <strong>the</strong> 1980 CKEDUP epibenthic organisms data, however, provided a prel imi -nary indication that taxonomic correlationsmay be more important than physicalfactors in explaining <strong>the</strong> variation inorgani sin densities. Neomysis mercedi sdensities were highly correlated withCrangon franci scorum densities; Scotto-W n a d e n s i s with ectinosomatid harpacticoid,Eurytemora affi nis, and CyclopsSpp. densities; and Cyclops SPp. highlysignificantly carrel ated with Crangonf ranci scorum, Neomysis mercedi s, andScottolana canadensis. Physical factors,on <strong>the</strong> o<strong>the</strong>r hand, provided only weak correlations,i .e., Cyclops spp. with tidalelevation and salinity, Scottolana canadensiswith tidal elevation and s u z ewater temperature, and ectinosomatid harpacticoidswith tidal elevation and date.Thus, while physical factors such as salinityapparently influence <strong>the</strong> distribution<strong>of</strong> epibenthic zooplankton taxathrough <strong>the</strong> estuary, <strong>the</strong> standing stock
Structure ot <strong>the</strong> various assemblages rnay velocities indicated that positive thigmobemore <strong>the</strong> result <strong>of</strong> <strong>the</strong> distribution <strong>of</strong> taxis, especially in daytime under no curfoodresources, <strong>the</strong>oretical ly detritus, rent flow, was over1 apped with positiveand carnivores on mei<strong>of</strong>auna. rheotaxis underthat behavioralcurrent conditions suchcompensation for down-Studies <strong>of</strong> epibenthic zooplankton in stream drift could occur up to 5-10 cmestuaries within <strong>the</strong> Straits <strong>of</strong> Juan deFuca and Georgia and Puget Sound have gensec-1velocities. This and data from similarstudies in <strong>the</strong> Squamish estuaryerally focused more upon <strong>the</strong>ir functional (Levings 1973) indicated that epibenthicrole, particularly as prey <strong>of</strong> juvenilesalmonids, than upon community structureamphipods were likely to be washed out <strong>of</strong><strong>the</strong> estuary at higher current velocities.within <strong>the</strong> estuaries. Nortncote et al.(1976) sampled epi benthic macroinvertebrates(>1 mm) in shallow sublittoral,slope, and channel habitats along 150 km<strong>of</strong> <strong>the</strong> Fraser River estuary and lowerLevings (1980b) fur<strong>the</strong>r examined <strong>the</strong>vertical distribution and abundance <strong>of</strong>river. Maximum density ('~100 m-2) and epibenthos in channel habitats <strong>of</strong> <strong>the</strong> lowstandingcrop (s5UO my m-2) occurred in er Fraser River estuary and illustrated<strong>the</strong> North and Main Arms regions <strong>of</strong> <strong>the</strong> that E. confervicolus was more abundantestuary. In most cases, comparisons ot in <strong>the</strong>-bottom drift net and pump samples,density and standing crop in <strong>the</strong> three where densities as high as 65 m-3 weredeptn habitats i 1 lustrated sharp decreas- reached.es with increasiny depth. Average taxadiversity tended to increase upriver andto be lowest at depths over 6 rn. Uominantepi benthic zooplankton taxa includedExtensive sampling <strong>of</strong> mei<strong>of</strong>auna in arnysids (Neomysis mercedi s, Acanthomysi s subsidiary tidal channel <strong>of</strong> <strong>the</strong> Nanaimospp.); dipteran and o<strong>the</strong>r insect larvae; River estuary has been conducted as partand amphipods ( Eogammarus confervicolus, <strong>of</strong> a joint study <strong>of</strong> <strong>the</strong> prey resources <strong>of</strong>Corophium spp.). Euryhal ine species such juvenile salmon in <strong>the</strong> estuary (Kask andas 1. ~nercedis and I. confervicolus ex- Sibert 1976; Sibert et al. 1977a; Siberttended 40 km up <strong>the</strong> estuary while dip- 1979; Sibert 1981). While <strong>the</strong> earliestteran and o<strong>the</strong>r insect larvae decreased study involved benthic core sampling <strong>of</strong>markedly between <strong>the</strong> lower mainstem and <strong>the</strong> mei<strong>of</strong>auna, 1 ater studies specifically<strong>estuarine</strong> stations. Benthic oligochaetes attempted to sample only epibenthic formsand moti le epifauna (Cranyon f ranciscor- more representative <strong>of</strong> <strong>the</strong> prey assemum;see Section 5.2) -so dominant blage available to foraging fish, ei<strong>the</strong>r-components <strong>of</strong> <strong>the</strong>se epi benthic sampl es. utilizing an epibenthic sled (Sibert etal. 1977a) or pump (Sibert 1981). Using<strong>The</strong> distribution, abundance, and a diver-operated sled, Si bert et al.behavior <strong>of</strong> epibenthic isopods (Gnorimo- (1977a) described average epibenthic harsphaeromaoreyonensis) and amphipods pacticoid copepod densities <strong>of</strong> 9,240 m-3w m spini corne, Eoyammarus (Ani so- which, a1 though quite substantial, wereg ~ ~ c o n f e r v i c o l were u s ~ inclutredn sti 11 <strong>of</strong>ten orders <strong>of</strong> mayni tude less than-and Chany's (1977) studies <strong>of</strong> <strong>the</strong> densities measured by comparable coreinfluence <strong>of</strong> current vel oci ties upon <strong>the</strong> sampl es. Structure <strong>of</strong> <strong>the</strong> sl ed-capturedbenthos <strong>of</strong> <strong>the</strong> Fraser Ri ver estuary. <strong>The</strong>y harpacticoid assemblage was numericallydocumented that <strong>the</strong> abundance <strong>of</strong> epiben- dominated by ectinosomids, Tachidius disthiccrustaceans collected in drift bay cipes, Parastenhelia hornel 1 i , and H z -samplers appeared to be affected by cur- emannia jadensis; Harpacticus sp., f-isberent velocities, with maximum abundances sp. and Heterolaophonte 1 i ttoral is alsooccurring in side <strong>channels</strong> with lower cur- occurred frequently in <strong>the</strong> sled samplesrent velocities, Associated laboratory but were not well represented in <strong>the</strong> corestudies <strong>of</strong> <strong>the</strong> activity patterns <strong>of</strong> E. samples, suggesting that <strong>the</strong>se are trueconfervicol us under di fferent currefit epibenthic forms.60
Fur<strong>the</strong>r definition <strong>of</strong> <strong>the</strong> structureand die1 fluctuations <strong>of</strong> epibenthic zooplanktonwas accomplished using an epibentnicpump with intakes located within5 cin and 30 cm <strong>of</strong> <strong>the</strong> sediment surface.<strong>The</strong>se experiments i 11 ustrdted that, despitehomogeneous water characteristics,significantly (2x to 20x) and persistentlyhigher densities occurred 5 cm from<strong>the</strong> bottom than 30 cm above it. Haroacticoid(i.e.., Harpacticus Septentrional is(= H. uni remis), Microarthridion lity-torare, ectinosomi ds , -- Dac ty l opSGcrassipes, Tisbe spp.) , cal anoid (Eurytemorahirundoides) , and cycl opoid cope-W(0ithona sp.) formed <strong>the</strong> major taxai n <strong>the</strong> assembl aqe. Harpactico ids averaaedbetween 32 ani 330 in <strong>the</strong> higierdepth strata and 370 to 2,800 m-3 in <strong>the</strong>lower strata. Thus, <strong>the</strong>se epibenthic or"hyperbenthi c" (Beyer 1958; Hesthagen1973) assemblages could originate fromboth upward rl~ovement <strong>of</strong> surface-dwell i ngbenthic species (Bell and Sherman 1980)and downward movement <strong>of</strong> planktonicspecies. A1 though <strong>the</strong> comparable roles<strong>of</strong> active migration and passive diffusionare unknown, Sibert (1981) suggestedthat hyperbenthic populations originatefrom both sinking plankton and scouredmei<strong>of</strong>auna which are physically entrainedin <strong>the</strong> turbulent boundary layer. It wasalso suggested that such entrainment maybe advantageous to <strong>the</strong> hyperbenthicoryani sms from <strong>the</strong> standpoint <strong>of</strong> hi yherconcentrations <strong>of</strong> food particles trappedwithin <strong>the</strong> turbulent layer. Given <strong>the</strong>physical parameters determining <strong>the</strong> conditionspromoting equi 1 ibri um betweensinking and turbulent mixing (frictionaldrag velocity, particle diffusion coefficient,and current velocity), <strong>the</strong> spatialdimensions <strong>of</strong> hyperbenthi c populationswithin various <strong>estuarine</strong> habitats and <strong>the</strong>temporal pattern <strong>of</strong> turbulent 1 ayer formationand persistence over tidal cyclesare likely to be highly variable. Unfortunately,such detai 1 ed data and analysesare not avai 1 able.While considerable sampling <strong>of</strong> epibenthiczoopl ankton has been conductedwithin <strong>the</strong> Strait <strong>of</strong> Juan de Fuca andPuget Sound (Simenstad et a1. 1979b;Simenstad et al. 198U), very little hasoccurred in <strong>estuarine</strong> ~nannel habitats.Blaylock and tioughton (1981) utilized <strong>the</strong>saw eqibenthic plankton pump used in <strong>the</strong>CREDOP studies on <strong>the</strong> Columbia Riverestuary (tioughton et al. 1980) to sampleepi benthic assemblages in CommencementBay. Although cluster analysis <strong>of</strong> <strong>the</strong>combined 1 i ttoral and sub1 i ttoral , <strong>estuarine</strong>and inarine saniples did not illustratedistinct epibenthic zooplankton assemblagesassociated with <strong>estuarine</strong> <strong>channels</strong>ites, <strong>the</strong> epibenthic assemblages in <strong>the</strong>blind (waterway) <strong>channels</strong> tended to beless diverse than <strong>the</strong> more marine or <strong>the</strong>mid-1 i ttoral si tes, While <strong>the</strong> harpacticoidcopepod assemblages were not describedtaxonoini cal ly by site, qua1 itativeassessment <strong>of</strong> <strong>the</strong> samples has indicatedthat Ti sbe spp. , Typhlamphiascus- ifer, and Hhynchotnalestrisspy were dominant taxa in <strong>the</strong>eplbenthic habitats <strong>of</strong> <strong>the</strong> <strong>channels</strong> (J.Cordel 1, Univ. Washington, personal communication).Corophium spp. was <strong>the</strong> onlyprevalent gammarid amphi pod; Microcalanussp. and Paracalanus sp. were prominentcalanoid c m o r y c a e u s spp. and Cyclopinasp. were <strong>the</strong> most common cycEpoidcopeyods; and Cumella vul aris was<strong>the</strong> dominant curnacean in t e channelassemblages.+-Simenstad and Cordell (1980) alsodescribed <strong>the</strong> composition and density <strong>of</strong>epibenthic organisms co1 lected at <strong>the</strong> end<strong>of</strong> a blind channel (City Waterway) in CommencementBay wi th <strong>the</strong> epi benthi c sled describedby Sibert et al. (1977a). Among<strong>the</strong> true epi benthic zoopl ankters capturedby <strong>the</strong> sled (as <strong>the</strong> sled skimmed <strong>the</strong> surfacesediments, <strong>the</strong> majority <strong>of</strong> <strong>the</strong> organismscaptured were benthic nematodes andpolychaete annelids), a low diversityassemblage <strong>of</strong> haroacticoid copepods wasprominent. ~ulba~~hiascus sp.' and Mesochcra1 i 11 jeborgi constituted <strong>the</strong> s-nant harpacticoid cope~ods and Tisbe sp.was abundant at seve'ral sites. T e r a i ldensity <strong>of</strong> epibenthic organisms within 10cm <strong>of</strong> <strong>the</strong> bottom was estimated to average42,020 m-3 and standiny crop 1.1 g nr3.A1 though <strong>the</strong>se diverse studies <strong>of</strong>epibenthic zoopl ankton were nei<strong>the</strong>r systematicnor Synoptic with regard to estu-
arine habitats, it 5 s evident that muchvariation in structure and standing cropwithin <strong>estuarine</strong> channel habitats exists.In cases such as bl ind, fine sediment<strong>channels</strong> with organic enrichment, <strong>the</strong>reis evidence for dramatically differentassembl ayes from more euryhal i ne, coarsersediment <strong>channels</strong> .5.4 PELAGIC ZOOPLANKTON AND NEUSTONPelagic estuari ne zooplankton andneuston originate from three generalsources (Cronin et a1 , 1962; Haertel andOsterberg 1967) : 1) those associatedwith freshwater water masses, 2) thoseassociated with oceanic water masses, and3) those endemic to <strong>the</strong> estuary and associatedwith euryhal Sne waters, Neustonicorganisms, a1 though constf tutiny lesswe1 1 -established assemblages in estuariesas compared to freshwater or f~ord habitats,where turbulence and mixing are notas extreme, may include both distinctpopulations <strong>of</strong> zoopl ankters as we1 l asterrestrial dri f t organisms transportedinto <strong>the</strong> estuary.Freshwater zoop 1 ank ters transportedinto <strong>the</strong> upper reaches <strong>of</strong> estuaries can<strong>of</strong>ten constitute a significant proportion<strong>of</strong> <strong>the</strong> estuary's zoopl ankton assemblage,especially in <strong>the</strong> 1 arge <strong>coast</strong>al estuarieswhere <strong>the</strong> riverine systems are largeenough to maintain stable zooplankton populationswithin <strong>the</strong> rlver itself. Thisis particularly true for <strong>the</strong> Columbia Riverestuary and Grays Harbor, where highdensities <strong>of</strong> <strong>the</strong> cladocerans Da hniaspp., Bosmina spy. , Ceriodayhnia -Y-s gua-+rangul a,~hanosoma brachyurum, <strong>the</strong>m d copeyod Dia tomus spp., and <strong>the</strong>cyclopoid copepods yc opS spp., especiallyC. vernalis, are commonly found duringsumFer months {tlaerte'l and Osterberg 1967;Simenstad and ~~c.jers 19811. Haertel andOsterberg (1967) recorded <strong>the</strong> highest density( 2,700 rn-3) <strong>of</strong> freshwater zooplankters37 km from <strong>the</strong> mouth <strong>of</strong> <strong>the</strong> ColumbiaRiver estuary duri ny <strong>the</strong> period <strong>of</strong> maximumtemperature and lowest turbidity<strong>The</strong> density <strong>the</strong>re fell to below 100 m-3during <strong>the</strong> winter period <strong>of</strong> low temyeraturesand high turbid3tY. Densities <strong>of</strong>pelagic zooplankton, i ncluding many fresh-water forms, in a riverine channel habitat<strong>of</strong> Grays Harbor reached maxima <strong>of</strong>only 30-60 rn-3 through <strong>the</strong> summer months(Simenstad and Egyers 1981).Oceanic zooplankton inundate estuariesvia <strong>the</strong> tidal intrusion <strong>of</strong> marinewater masses and become most prominentduring periods <strong>of</strong> lowest riverine di s-charge. Along <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> <strong>coast</strong><strong>the</strong> prominent marine zoopl ankters transportedinto <strong>coast</strong>al estuaries include <strong>the</strong>cl adocerans Evadne nordmanni and Podonspp., <strong>the</strong> cal anoid copepods Cal anus spp.,Pseudocal anus mi nutus, Cent ropayesabdominm Epilabidocera amphitrites,and Acartia spp., and <strong>the</strong> cyclopoidcopepodsyeaeus angl i cus and Oi thonasimilis; E ilabidocera is a neustonicform.Conslderab e seasonal variation indominant zoopl ankters transported into<strong>the</strong> estuary occurs as a result <strong>of</strong> changesin nearshore currents and nearshore marinecommunity structure. Miller (1972)and Frolander et al, (1973) illustratedthat nor<strong>the</strong>rn <strong>coast</strong>al or subarctic oceanspecies, such as <strong>the</strong> marine calanoid copepodsAcartia clausi and Pseudocalanussp., dominated <strong>the</strong>oopl ankton assembl aye<strong>of</strong> Yaquina Bay in summer, reflectingsou<strong>the</strong>rly surface currents <strong>of</strong>fshore, whileduring <strong>the</strong> winter neritic species characteristic<strong>of</strong> <strong>the</strong> California <strong>coast</strong>al assemblaqes such as Paracal anus --~arvus . Cteno--- calanus vanus, 'Clausoca ~anus arculcorni s,and <strong>the</strong> cmuoia ., rcoueood Corvcaeus - anul i-4 - -.- cus were transuortid' into <strong>the</strong> bay froinnorthward-f lowi ng nearshore currenis andbecame codominant with A. clausi.--Prevalent marine zoopl ankters inGrays Harbor also varied over <strong>the</strong> sprinyfallperiod as documented by Simenstadand Eggers (1981). ~vadne- nordmanni ,Podon sp., Pseudocalanus spp., Acart ialongiremis and A. tonsa were c o m m o ~duriny summer Throughmid-fa1 1 ; Calanussp. and Metridia lucens occurred yredomi nantly in late winter to early spring;and Centropages abdonlinal is and Acartia--clausi occurred abundantly from springthrouqh early surnmer. Densities <strong>of</strong> <strong>the</strong>marine zooplinkton assemblage in <strong>the</strong> ColumbiaRiver estuary appeared to peak at1.750 m-3 in <strong>the</strong> fall, with average
densities <strong>of</strong> % 500 throughout <strong>the</strong> year(~aertel and Osterberg 1967 ). Densities<strong>of</strong> neritic zooplankton at <strong>the</strong> entrance toGrays Harbor, which was dominated wholelyby marine euhal ine forms, reached an earlymaximum <strong>of</strong> %850 m-3 in April and a second,fa1 1 rnaxima <strong>of</strong> %200 m-3 but averaged~200 m-3 over <strong>the</strong> entire period. Meanstanding crop illustrated yreater fluctuations;estimates in <strong>the</strong> spring tell between200 my m-3 in April and 1 y m-3in early June but reached a maximum <strong>of</strong>only a10 mg m-3 in <strong>the</strong> fall. <strong>The</strong> averagemean standing crop over <strong>the</strong> entire periodwas 55 mg 111-3.Endemic zoopl ankton which sustainpopulations within <strong>Pacific</strong> <strong>Northwest</strong><strong>estuarine</strong> <strong>channels</strong> are dominated by <strong>the</strong>calanoid Eurytemora spp.; E. affini; predomi-. nates in <strong>the</strong> Columbia Hivertuarv(Haertel and Osterberg 1967; English 2al. 1980) while - E. americana appears toprevail in many <strong>of</strong> <strong>the</strong> o<strong>the</strong>r <strong>coast</strong>alestuaries such as Grays Harbor (Simenstadand Egyers 1981), Yaquina Bay (Frolanderet al. 1973), and <strong>the</strong> Salmon Riverestuary (Johnson 1981). Eurytemora tendsto completely dominate <strong>the</strong> zoopranktonassemblages in <strong>the</strong> mesohaline reyions <strong>of</strong><strong>the</strong>se estuaries and can attain high populationstanding stock levels under certainlow riverine discharge salinity regimes.Haertel and Osterberg (1967) reportedtwo peaks in Eurytemora density in<strong>the</strong> Columbia River estuary, one in April(108 x 103 m-3) and ano<strong>the</strong>r in July (39 xlo3 mm3). Eurytemora were most prevalentwhen surface salinities were 0.Z-8°/00,when <strong>the</strong> mean <strong>of</strong> <strong>the</strong> top and bottom salinitieswas 0.2-16°/00, and when <strong>the</strong> bottomnull zone minimized tidal flushing losssalinitywas greater than 0.2°/00. x- es. <strong>The</strong> abundance <strong>of</strong> adults was, howevtemorain Grays Harbor was second (20% <strong>of</strong> er, controlled by intense, size-selectivemean total density) only to Acartia cla~si predation by zooplanktivorous pelagic(22%) and also illustrated two denslty school iny fishes (see Section 9.1).maxima, one in late April (408 m-3) andano<strong>the</strong>r from Auyust to <strong>the</strong> end <strong>of</strong> OctoberIn addition to normal sexual repro-('~80 m-3). In Yaquina Bay, Johnson duction <strong>of</strong> overwintering adults, replen-(1981) documented that, unlike ecartia i shment <strong>of</strong> endemic zoopl ankton populationsclausi which occurs seasonally ln <strong>the</strong> after low abundances during unfavorablewinter and Spring months may also be-reaches, <strong>the</strong> congeneric 6. calif<strong>of</strong>niensiswas able to persist as an endemlcm i o n in <strong>the</strong> upper region <strong>of</strong> thatestuary.Maintenance <strong>of</strong> ende~ni c z00p1 anktonpopulations in Paci t ic <strong>Northwest</strong> <strong>estuarine</strong>cnannels can pose a major problem dueto <strong>the</strong> typically short flushing times,high deyree <strong>of</strong> turbulent mixing, and netseaward flow common at almost all depthsduriny <strong>the</strong> spring and summer. Unlike <strong>the</strong>i ndi yenous <strong>estuarine</strong> zooplankton popul a-tions in o<strong>the</strong>r regions, which haveevolved reproductive rates and verticalmiyration to compensate for <strong>the</strong> seaward1 oss <strong>of</strong> zoopl ankters , E urytemora popul a-tions in pacific <strong>Northwest</strong> <strong>coast</strong>al estuariesappear to be more vulnerable to depletionduriny high di scharge flushing.Possible a1 ternative rnecnani sms, such aslateral migration or entrainment in lowvelocity water masses such as in <strong>the</strong> nullzone or epibenthic boundary layer, mayexpl ain <strong>the</strong> persistence <strong>of</strong> Eurytemorapopul ations in <strong>the</strong>se systems. Never<strong>the</strong>less,extreme riveri ne discharge andflooding have been reported to reduceEurytemora populations in <strong>the</strong> ColumbiaRiver by three orders <strong>of</strong> magnitude(Haertel and Osterberg 1967).A classic study <strong>of</strong> <strong>estuarine</strong> maintenancein a pelagic zooplankton populationis Johnson's (1981) revealing analysis <strong>of</strong>Acartia californiensis in Yaquina Bay.m r s i s t e n t occurrence <strong>of</strong> we1 1-def inedcohorts in <strong>the</strong> upper region <strong>of</strong> <strong>the</strong> estuarywas concluded to result from short lifeexpectancy <strong>of</strong> adult females, with minorreinforcement from spri ny tides. Hssum-ing passive behavior, tidal flushing wasestimated to remove a rnaxirnum <strong>of</strong> 3.4% to8.7% per day, but actual behavioral utilization<strong>of</strong> <strong>the</strong> landward flowing countercurrentand residence in <strong>the</strong> estuary'senhanced by <strong>the</strong> hatching <strong>of</strong> dormant orresting eyys which have overwintered inbottom sediments, as has been documented
for Acartia cal iforniensis in Yaquina t3ay acterization <strong>of</strong> pelagic zooplankton and(Johnson 1981).neuston commorl to <strong>estuarine</strong> habitats <strong>of</strong><strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> are presented inA yeneralized illustration and char- Fig. 5.4 and Table 5.4.CHANNEL SLOPESTONIC (DRIFT) INSECTSONlC CALANOIDWASPSEPU.bMQCara mphitr4ssMARINE COPEPODSP $ ~ ' minutus m .Evadne nordmMnrcolycwus mg*us Cm*, s(M0x)ronn rm*ls . L(,EAMEGALOPSFISH EGGS & LARVAEFig. 5.4. Representative ill ustration <strong>of</strong> common pelagic zooplankton and neuston assemblages<strong>of</strong> <strong>estuarine</strong> <strong>channels</strong> <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.64
Table 5.4. Itemization and characteristics <strong>of</strong> pelagic zooplankton andneuston common to <strong>estuarine</strong> channel habitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.TaxaChannel~abi tats1Re1 evantSal i nity Life History~ssociations2 CharacteristicsCOELENTERATACordyl ophora sp.POLY CHAETAPol ynoi daeSpionidaeM E,P LarvaeME7PME, PLarvaeLarvaeGASTROPODAMytilus sp.VENEROIDAMacoma sp.MM7SM-BE-ME-ME-MLarvae and unsettledjuvenileLarvae and unsettledjuvenileLarvae and unsettledjuvenileROTIFERABrachi onus spp.Asp1 anchna spp.R-MR-MCLADOCERADaohnia SDD.Chydorus spp.Di aphanosoma brachyurumR-0R-0R-0E-ME-MR-0R-0R-0COPEPODACALANOIDACalanus spp.Paracal anus spp.Pseudocal anus mi nutusMetridia lucensCentropages abdominal i sDi aptornus spp.Eurytemora spp.Epi 1 abidocera amphi tri tesAcartia spp.E-ME-ME-ME-ME-0R-0R-EE-0E-M(continued)55
Table 5.4.Continued.TaxaHARPATCICOIDAChannel~abi tats1Re1 evantSal i nity Life History~ssoci at ions* CharacteristicsCYCLOPOIDAParacyclops fimbriatusOi t hona simi 1 i sBALANOMORPHA M- B Cypri s 1 arvaeMYSIDACEAAcanthomysi s spp.Neomysi s spp.CUMACEALeucon spp.CumelTa spp.MYSM-BE-MR-EAMPHI PODACorophi urn spp. R-E Pri nci pal 1 yadult males andEogammarus confervicol usM- Bjuveni lesPrincipallyadult males andAni sogammarus spp.juvenilesMYSJuvenilesISOPODAGnorimosphaeroma oregonensi sBOPY R I DAE M,S Juveni 1 esDECAPODACrangon spp. R-E PrincipallyCancer spp.PI NNOTHER IDAEUpogebia pugettensi sM-BE-ME-0E-MjuvenilesLarvaeLarvaeLarvae(continued)G6
TaxaTELEOSTE IEngraul is mordaxOSMERIDAEGAD I DAECottus asperGOB IDAEINSECTAEPHEMER ILLIDAEGERRIDAEPLECOPTERAPERLODIDAECHIRONOMIDAETab1 e 5.4.Concl uded.Re1 evantChannel Sal i ni ty Life History~abitatsl ~ssociations2'~haracteristicsM E-M Eggs and larvaeM E-0 Eggs and larvaeM E ,P LarvaeM-B R- E LarvaeM E-0 LarvaeM- B R-EM- B R-EM-BR-EM-BR- EM- B R-E Incl udi ng 1 arvaeARACHNIDAHYDRACARINA M- B R- E1~ = mainstem; S = subsidiary; B = blind.ZR = riverine; 0 = oligohaline; M = mesohaline; P = polyhaline;E = euhaline.
CHAPTER 6FISH ASSEMBLAGES OF ESTUARINE CHANNELSAccording to tnei r association with<strong>the</strong> bottom or water column, fishes <strong>of</strong>Paci fic <strong>Northwest</strong> <strong>estuarine</strong> <strong>channels</strong> canbe cateyori zed respectively as demersalor pelayic. In many instances, however,<strong>the</strong>re is considerable overlap in speciesoccurrences in <strong>the</strong> two habitats due tobehavioral (vertical miyration, salinitypreterences) or 1 i fe hi story (demersal orpelayic larvae, spawning activity)characteristics.6.1 DEMEHSAL FISHESDespite <strong>the</strong> typical ly dynamic cnaracteristics<strong>of</strong> <strong>the</strong> benthic environs <strong>of</strong> <strong>estuarine</strong>channel habi tats, diverse assemblayes<strong>of</strong> derrlersal fish have become adaptedto live and reproduce amid <strong>the</strong> turbulentnixiny, high turbidities, low light levels,and variable food resources <strong>the</strong>re.Unlike <strong>the</strong> salmonids , which have beenstudied extensively in many Paci tic <strong>Northwest</strong>estuaries, de~nersal fish assemblayeshave been relatively ignored. Only recentlyhave comprehensive research proyracrlssuch as <strong>the</strong> CREOOP studies on <strong>the</strong>Columbia River estuary and those fundedin Grays Harbor by <strong>the</strong> U.S. Army Corps <strong>of</strong>Enyineers documented de~nersal fish assemblagesin channe Is throughout <strong>the</strong> estuaries,Syn<strong>the</strong>sis <strong>of</strong> <strong>the</strong>se sources (Natl.Mar. Fish. Serv. 1980, 1981; Simenstadand Eggers 1982; C. Simenstad and D.Ar~nstrony, School Fish., Univ. Wash..unpublished data) and more 1 imited informationfrom <strong>the</strong> Columbia River estuary(tlaertel and Osterberg 1967; Durkin 1975;Durkin et al. 1976, 1979, 1981; Higley eta1 . 1976), o<strong>the</strong>r <strong>coast</strong>al Oregon estuaries(Percy et al. 1974; Heimers and Baxter1976; blullen 19771, <strong>the</strong> Fraser River estuary(Northcote et al. 19791, <strong>the</strong> DuwarnishRiver estuary (lufatsuda et a]. 1968), andCommencement 8ay (We i tcamp and Schadt1981) indicate that 43 species (Table 6.1)<strong>of</strong> demersal fish occur commonly. Uf<strong>the</strong>se, nine species (denoted by *) generallyoccur in most estuaries (Fig. 6.1).Assembl aye structure varies si gni ficantlyamong <strong>the</strong>se estuaries, however. Sources<strong>of</strong> this variation are myriad but appear torelate principally to <strong>the</strong> relative extent<strong>of</strong> salinity intrusion, <strong>the</strong> characteristics<strong>of</strong> <strong>the</strong> freshwater watershed, yeoyraphi cregion, and <strong>estuarine</strong> microhabi tat.<strong>The</strong> effect <strong>of</strong> sal ini ty intrusion andflushing characteristics in structuriny<strong>the</strong> assemblage is most evident when <strong>the</strong>decnersal fish assemblages <strong>of</strong> <strong>the</strong> Columbiaand Fraser River estuaries are co~npared tothose <strong>of</strong> less freshwater-dominated codstalestuaries 1 ike Coos and Yaquina Bays.Whereds euryhal ine taxa such as <strong>the</strong> <strong>coast</strong>alsurfperches (<strong>the</strong> hexagrarn~nidsspp.; lingcod,commonly inside <strong>the</strong> 1 atter bays, <strong>the</strong>y seldomenter <strong>the</strong> Colu~nbia or Fraser Riverestuaries beyond <strong>the</strong> narrow euryhal i neregion within <strong>the</strong> first 2-3 km.<strong>The</strong> diversity <strong>of</strong> <strong>the</strong> demersal fishassemblage within a given estuary typicallyvaries as a function <strong>of</strong> <strong>the</strong> fishesisal i ni ty tolerances and habitat requirements.<strong>The</strong> National Marine Fisheries Ser-vice (1981) described <strong>the</strong> diversity (Shannon-WeaverIndex, H1 ) <strong>of</strong> bottom trawl -capturedfishes in <strong>the</strong> Columbia River estuaryas reaching a maximum mean value (H'; =2.4) between 9 and 23 km upstream from <strong>the</strong>mouth <strong>of</strong> <strong>the</strong> estuary and declining rapidlywhen proceeding upstream to a minimum H'x= 0.8) at <strong>the</strong> riverine extreme <strong>of</strong> <strong>the</strong> estuary(Fig. 6.2a). This conforms closelyto <strong>the</strong> results <strong>of</strong> Haertel and Osterberg(1967), who indicated that <strong>the</strong> greatestnumber <strong>of</strong> species and abundances <strong>of</strong>fishes occurred consistently within <strong>the</strong>
Table 6.1. Itemization and characteristics <strong>of</strong> demersal fishes common to <strong>estuarine</strong> <strong>channels</strong><strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.--- ---.------------.-----TeT;i;vd%i -meTaxa Channel Salinity Sediment life history--- (cmnon -- name) -- --- --- ----- habitats1 - associat ions? associations3 characteristics'! -PETROMYZONTIDAE+ %a%;+L. lridentataT~acif ic laniprey)M- S R-E N PM-S H-E N PSUUAL lDAESqualus acanthias M E N F-€8TSp%ij-domiRAJ 1 DAERa a binoculataSi tj i S T T - fM E S-G 0-EBACIPENSERIOAEAci enser medi rostris H M-E N F-EBP- breen s t u F e rA. transmontanus H R-E SC-B F-EIT~hi te sturgeon)SALMON I DAEProsoem wil liamsoni H R-H N F-El3m n t a n ~ iZiTitXsTCYPRINIDAEC rinus car io*rci7+*M locheflus caurlnus7 k i U m -Rhinichthys falcatusKeojard-dace)Richardonius balteatus7ilZEG--STn?-ieS;r----M-SM-sM-SM- SR-N SC-S 0R-N SC-G F-El3F-EM0-EllCATUSTOMI DAECatostomus macrocheilusrime sucker)M-S R -H N F-El3(;AD I OAES-CF-EPSYNGNATHIDAES n nathus le torh nchus-hi-CENTRARCH IDAEPomoxis annularis-pIiicrappie)-M-ESC-G 0-EP; Particularlyassocfated wt<strong>the</strong>elgrass and macroal yaeF-EPF-EPPEHCIOAEPerca f lavescensTvTTTow perch)(continued)69
Tab1 e 6.1.Cont i nued.--RelevantTaxa Channel Salinity Sediment life history(cornon name habitats1 - associations2 associations3 characteristics4 -EMBIOTOCIDAEAmphisitichus rhodoterusmdtail surfperch)Embiotica lateralistStripedseaperchlS-C 0-EP; Particularly associatedwith eel grass,macroal gae, andstructuresM-B 0-E SC-B F-EP; Particularly associatedwith eel grass,macroal gae, andstructuresM-SP-E G-Cn F-EPMP-E N F-EPH. anale MTsootfin surf~erch 1ti 'elli ticumT i i h i r c h ) *P-E N F-EBP-E N F-EBST ICHAEIDAE*Lum enus sa ittt-*r&acx )PHOL IDAEPhol is ornata(Saddle~unne 1 )M-B 0-E SC-G F-MB; Common to eelgrassbedsS-B M-E S-G F-EP; Particularly associatedwith rnacroal yaeAMMOOYT IDAEHEXAGRAMMI DAEH. 1 agocephalusTROC~ green1 i ny)0 hiodon elonyatus?&ICOTT IDAE*Cottus aspert m l y sculpin)M-SM-SM-BM- BM-EM-EM-ER-MES-GSC-GS-C0-EP; Frequently buriesin sand; o<strong>the</strong>rwisepelayicF-EB; Particularly associatedwith microal gae;Ipelagic larvae andearly juvenilesIF-EB; Particularly associatedwith mi croal yae;pelagic larvae andearly juveni les0-EB; Particularly asso- Iciated with microalgae;Ipelagic larvae andearly juvenilesF-EB*Le tocottus armatus7 h . a w c u l pi n)Scor aenichth s marmoratus7m:+,M-6MR-EP-ESC-CS-CAGNOIDAEStel lerina xyosterna M P-E S-C F-EB(Pri cklebreast poacher)CYCLOPTER~OAEM- S M-E S-C F-EP(con ti nued)70
Table 6.1. Concluded.- - -. .- - .--- *-- '----. -- - -- .- - -RTeeVnt-' - ---Ta xa Channel Salinity Sed i mnt 1 ife history(comnon name) - ------- - habitats1 __--associatio_n~~ asso~iati~~s~s~~5hara~teristi~s4 --L. rutteri M-S P-E S-C F-EPTRi-snai1 fish)Citharichth s sordidusd d ~ .*Fipstiy;euseck e sanddab)M- S M-E S-C F-EP; Pelagic larvaeM-SM-EF-EP; Pelagic larvaePLEURONECTIDAEM-SS-CF-EB; Pelayic larvaePLEURONECTIDAE - continued*Par0 hr s vetulusM-Bv * s rM-E SC -C F-EP; Pel agl c 1 arvae*Platichth s stellatus M-B H-E SC-C F-EB; Pelagic larvaeT s G i + k u rPsettichthys melanostictus M-S M-E S-C F-EB; Pelagic larvaeIsand sole)*species prevalent in all <strong>Pacific</strong> <strong>Northwest</strong> <strong>estuarine</strong> <strong>channels</strong>.= mainstem; S = subsidiary; B = blind2~ = riverine; O = oligohaline; M - mesohaline; P = polyhaline; E = euhaline~ S C = siltlclay; S = sand; G = yravel; C cobble; B - boulder; Cn = consolidated; N nodefinitive sediment association.4~ = parasitic on o<strong>the</strong>r fish; F- facultative, 0- = obligate; PP a pelagic planktfvore; EP =epibenthic planktivore; EB = epibenthic benthivore; MB = meiobenthic benthivore; 0 8 omnfvore.oligohaline to mesohaline regions nomatter where this mixing region waslocated within <strong>the</strong> estuary due to variabilityin river discharge. Durkin et al.(1981) also indicated that abundance <strong>of</strong>demersal fish was hiyhest in those channel("scour") sites witnin <strong>the</strong> mixing ornull zone region <strong>of</strong> <strong>the</strong> estuary, whilediversity decl ined uniformly as distancefrom <strong>the</strong> mouth <strong>of</strong> <strong>the</strong> estuary increased.<strong>The</strong> compounded effects <strong>of</strong> fish emigration,immi yration, and recruitment <strong>of</strong>juveniles, and <strong>of</strong> river discharge onsalinity distribution within <strong>the</strong> estuaryalso account for seasonal shifts indiversity <strong>of</strong> demersal fish assembl ayes.From <strong>the</strong> same 18-month, 22-site bottomtrawl sampling series cited above, <strong>the</strong>National Marine Fi sheries Service (1:81)also documented that peak diversity (H, =2.2) occurred between October , ahdDecember, and mininium diversity (H; =1.2) occurred between May and July (Fig.6.2b). <strong>The</strong> occurrence and extent <strong>of</strong> <strong>the</strong>density minimum may, however, be unrepresentativebecause <strong>of</strong> <strong>the</strong> unusual effects<strong>of</strong> <strong>the</strong> drarnatical ly-increased turbiditylevels during this period as a result <strong>of</strong><strong>the</strong> May 18, 1980 eruption <strong>of</strong> Mt, St.Helens in <strong>the</strong> Columbia River watershed.Among <strong>the</strong> principal demersal fishes in<strong>the</strong> estuary, starry flounder, pricklysculpin, and <strong>Pacific</strong> staghorn sculpini 1 lustrated tew major changes in nurnericalavailability over <strong>the</strong> 18-month period;availabilities <strong>of</strong> shiner perch, <strong>Pacific</strong>sand lance Enylish sole, and buttersole, on <strong>the</strong> o<strong>the</strong>r hand, fluctuated bothmonthly and seasonal ly ; snake prick1 e-back, sand sole, and <strong>Pacific</strong> tomcodavailability varied intermediately on aseasonal scale.6.2 PELAGIC FISHESUnl i ke demersa I tish assemb 1 ages,pel ayic fishes in <strong>estuarine</strong> channelhabitats otten occur sporadically because
Fig. 6.1. Representative illustration <strong>of</strong> common fish assemblages <strong>of</strong> <strong>estuarine</strong><strong>of</strong> <strong>the</strong> Paci f ic <strong>Northwest</strong>.<strong>channels</strong>-:x 2 .r,*$aW>8 1.-:X 2.I>5 -WZ0 1..10 10 20 30 40 50 60 FEE MAR AQR MAY JUNE JULY hUC SEPT CCT NOV M C JAN FEB MARMSTANCE FROM MOUTH OF ESTUARY (km) 19001981DATEFig, 6,2. Mean Shannon-Weaver diversity index (HIK) <strong>of</strong> demersal fishes in <strong>the</strong> ColumbiaRiver estuary as a function <strong>of</strong> location along <strong>the</strong> longitudinal axis <strong>of</strong> <strong>the</strong> estuary (A)and aver <strong>the</strong> 18-month sampling period (B) ; figure from Natl. Mar. Fish. Serv. (1981).7 2
<strong>of</strong> <strong>the</strong>ir motility and characteristic associationwith discrete water masses or asa function <strong>of</strong> life history patterns. Forinstance, <strong>the</strong> occurrence and residencetime in <strong>the</strong> estuary <strong>of</strong> anadromous speciesis general ly a function <strong>of</strong> miyratorybehavior. Many species occur solely aspelagic 1 arvae and juveni 1 es (meropl ankton)during brief periods in <strong>the</strong>ir earlylife history but emigrate from <strong>the</strong> estuary,become demersal , or move into adjacenthabitats as juveniles and adults.Similar to <strong>the</strong> information aboutdemersal fish, <strong>the</strong> majority <strong>of</strong> <strong>the</strong> comprehensivestudies <strong>of</strong> pel agic fish assemblayesin <strong>estuarine</strong> <strong>channels</strong> <strong>of</strong> <strong>the</strong> regionhave occurred in <strong>the</strong> larger estuariessuch as <strong>the</strong> Columbia River (Haertel andOsterberg 1967; Durkin et al. 1979, 1981;National Marine Fisheries Service 1980,1981), Grays Harbor (Simenstad and Eggers1981), and <strong>the</strong> Fraser River (Northcote eta1 . 1979) ; some small er, <strong>coast</strong>al estuarieshave been surveyed, however, i ncl udingCoos Bay (Cummings and Schwartz 1971),Ti 1 lamook Bay (Cummings and Berry 1974;Forsberg et al. 1975), <strong>the</strong> Umpqua River(Mullen 1977), and Sixes River (Keimersand Baxter 1976). Ichthyopl ankton hasalso been addressed specifically in <strong>the</strong>Columbia River estuary (Mi si tan0 1977;English 1980), Yaquina Bay (Pearcy andMyers 1974), and Humbol t Bay (Eldridgeand Bryan 1972) and incidentally in GraysHarbor (Simenstad and Eggers 1981). Syn<strong>the</strong>sis<strong>of</strong> <strong>the</strong>se sources indicates that 36taxa representing 16 families are commonfishes in <strong>the</strong> pelagic assemblages <strong>of</strong> <strong>Pacific</strong> <strong>Northwest</strong> estuaries (Table 6.2).Of <strong>the</strong>se, 13 are anadromous, 16 appearexclusively as ichthyoplankton, and only<strong>the</strong> remaining eight comprise taxa whichcould be considered to maintain extendedresidence in <strong>estuarine</strong> channel s.Unlike <strong>the</strong> pattern <strong>of</strong> demersal fishassembl aye diversity in <strong>the</strong> ColumbiaKiver estuary, <strong>the</strong> National Marine FisheriesServise (1981) documented maximumdiversity (HT = 1.7) <strong>of</strong> pelagic (purseseine-cauyht) fishes in <strong>the</strong> central mixingregion <strong>of</strong> <strong>the</strong> estuary, 20 to 35 km from<strong>the</strong> mouth, and below average diversityvalues in both euryhaline and riverineregions (Fig. 6.3a). Temporal diversity<strong>of</strong> <strong>the</strong> pelagic fish assemblage was alsodramatically different from <strong>the</strong> demersalassemblage. In an almost mirror image <strong>of</strong><strong>the</strong> pattern <strong>of</strong> <strong>the</strong> demersal, fish assemblage,maximum diversity (Hz = 2.2) <strong>of</strong>pelagic fishes occurred in tne, spriny anddeclined to a winter minimum (ti- = 0.5) inan almost mirror image <strong>of</strong> <strong>the</strong>Xpattern <strong>of</strong><strong>the</strong> demersal fish assemblage (Fig. 6.3b).As noted earlier, however, <strong>the</strong> effects <strong>of</strong>increased turbidity from <strong>the</strong> eruption <strong>of</strong>Mt. St. Helens in May 1980 may biasinterpretations <strong>of</strong> <strong>the</strong> May-July 1980data.6.2.1 Resident Pelagic FishesAmong <strong>the</strong> common pelagic fishes in<strong>estuarine</strong> <strong>channels</strong>, <strong>the</strong> clupeids (herrings),enyraul ids (anchovies), osmerids(smelts), a<strong>the</strong>rinids (silversides), andammodytids (sand 1 ances), commonly referredto as a group as "baitfish," comprise <strong>the</strong> majority <strong>of</strong> <strong>the</strong> non-anadromous,resident fishes; <strong>the</strong> three-spine stick1 e-back comprises <strong>the</strong> only non-baitfish resident.<strong>Pacific</strong> herring utilize <strong>Pacific</strong><strong>Northwest</strong> estuaries for spawning and rearing<strong>of</strong> larvae and early juvenile stages.Spawning typical ly occurs in shall ow subtidalhabitats between January and July,with considerable variation among estuaries.Spawning in <strong>the</strong> Columbia Riverestuary occurs between March and July andmay i nvol ve several major spawni ngs (Mis i-tan0 1977; Natl. Mar. Fish. Serv. 1981).In Yaquina Bay herring spawn earlier,between January and March (Pearcy andMyers 1974), and may a1 so undergo as manyas four major spawnings (Steinfel d 1972).Accordingly , 1 arvae may occur in <strong>the</strong><strong>channels</strong> over a protracted period <strong>of</strong>time, between March and August in <strong>the</strong>Columbia River estuary (Mi si tan0 1977)and between January and May in YaquinaBay (Pearcy and Myers 1974). Spawninymay be annually sporadic, however, asboth English (1980) and Simenstad andEggers (1981) reported low abundances orno herring larvae in <strong>the</strong> Columbia Riverestuary and Grays Harbor, respectively,in 1980. Juvenile herring, whe<strong>the</strong>r originatingwithin or transported into <strong>the</strong>estuary as larvae or post-larvae, tend to
Tab1 e 6.2 I temi ration and characteris tics <strong>of</strong> pelagic fishes comnon to <strong>estuarine</strong> <strong>channels</strong><strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.----.--- -Channel Salinity Re1 evant 1 i fe- Taxa-- habitats1 associations2 hi story characteristics3CLUPE IDAEAlosa sa idissima~ i *ENGHAULIDAESALMONIDHEOncorh nchus gorbuscha-Fix-hG)0. keta (chum salmon)U. kisutch (coho salmon)g. 'ner'kasockeye salmon)0 tsfiaw tscha76 h b n 1Salmo clarkiTcutth-rou t )S.t9a; rdneriee head trout)Sal vel inus malma'(Do1 ly Varden)0-E 0-PP; Anadromous0-E 0-PP; Also occurs in ichthyoplankton;spawn in estuaryM M-E 0-PP; Occur principally aslarvae and juvenilesM-B K-E F-PP; AnadromousM-BM-BM-SM-SR-ER -ER-ER -E0-EP ; AnadromousF-EP; Anadromous0-PP; AnadrornousF-EP; AnadromousM-B R-E F-PPs ; AnadromousM-B K-E F-PP; AnadromousM-S H-E F-PPs; AnadromousOSMEH I DAEH omesus retiosusfhlh-,S irinchus thaleichth sMM-SM-SM-SM-EM-E0-E0-E0-PP; Also occurs in ichthyoplanktonF-PP; Also occurs in ichthyoplanktonF-EP; Anadromous ; a1 sooccurs in ichthyoplanktonC-PP; Anadromous ; a1 sooccurs in ichthyoplznktonMicro adus roximusM-E 0-EP; Occurs only in ichthy--mktok oplankton; demersal as juvenileand adultATHER INIUAEAtnerinoys affinis M-S 0-E0-PP; Anadromous~asterosteus aculeatusnhree-spined stick1 eback)M-BR-E0-EP(continued)74
Table 6.2. Continued.- ---Channel Sal i nityRe1 evant 1 4Taxa -. habi tats1 associations2 hi story characteri stics3 -fkPERCICHTHYIDAEMorone saxatilis- m p mM R-E F-EP; Anadr<strong>of</strong>nousSTICHAEIDAE\urnpenus sagittaSnake prick1 eback)PHOC I DAEPhol is ornataw e m u n n e l )AMMODYTIDAEArnmod tes hexa terus-&s*M-S M-E 0-PP; Occurs only in ichthyo2lankton;moves to demersalhabitats as juveniles andadultsM-EM-E0-PP- Occurs only in ichthyoplenkton;moves to demersalhabitats as juveni 1 es andadults0-PP; Also occurs in ichthyoplanktonGOBI IDAEClevelandia ios(Arrow goby)-SCORPAENI DAESebastes melano sm o dSebastes spp.- ( = h )M-SM-EM-EP-EM-E0-PP; Occurs only in ichtiiyoplankton;moves to shallow1 ittoral habitats as juvenilesand adults0-PP; Occurs only in ichthyoplanktmmoves to shallowlittorsl habitats as juvenilesand adultsF-PP; Also occurs in ichthyoplankton0-PP; Occurs only in ichthyoplanktonHEXAGRAMMI DAEHexa rammos spp.*)0 hiondon elongatus-hM-EM-E0-PP; Occurs only in ichthyoplankton;moves to demersalhabitats as juvenile andadult0-PP.. Occurs only in ichthyoplankton;moves to demersalhabitats as juveni 1 e andadultC OTT I DAECottus asperv - l y scul pi n)M-BB-P0-PP; Occurs only in jchthyoplankton;moves to demersalhabitats as junen i 1 e andadult(continued)7 5
--- Channel Sal inity ~ eeiant l 1 i feTaxa habitats1 associations2 hi story characteri stics3Tab1 e 6.2.Concl uded.Le tocottus arrnatus.ldkiEXighorn scul p~ n)Scor aenichth s marmoratus7-PLE URONECT I DAElso setta isole is-&o+Paro hr s vetulusn+srPlatichth s stel latus1 4 u rPsettichth s me1 anostictus7-e-M-tcMM-EM-E0-PP; Occurs only in ichthyoplankton;moves to demersalhabitats as juvenile andadult0-PP; Occurs only in ichthyoplankton;moves to demersalhabitats as juvenile andadult0-PP; Occurs only in ichthyoplankton;moves to demersalhabitats as juvenile andadultM M-E 0-PP; Occurs only in ichthyoplankton;moves to demersalhabitats as juvenile andadultM M-E 0-PP; Occurs only in ichthyoplankton;moves to demersalhabitats as juvenile andM 0 -Eadult0-PP; Occurs only in ichthyoplankton;moves to demersalhabitats as juvenile andadultM M-E 0-PP; Occurs only in ichthyoplankton;moves to demersalhabitats as juvenile and- -adult1~ ,. mainstem; S = subsidiary; B = blind211 rlverlne; 0 = oligohaline; M mesohaline; P polyhaline; E = euhaline30- obligate; F- = facultative; PP = pelagic planktivore; EP = epibenthicplanktivore; PPs = pelaylc piscivorerear in <strong>estuarine</strong> waters usually b 2UQ/,,sal fni ty through summer and late fa1 1. Atleast among <strong>the</strong> <strong>coast</strong>al estuaries, fewjuvenile herring contlnue to reside longerthan 8-10 months. Although <strong>Pacific</strong>herrf ny have been reported in inlandestuaries (Fraser River, Northcote et a1 .1979; Squamish River, Levy and Levings1978; Duwamish River, Matsuda et al.1968), most herring spawning and rearingappears to occur in <strong>the</strong> adjacent bays andfjords <strong>of</strong> Puget Sound and <strong>the</strong> Straits <strong>of</strong>G@orgia and Juan de Fuca (Miller et al.1978, 1980; Miller and Borton 1980;Trumble et al. 1977; Meyer and Adair1978; Fresh 1979; Fresh et al. 1979;Gonyea et al. 1982). Herring spawningappears to be highly correlated with <strong>the</strong>occurrence <strong>of</strong> substrates suitable for eggdeposition, such as eelgrass and macroalgae,and with moderately high water flushingrates. This may explain why herringspawning tends to be more pronounced insuch <strong>coast</strong>al estuaries as Yayuina Bay andCoos Bay than in more freshwater-dominatedestuaries such as <strong>the</strong> Columbia River estu-
1 , , , , , , , , I , , , , , . . , . . , , ,, . i0 10 2 0 30 40 50 . 60 FEE MAR IPR MAY JUNE JULY LI.#Q SEPT OCT NOV MC JAN FE8 MARDISTANCE FROM MOUTH OF ESTUARY (km)1680 1981DATEFig. 6.3. Mean Shannon-Weaver diversity index ( H I x ) <strong>of</strong> pelagic fishes in <strong>the</strong> ColumbiaRiver estuary as a function <strong>of</strong> location along <strong>the</strong> longitudinal axis <strong>of</strong> <strong>the</strong> estuary (A)and over <strong>the</strong> 18-month samplina period (B) ; figure from Natl . Mar. Fish. Serv. (1991!.ary, which has no extensive eelyrass orkelp bed habitats. Keariny <strong>of</strong> larvae andjuveniles in <strong>channels</strong> appears initiallyto be a function <strong>of</strong> <strong>of</strong>fshore-<strong>estuarine</strong>circulation and later, with <strong>the</strong>ir recruitmentfrom <strong>the</strong> plankton to <strong>the</strong> nekton, afunction <strong>of</strong> prey (cal anoid copepods, i .e.Acartia clausii , Pseudocalanus sp.)availabi 1 i t n s s e l l 1964; Pearcy andMyers 1974).Most nor<strong>the</strong>rn anchovy eggs, larvae,and juveniles which occur in <strong>the</strong> region's<strong>estuarine</strong> <strong>channels</strong> oriyi nate from spawningpopulations in adjacent <strong>coast</strong>al waters,although spawning has been reportedin bays and passages <strong>of</strong> Puget Sound (Mil l-er and Borton 1980). Kichardson (1973)described concentrations <strong>of</strong> anchovy larvaein near-surface strata <strong>of</strong> <strong>the</strong> ColumbiaKiver plume between June and August andsuggested that a spawning stock <strong>of</strong> anchovieswas particularly associated with <strong>the</strong>plume. Eggs appear to be commonly transportedinto <strong>the</strong> Columbia River estuarybetween Apri 1 and September. English(1980) described maximum densities (-1500m-2) in June at locations nearest <strong>the</strong>mouth <strong>of</strong> <strong>the</strong> estuary. Hatching <strong>of</strong> <strong>the</strong>seeggs within <strong>the</strong> estuary and fur<strong>the</strong>r transport<strong>of</strong> larvae into <strong>the</strong> estuary accountfor increased concentrations <strong>of</strong> 1 arvaeand post-larvae in <strong>the</strong> euhaline to meso-ha1 ine regions over an extended period,January through November ( Mi si tan0 1977).Pearcy and Myers (1974) also collectedlarval anchovies (1.6 x 10-3 m-3) fromYaquina Bay in July through Septemberalthough densities were not as high asreported in <strong>the</strong> Columbia River estuary.Probably due to a general 1 ack <strong>of</strong> signifi-cant sampl ing effort for small , school ingpelagic fishes in <strong>the</strong>se estuaries, juveni1 e nor<strong>the</strong>rn anchovy between post-larvaland <strong>the</strong> 2+-year age classes have not beenreported extensively. <strong>The</strong>re i s qua1 i tativeevidence, however, that <strong>the</strong>y are commonwithin estuaries (T. J. Durkin, NMFS,Harnmond, OR; pers. conirn. ) - Age 2+ andlater aye classes can be sampled bypurse seines and are reported to occurabundantly in <strong>the</strong> lower reaches <strong>of</strong> <strong>the</strong>Columbia Kiver estuary through much <strong>of</strong><strong>the</strong> year (Nat. Mar. Fish. Serv. 1980,1981; Durkin et ale 1981 ) - Simenstad andEggers (1981) estimated that adult anchoviesmaintained residence in Grays Harborfor up to 6 weeks during two ~~eriods,mid-~une to early August and late ~ugustto early October, and resided longest in<strong>the</strong> region just inside <strong>the</strong> mouth <strong>of</strong> <strong>the</strong>estuary. Juvenile anchovy, on <strong>the</strong> o<strong>the</strong>rhand, sustained residence for a long as11 weeks, during mid-July to earlyOctober, in <strong>the</strong> mixing zone fur<strong>the</strong>r up<strong>the</strong> estuary.
Whitebait and surf smelts comprise<strong>the</strong> non-anadromous osmerids which utilize<strong>the</strong> region's estuaries. While spawninghas not been reported in <strong>coast</strong>al estuaries,surf smelt spawn on polyhalinebeaches <strong>of</strong> Puget Sound and <strong>the</strong> Straits <strong>of</strong>Georgia and Juan de Fuca (Hi 1 ler and Borton1980) and may spawn within <strong>the</strong> lowerreaches <strong>of</strong> some <strong>of</strong> <strong>the</strong> more marine-infl u-enced <strong>coast</strong>al estuaries (Quill ayute Riverestuary, Chi twood 1981). Whitebait smeltare rare inside <strong>the</strong> Strait <strong>of</strong> Juan deFuca, which is at <strong>the</strong> nor<strong>the</strong>rn limit <strong>of</strong><strong>the</strong>ir geographic range (Hart 1973), andlittle is known about <strong>the</strong>ir spawningbehavior o<strong>the</strong>r than that <strong>the</strong>y are presumedto spawn in <strong>coast</strong>al waters (Hart1973). Osmerid eggs are common throughmuch <strong>of</strong> <strong>the</strong> Columbia River estuary duringApril and May (English 1980) and <strong>the</strong>larvae are probably present untll January(Mi si tan0 1977) ; <strong>the</strong>y were not reported,however, during Pearcy and Myers ' (1974)extensive survey <strong>of</strong> Yaquina Bay ichthyoplankton.Both s~nel ts are present asjuveniles in <strong>the</strong> Columbia River estuarythrough most <strong>of</strong> <strong>the</strong> year and have beenreported in relatively hi yh densitiesduring several months, i.e., June-July in<strong>the</strong> case <strong>of</strong> surf smelt and July-Augustfor <strong>the</strong> whitebait smelt (Natl. Mar. Fish.Serv. 1981).Topsmelt is <strong>the</strong> least comnion <strong>of</strong><strong>the</strong>se nonanadronious pel agic fishes andoccurs exclusively in <strong>coast</strong>al estuariessouth <strong>of</strong> <strong>the</strong> Columbia River where spawningpopulations are reported in Coos Bay(Schultz 1933) and <strong>the</strong> Umpqua River estuary(Mullen 1977) between late May to earlyJuly. In both estuaries topsmelt capturecontinued in <strong>the</strong> upper reaches <strong>of</strong>tne estuary from late August throuyh Septemberand may have included as many asthree age classes (if 0-age class fishare presumed to remain within <strong>the</strong> estuaryafter hatching) residing in <strong>the</strong> estuary(Schul tz 1933).<strong>Pacific</strong> sand lance are a schooling,pelagic fish which is <strong>of</strong>ten associatedwith <strong>the</strong> bottom in sandy habitats (seeSection 6.1) where <strong>the</strong>y periodically bury<strong>the</strong>mselves (Hart 1973), a behavior relatedto photoperiod, food availability, andhunger (Kuhlman and Karst 1967; W i nslade1974a, b, c). <strong>The</strong>ir attenuated body formand rapid swimming speed makes <strong>the</strong>m one<strong>of</strong> <strong>the</strong> hardest species to capture, muchless quantitatively assess <strong>the</strong>ir standingstock, and it is questionable that <strong>the</strong>irutilization <strong>of</strong> <strong>Pacific</strong> <strong>Northwest</strong> estuarieshas been documented adequately. Larvaehas been reported in euhaline-polyhalineregions <strong>of</strong> <strong>the</strong> Columbia Riverestuary in March-April (Mi si tan0 1977)and in Yaquin Ba in moderate densities(3.5 x 10-3 m ) from January throughMarch (Pearcy and Nyers 1974). <strong>The</strong> latterstudy illustrated that sand lancelarvae were more abundant <strong>of</strong>fshore andprobably were transported into <strong>the</strong> estuaryvia tidal exchange. In <strong>the</strong> case <strong>of</strong>tne Columbia River estuary, sand lancewere captured throughout <strong>the</strong> year andwere periodical ly abundant (Nat. Mar.Fish. Serv. 1981). Larval sand lancehave been collected in <strong>the</strong> mesohalineregion <strong>of</strong> Grays Harbor, and common, abundantoccurrences <strong>of</strong> juveniles have occurredin polyhaline regions <strong>of</strong> <strong>the</strong> outerestuary (Simenstad and Eggers 1981).Threespi ne sticklebacks are ubiqui -tous fish which have been reported from avariety <strong>of</strong> freshwater and marine habitats(Hart 1973; Wydoski and Whitney 1979).<strong>The</strong>y inhabit a variety <strong>of</strong> <strong>estuarine</strong> habitatsand are common in <strong>the</strong> surface waters<strong>of</strong> blind, subsidiary, and mainstem <strong>channels</strong>but are also found among littoralmacrophytes. Reproduction occurs in bothfreshwater and marine habitats (Hart1973), although Vrat (1949) has questioned<strong>the</strong> effectiveness <strong>of</strong> reproduction in salineenvironments, Most <strong>of</strong> <strong>the</strong> comprehensivestudies in <strong>the</strong> reyion's estuariesillustrate consistent occurrences, abundances,and spatial distributions throughoutmost <strong>of</strong> <strong>the</strong> year (Mullen 1977; Northcoteet al. 1979; Natl. Mar. Fish. Serv.1980, 1981; Simenstad and Eyyers 1981),althougn a few, typically those <strong>of</strong> inlandestuaries, report fewer and less consistentoccurrences (Matsuda et al. 1968;Levy and Levinys 1978).6.2.2 Anadramous Pelagic FishesAmong <strong>the</strong> anadromouspelagic fishes78
utilizing <strong>estuarine</strong> <strong>channels</strong>, over halfare salmonids (Table 6.2). Because <strong>of</strong><strong>the</strong>ir commercial and recreational importance,<strong>Pacific</strong> salmon and anadromous trouthave long been <strong>the</strong> focus <strong>of</strong> intensivestudies in estuaries throughout <strong>the</strong> regionboth as juveniles migrating from freshwaterto rear in inarine habitats and asadults returning to spawning rivers. Although<strong>the</strong>re i s no comprehensive syn<strong>the</strong>si s<strong>of</strong> this mass <strong>of</strong> knowledge, Iwamoto andSalo (in prep.), Ourkin (1982), Healey(1982), Myers and Horton (1982), andSimenstad et a1 . (1982b) have includedmuch <strong>of</strong> <strong>the</strong> existing information on <strong>estuarine</strong>utilization by salmon and fur<strong>the</strong>rreferences can be secured from Levy(1980b) and Columbia River Estuary DataDevelopment Progra~rt (1980). Wh i 1 e <strong>the</strong>rehas been no coinparable syn<strong>the</strong>ses <strong>of</strong> <strong>the</strong><strong>ecology</strong> <strong>of</strong> anadromous trouts in this region,Royal (1972) provides <strong>the</strong> most comprehensivediscussion to date.Anadromous trouts--cutthroat, steel -head, and Do1 ly Varden--are comparativelyless abundant than <strong>the</strong> salmon and appearto utilize <strong>estuarine</strong> habitats sparingly;<strong>estuarine</strong> <strong>channels</strong> act principally ascorridors for <strong>the</strong>ir seasonal migrationsbetwen freshwater spawning habitats andmarine feeding habitats. After 2 to 9years (typically 3 years) in freshwater,<strong>coast</strong>al cutthroat initially immigrate to<strong>estuarine</strong> and marine habitats during <strong>the</strong>spring and reside <strong>the</strong>re until late summerand fall (Wydoski and Whitney 1479). Ofall <strong>the</strong> trouts, cutthroat trout and DollyVarden may utilize <strong>estuarine</strong> <strong>channels</strong> <strong>the</strong>most, since throughout <strong>the</strong>ir marine period<strong>the</strong>y appear to stay in <strong>the</strong> vicinity <strong>of</strong><strong>the</strong>ir home streams and <strong>of</strong>ten reside permanentlywithin estuaries (Levy and Levings1978). A1 thouyh sustained <strong>estuarine</strong> residencehas seldom been illustrated, ljiger(1972) indicated that pre-smolt cutthroat(up to 170 mm FL~) which moved into <strong>the</strong>Alsea River estuary in <strong>the</strong> later part <strong>of</strong><strong>the</strong> spring emigration maintained nonmigratoryresidence within <strong>the</strong> estuary.Both steel head and Do1 ly Varden immigratethrough <strong>the</strong> estuary from freshwater to4~~ = Fork length.<strong>the</strong> ocean in late winter and spring, althouyh<strong>the</strong> racial population structure <strong>of</strong>steelhead is such that some juvenilesteelhead may be found migrating to seaduring every nlonth <strong>of</strong> <strong>the</strong> year (Wydoskiand Whi tney 1979). Similarly, whileDolly Varden appear to be liini ted to sub-sequent emigration back into freshwaterin late summer though early fall, miyratingsteelhead may pass through <strong>the</strong> estuariesthroughout <strong>the</strong> year. <strong>The</strong> principalperiods when adult steelhead ascend spawningstreams is from December to March(termed "winter run1' fish) or betweenJuly and September (I1sumrner run")(Wydoski and Whi tney).<strong>The</strong> occurrence and extent <strong>of</strong> utilization<strong>of</strong> <strong>estuarine</strong> channel habitats byfive species <strong>of</strong> <strong>Pacific</strong> salmon are highlyvariable because <strong>of</strong> <strong>the</strong>ir diverse lifehistory patterns (Table 6.3). Extendedoccupation <strong>of</strong> estuaries beyond <strong>the</strong> normaltime required for direct migration to andfrom <strong>the</strong> ocean is suggested to benefitsalmon by providiny an environment forproductive foraging, physiological transi-tion, and refuyia from predators (Simenstadet al. 1982b). Estuarine residence,<strong>the</strong> habitats occupied, and <strong>the</strong> total residencetime <strong>of</strong> outmigrating juveniles aredetermined primarily by <strong>the</strong> timing <strong>of</strong> andsize at entry into <strong>the</strong> estuary. <strong>The</strong>se,in turn, are correspondingly influencedby numerous abiotic and biotic factorsoperating in <strong>the</strong> freshwater system, i.e.,time <strong>of</strong> adult spawning, stream temperaturesduring and after egg incubation,fry size and condition, population densityin <strong>the</strong> strearn, food quality and quantity,stream discharge and turbidity,physiological change, tidal cycles, andphotoperiod (Iwarnoto and Salo, in prep. ).Juvenile pink and chum salmon typically enter <strong>the</strong> estuaries at 30-40 mm FL,and occupy littoral and shallow suh-1 i ttoral habitats in <strong>the</strong> estuary. When<strong>the</strong>y are 45-55 mm FL, <strong>the</strong>y begin occupying<strong>the</strong> pelagic surface <strong>of</strong> <strong>channels</strong> until<strong>the</strong>y leave <strong>the</strong> estuary. Similarly, subyear1ing (<strong>of</strong>ten referred to as "fry")chinook salmon which enter <strong>the</strong> estuary30-50 mm FL in size also tend to occupy
Table 5.3. Life history characteristics <strong>of</strong> five species <strong>of</strong> <strong>Pacific</strong> salmon in nor<strong>the</strong>astern<strong>Pacific</strong> Ocean region (modified from Simenstad, in press).WdzsmrySat wn Spec i CIWare Pink C*n hho--- Qcteye Chinmi.%amins ioc~t%on km ?n wall trtbutaries SQat In malt triautdrler Pttadriiy in swll rivers PribUtdries f5 Ibkes. in trlb~t6rles. mstand Timingand e~t~arjne intertida:, amt <strong>estuarine</strong> rwemidat. am trfbutss>es t n sloe ~ ~ s &iony r lare shore- in win rivers. occurs overmbt ln large CrlDUtdrl65d<strong>of</strong>f =in rivers; occursost ln Jars crtaitarles mannels <strong>of</strong> Larye rivers,am niin rlvers. ~ccurs =Curs over one to tatine, occurs over ta t<strong>of</strong>arr mntns fros lateone to tro mntns in fallexcept tor .spri% cnrnook-~ v e r o l q ~ o t w ~ orermemtnfr[*edrl~ ~ s r np~tfrsfromlatefall s~rertoldtefdll populatrons, wnicn spawnedrly fdl t. pti~rlly OQd fa! 1 throvyn earl1 dnter tnrqn early winter over three to SIX mntn5 lnyeam in ~aclflc northwestand Sov<strong>the</strong>arsernsprlny thruuyn early fall.snll s&aner runs occur inLIIsLI, even yearr Puet sound and <strong>the</strong> ColuslelsahereI* hid~kabia River and a wlnter runoccurs In tne SacrarrntoRiver%rat ton <strong>of</strong> EygOevelopentI ~ ~ i <strong>of</strong> n g FrrEmergenceFresnwater RedringTimIny and DurationOuration and Timlng<strong>of</strong> Cnlgrdtton toEstuaryDuration andLOC~~~MI <strong>of</strong>Residence lnEstuary andNearsnore MarineEnvl ronar?ntPreferred PreyOradnlsms InM%yration andResidence In Horth<strong>Pacific</strong>fnree to t3ve nsntnsBid- to late ulnterUsually aigrate~tseoiately afterenergenceOccurs over one wnfnbetween rid-winter toearly sprinyLess tnan one wtek inshallm habitats. threeto five weeks in neritlcndot tatsCalanoia copeyoas. andlarvacedns In neritlcAlong cwst in wlf <strong>of</strong>Alaska, Easterr, BeringSea dnd Aleutian lslandsfor approxiniltely OMyearTnree to I1 we mtnr la to fln wtbs Three to five mnths Tnree ro five mtnsma- to 1dLe nnter.early spring(nd-wlnterEarly to late winter0 ~ ~ 6 slyrate 1 1 ~Thrwyhwt <strong>the</strong> year. Tnrou* one to tnreeil*.edtately afzermergence. one -nth12-28 months In stream.as lonq as three yearsyears in lakeurlmin AlaskaOccur5 over one rantn Uccurs orw one to four Utcurs over one to t*om+*(ten rld-rSntcr ma motns In lste winter to wncns In early r5 latelate spring earl] :ur S P ~ ~ Wb e to tnrep weeks in Un to hm mntns rn Short-tern, one to t4snallw ndbitdts, three neritfc nabttats: sols weeks in nericic nabitatsto live pets in nerittc ertendRd rearing, up tohaottlts; SDle extended SIR mntns. in inlandrearing. up to six seasuontn5. in 1nlrM searHdrpa~tl~~id copepods and -rid ampnlpods in Juvenile snrinp aodrid ~ hlyods in shaltor s~bllttordl wuha~slias in nerltlcinal lor sui~itloral nab~tass; decapod larvae nabitatshabitats; ~dldII0id and wpnaustids Incooe~as, deca~~d larvae. neritic nabitatsand iarvaceans' in neritichabitats&long <strong>coast</strong> in Gulf <strong>of</strong> Alony <strong>coast</strong> in Gulf ot Alooy <strong>coast</strong> and in GulfAlaska, Eastern Bering Alaska and Eastern <strong>of</strong> Alaska for t*it toSea and Aleutian Islands Aleutian Island for one, tnree years except forfor tnree to flve years usually two years western Alaska@puIations, which alsomature in &ring Sea andAleutian IslandsTiming <strong>of</strong> Return Late sumr to early fall Edrly fall to early Late sufmner to mid-fall Hld-sumr to early fallMiyratlon towinterEstuarylNatalSt ream -me-winter to lace sprinyexcept for 'spriny chinook"populations, wnich emergefraa fall thrwg mfdwtnterSprsny through suumer,tnree to fwr mnths $0stream, except for "sprlnychiwok' populdtians, wnichtend to rear for full yearin estuaryOccurs over one to twomntns from &a-minter tolate suner except for'spriny chinookm @pulatrons.wnicn emgrate fraafell rnroup winterb e to tnree weeks insnallw habitats, tn, tosix weeks in neriticnab1 tats. some extendedrearlny. elynt to ten reeksor lonyer. In ldryeestuaries and inland seasbaamaria anylnipods,cumceans, and emeryent andorirt insects in shallowsubl~ttoral nabitats; driftinsects, deCaood larvde andfish larvae in neritichdbitdtSAlony codst in bult otAlaska, Eastern Bering Seaand AleUtldII ISldnds torone to flve. typicallytnree yearsFdll except for "sprlnychinook" ~opulations, wnicnreturn in mid-spr(nytnrougn earl> fall ---
1 i ttoral and shal low sub1 i ttoral habitats,particularly sal t marshes, mudflats, and foreshore areas before <strong>the</strong>ygrow larger and move into <strong>the</strong> pelagicenvirons (Levy and Northcote 1981; Congletonet a1 . 1982). Little is known about<strong>the</strong> distribution <strong>of</strong> chinook (fry) duringflood tide cycles when sal tmarsh and mudflathabitats are inundated. It is <strong>of</strong>tenpresumed that <strong>the</strong>y move about and feedover <strong>the</strong> littoral flats. Healey (1980),however, captured no juveni le chinook(fry) in this habitat <strong>of</strong> <strong>the</strong> NanaimoRiver estuary during purse seinesampling at flood tide and <strong>the</strong> fish werefound across <strong>the</strong> landward margin <strong>of</strong> <strong>the</strong>flats along <strong>the</strong> edge <strong>of</strong> <strong>the</strong> saltmarsh. Asimilar distributional pattern was alsodocumented for juvenile chum in <strong>the</strong> NanaimoRiver estuary (Healey 1979). But <strong>the</strong>fish are at least periodically congreyatedin <strong>the</strong> blind and subsidiary <strong>channels</strong>which transect most littoral and shallowsublittoral flat habitats during ebb tidecycles, and it is here that most biologicalsampling has been concentrated (Fig.6.4). Finger1 in'g and year1 ing chinookand coho smol ts emi grate directly into<strong>the</strong> pelagic habitats <strong>of</strong> <strong>estuarine</strong> <strong>channels</strong>and, except for occasional foraysinto shal low sub1 i ttoral nabi tats, residewithin this habitat until <strong>the</strong>y depart <strong>the</strong>estuary.Almost a1 1 juvenile salmon migrateinto <strong>estuarine</strong> habitats between mid-winterto late summer, with some Speciesi 1 lustrating concentrated migration periods(pink, chum, sockeye) and o<strong>the</strong>rs(coho, chinook) protracted migrations asa result <strong>of</strong> variable population (racial)and environmental factors. Table 6.4( Simenstad et al. 1982b) summarizesdocumented species residence times (totaltime juvenile salmon <strong>of</strong> particular speciesoccur in <strong>estuarine</strong> habitats) for WashingtonState estuaries, and illustrates thatjuvenile pinks may occur in some estuariesover as little as four weeks whilejuvenile chinook may occur over as longas 29+ weeks. In estuaries adjacent toPuget Sound and <strong>the</strong> Straits <strong>of</strong> Georgiaand Juan de Fuca, where resident chinook("blackmouth") and coho salmon populationsare sustained, juvenile and imature chi-nook and coho may continue to frequenteuhal ine seglnents <strong>of</strong> <strong>estuarine</strong> channel ssporadical ly throughout <strong>the</strong> Year (Simenstadet a1 . 1982b).Species residence times, however, reflectboth <strong>the</strong> variable turnover in transitionalmigrants from a diverse spectra<strong>of</strong> stocks and variable ~eriods <strong>of</strong> SUStainedresidence <strong>of</strong> each cohort groupwithin <strong>the</strong> estuary. unfortunately, <strong>the</strong>extensive and expensive method01 ogy haslimited <strong>the</strong> number <strong>of</strong> re1 iable estimates<strong>of</strong> individual residence times and identification<strong>of</strong> <strong>the</strong> factors regulating <strong>estuarine</strong>residence. Simenstad et a1 . (1982b)have 1 isted estimates <strong>of</strong> maximum residencetime for cnum, coho, and chinook salmon,including several specific to <strong>estuarine</strong>channel habitats, in Washi ngt0n estuaries(Table 6.4). Both juvenile chum and chinook(fry) appear to have short residencetimes in saltmarsh tidal <strong>channels</strong>, on <strong>the</strong>order <strong>of</strong> tour and six days, respectively(Conyelton et al. 1982). This is fur<strong>the</strong>rsupported by Levy and Northcote's (1981)approximation <strong>of</strong> 6 days individual resi -dence time <strong>of</strong> juvenile chinook in aFraser Hi ver estuary bl i nd tidal channel.However, because nos t <strong>of</strong> <strong>the</strong>se sal t-narsh/mudflat tidal channel studiesexamined residence in only one <strong>channels</strong>ystem and because occupation <strong>of</strong> aspecific channel may be brief, overallresidence throughout <strong>the</strong> bl i nd and subsidiary<strong>channels</strong> <strong>of</strong> sal marshes and tideflats may be significantly longer. Levyand Northcote (1982) indicated maximumindividual residence times <strong>of</strong> 30 days forjuvenile chinook (fry), 11 days for chum,and two days for pink. Levy et al.(1979) had also indicated that juvenilechinook (fry) had <strong>the</strong> Strongest fidel ityto particular tidal channel areas,followed by juvenile chums, and juvenilepinks. <strong>The</strong>y suggested shortest residencyfor juvenile pink salmon, intermediateresidency for juvenile chum, and longestresidency for chinook (fry); <strong>the</strong> variationin residency was possibly related to<strong>the</strong>ir distribution within <strong>the</strong> <strong>channels</strong> and<strong>the</strong> timing <strong>of</strong> emigration on ebbing tides.Detailed mu1 tivariate analyses <strong>of</strong> spatialdifferences in tidal channel uti l izationby juvenile salmonids in Fraser River
Fig. 6.4. Tidal channel trap net set in blind channel <strong>of</strong> Fraser Rivar estuary to samplejuvenile salmon utilizing saltlnarsh habitat; net is set at flood slack (A), allowed tosarrrple thr-ough <strong>the</strong> ebb tide (R, C) , and sarllpl ing culrllinated at ebb slack (0) when only asnrall depth <strong>of</strong> water remains in <strong>the</strong> channel (photographs courtesy <strong>of</strong> David Levy. NestwaterResearch Centre, University <strong>of</strong> British Colurnhia, Canada).saltnrarshes has also indicated that juverillech~nook (fry) abundance IS highlycorrelated to <strong>the</strong> amount <strong>of</strong> habitat ava~lableto <strong>the</strong> frsh, Lower (bank) elevat~onareas tend to support higher dens'ities <strong>of</strong>juvenile chinook (fry) (Levy and Northcow1981). Variables included tidalchannel descriptors such as inouth wldth,station width, channel length, channelorder, sub-channel length, mean angle <strong>of</strong>cnannel bank, tidal slope, high tideheight. tidal channel area, bank elevation,area <strong>of</strong> subtidal refugia, and number<strong>of</strong> hours <strong>of</strong> tidal channel subrnergenceprior to sampling; (see Appendix 6).Following residence and growth in<strong>the</strong> littoral flat <strong>channels</strong>, juvenile chumand chinook (fry) move into larger subsidiary and mai nstern <strong>channels</strong> (Heal ey 1979,1980; Simenstad and Eggers 1981). Thistransition from 1 i t toral and shall ow sub-
Table 6.4. Species residence times (weeks)' <strong>of</strong> juvenile salmon in !lashinaton Statcestuaries; niaxiiliuni individual residznce times (days) are indicated in paren<strong>the</strong>szs (froniSiinenstad et a1 . 1982b).-- .-- ----- . .- -----.-- -- ---.--- EstuaryP iii -----CXUmum-Sock ey e. CKook-. -.-.- .-- - Source- - - --- - ---- - -.- . ---- ---Nor<strong>the</strong>rn Puget Sound (nearshore) 4 6 12 12 6 Miller et al. 1978North Sound (Bellingham Bay) 11+ 114(Bellingham Bay) 7+ 7( nearshore) 4 6 6Skagit BaylPort Susan (Kiket Island) 13 13 12(saI tmarsh) 14+, (4)Elliott Bay (lower Duwamish)(estuary)(lower Duwami sh)Cornencement Bay (estuary) 16+ B 9(Hylehos Waterway) 9ll+ Tyler 19646+, (-20) Sjolseth 196R6 Miller et al. 1978;Fresh 191915, (50) Stober et al. 1973b16+, (6) Longleton et dl. 19G28. (42) Bostick 19558 Salo 136916+ Mcyer et al. 1981b9+ Puyallup lndian Nation,unp11bl.8+ Meyer et dl. 198laNisqually Reach 12 17+ 15, (-40) 11+ Fresh et dl. 1979Hood Canal 18 23, (32) 15, (6) 13 Salo et al. 1900Strait <strong>of</strong> Juan de Fuca 14 14 14 16+ Slmenstad, unpuhl.Quil layute River estuary 5, (32) 18+ Chi twood 1981Grays Harbor 10 Wendler et al. 1954lo+, (-30) 12 29+, (489) Simenstad and Eggers 1981- - - - - - - --I- and + indicate less than and greater than <strong>the</strong> values given, respectively.littoral channel habitats to utilization<strong>of</strong> pelayic, mainstem channel habitatsgenerally occurs when both juvenile chumand chi nook (fry) reach 50-60 mm FL (Levyet al. 1979; Healey 1980; Levy and Northcote1981, 1982; Keimers 1973; Simenstadand Eggers 1981). A number <strong>of</strong> mechanismsaccounting for this shift in habitat utilization have been proposed, incl uding salini ty and temperature preference (Dun ford1975; Healey 1980), behavioral responsesas a function <strong>of</strong> density and size (Reimers1973; Myers and Horton 1982), and <strong>the</strong>avai 1 abi 1 i ty <strong>of</strong> preferred prey oryanismsor ontogenetic chanyes in food habits(Simenstad and Eggers 1981; Simenstad andSalo 1982).Individual residence times in <strong>the</strong>mainstem <strong>channels</strong> vary as a function <strong>of</strong><strong>the</strong> period in <strong>the</strong> salmon miyration, size<strong>of</strong> <strong>the</strong> fish, and density <strong>of</strong> <strong>the</strong> <strong>estuarine</strong>popul ation. Juveni 1 e pink salmon appearto emigrate directly out <strong>of</strong> <strong>the</strong> estuary,since no records <strong>of</strong> pelagic residence areavailable for Washington (lable 6.4) oro<strong>the</strong>r estuaries in <strong>the</strong> region. Juvenilechum may reside in pelayic habitats <strong>of</strong>mainstem <strong>channels</strong> for an additional twoto four weeks (Table 6.4; Manzer 1956;Mason 1974; Healey 1979) but seldom occurin <strong>the</strong>se environs when larger than 75-80mm FL. Healey (1979) also indicated thatjuvenile chums from <strong>the</strong> early portion <strong>of</strong><strong>the</strong> outmiyrating popul ation resided in ttleNanaimo River estuary considerably longerthan those which entered <strong>the</strong> estuary laterin <strong>the</strong> outmigration. Salo et al. (198O),Simenstad and Salo (1982) and Bax (1982),however, have documented <strong>the</strong> opposite relationshipin Hood Canal, where migrationrates tended to be higher and residencetimes shorter for <strong>the</strong> earlier outmlyratingpopulation. Juvenile chinook (fry)may reside in <strong>estuarine</strong> <strong>channels</strong> 1 ongerthan six months, but residence is quitevariable among estuaries. Keirners (1973)identified five 1 ife history variationsin <strong>the</strong> population <strong>of</strong> fall chinook inSixes River, Oregon. <strong>The</strong> prominent type
esides in <strong>the</strong> estuary a relatively shorttime (eight weeks) before emigrating to<strong>the</strong> ocean whereas a second type rearsalmost twice as long but is measurablyless abundant in <strong>the</strong> estuary (17% <strong>of</strong>total migrants); <strong>the</strong> latter life historytype, however, typical ly contributed over90% <strong>of</strong> <strong>the</strong> returning adults. <strong>The</strong> o<strong>the</strong>rtypes passed rapidly throuyn <strong>the</strong> estuaryei<strong>the</strong>r as fry or as yearling smolts butwere seldom abundant. A1 though earl ierwork (Simms 197U) estimated brief, i .e.,10-15 days in spring and summer and 7-10days later in <strong>the</strong> year, residence tirnesfor juvenile chinook (fry) in <strong>the</strong> Colun~biaKiver estuary, rnore recent results (Natl .Mar. Fish. Serv. 1981) trom on-goiny narkand recapture experiments have indicatedextended residence from Apri 1 throuyhOctober. Residency patterns very simi 1 arto those documented in <strong>the</strong> Sixes Kiverestuary have also been described for juvenilefall chinook (fry) in Grays Harbor(Simenstad and Eggers 1981), <strong>the</strong> Ouwami shRiver estuary (Salo 1969), and <strong>the</strong> QuillayuteRiver estuary (Chi twood 1981).Chinook snio Its (year1 ing) probably appearin <strong>estuarine</strong> <strong>channels</strong> only transitional ly ,as no significant <strong>estuarine</strong> residencetimes have been described for this lifehistory type. Similar to yearling chinook,coho smolts also utilize <strong>estuarine</strong><strong>channels</strong> principal ly as corridors for directemigration to <strong>the</strong> ocean (SjolSeth1969; Simms 1970; Chitwood 1961; Natl .Ilar. Fish Serv. 1981), but residence timesas long as four to eight weeks have beendocumented (Grays Harbor, Simenstad andEggers 1981). No information on individualresidence times <strong>of</strong> sockeye smolts isavailable nor is <strong>the</strong>re an indication that<strong>the</strong>y utilize <strong>estuarine</strong> <strong>channels</strong> o<strong>the</strong>rthan for <strong>the</strong>ir immediate migration fromlacustrine rearing habitats to <strong>the</strong> North<strong>Pacific</strong> Ocean. In fact, <strong>the</strong> occurrence <strong>of</strong>juvenile sockeye in <strong>estuarine</strong> <strong>channels</strong>has only been documented for <strong>the</strong> ColumbiaRiver (ktl, Mar. Fish. Serv. 1980, 1981),Fraser River (Northcote et al. 1979), and<strong>the</strong> Quillayute River estuaries (Chitwood1981).Entry <strong>of</strong> adult salmon into <strong>estuarine</strong><strong>channels</strong> prior to <strong>the</strong>ir migration upriveroccurs essentially year-round, although<strong>the</strong> maximum migration period is typicallybetween July and September (Table 6.3 and6.5). Although tirning <strong>of</strong> return is principallydetermined uy <strong>the</strong> genetic attributes<strong>of</strong> <strong>the</strong> different species and populations,external influences such as oceanictemperature and current patterns, preyresources and photoperi od add el enients <strong>of</strong>variability to <strong>the</strong> temporal distribution<strong>of</strong> returning spawners (Simenstad et al.1982b). Once in <strong>the</strong> estuary, fish mayaygregate in specific, "staginy" areasbefore initiating <strong>the</strong> final phase <strong>of</strong><strong>the</strong>ir spawniny III~ gration; upriver movementsare probably stimulated by increasesin river discharge, changes in watertemperature and air pressure, and tidalcycles. As a result, residence time <strong>of</strong>adults within <strong>estuarine</strong> <strong>channels</strong>, althouyhtypically brief, has been estimated torange from 1-6 weeks (Simenstad et al.1982b; Table 6.5) and <strong>the</strong> fish are <strong>of</strong>tensubjected to intense corn~nercial andrecreational exploitation in <strong>the</strong>sechannel staying areas duri ng this period.O<strong>the</strong>r anadrornous fishes include Americanshad, longfin smelt, eulachon, andstriped bass. Of <strong>the</strong>se, American shad andstriped bass are distributed principal lyin <strong>the</strong> sou<strong>the</strong>rn <strong>coast</strong>al estuaries <strong>of</strong> <strong>the</strong>region, a1 though striped bass have beenreported in Puyet Sound (Mi 1 ler andBorton 1980) and American shad occur inapparent spawning popul ations in severalPuget Sound estuaries--Nooksack, Skagi t,Sti 1 layuamish, and Skykomi sh (Mi 1 ler andBorton 1980). <strong>The</strong>se latter two specieswere not oriyinally indigenous to <strong>the</strong>west <strong>coast</strong> and have continued to expand<strong>the</strong>ir distribution from San Francisco gaywhere both were introduced in <strong>the</strong> late180U's or from <strong>the</strong> Columbia Kiver whereshad were introduced in 1885-1886 (Hart1973; Wydoski and Whitney 1979).American shad are <strong>the</strong> rnore prominent,especially in <strong>the</strong> large <strong>coast</strong>al estuariessuch as <strong>the</strong> Columbia Kiver and GraysHarbor. In <strong>the</strong> Columbia River <strong>the</strong> adultmigration through <strong>the</strong> estuary is usuallyinitiated in May, coincident with 13-18OCwater temperatures (Leggett and Whitney1972), and peaks in June and July. Juvenile (young-<strong>of</strong>-<strong>the</strong>-year) shad enter <strong>the</strong>
Table 6.5. General <strong>estuarine</strong> run ti1:iing and estilllated il,dividua] residerice til:les foradult <strong>Pacific</strong> salrilorl in 'lashinnton State estua,.ies (froln Silllenstad ct a1 . 198:'b).-- ---- - _.fimdfgd -i;;divi-d;al-resraence-P--Run timing 1(tine in days)Seec i es eik ~-d;;@---- Ka. x.rm-.m----- -- ---- -.--- - -- - -- -- -- -- ____--______._._____--I_"_.-___----------KirrcnumBa ta souic2--- -Pink Late July-early Aug. June-Sept. 6.9 13.7 Barker 1979(only in odd years) 8.1 32.2 Barker 1979Sockeye July June- Aug. -Coho Late Oct. Sept.-Nov. 13.0 40.0 Eames et dl. 1981;in press9.2 14.7 Barker 1979Chi nook Late Aug.-early Sept. July-Sept. 27.4 39.6 Stauffer 1970Mi d-0ct.-early Nov. Sept.-Dec. 11.0 40.0 Eames et dl. 1981;in press3.0 6.8 Rarker 197913.0 20.6 Olney 1976f I*,,:,vdr' >us Wdr:lillg toll Depdt't:ileflt <strong>of</strong> Fisheries (ifarves t Yandc]cr?ct~t nivision) d??n sources.estuary beginniny in Auyust and reside<strong>the</strong>re, reaching maxi~rlunl density inNovember and December, unti 1 eniigrat ingto <strong>the</strong> ocean as yearlinys when <strong>the</strong> youny<strong>of</strong>-<strong>the</strong>-yearshad become nurnerous in October(Ha~riniann 1981; Natl. Mar. tish. Serv.1981). Simenstad and Eyyers (1981) reporteda rnaxi~num sustained residence <strong>of</strong>at least 10 weeks, but <strong>the</strong>ir sampling didnot extend beyond October.Lonyfin smelt and eul achon are anadroriiousosmerids that mi y rdte throuyh Pacif ic <strong>Northwest</strong> estuaries as adults durinywi nter months, but solrie spawn ing Itlay actually occur in <strong>the</strong> more freshwater-dominatedsysterris such as <strong>the</strong> Columbia Kiverestuary (Mi si tano 1977; kt1 . Mar. Fish.Serv. 1981). Up to three different ageclasses <strong>of</strong> longtin smelt, dominated by<strong>the</strong> young-<strong>of</strong> -<strong>the</strong>-year and year1 inys, wereidentified in <strong>the</strong> Colurnbia River estuary(Iktl. Mar. Fish. Serv. 1981). ~esidenceuf young-<strong>of</strong>-<strong>the</strong>-year was sustained fromJune throuyh <strong>the</strong> winter <strong>of</strong> <strong>the</strong> followingyear but was confused by <strong>the</strong> influx <strong>of</strong>spawniny adults in <strong>the</strong> fall. Occurrence<strong>of</strong> lonyfin smelt documented by simenstadand Eggers (1981) indicated more ephemeraldistribution <strong>of</strong> juveniles in GraysHarbor, at least in <strong>the</strong> inner reaches <strong>of</strong><strong>the</strong> estuary, where three major influxes(<strong>the</strong> longest residence lasti rig 3 weeks)were evident betweerr March and October.Juvenile longt in s~rrel t also appear touti 1 i ze <strong>estuarine</strong> <strong>channels</strong> within PuyetSound (Duwa~rii sri, Skyko~rii sh, St i 1 1 i yuamish, Skagit and Nooksack Kiver estuaries;Miller and Borton 1980) and <strong>the</strong> Straits<strong>of</strong> Georyia (Fraser River estuary; Northcoteet al. 1Y7Y), but <strong>the</strong>y are much morecolilmon in <strong>the</strong> nerit'ic hdbi t"ats outsidetne estuaries proper (Stuber et dl.1973a; Miller et al. 1978, 1980; Fresh1979). Colrlpared to lonytin smelt, eulachonare so~r~ewhat 1 ess prominent i n<strong>estuarine</strong> <strong>channels</strong>, but both adults dndjuveniles are comrnon in estuaries <strong>of</strong>rivers with spawniny populations, notably<strong>the</strong> Colunibia Hiver (Smi ti1 and Saalfield1955; Haertel and Osterberg 1967; Natl .Mar. Fish. Serv. 1981), Fraser Kiver(McHugh 1939, 1940; Nortncote et al.1979), Squamish Ki ver (levy and Levi nys1978), Nooksack Kiver (Mydoski and Whitney1979), and Puyal ]UP River (CommencementBay, Miller and B0rton 1980) estuaries.AI though eul achon were reported to occurin tirays Harbor (Smith et a1 . 1980), nonewere captured duriny <strong>the</strong> extensive samplinyin that estuary described by Simenstadand Egyers (1981). <strong>The</strong>ir occurrencein <strong>the</strong> Columbia River estuary js concentratedbetween February and May as a re-
sult <strong>of</strong> <strong>the</strong> migration <strong>of</strong> adults into <strong>the</strong> where <strong>the</strong>y are as abundant as, or secondestuary and its tributaries and <strong>the</strong> down- in abundance to, <strong>the</strong> predominant <strong>Pacific</strong>stream drift <strong>of</strong> <strong>the</strong> yolk-bearing larvae herring larvae, but <strong>the</strong>y are relativelythrough <strong>the</strong> estuary (Misitano 1977; ktl. rare in and north <strong>of</strong> <strong>the</strong> Columbia RiverMar. Fish. Serv. 1981). Despite this estuary.brief occurrence, Mi sitano (1977) listedeul achon as <strong>the</strong> second most abundant (19%Occurrence <strong>of</strong> ichthyopl ankton in <strong>the</strong><strong>of</strong> total) larval, post-larval, and juve- region's estuaries is essentially ani le fishes in <strong>the</strong> Columbia River estu- winter-spring phenomenon, both in termsary. Prolonged residence within <strong>the</strong> <strong>of</strong> species richness (as many as 18 speestuaryappears to be minimal, however. cies per sample) and density (maximabetween 0.4 and 11.0 larvae m-3) in <strong>the</strong>Althouyh only a relatively recent <strong>coast</strong>al estuaries. Tidal and die1addition to <strong>the</strong> anadromous fishes in <strong>the</strong> variation can be considerable and isregion, striped bass have become promi- <strong>of</strong>ten associated with location in <strong>the</strong>nently established in Coos Bay (Roye estuary; for example, tidal excursion <strong>of</strong>1979) and Umpqua River estuary (Mu1 len water inasses with particul arly high densi-1972, 1974; Ratti 1979a). Residence <strong>of</strong> ties <strong>of</strong> larvae can result in high catchesadults in Coos Bay may be continuous, during ebb tide periods (Pearcy anda1 though some may emigrate to <strong>the</strong> ocean, Myers 1974), especially in situationsand <strong>the</strong>n migrate upriver to spawn between where shal low sub1 i ttoral and 1 i ttoralMay and July. Juveniles spend <strong>the</strong> first flat habitats are sources <strong>of</strong> larvae.year in ri verine habitats before immigra- Contributions <strong>of</strong> predoini nantly <strong>of</strong>fshore,ting to <strong>the</strong> estuary. i.e., marine, species into <strong>the</strong> moresaline, lower reaches <strong>of</strong> <strong>the</strong> estuaries6.2.3 Ichthyoplankton also promotes higher species richness in<strong>the</strong>se regions. Pearcy and Myers (1974)In addition to those pelagic fishes itemized 19 taxa <strong>of</strong> fish larvae in Yaquinawhich are found in <strong>estuarine</strong> <strong>channels</strong> Bay which were characteristic <strong>of</strong> <strong>of</strong>fshorethroughout <strong>the</strong>ir development from 1 arvae assemblages, as compared to ten taxa assoorpostlarvae to at least juvenile stag- ciated with bay assemblages, and Misitanoes, approximately 17 species also occur (1977) documented a steady decline in <strong>the</strong>as prominerit ichthyoplankters but move number <strong>of</strong> species <strong>of</strong> larval, post-larval,ei<strong>the</strong>r into o<strong>the</strong>r microhabi tats within and juvenile fishes collected at progress<strong>the</strong><strong>channels</strong> or into adjacent <strong>estuarine</strong>, ively more <strong>estuarine</strong> to riverine l0camarine,or riverine habitats (Table 6.2). tions in <strong>the</strong> Columbia River estuary.Those which undergo ontogenetic transpositionfrom pelagic to demersal modes with- While many <strong>of</strong> <strong>the</strong> same assemblagesin <strong>the</strong> <strong>channels</strong> include <strong>Pacific</strong> tonlcod, and patterns that occur in <strong>the</strong> <strong>coast</strong>alsnake prickleback, saddleback gunnel , estuaries may characterize inland esturockfishes,yreenlings and lingcod, all aries, <strong>the</strong>re is no comparable informationfour species <strong>of</strong> cottids and four species on <strong>the</strong> ichthyoplankton in <strong>estuarine</strong> chan<strong>of</strong>pleuronectids. Of <strong>the</strong>se, prickly, nels inside <strong>of</strong> <strong>the</strong> Strait <strong>of</strong> Juan de<strong>Pacific</strong> staghorn, buffalo scul pins, and Fuca. Blackburn's (1973) documentationsnake prickleback are <strong>the</strong> more common and <strong>of</strong> <strong>the</strong> ichthyoplankton assemblages <strong>of</strong>fabundant(Eldridge and Bryan 1972; Pearcy shore <strong>of</strong> <strong>the</strong> Skagit River delta indicateand Myers 1974; Mi si tan0 1977; Simenstadand Eggers 1981). bong those whichthat taxonomic simi 1 aritieswith <strong>the</strong> addition <strong>of</strong> severalmay exist,species <strong>of</strong>settle out in adjacent habitats, <strong>the</strong> baygoby is <strong>the</strong> most prevalent as an ichthyogadids(<strong>Pacific</strong> cod, Gadus macrocephalus,and <strong>Pacific</strong> hake, ~e-cius productus)p1 ankter before it assumes its ultimate and pl euronectids (slender sole, Lyopsetjuvenileand adult residence in shallowsub1 ittora] and 1 i ttoral f 1 at habitats.%.exilis), but spatial or tempormtri buti on and abundance <strong>of</strong> 1 arvae withinBay goby larvae are especially abundant <strong>the</strong> estuary's channel habitats were notin <strong>the</strong> more sou<strong>the</strong>rn <strong>coast</strong>al estuaries assessed.86
CHAPTER 7BIRD ASSEMBLAGES OF ESTUARINE CHANNELSAlthough some <strong>of</strong> <strong>the</strong> resident andmigratory bird species utilizing <strong>Pacific</strong><strong>Northwest</strong> estuaries do not frequent channelhabitats, most <strong>of</strong> <strong>the</strong>se estuaries'avian fauna occupy <strong>channels</strong> at some timefor foraging and roosting, and some aredependently bound to <strong>the</strong> habitat throughcritical food web 1 inkages. Severalspecies, notably <strong>the</strong> migratory waterfowl ,can occur in such high abundance that<strong>the</strong>y play significant, though <strong>of</strong>tenseasonal, roles in <strong>the</strong> food-web dynamics<strong>of</strong> <strong>the</strong>se estuaries.Adopting Peterson and Peterson's(1979) classification <strong>of</strong> 1 ittoral flatbirds into ecological assembl ayes or"guilds, "5 <strong>estuarine</strong> channel birds havebeen categorized into four assemblagesprimarily as a functon <strong>of</strong> <strong>the</strong>ir foragingbehavior: 1) shallow-probing and surfacesearchingshorebirds; 2) waders; 3) surfaceand diving waterbirds; and 4) aerialsearchiny bi rds.Habitat-specific inventories and descriptions<strong>of</strong> birds <strong>of</strong> <strong>Pacific</strong> <strong>Northwest</strong>estuaries are rare and typically inadequatein <strong>the</strong> scope and resolution <strong>of</strong> <strong>the</strong>documentation <strong>of</strong> bird di stri bution, abundance,behavior or <strong>ecology</strong>. Jones andStokes Associates, Inc. (in prep.) is <strong>the</strong>most complete in terms <strong>of</strong> temporal (seasonal) and spati a1 (habitat, areal ) documentation<strong>of</strong> birds occurriny in any oneestuary (e.y., <strong>the</strong> Columbia River). 0th-5~ will refrain, however, from using<strong>the</strong> term "guild" because <strong>of</strong> <strong>the</strong> assumption<strong>of</strong> common exploitation <strong>of</strong> an investigator;defined resource (Root 1967; Jaksic1981), opting instead for "assemblage,"which is more broadly defined as a group<strong>of</strong> syntopic related taxa.er estuary-oriented accounts includeYocum and Keller (1961), Ives and Saltzman(197O), Smith and Mudd (1976a), Seaman(1977), Crawford and Edwards (1978),Peter et al. (1978), and Edwards (1979).More taxa-speci fic documentation includesWetmore (1924) on grebes, Henny and Be<strong>the</strong>rs(1971) and Bayer (1978) on great blueherons, Erskine (1971) on buff1 eheads,Couch (1964) on sandpipers, Pen1 and (1976)on terns, and Vermeer and Levinys (1977)on ducks. General references descri bi nyspecies <strong>of</strong> <strong>estuarine</strong> birds and some <strong>of</strong><strong>the</strong>ir habits in <strong>Pacific</strong> <strong>Northwest</strong> estuariesinclude Gabrielson and Jewett (1940),Jewett et al. (1953), Eaton (1975), Salo(1975), Manuwal (1977), and Simenstad eta1 . (1979a). <strong>The</strong> most authoritative,quantitative information, that includedin Wahl et a1. (1981), encompassednor<strong>the</strong>rn Puyet Sound and <strong>the</strong> Straits <strong>of</strong>Georgia and Juan de Fuca but seldom coveredor ditferentiated bird assemblagesin true <strong>estuarine</strong> <strong>channels</strong>.Syn<strong>the</strong>sis <strong>of</strong> <strong>the</strong>se references and <strong>of</strong>pertinent <strong>coast</strong>al inventories (U. S. Dep.Interior 1971; Monroe et al. 1974; Kreag1979a, b, c; Ratti 1979a, b; Roye 1979;Starr 1979a, b; Proctor et 31. 1980; Beccasioet al, 1981) indicate that 59 species<strong>of</strong> birds are common to <strong>the</strong> region's<strong>estuarine</strong> channel habitats, 23 <strong>of</strong> whichcould be considered prevalent (abundant)(Table 7.1; Fig. 7.1, 7.2).7.1 SHALLOW-PROBING AND SURFACE-SEAKCHINGSHOREBIRDSCharacteristic <strong>of</strong> <strong>the</strong>ir foraging onor within sediment surface layers, birds<strong>of</strong> this assemblage occupy shore1 i ne envi -rons constituting <strong>the</strong> boundaries betweenchannel and o<strong>the</strong>r <strong>estuarine</strong> habitats.Comprising slightly more than 25% <strong>of</strong> <strong>the</strong>
Table 7.1. Itemization and characteristics <strong>of</strong> birds comon to <strong>estuarine</strong> <strong>channels</strong> <strong>of</strong><strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>, organized by assemblage.TaK- -- --- - ---I-- 3-ann T----- SaTTnnyTeTi;aX me- '-%blage- --- -(conmon - name) - --habi tats1 associ ations2 history characteristics3 ------- --Shal low-problng and Haernato us bachmnl M E 0 -8surface-search1 ng o d b ~ a c oystercatcher)kshorebirds*~haradrtus alexandrt nus M-B0-B; Seasonal transient(5nowyoTerl-C. seml alrnatus~se*orcr)M-B R -E 0-B; Seasonal transientPluvial is s uatarol ama-1 &-p~r)M-BR-E0-B;Seasonal transientM-BR -E0-BM-BR-E0-B;Seasonal transientM-BR-E0-BL scolo aceus~io~&3owlA hrlza vlr ate~&*ifaP--- -tcherlM-Bn,sArenarla inter resM,S~ ~ ~ U Z Y O ~R-EM-E0-E0-B0-8; Seasonal transient0-B; Seasonal transient*cat ldrl s a1 baTSiinnGFfl ngl-M-BR -E0-8; Seasonal transientM-B0; Seasonal transientM-BR-E0*c. maurl M-B R -E(~6s~e%-sandplper)C. minutllla M-B R-EReTsXnii per )Ph;arop;s 1 oba tus M M-E-nec ed phalarope)00-80,F-PK;Seasonal transientWaders*~rin~a wl anoleuca H-0 R -E'IT;rc?atci;~T&wTeigsF-0;Seasonal transient*~rdea herodias M-B R-ETr;F6StTiTGTTiiron)0-PSBubulcus I blsTFa'FKTeeFet)R-EF-PSCasnerodius a1 busTGreat egretr-S9-retta thul anowy eg-M-BM-B(continued!R-E0-PS0-PS
-Table 7.1. Continued.Taxa ---Tli%ini - -TaTfnTQ-- - - e evant lffe- ---Assemblage ( comno n name) habitats1 associations2 hlstO~1characteri~ti~~3 'Surface and diving *~echmophorus Occidental iwaterbirds mestern grebe) R -E 0-PS;;dfceis auri tusorne gG&'l--ke%&%?grebe) M,S R-EF-ps; seasonal transient0-PS; seasonal transientP. nigricollisEared grebe)R-E 0-PK; Seasonal transienthala lac roc or ax auri tus MsS R-E 0-PS7Doubl e-crested0Pm)rant)* b e ~ m r a n t ) M.S M-E F-PSergus us mer anser M-B R-E 0-PSKGiEn me:ganser)M. serrator M-8 R-E F-PS; Seasonal transientTRea-breasted merganser)M M-E 0-PS; Seasonal transientCepphus columba M M-E F-PS(Pigeon @71Ekt)Cerorhinca monocerata(Rhinocerosauklet)M-EBrach rarn hus mannoratus M H-E F-PSm e rBranta bernicl a s.6 R-E 0-H; Seasonal transient-m)-*~nas platyrhynchos M-8 R-H 0, F-H; Seasonal tranmaTlard)sient; primarily roostingin habi tatA. acuta M-0 R -M 0. F-H; Primarily roost-T~oZliFn pintail )Ing in habitatA. crecca M-B R -M 0, F-H; Seasonal tran-TGrGGXnged teal )sient; Primarily roostingin habitat*A. a~nericana<strong>The</strong>rican wigeon)M-B0. F-H; Seasonal transient;Primarily roostingin habitatAythya valisineria(Canvasback 1M-BR-M0, F-H; Seasonal transient;Primarily roostingin habi tatA. marilaTGrFZiF"-scdup )M-S R -E F-8; Seasonal transient(continued)89
Concluded.niT--' TinTfy---'---- - Pelevatt 1 i fe ---'-Ise:ge ------~-.-------~--_----_------------ (common name) habl tats1 associatfons2 --. hlsto!y characte?2st~c?Table 7.1.-'-Tar- ------.-Surfac~ dnd drviny 'A, afffnlswd terb t rds - cnnt 'd. ResrCerf?ICaup)M-S R-E 0. F-B; Seasonal transient.Primarily roostingin habitatBucephela clanpule M-R R-E B-0; Seasonal transientKooibniijaTiicriG~P70. albeolarnurtl e ~ ~ i d )M-I3 R-E F - 0'Relanl tta fusce M-§ R -E F-B; Seasonal transient7Zlh'fT e-iTn33ddS~ o t er)'M. perrpfclllata M-S R -E F-BTSurT scotE-i.T--'Acrtal-searching birdsCrr 1.alc ond-trj&tshrr)'lsrur 91 rucescrnr M-H R -E F -0~aucou"s=%Tnghd 9111 1)L. occfdentalis M-8 R-ETLer t'i;riT gun T 'I. calf forn$cus 4l-R R-E F-B; Seasonal transientlGaT ir<strong>of</strong>ifL-giu7111. drlawarensit M-R R -E F-0; Sesronal transientmi ng-bTT7ad gull1. LeecCrl"p~t~i M-5 R-E F-B, Learonal tran~icntTiicc~rannT.~u\ I )'L. phftabelphta n-5 M-E F -PYIBanipYif$ s girl 1 )M,S W-E 5-PS; 5casonal transient*s. casptaFCaspidn tern)M,5 M-E F -P\; kasonal transientPel ~c .%nus occ1denf.d~ 1 \ M P-E 5-PS; 5easonal transientpF;i,-T6"l Fini - -- . -Stercorarlus paras!_tljfu~ H-B R-E F-PS, K. Searondltransient--. -.- -- - > * - ---?h+a
Anab plalyrhyn~hnsA dmBrh^BndLITTORAL FLATSSUBSIMARY CHANNELSBLlNCJ CHANNELSFig. 7.1. Representative i 11 ustraii on <strong>of</strong> common bird assemblages <strong>of</strong> cstuarine <strong>channels</strong><strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.common species and five <strong>of</strong> <strong>the</strong> prevalentspecies (three families in <strong>the</strong> orderCharadri i formes; Haematopodidae, Charadri -idae, and Scol opacidae) , <strong>the</strong>se shorebirdsare typically seen actively feeding in<strong>the</strong> substrate along <strong>the</strong> shorel ine, particularlyat high tide when littoral flathabitats, <strong>the</strong> preferred foraginy habitat<strong>of</strong> most, are inundated. Due to <strong>the</strong> yenera1lack <strong>of</strong> daylight minus tides betweenSeptember and February, much <strong>of</strong> <strong>the</strong> fallwinterforaging by this assemblage isconceritrated closer to and about <strong>channels</strong>hore1 ines. Some (kerican bl ack oystercatcher,snowy plover, whimbr~l , bothdowitchers, dunlin, knot, sanderling)appear singly or in small, looselyassociated groups whil e o<strong>the</strong>rs (sandpipers,surfbird, ruddy turnstone) occurin dense, tightly associated flocks.Considerable habitat parti tioninyresults as a function <strong>of</strong> <strong>the</strong> heterogeneity<strong>of</strong> shoreline substrates. Thus, currentand wave exposure which influencessediment characteristics <strong>of</strong> <strong>channels</strong>horel i nes deternlines, to a 1 arye extent,<strong>the</strong> species composition <strong>of</strong> this assemblaye. For example, black oystercatchersare typically found along rocky cliffs,headlands, and jetties in <strong>the</strong> euhalineregion <strong>of</strong> those estuaries which possessthis habitat (predominantly in Oregon) ;dun1 ins. western sandpi yers, sander1 i ngs ,and knots appear commonly on exposed sandbeaches in <strong>the</strong> lower reaches <strong>of</strong> <strong>the</strong> estuaries; and whimbrels and dowitchers characterize<strong>the</strong> more protected, inner baysand flats. Tidal fluctuations affecting<strong>the</strong> avail abil i ty <strong>of</strong> preferred foraginghabitats and microhabi tats, however,
. .t-lq. 7.7. Representative avifauna <strong>of</strong> <strong>estuarine</strong> channel habitats in <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>:A) feeding dowitchers; 6) sprin~ flock <strong>of</strong> western sandpipers, dunlins, and shortbi.1led dowi tchcrs; C) feeding nmle nor<strong>the</strong>rn pintai 1s; D) adult CGlIlrlion loon (Gavi?. i1111ner)ir winter !;lui!iage; E) fll1 +lock <strong>of</strong> California and tieernlann's gulls; and, F) adult aonaparte';gill1 in winter pl~ii~~age. Ail photographs courtesy <strong>of</strong> Dr. Dennis Pau!son, LJniversiiy<strong>of</strong> Washington.
induce considerable ~lioveinent about <strong>the</strong>estuary and many species periodicallyfrequent a diversity <strong>of</strong> habitats. Assuch, considerable spatial overlap inforaying space is imposed upon <strong>the</strong>seshorebirds, which may be responsible for<strong>the</strong> evolution <strong>of</strong> diverse feeding behaviorsand bi 11 morphologies (Kecher 1966).Distribution <strong>of</strong> <strong>the</strong> assemblayethrouyhout <strong>the</strong> region is relativelyuni forni wi th some exceptions (Beccasio etal. 1981). For example, snowy ploversare concentrated along <strong>the</strong> marine margins<strong>of</strong> <strong>the</strong> sou<strong>the</strong>rn estuaries and dun1 ins appearmore in <strong>the</strong> central <strong>coast</strong>al estuaries(1.. Tillamook Bay, Willapa Bay,Grays Harbor), and, in general, <strong>the</strong> migratoryspecies are more commonly encounteredin abundance along <strong>the</strong> <strong>coast</strong>al estuariesthan in <strong>the</strong> inland estuaries, which areinore re~iioved from <strong>the</strong> mainstream <strong>of</strong> <strong>the</strong>Pacitic Flyway.Approxiinately a third <strong>of</strong> <strong>the</strong> assemblayeare migrants and <strong>the</strong>ir abundancestypical ly reach maxima in spring (Apri 1 -May) and fa1 1 (September-November) , when<strong>the</strong>y are migrating through <strong>the</strong> <strong>Pacific</strong><strong>Northwest</strong>. Intermediate 1 eve1 s <strong>of</strong> abundancein <strong>the</strong> winter are associated withoverwinteriny <strong>of</strong> soine species in <strong>the</strong> estuaries.This variation is illustrated by<strong>the</strong> corrected aerial estinlates <strong>of</strong> totalshorebird abundances in Grays Harborbetween September 1974 and October 1975which fl uctuated between averages <strong>of</strong>65,833 in spriny, 19,700 in summer, 52,500in fall and 21,533 in winter (Smith andMudd 1976a). Similarly, Jones and StokesAssociates, Inc.'s (in prep.) summary <strong>of</strong><strong>the</strong>ir 1980-1981 CKEDDP studies <strong>of</strong> <strong>the</strong>avifauna in <strong>the</strong> Columbia River estuaryindicated densities <strong>of</strong> "peeps" (confinedto <strong>the</strong> "key" species <strong>of</strong> dunlin, sanderling,a d western sandpiper) as high as378 km- 9 in spring , 766 ~J-I-~ in fa1 1, and961 kin-2 in winter, but peeps arevirtually absent in <strong>the</strong> summer. Distribution<strong>of</strong> <strong>the</strong> assemblage was also broadest,essential ly covering <strong>the</strong> whole estuarybut concentrating on mid-estuary, in <strong>the</strong>spriny and was more restricted in <strong>the</strong>fa1 1. Significant overwintering was observedonly at one site in <strong>the</strong> upper estu-ary, although "peep" density along a linear transect was estinldted at 337 km-Iduriny that period.7.2 WADERSThi s assernbl age, confined to bi rdsthat wade throuyh shal low-water portions<strong>of</strong> <strong>the</strong> channel in search <strong>of</strong> invertebrateand fish prey, is composed <strong>of</strong> two yroupswhich are quite di fferent in distributionand ecol oyy. Greater ye1 1 owl egs (Fami lyScolopacidae) forage a1 ony channel shoresand shallows in water 5 to 10 cm deep andthus are found within channel haoitatsonly when blind <strong>channels</strong> are tidally dewatered.Like inany <strong>of</strong> <strong>the</strong> o<strong>the</strong>r shorebirds,<strong>the</strong>y are seasonal transients whoare most abundant in <strong>the</strong> reyion's estuariesduring spring and fall niiyratoryperiods.Great blue herons and eyrets (tamllyArdeidae) are <strong>estuarine</strong> residents thatnest in wetland and adjdcent upland, andforage in marshes, littoral flat, andchannel habitats in waters 41 m deep. In<strong>channels</strong>, this includes shore1 ine andslope areas <strong>of</strong> iirainsten~ <strong>channels</strong> and shallowsubsidiary and bl ind <strong>channels</strong> throughout<strong>the</strong> estuaries. Great blue herons aredistributed ubiquitously throuyhout <strong>the</strong>region while eyrets are locdted principallyin <strong>the</strong> <strong>coast</strong>al estuaries <strong>of</strong> nor<strong>the</strong>rnCalifornia and sou<strong>the</strong>rn Oregon (Beccasioet al. 1981). <strong>The</strong> density <strong>of</strong> herons in<strong>the</strong> Columbia Kiver estuary peaked atalmost 3 km-1 <strong>of</strong> linear transect surveyedduring <strong>the</strong> summer months due to recruitment<strong>of</strong> young, but averaged between 1 and2 km-1 during o<strong>the</strong>r seasons. Althoughdistributed through all estudrine regions,herons tended to be concentrated In <strong>the</strong>central (i e. , 01 igohal ine-polyhal ine)region ot that estuary. Part <strong>of</strong> thisheterogeneity was due to <strong>the</strong> proximity toheron nestiny colonies in <strong>the</strong> vicinity otYounys Bay, Karlson Island, Ryan Island,and 8rown's Island (Jones and StokesAssociates, Inc., in prep.). Much higherdensities have been observed on <strong>the</strong> basis<strong>of</strong> linear shoreline; as many as 30 to 50immature herons have been observed perlinear km <strong>of</strong> shoreline in Grays Harborduring <strong>the</strong> summer (Dr. Dennis Paulson,
Burke Mus., Univ. Wash. Seattle, WA;pers. comcn. ) .7.3 SURFACE AND DIVING WATERBIRDSAno<strong>the</strong>rgredorninant bi rd assemblagefound in <strong>estuarine</strong> channel hahi tats isthat <strong>of</strong> <strong>the</strong> surface and diving waterbirds,which constitute over 40% <strong>of</strong> both <strong>the</strong>total comnon and prevalent species (Table7.1) and include members <strong>of</strong> four farnil ies(Podicipedidae, grebes; Phal acrocoracidae,corntorants; Anatidae, waterfowl; andAlcidae, alcids). Unlike birds <strong>of</strong> <strong>the</strong>o<strong>the</strong>r assembl ages , <strong>the</strong>y ut il i ze <strong>the</strong> channelwater directly for hoth roosting andforaging. A1 though a1 1 roost on openwater, during Feeding some are conf ined tocertain channel microhabi tats by <strong>the</strong> constraints<strong>of</strong> <strong>the</strong>ir foraying behavjor andprey preferences. Benthic herbEvorez(brant, mallard, nor<strong>the</strong>rn pintail, greenwingedteal , canvasback) and carnivores(doubl e-cres ted curr~iorant, horned andred-necked grebes, qreater and lesserscdup, contrliori goldeneye, buf t 1 enedd,whi te-winged and surf scaters, p iyeongull lernot) teed in shal low, ctldnnel slopedrrds where yl ant and anillla1 taud resourcerdre wrthln <strong>the</strong>ir resy~ctfve dlvlngranges, whi l e pet dgic piscivor~s (pelagicCOnlloraRt, conlnon and red-breasted IrrPryanser,Bonaparte's gull ) and plankt tvores(eared grebe) tend to congreyate d 1 ongtidal fronts whlch congregate <strong>the</strong>lr prey.Same species, ydrtr culariy tne yiscivorousspcles, are turrner restricted tocrlaflnrl s 1 n <strong>the</strong> euna l inr-mesoha1 i n reglansot <strong>the</strong> estuary. Smith and Mudd(19fbi3) il lustrated ttw areal dlstributrarlut seabirds (inciudlng rlllnocerosduklet~, coti\i\ion ttiurres, warnlcid rtlurrel~ts,plyeon yui 1 Ie~tlots) 10 (;rays Harborto be conllncd to rtldnnel hdbttdt li1 tll~outer castudry wllere water ciepth was qreaterthan O tri relatlve to MLLW (Ely, 7.3).Ul~trlbutlon~ <strong>of</strong> pelaytc cormorant anr!surt scoter were sirni 1 ar ly concentrdtedin lower dnd mid-estuary regions ot <strong>the</strong>C~lunlirta River estuary, while o<strong>the</strong>rspecles (ma11 drd, Anterican wlyearl, andcaarri
Fig. 7.3. Seabird (primarily rhinoceros auklets, common murres, marbled murrelets, andpigeon guillemots) distribution in Grays Harbor, Washington, October 1974 to September1975; stippled area indicates littoral sand or mudflat habitat and hatched area indicatesseabird occurrence (figure from Smith and Mudd 1976a).7.4 AERIAL-SEARCHING BIRDSAerial-searching birds include bothterrestrial (be1 ted kingfisher, swallows,osprey, bald eayle) and waterbi rds (gul ls,terns, and brown pelican) which fly overand along <strong>channels</strong> whi le foraying forprey over, on, or just within <strong>the</strong> watersurface. Waterbirds also roost on <strong>the</strong>surface.Be1 ted kingfishers, ospreys, andbald eagles all require perches in <strong>the</strong>proxiini ty <strong>of</strong> <strong>the</strong>ir common foraging habitatand thus are less prevalent or absentover <strong>channels</strong> in large expanses <strong>of</strong> openwater such as occur in <strong>the</strong> lower regions<strong>of</strong> many estuaries. In <strong>the</strong> Columbia Riverestuary, for example, <strong>the</strong> di stri butionand abundance <strong>of</strong> bald eagles is centeredin <strong>the</strong> central region <strong>of</strong> <strong>the</strong> estuarythrough most <strong>of</strong> <strong>the</strong> year (Jones and StokesAssociates, Inc., in prep.). <strong>The</strong> proximity<strong>of</strong> foraging habitats to nesting sitesmay also restrict <strong>the</strong> effective distribution<strong>of</strong> <strong>the</strong>se birds along <strong>the</strong> estuary.Gulls and terns, however, are muchmore widely distributed through tne estuariesas <strong>the</strong>J r a ~ i d cover l ~ broad expanses<strong>of</strong> open water during <strong>the</strong>ir feeding foraysaway from <strong>estuarine</strong> breeding colonies.Much <strong>of</strong> tnis wide aerial distribution isdue to <strong>the</strong> relatively dynamic nature <strong>of</strong><strong>the</strong>ir prey resources, such as macrozooplanktonand small, schooling fisheswhich occur sporadically with shiftinycurrents and tidal fronts throughout <strong>the</strong>estuary; tidal inundation and exposure <strong>of</strong>benthic and sessile organisms alony <strong>channels</strong>hores also contributes to movement<strong>of</strong> gulls which prey upon <strong>the</strong>se organisms.
While <strong>the</strong> terrestrial-associ atedbirds <strong>of</strong> <strong>the</strong> assemblage are estuary residents,both mew gulls and <strong>the</strong> two ternsare seasonal transients, a1 though inopposite patterns. Mew gulls, like most<strong>of</strong> <strong>the</strong> waterfowl, migrate out <strong>of</strong> <strong>the</strong> region'sestuaries during <strong>the</strong> summer. <strong>The</strong>maximum abundances recorded in Grays Harborbetween October 1974 and September1975 occurred in December though April(maximum <strong>of</strong> 1.4 km-1 along a channeltransect in upper estuary in March) and<strong>the</strong> gulls were absent froin May throuyhJuly (Smith and Mudd 1976a). Jones andStokes Associates, Inc. (in prep. )reported maximum mew gull densities <strong>of</strong>193 km-2 in fall 1980 and 400 km-2 inwinter 1980-1981 in <strong>the</strong> Columbia Riverestuary. Common and Caspian terns aresummer immigrants into <strong>the</strong> large <strong>coast</strong>alestuaries and Caspian terns breed in large<strong>estuarine</strong> colonies throughout <strong>the</strong> region(Beccasio et al. 1981). High densities<strong>of</strong> common terns occur in Grays Harbor inMay (2.6 km-1 along channel transect inupper estuary) and equally so in September.Caspian terns, which breed onWhitconib Island in <strong>the</strong> lower estuary fromMay to October (Penland 1976), are mostabundant (18 km-1) in channel habitatsduriny July when food requirements forfledglings are at a maximum (Smith andMudd 1976a). <strong>The</strong> density <strong>of</strong> Caspianterns in <strong>the</strong> Columbia River estuaryreached %93 km-2 during summer 1980censuses by Jones and Stokes, Associates,Inc. (in prep.).As <strong>the</strong> "Cal i fornia" subspecies, <strong>the</strong>brown pelican is an endangered specieswhich occurs in small aggregations <strong>of</strong>iirimatures as tar north as Grays Harborand is a fa1 1 (Auyust-September) occupant<strong>of</strong> <strong>the</strong> euhaline regions <strong>of</strong> a number <strong>of</strong><strong>the</strong> <strong>coast</strong>al estuaries to <strong>the</strong> south (WillapaBay, Columbia River, Coquille, Chetcoand Humbolt Bay) (Beccasio et al. 1981).
CHAPTEK 8MAMMALS UF ESTUAK IN€ CHANNELSTerrestrial, aquatic, and marine mammalsutilize <strong>estuarine</strong> channel habitatsto varying extents and for various purposes.A1 though rrrembers <strong>of</strong> adjacent wetlandor upland communities, terrestrial mammals periodical ly forage along <strong>the</strong> shoreline boundaries with channel habitats.Aquatic marnrnals actually uti 1 i ze <strong>channels</strong>for much <strong>of</strong> <strong>the</strong>ir principal foraying.Compared to terrestrial and aquatic mammals, marine marnrnals occupy <strong>channels</strong> extensively,some exclusively, for foraging,movement, migration, restiny, andreproduction. O<strong>the</strong>r than rnan, <strong>the</strong>y constitute<strong>the</strong> predominant ~roportion <strong>of</strong> <strong>the</strong>tertiary consumer level (see Chap. 9).One terrestrial (procyonid), fouraquatic (one each castorid, cri cetid, capromyid,and mustelid), and four marine(all pinnipeds) mammals are common tochannel habitats in <strong>Pacific</strong> <strong>Northwest</strong> estuaries(fig 8.1; Table 8.1). In additionto <strong>the</strong>se, o<strong>the</strong>r marine mmmals such asorca or killer whale (Orcinus E) , har-IFig. 6.1. Representative illustration <strong>of</strong> common mammal assemblages <strong>of</strong> <strong>estuarine</strong> thannels<strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.i
Table 8.1. Itemization and characteristics <strong>of</strong> terrestrial, aquatic, and marinemammals common to estuarir'e channel habitats in <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.---Re 1 evantChannel Salinity 1 i fe hi storyTaxa habitats1 associations2 --- characteri stics3Terrestrial :Procyon 1 otorm n rAquatic:Castor canadensi s(American beaver )-Ondatra zibethicapiizzt)-Myocastor coypus-r-)Lutra canadensi sm d i a n river otter)Marine:K-Es ,B R-0S,BS,BM-BR-MR-MR-E0-HO-H0-H0-ECEumetopias jubata M,S K-E F-PC(Nor<strong>the</strong>rn sea 1 ion)Zalophus cal i forni anus M, S R-E F-PC(California sea lion)~hoca vi tul ina richardiK-EF-EC(Harb0FTzJ-J-Mirounga anyustirostrls M P-E F-PC(Nor<strong>the</strong>rn elephant seal)IIII= Mainstem; S = Subsidiary; B = t31 ind.2~ = Riverine; 0 = Oligohaline; M = Mesohaline; P = Polyhaline; E =Euhaline.30- = obligate; F- = facultative; EC = epibenthic carnivore; PC = pelayiccarnivore; H = herbivore.bor porpoise (Phocoena phoccya), graywhale (Exchrichti us robustus and minkewhale (~alaenoptera acutorostrata) havebeen reported sporadical ly in <strong>the</strong> region ' sestuaries. As with <strong>the</strong> avian assemblages,comprehensive documentation <strong>of</strong> mammal assemblagesin <strong>the</strong> region's estuaries isrelatively recent and limited to <strong>the</strong><strong>coast</strong>al estuaries in <strong>the</strong> vicinity <strong>of</strong> <strong>the</strong>Columbia River, e.g., Grays Harbor, WillapaBay, Columbia River estuary, TillamookBay, and Netarts Bay (Smith and Mudd1976b; Howerton et a1 . 1980; Dunn et a1.1981; Beach et al. 1981) and in <strong>the</strong> less<strong>estuarine</strong>environs <strong>of</strong> nor<strong>the</strong>rn Puqet Soundand <strong>the</strong> Strait <strong>of</strong> Juan de Fuca (Everitt1980; Everitt et a1 . 1980). Quantitative(population sizes and dynamics) studies <strong>of</strong>terrestrial and aquatic mammals in <strong>Pacific</strong><strong>Northwest</strong> estuaries are rare or nonexi stent.Assemblage accounts <strong>of</strong> distributionsand population assessments <strong>of</strong> marine mammals, however, have been available since<strong>the</strong> 1940's (Scheffer and Slipp 1944, 1948;Manzer and Cowan 1956; Cowan and Guiguet1965; Bigg 1969; Pike and MacHskie 1969).
Extensive population biology and ecoloyystudies ot pinnipeds in <strong>estuarine</strong> habitatshave occurred duriny <strong>the</strong> past twodecades (Pearson 1969; Pearson and Verts1970; Mate 1975; brow^ and Mate 1979;Calanlbokidis et al. 1978, 1979; Brown1980; t3owl by 1981; K<strong>of</strong>fe 1981). i3ecassioet al. (1981) included <strong>the</strong>se commoninarnmal species in <strong>the</strong>ir colnprenensiveecological inventory <strong>of</strong> <strong>the</strong> <strong>Pacific</strong>Coast.8.1 TEKKESTKIAL MAMMALSRaccoons are one <strong>of</strong> <strong>the</strong> few terrestrialmammals which trequents channelhabitats in conjunction with <strong>the</strong>ir principaluse <strong>of</strong> adjacent littoral tlat, saltand freshwater marsh, and riparian swamphabitats. Utilization <strong>of</strong> <strong>the</strong> channel isalniost exclusively contined to foraginyfor shal low-water fauna. Feeding periodicityand intensity is principally a function<strong>of</strong> tidal cycles. A1 though raccoonshave been observed feeding during bothday- and nighttime, <strong>the</strong>y appear to prefernighttime low tide periods when <strong>the</strong>y cansafely foraye across littoral flats(Smith and Mudd 1976b; Dunn et al. 1981).Thus feeding activity tends to be seasonalin nature, i.e., more intensive in falland lowest during spring. Raccoons in <strong>the</strong>Columbia Ki ver estuary have been observedthrough all <strong>estuarine</strong> regions, from <strong>the</strong>euhaline region <strong>of</strong> <strong>the</strong> Ilwaco Channel to<strong>the</strong> marsh <strong>channels</strong> <strong>of</strong> Puyet Island, althoughpeak observations occurred in <strong>the</strong>complex system <strong>of</strong> islands and <strong>channels</strong> inCathl amet Bay (Dunn et a1 . 1981).8.2 AUUATIC MAMMALSAmerican beaver are common only insmall subsidiary and blind <strong>channels</strong> whichi ntersect freshwater marsh and riparianhabitats, particularly si tka willow (Sal ixsi tchensi s) , creek dogwood (Cornus stolo--1 nifera 'or similar habitats in riverinemesohalinemarshes such as <strong>the</strong> CathlametBay area <strong>of</strong> <strong>the</strong> Colunbia River estuary(Wash. Dep. Game 1981). Extremely small<strong>channels</strong> may be dammed and permanentlyoccupied (denning and resting) by beaverin some instances.Muskrat have a broader spectrum <strong>of</strong>habitat utilization than beaver, beingmore common in <strong>the</strong> sedge (Carex spp.),horsetai 1 (Equi setum spp. ), and bul rush(Sci rpus sp-and freshwater habi -tats in addition to <strong>the</strong> riparian habitatsoccupied by beaver (Smith and Mudd 1976b;Wash. Dep. Ga!ne 1931). Denning and resting,however, a1 so occur in close associationwi tti steep-sided <strong>estuarine</strong> (principally subsidiary and b1 ind) channel sadjacent to or in <strong>the</strong>se habitats and, assuch, cor~stitute critical habitats forthis species (Dunn et a1 . 1981). Feedingand o<strong>the</strong>r activities almost always occurless than 60 ni. from <strong>the</strong> channel den andprincipally during high tide and nocturnalhours, perhaps to facilitate access t<strong>of</strong>eeding areas along <strong>the</strong> channel banks andto miniinize vul nerabil i ty to predators.Nutria habitats overlap somewhatwith those <strong>of</strong> American beaver in <strong>the</strong>iroccupation <strong>of</strong> marsh and riparian swamphabitats. In tne Columbia River estuary<strong>the</strong> most common features <strong>of</strong> nutria habitatare compl ex steep-sided tidal channel systemswithin extensive high marshes (pri n-cipal ly reed canarygrass, Phalaris arundinacea/cattail, Typha sp.),whererprincipal forage plants (see Section 9.1)are readily available (Dunn et a1 . 1981).Unlike muskrat, nutria appear to maintainextensive home ranges (%U. 4 km2) containinyseveral habitats and to have no seasonalor die1 periodicity to <strong>the</strong>ir activity patterns,Among <strong>the</strong> terrestrial and aquaticmammals <strong>the</strong> Canadian river otter undoubtedlymaintains <strong>the</strong> highest utilization <strong>of</strong><strong>estuarine</strong> <strong>channels</strong> and is <strong>the</strong> only specieswhich comrnonly occupies mainstem <strong>channels</strong>.A1 though most observations <strong>of</strong> river otterin <strong>the</strong> Columbia River estuary were correlatedwith sitka spruce (Picea si tchensi s)and/or si tka wi 11 ow-domi nated forest, otterwere typically associated with complexchannel networks <strong>of</strong> tidal creeks andsloughs (subsidiary and bl ind channel s)which <strong>of</strong>fered easily accessible, concentratedprey resources (cl arns, crayfish,and dernersal fishes) during periodictidal dewatering (Dunn et al. 1981). InGrays Harbor, river otter have been
observed only in tributary rivers andstreams, although it is assunled that <strong>the</strong>yutilize tne open waters <strong>of</strong> <strong>the</strong> estuary(mainstem channel s) to travel betweentributdries (Smith and Mudd 1Y76b). Ottersalso are relatively adaptable to tnepresence <strong>of</strong> man as lony as critical habitatand food resources are maintained;Cowan and tiui guet (1965) considered <strong>the</strong>in<strong>the</strong> most numerous aquatic mammal inVancouver (U.C., Canada) Harbor.8.3 MARINE MAMMALSHarbor seals and Cali tornia andnor<strong>the</strong>rn sea lions are both common andabundant in Pacitic <strong>Northwest</strong> estuariesa1 thauyh densities fluctuate seasonal lyas a function <strong>of</strong> feeding and breeding ~nigrations(Mate 1975). Nor<strong>the</strong>rn elephantseals are less abundant in <strong>the</strong> region andnrr more concentrated seasonally in <strong>the</strong>sou<strong>the</strong>rn extrane <strong>of</strong> <strong>the</strong> region. Whileall four species occur frequently incodstdl estuaries, nor<strong>the</strong>rn elephantseals dnd Cali tornia sea lions tend to beless abundant in <strong>the</strong> inland estuaries <strong>of</strong>Puget Sound.Nor<strong>the</strong>rn sea l ions are most abundantin <strong>the</strong> reyion during <strong>the</strong> non-breeding seasonbetween late fall and early sprinyand, except for a snlall population alongttre outer <strong>coast</strong> during <strong>the</strong> summer (Everittand Jeffries 1979), are usually absentfrom <strong>the</strong> region frorn Mdy through July.Total counts <strong>of</strong> nor<strong>the</strong>rn sea lions inWashinyton in 1976 and 1978 peaked at'L450 in February-March and at 2600 inSel~tewber-October (Everi tt et a1 . 1980).Hgt Beach et al. (1981) indicated thatnor<strong>the</strong>rn sea lion populations in 1981vdried considerably among three haul outsltes in <strong>the</strong> vicinity <strong>of</strong> <strong>the</strong> ColumbiaRiver estuary; whi 1 e occupation <strong>of</strong> <strong>the</strong>south jetty site at <strong>the</strong> mouth <strong>of</strong> <strong>the</strong>river was concentrated between Januaryand May, maximurn abundance at TillamookHead, Oreyon, occurred in May and Juneand did not occur at Three Arch Kocksuntil October-November. Much <strong>of</strong> thisvariation appears to be associated withshifts in preterred foraging habitat andlocation alony <strong>the</strong> <strong>coast</strong> duriny <strong>the</strong> summerand a potential movernent <strong>of</strong> sea lionsinto inside waters during <strong>the</strong> wintermonths (tveritt et al. 1980). Occupdtion<strong>of</strong> <strong>coast</strong>al estuaries <strong>of</strong>ten coincides withpredictably high concentrations <strong>of</strong> prey,sucn as eul acrion and spring chinook salmonspawni ng micjrati ons through <strong>the</strong> ColumbiaRiver estuary in winter and spring(Beach et al. 1981). Movement in and out<strong>of</strong> <strong>the</strong> estuary must be relatively dynamicduriny this period, ds no haulout areasare reported to occur within <strong>the</strong> estuary.California sea lions also occur in<strong>Pacific</strong> <strong>Northwest</strong> estuaries during <strong>the</strong>non-breediny season between Uctober andMay, when <strong>the</strong>y move northward from oreedinysites at and south <strong>of</strong> San Miyue1Island, California. <strong>The</strong>y follow <strong>the</strong> sameyeneral auundance di stribution pattern as<strong>the</strong> nor<strong>the</strong>rn sea 1 ion but are generallymore abundant in <strong>coast</strong>al estuaries andless abundant in inland waters (Everittet al. 1980; Beach et al. 1981). Everittet a1 . (1980), however, reported extendedhaul iny out <strong>of</strong> California sea lions athaulout areas in tne Port tiardner area <strong>of</strong>Puyet Sound, a signi f icant expansion <strong>of</strong><strong>the</strong>ir uti l i ration and abundance in insidewaters.In <strong>the</strong> Columbia Kiver estuary forayingCalitornia sea lions are numerousthrougnout <strong>the</strong> estuary during <strong>the</strong> springfish migrations, occurring as far upriveras Uonnevi 1 le Dam, a1 though no hduloutsites have been documented to occur within<strong>the</strong> confines <strong>of</strong> <strong>the</strong> estuary, This sea1 ion is credited with some fish and fishinggear damage irt <strong>the</strong> fa1 1 and is consideredto be <strong>the</strong> rnajor cause <strong>of</strong> year danagein <strong>the</strong> lower river and estuary during <strong>the</strong>1981 winter season (Beach et a1 . 1981).Of a1 1 marine mammals, <strong>the</strong> <strong>Pacific</strong>harbor seal is <strong>the</strong> most ubiquitous andabundant and is <strong>the</strong> only breeding pinnipedin <strong>the</strong> region (Scheffer and Slipp1944; Everitt et al. 1980). <strong>The</strong> State <strong>of</strong>Washinyton is estimated to provide refuyeto over 7,000 harbor seals (Everi tt eta\. 1980). Beach et a1 . (1981) estimated5,000-6,000 harbor seal s present in <strong>the</strong>irstudy area between Grays Harbor andNetarts Bay, including at least 55 hauloutsites in <strong>the</strong> five major estuaries
COLUMBIA RIVER ESTUARYiWILLAPA3000BAY3000 -GRAYS HARBOR2000 -1000 -0J ' F ' M ~ A ' M ' J ' J ' A ' S ' O ' N ' D 'MONTHFig. 8.3. Maximum total abundance (aerial counts) <strong>of</strong><strong>Pacific</strong> harbor seals at haulout sites in three <strong>of</strong> Washington's<strong>coast</strong>al estuaries in 1980 (open symbols) and in1981 (closed symbols) (figure redrawn frm data <strong>of</strong> Beachet al. 1981).
<strong>the</strong> 1 atter <strong>of</strong> which include carnivoroustaxa such as Nephthys and Eteone. Whilesome organi srns('i.e,,Acmaem - gastropods)are assumed to graze discrirninatelyupon microal yae, it has com~nonly beenassumed tnat most capture and inyest foodparticles simply on <strong>the</strong> basis <strong>of</strong> size asa function <strong>of</strong> filtering or o<strong>the</strong>r feedinymorphologies. It has become readily apparent,however, that selective ingestion<strong>of</strong> food particles occurs, perhaps on <strong>the</strong>basis <strong>of</strong> che~ni cal and/or physical composi -tion (1.. Tietjen and Lee 1977 fornematodes; Fauchald and Ju~i~ars 1979 for?olychaetes), and that "food" can becomposed ot a combination <strong>of</strong> benthicmicroalyae, detritus, pelagic phytoplankton,and meiotauna. More recent studieshave indicated that observed particleselection patterns are more <strong>the</strong> result <strong>of</strong><strong>the</strong> mechanics <strong>of</strong> particle handling than<strong>of</strong> behavioral responses to particle characteristics(Junlars et al. 1982; Tayhon1982). DOC, as we1 1 , may be assimi 1 atedin <strong>the</strong> feediny process or many depositfeeders (Stephen 1967; Steward 1979;Levinton 1980). <strong>The</strong> resulting finitepartitioning <strong>of</strong> food resources explains,within <strong>the</strong> constraints <strong>of</strong> temperature andsalinity tolerances, much <strong>of</strong> <strong>the</strong> disparatestructuring <strong>of</strong> benthic infauna assemblayesand standiny stock (see Section5.1) as a function <strong>of</strong> sediment grainsize, stability, and organic content(Sanders 1959).Motile epitauna are principallybenthic carnivores preying upon benthicinfauna or sessile epi fauna. Of <strong>the</strong> ninerepresentative species (Table 5.2), twaasteriods are obl igate feeders on sessilebivalves, yastroyods, barnacles, and seaurchins ; two crabs are tacul tative carnivoreson everything from benthic infauna,including rnei<strong>of</strong>auna, to fish; and threeshrimp species are obligate mei<strong>of</strong>aunacarnivores. Only two species, <strong>the</strong> crayfish<strong>Pacific</strong>astacus leniusculus, andhermit crabs (Payurus-spp.), are, by <strong>the</strong>irdetri ti vory, prlrnary consulners.A1 though <strong>the</strong>re is very 1 i ttle specificprey composition or feeding behaviorinformation on <strong>the</strong>se consumers in <strong>estuarine</strong><strong>channels</strong> habitats, <strong>the</strong> diets <strong>of</strong> cran-gonid shrimps and cancrid crabs, <strong>the</strong> principal invertebrate secondary consumers i n<strong>the</strong> community , have been exami ned fromseveral <strong>coast</strong>al estuaries. Prel iminaryanalyses <strong>of</strong> <strong>the</strong> stomach contents <strong>of</strong>Crangon franciscorum collected fromdifferent locations <strong>of</strong> <strong>the</strong> Columbia Riverestuary in June 1481 (C. Simenstad, Fisn.Kes. Inst., unpubl. data) indicate that atthat time C. franciscorum was preying primarily on infauna and epi fauna, includingool vchaete annel ids. Coroohium s~o. amuhi -pods, and <strong>the</strong> harpacticoid copepod scottolanacanadensi s. <strong>The</strong>re was l i ttle differencein diet amons <strong>the</strong> four locations fromwhich shrimp werQ examined. Three cranyonidsfrom Grays Harbor were also carnivorouson benthic infauna (Armstrony etal. 1982). C. franciscorum was found t<strong>of</strong>eed principa-lly on polychaete annel ids(15.4% trequency <strong>of</strong> occurrence) and unidentifiedcrustaceans (14.5%)) while C.niyricauda and C. stylirostris had prey3upon crustaceanr (12.7% and 11.5%. respect'ively)and small' bivalve mol lusds (19.0%dnd 7.72, respectively). A1 though notevident in <strong>the</strong>se data, C. franciscorummay also be a major preditor on rnysids(i.e., N. mercedis), as has been reportedin <strong>the</strong> Sacramento-San Joaquin Riversestuary (Sieyf ried 1982).Prey composition <strong>of</strong> Dungeness Crabsin Grays Harbor varied according to predatorsize, die1 and seasonal cycles, andlocation in <strong>the</strong> estuary. In general, however,crabs (60 mm carapace width preyedprinlari 1 - Y upon . bivalve moll uscs (Tell inaspp., & arenaria, Cryptomya californ--- ica. Macoma suu.. ,. , Cardiidael and smallcrustaceans (amphi pods, harpatticoid copepods,tanai d~). Intermedi ate-sized crabsbetween 61 and 100 mm carapace widthpreyed equal ly upon small crustaceans,fish (1 ingcod, <strong>Pacific</strong> sanddab, <strong>Pacific</strong>sand lance, <strong>Pacific</strong> herring, <strong>Pacific</strong> tomcod,sand sole, shiner perch, longfinsmelt, <strong>Pacific</strong> staghorn scul pin), and1 arger crustaceans (Crangon spp. ; mudshrimp, Call ianassa cal i forniensis; Dungenesscrab), and 1 ess so on bi val ve mol -lusks. Large crabs >I00 mrn carapace widthpreyed predominantly upon fish, less onsmall crustaceans, and measurably l ess onlarge crustaceans and bivalves.
A1 thouyh <strong>the</strong>re is considerable variationin opinion about food preferences(Coul 1 1973), epi benthic zoopl ankton canprobably be characterired as detritivores,as is <strong>of</strong>ten illustrated by <strong>the</strong>ir prominencein detritus a ~ ~ ~ m ~ lareas a t i ~ such nas <strong>the</strong> null zone (see Section 2.5.1). Assuch, <strong>the</strong>y may play a critical role in<strong>the</strong> initial biological (fragmentation)conditioning <strong>of</strong> detritus (see Section4.4) Harpacticoid copepods, in particular,have been found to rely heavilyupon heterotrophical ly-produced carbon in<strong>the</strong> fomi <strong>of</strong> bacteria associated withdetritus (Provasoli et al. 1959; Brownand Sibert 1977; Sibert et al. 1977b;Kieper 1978; Vanden Berghe and Berymans1981 amony inany). Considerable speciesspecificvari abi 1 i ty in food preferencesmay exist, possibly reflecting divergentfunctional (i e. , mandible) morphologyand behavior (Marcotte 1977 and pers.coam,; Vanden Berghe and Bergmans 1981).This characterization as specialists,in terms <strong>of</strong> nutritional preferences andrequirements and <strong>the</strong> ability to utilizespecific foods, may explain <strong>the</strong> <strong>of</strong>ten extremefluctuations in epi benthic zoopl anktonassemblaye structure observed in verydynamic estuaries such as <strong>the</strong> ColumbiaRiver (Houghton et al. 1980). Some prominenttaxa, particularly Eurytemora atfin-- is, can effectively feed on both detritusand phytoplankton, and it has also beensuggested fur<strong>the</strong>r that algal cells may actually contribute some trace metabolitenecessary tor normal egy production(Heinle et al. 1977). <strong>The</strong> presence <strong>of</strong>protozoa in association with <strong>the</strong> detritusmay also form a critical link between <strong>the</strong>detrital POC and assimi 1 ation pathways <strong>of</strong>epibenthic copepods. Mysids such asNeomysis mercedis may, in addition tobeing d e m e s and phytoplanktongrazers, be carnivores. A1 though <strong>the</strong>yare reported to consume primarily diatomsin <strong>the</strong> Sacramento-San Joaqui n estuary(Kost and Knight 19751, Houyhton et al.(1980) illustrated that N. mercedis in<strong>the</strong> Columbia River estuary f e v t u n -istical ly upon mei<strong>of</strong>auna and zooplankton(cladocerans, cyclopoid, harpacticoid,and cal anoid Copepods ; roti fers) whichwere numerical 1 y prominent within <strong>the</strong>epibenthic region. Thi s feeding mode wasalso verified by ~iegfried and Kopache(1980), who found that, althouyh not aparticularly active predator, N. mercedisi n <strong>the</strong> Sacra~r~ento Ki ver estuary derived>80X <strong>of</strong> its energy via carnivory onroti fers and copepods ; di rect herbivoryappeared, in fact, to be <strong>of</strong> importanceonly during <strong>the</strong> spring diatom bloom.Wilson (1951) described N. rnercedis in<strong>the</strong> Nicomekl and serpentine Rivers Estuariesas feediny on both vl ant (diatoms,din<strong>of</strong>lagellates, blue-green alyae, vascularplant detritus) and animal matter(copepods and mysids), Johnson (1981)also describes <strong>the</strong> trophic role <strong>of</strong> N.mercedis in t3ri tish Col urnbia eStuari6?channelhabi tats.Estuarine pel ayic zooplankton andneuston, ~erhaps ref 1 ect i ny <strong>the</strong> lowerternporal and spatial diversity <strong>of</strong> avai 1-able food resources in <strong>the</strong> water columnas compared to bentnic and epibenthicenvirons, i 1 lustrate more 1 imited feedingstrateg ies. Most are suspension feeders(Davis 1949; Poulet 1973;Kichman et al.1977; Lonsdale et al. 1979), althoughsome omnivorous and carnivorous taxa arealso prominent (Anraku and Omori 1963;Gaul d 1966; Mu1 len 197 7) . In <strong>the</strong> case <strong>of</strong><strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> estuaries, vredomi -nant zoopl ankters incl ude both herbivores(i e., Eurytemora spp., Pseudocalanusspp., and Corycaeus angl icus) and omnivores(Acartia spp. ), which <strong>the</strong>rnsel vesmav be trovhically linked (Hodqkin andNext to <strong>the</strong> avian assemblages, demersalfishes illustrate <strong>the</strong> rr~ost diversespectrum <strong>of</strong> Food web linkages and trophiclevels in <strong>the</strong> habitat. This includes afew primary consumers (i.e.,comnion carpfeed considerably upon algae and o<strong>the</strong>rplant material as we11 as detritus;Wydoski and Whitney 1979), many secondaryconsumers and some species (i.e.,doyfish,linycod) which could be consideredtertiary COnSUmerS although <strong>the</strong>y are, inturn, susceptible to predation by o<strong>the</strong>rtertiary Consumers such as marine mammal sand, <strong>of</strong> course, man. Some species may,throughout <strong>the</strong> ontoyenet ic chanyes in
feeding behavior, encompass several troph- greater selectivity upon predominantly feiclevels and prey assemblages; white male A. californiensis and both sexes <strong>of</strong>sturgeon, for instance, are reported to -- A. clGsi. Considering <strong>the</strong> overall dietsconsume everythiny from epibenthic zoo- <strong>of</strong> <strong>the</strong>se three pl anktivores, adult femal eplankton as juveniles to salnion and house - A. californiensis composed 34.1% <strong>of</strong> <strong>the</strong>cats (a prime illustration <strong>of</strong> interhabi- total number and 53.6% <strong>of</strong> <strong>the</strong> -A. cal i forn-tat 1 inkages!) as adults. Ainong <strong>the</strong> iensis fraction.reprcserltative species (Tab1 e 6.1)facul tati ve epi benthic benthivores (17species; 40%) and facultative epibenthic <strong>The</strong> five species <strong>of</strong> juvenile salmon,pl anktivores (12; 28%) predominate, fol - whose food habits have been studied extenlowedby obligate epibenthic benthivores sively (summarized in part by Levy and(5: 12%) , obligate epibenthic plankti- Levings 1978; Levy et al. 1979; Northcotevores (4; 9%), omnivores and parasites et al. 1979; Levy and Northcote 1981;(2; 5%), and facultative meiobenthic Durkin 1982; Healey 1982; and Simenstadbenthivoes (1; 2%). This composition et dl. 1982b), also illustrate <strong>the</strong> variedchanyes, <strong>of</strong> course, with seasonal changes prey resource uti 1 i zation patterns whichin assembl age structure and with growth have evolved among congeneric taxa, Juveanddevelopment <strong>of</strong> resident species.nile pink salmon occupy shallow sublittora1habitats for very short periods (days)Reflecting <strong>the</strong> re1 ative simp1 icity before moving rapidly to pelagic channel<strong>of</strong> <strong>the</strong>ir prey resources, pelayic fishes or neritic habitats, feeding predominantalsoi 11 ustrate less diverse feeding ly upon cal anoid copepods and larvaceans.strateyies tnan <strong>the</strong> deinersal assemblage. Contrastingly, juvenile chum salmon typi-Of <strong>the</strong> representative species (Tabl e G.2), cal ly occupy shal low subl i ttoral habiallbut two are primarily planktivorous, tats, es(~eciall1 sand-eel grass, forwith onlj cutthroat trout and Dolly Var- several weeks feeding upon epibenthicden exploiting o<strong>the</strong>r fishes. Two thirds zooplankton, particularly harpacticoid(24) <strong>of</strong> <strong>the</strong> species are obligate pelagic copepods and gammarid emphipods; uponpl anktivores , i ncludiny two-thi rds <strong>of</strong> growing to 50-60 mm FL, tne juveni 1 e<strong>the</strong>se (16) which occur only as pelagic chums also shift to pelagic channel orlarvae. Four each (11%) are facultative neritic habitats where <strong>the</strong>y feed uponpelayic pl anktivores or epibenthic pl ank- calanoid copepods, decapod 1 arvae, andtivores and two each (6%) are obliyate 1 arvaceans. Juvenile coho salmon feedepi benthic pl anktivores or facultative principally upon gamrnarid amphi pods durpelagicpi scivores. While <strong>the</strong> dominant i ng <strong>the</strong>ir relatively brief occupation <strong>of</strong>zooplankton taxa comprise <strong>the</strong> principal shallow subl i ttoral habitats, particularpreyresources <strong>of</strong> <strong>the</strong> planktivores, con- ly exposed yravel beaches, and upon decaslderablesize- or taxa-selective preda- pod larvae and euphausiids after movingtion characterizes individual species and into eplayic or neritic habitats. Sur-1 i fe hi story stayes. prisingly little is known about <strong>the</strong> <strong>estuarine</strong>foraying behavior or prey composi-This was effectively illustrated by tion <strong>of</strong> juvenile sockeye salmon due toJohnson's (1981) detailed examination <strong>of</strong> <strong>the</strong>ir rapid emmi yration throuyh <strong>estuarine</strong><strong>the</strong> diets <strong>of</strong> three prominent pel agic and nearshore marine habitats. Juvenileplankti vores in Yaquina Bay-- juvenil e shrimp and euphausi ids have been reportednor<strong>the</strong>rn anchovy, topsinel t, and surf as <strong>the</strong> prey <strong>of</strong> juvenile sockeye miyratinysmelt--relative to predation rates upon out <strong>of</strong> Puget Sound. Small juvenile chi-Acartia californiensis. When foraying in nook salmon tend to utilize shallow sub<strong>the</strong>water column, juvenile anchovy were littoral, salt marsh, or mudflat habitatshighly selective toward <strong>the</strong> larger female early in <strong>the</strong>ir <strong>estuarine</strong> residence, and- A. cali forniensi s and A. clausi , Eury- feed upon yarnmarid emphi pods, cumaceans,ternora affinis, and <strong>the</strong> clad-n podon; and emergent and drift insects. Upon growsurfsmemectedsimilar feeding =- iny larger or upon enteriny <strong>the</strong> estuarytivity while topsmelt reflected even at a 1 arger size as sm01tS (60-70 mm EL),106
<strong>the</strong>y move into pelayic or neritic habitatsbut continue to feed upon drift insects,as well as decapod and tish larvae.Extremely Selective forayiny is also <strong>of</strong>tenevident within <strong>the</strong>se broad prey categories.For example, in shallow sublittoralhabitats juvenile chum salmon tendto feed on a narrow spectrum <strong>of</strong> harpacticoids>75 pm in length and, at least witninPuyet Sound, particularly <strong>the</strong> speciesHarpacticus uni remi s. When in <strong>the</strong> pelayichabitats, <strong>the</strong>y appear to select re1 a-tively rare but very large (>2 mlil inlength) calanoid copepods such as Calanusspp. and Epilabidocera spp. instead <strong>of</strong>o<strong>the</strong>r, more numerousbut small er cal anoid(i e., ~eudoca'lanus sp.) and cyclopoid(i.e. , Corycaeus spp. ) copepods (Simenstadet al. 1980). Several <strong>of</strong> <strong>the</strong> o<strong>the</strong>rspecies <strong>of</strong> juvenile salmon show similarlyselective foraying(Table 9.1).in estuari ne~hdn~el SFood habits data addressin9 <strong>the</strong> region'sbird fauna which specifically oc-Curs In <strong>estuarine</strong> channel habitats is almostnon-existent and essenti af ly l imi tedto semi -qua1 itative data from GraysHarbor (Salo 1975; Smith and Mudd 1976a).Food web re1 atjonshi ps <strong>of</strong> more marine/<strong>coast</strong>al bird dsselllblayes have been Summarizedby Sirnenstad et al. (197%) in<strong>the</strong>ir syn<strong>the</strong>sis <strong>of</strong> nearshore and neritichabitats <strong>of</strong> <strong>the</strong> nor<strong>the</strong>rn Puyet Sound andStrait <strong>of</strong> Juan de Fuca ecosystem. Of <strong>the</strong>four syntopic species <strong>of</strong> marine divingbirds examined by Scott (1973) in <strong>the</strong> vicinity<strong>of</strong> Yaquina Uay, two (common murreand Brandt 's cormorant) may have acqui redTable 9.1. Principal preferred prey taxa <strong>of</strong> juvenile salmon in <strong>Pacific</strong> <strong>Northwest</strong> estuariesbased on 1 i terature and o<strong>the</strong>r stomach contents data sources.JuvenileSizesalmonclassspecies (mm,FL) Preferred prey taxaOncorhynchus gorbuschaPink salmon0. keta, chum salmon - -40-60 Calanoid copepods, Pseudocalanus spp.Larvaceans Oi kopleura sp.35-55 Harpacticoid copepods Harpacticus uni remi sGamri~arid amphipod Corophium syp.Cumacean Cumel 1 a vul garis- 0. kisutch, coho salmon >55 Calanoid copepods Galanus Spp., EyilabidoceraGammardi amphi pods Eoyanln~arus spp.!orophi urn spp.Ca anoid copepods Eurytemora sp. , Cal anus sp.-- U. nerka, sockeye salmon 45-91 Adult insects Dipterans, Ho~nopteraEuphausiids Thysanoessa spp.- 0. tshawytscha, chinook 35-75 Chironomid larvae and pupaesalmon Gammarid amphi pods Eoyammarus spp. ,Corophiurn spp., Aniso amnarus spp.~umaceans -cumel la V*Isopods Gnorimosphaeromd oregonens j s> 75 Adult insects Diptera, Homoptera
a portion <strong>of</strong> <strong>the</strong>ir diet from within <strong>estuarine</strong>habitats; coincidental ly, it was<strong>the</strong>se same two species which Wiens andScott (1975) calculated to cycle <strong>the</strong>yreatest annual flow <strong>of</strong> tropnic eneryy.<strong>The</strong> four representat i ve bi rd assemblayesillustrate a dfverse spectrum <strong>of</strong>feeding types (Tab1 e 7.1). Shal low-probinyand surface searching-shorebi rds, as<strong>the</strong> assemblage irnpl ies, are prfncipal ly(71%) obligate benthivores which teed onbenthic intauna and epibenthic zooplanktonalong <strong>the</strong> channel margin; toe o<strong>the</strong>rspecies are on~nivores whose diet includesV~SCUI ar plant matter (including seeds)froill adjacent marsh or terrestrial habitats.Waders are ei<strong>the</strong>r functional benthivoreswho prey on similar, though somewhatdeeper, benthic organisms as <strong>the</strong>first assemblage or dre carnivorous (obl i-gate or functional piscivores) on fishesand motile epi faunal invertebrates whichventure into shal low sub1 i ttoral areas <strong>of</strong>ttie habitat. Surface and diviny waterbirds,<strong>the</strong> 1 argest assemblage, includesseven feediny types, over a third <strong>of</strong>which are functional benthivores. Ubligateand functional piscivores and omnivoreseach conrprise 19% <strong>of</strong> <strong>the</strong> total number<strong>of</strong> species in <strong>the</strong> assemblage althouyhomnivores usually utilize <strong>estuarine</strong> <strong>channels</strong>only for roostiny, Obligate herbivoresand obl iyate and function1 pl ankt i-vores were represented by one specieseach. Amony <strong>the</strong> nine representativederial -search i ny bl rds, two-thi rds arehiyher level carnivores, ei<strong>the</strong>r piscivoresor avivores, while two are obliyateinsectivores and one is an obligateylanktivore.Recent studies In <strong>the</strong> Columbia Riverand adjacent estuaries have provided <strong>the</strong>first datd directly focused upon <strong>estuarine</strong>util ization by aquatic (Dunn et a1 .1981) and marine mammals (Howerton et al.1980; Beach et al. 1981) which includeschannel -specific food habl ts information;previous i nvesti yations tended to beei<strong>the</strong>r semi -quanti tat1 ve and not <strong>channels</strong>pecific(Smith and Mudd 1976b) or wereoriented toward marine and neritic habitats(summarized by Simenstad et al,1979a and subsequently by Everitt andJeffries 1973; Everitt et al. 1980).Among <strong>the</strong> five representative terrestrialand aquatic mammals (Table 8.1),three are obligate herbivores whichobtain <strong>the</strong>ir plant foods in adjacentterrestrial and wetland habitats whiletwo are epibenthic carnivores whichventure into channel habitats to feed.Beaver feeding activity in <strong>the</strong> ColumbiaRiver occurred principal ly in Si tkaspruce habitat during a1 1 seasons exceptwinter, when activity in <strong>the</strong> Sitka wil lowhabitat was higher (Dunn et dl. 1981).Muskrat and nutria, on <strong>the</strong> o<strong>the</strong>r hand,forage principal ly in high marsh habitats(Section 8.2), where muskrat preferentiallyeat water parsnip (- suave), Lyngbye'ssedge (Carex lynqbeyinnd s<strong>of</strong>tstgnbul r?lSh (Sci rpus val idus) ; and nutriafeed on a broader spectrum <strong>of</strong> plants, in-sedge, tufteds itosa),7h water parsnip, and s o m mbuirush (Howerton et al, 1980; Dunn etal. 1981). While muskrat illustrated nomajor seasonal variation in <strong>the</strong>ir foragingbehavior, nutria feeding (no. feedingsites hectare-1) appeared to reach amaximum in <strong>the</strong> fall and minimum in <strong>the</strong>sulnner: <strong>The</strong> reed canarygrasslca ttailhabitat was <strong>the</strong> most common foraging habitatin <strong>the</strong> spring and summer, Lyngby'ssedye/horsetai 1 in <strong>the</strong> fa1 1, and colonizings<strong>of</strong>t-stem bulrush during <strong>the</strong> winter.Raccoon, <strong>the</strong> only truly terrestrial mammalutilizing <strong>estuarine</strong> <strong>channels</strong> forfood resources, prey principal ly uponmolluscs (e.g., clams such as Corbiculamani lensis and Anodonta sp. ), moti leepibenthic crustaceans (e.y., crayfishand crabs), and fishes (e.g., eulachon,sculpins such as Cottus sp., carp, andstarry flounder) with secondary inputfrom birds (particularly waterfowl ) andpl ant (rosaceae) seeds and frults (Dunnet al. 1981). River otter in <strong>the</strong> ColumbiaRiver estuary generally overlappedwith raccoon in <strong>the</strong>ir prey cornposition(principally crayfish, carp, Cottus sp.,scul pins, and starry flounder), ected
a diet generally si:nil ar to that reportedby Hi rscni (1978).A1 1 four represer~tati ve marine mammalsare facultative carnivores, threefocusiny tnei r toraging principal ly uponpelagic prey assemblages and one on epibenthicassemblages (Table 8.1). Nor<strong>the</strong>rnsea lions follow baitfish (e.y.,euldcnon) and salmon (e.~., spriny chinook)into estuaries such as <strong>the</strong> Columbia(Beach et al. 1981), feeding principallyat night and probably a1 so corisu~ning o<strong>the</strong>rschooling or large pelagic fishes inchannel habitats (Simenstad et a1 . 1979a).As with <strong>the</strong> nor<strong>the</strong>rn sea lion, noquantitative data on <strong>estuarine</strong> prey <strong>of</strong>California sea lions is available forthis region, but it would be reasonableto assuae thdt o<strong>the</strong>r pelagic schoolingfishes (e.y., <strong>Pacific</strong> herring, nor<strong>the</strong>rnanchovy, <strong>Pacific</strong> sand lance) and largedemersal species (<strong>Pacific</strong> tomcod, starryflounder) a1 so constitute potential preyin <strong>estuarine</strong> <strong>channels</strong>.In addition to <strong>the</strong> focused, intensiveforaying on eulachon in <strong>the</strong> ColumbiaRiver, harbor seals <strong>the</strong>re and in o<strong>the</strong>restuaries <strong>of</strong> <strong>the</strong> region prey upon o<strong>the</strong>rpel ayic school iny and dernersal tish assemulages and moti 1 e nlacroi nvertebrates <strong>of</strong>channel and l i ttoral flat habi tats(Scheffer and Sperry 1931; Scheffer andSlipp 1944; Fisher 1952; Simenstad et at.1979a; brown 1980; Everitt et al. 1980;Beach et al. 1981; Sow1 by 1981). Accordinyly,principal prey species will includeeul achon, nor<strong>the</strong>rn anchovy, whitebaitsmelt, <strong>Pacific</strong> sand lance, lonyfinsmelt, and <strong>Pacific</strong> herring amony <strong>the</strong>schooliny pelayic fishes; <strong>Pacific</strong> torncod,<strong>Pacific</strong> staghorn scul pin, snake prickleback,Enyl ish sole, starry flounder,shiner perch, 1 inycod, and bay yoby amony<strong>the</strong> demersal fish assemblage ; and cranyonidshrimp and Dungeness crab among <strong>the</strong>moti 1 e macroi nvertebrates. O<strong>the</strong>r preywhicn have been reported as prominent inharbor seal diet spectra, includingPaci fit hake (Merl uccius productus), walleyepol lock (<strong>The</strong>ragra chalcogramma) ,<strong>Pacific</strong> cod (Gadus n~acrocephalus) , variousspecies <strong>of</strong> rockfish (Sebastes spp.),rex (Glyi~tocephalus - zachmpetral e(Eopsetta jordani), and Dover soles(Microstomus pacificus), are probablycaptured in non-estuarne habitats or in<strong>the</strong> outer liarg gin ot <strong>the</strong> estuaries' euhalineregions. Considerable inter-estuaryand seasonal variation in diet coa~ositionalso persists. Beach et al.'s(1981) analysis <strong>of</strong> harbor seal scat collectedbetween June 1980 and April 1981in <strong>the</strong> three major <strong>coast</strong>al estuaries <strong>of</strong>Washington indicates significant rank importance(based on frequency <strong>of</strong> occurrence)differences. For example, Paci f iccod (20X), unidenti tied crustaceans (la%,probably crangonid shrimp and Dunyenesscrab), <strong>Pacific</strong> stayhorn sculpin (16%).lonyfin smelt (15%), nor<strong>the</strong>rn anchovy(14%), eulachon (13%), and snake prickleback(lC)%) were important in <strong>the</strong> ColumbiaHi ver estuary; nor<strong>the</strong>rn anchovy (21%),<strong>Pacific</strong> stayhorn scul~in (19X), unidentifiedcrustaceans (15%), shiner perch(13%), Dunyeness crab (12%), and starryflounder (1UX) domindted <strong>the</strong> prey spectrumin Willapa Bay; and nor<strong>the</strong>rn anchovy(49%), <strong>Pacific</strong> staghorn sculpin (34%),English sole (23%), <strong>Pacific</strong> tomcod (17%),Dunyeness crab (15%), and starry flounder(11%) predominated in Grays Harbor.Unequal monthly and total sample sizesand <strong>the</strong> inherent biases <strong>of</strong> frequency <strong>of</strong>occurrence data should be taken intoaccount in evaluating <strong>the</strong>se differencesbut <strong>the</strong> structural variability, as wellas <strong>the</strong> commonality, in food web linkayesbetween harbor seals and <strong>the</strong> variablesecondary consumer levels in <strong>the</strong> threeestuaries is apparent.Seasonal diet variability is alsoobvious. 8each et al. (1981) also describedseal forayiny in <strong>the</strong> ColumbiaRiver estuary as shifting markedly fromeulachon in <strong>the</strong> winter, to lampreys(class Aynatha, principally Lampetraspp.) in early spring, moti le macrolnvertebrates(crustacea) in late spriny, anda diverse, opportunistic selection <strong>of</strong>fishes trom summer to winter months.Seasonal shifts in Willapa Bay harborseal diets were re1 atively di tferent,from crustaceans in winter, to nor<strong>the</strong>rnanchovy from spriny through late summer,and a broader spectrum <strong>of</strong> tish species(led by <strong>Pacific</strong> stagnorn scul~in and
nor<strong>the</strong>rn ancnovy) trom sumer throughfa1 1. Likewise, Grays Harbor seals maintaineda relatively different seasonaldlct pattern: frm Pacfic staghornsculplns, pleuronectids, <strong>Pacific</strong> romcod,and crangonrd shrimp in <strong>the</strong> winter, to adiverse array <strong>of</strong> tisrl anu Uunyeness crabtn <strong>the</strong> summer, to an emphasis upon nor<strong>the</strong>rnancnovy In late sunmer, to <strong>Pacific</strong>staynorn sculptn and Enylisti soie in <strong>the</strong>fall.In addttion to <strong>the</strong>se natural preyitems, harbor seals, in conjunction withCalltornfa sea lfons, are also consideredto ue <strong>the</strong> principal cause <strong>of</strong> nlcsrfne mammaldarndye to fishing year but appear tobe ~lntost ~*o\ety responsible for damagetrt nc?t-~bpt~red Zfsh, which accounts toraa high as 7% <strong>of</strong> <strong>the</strong> sdmpled catch (Beachct 41. 1PliS1).Rltnuugh tncre are not data ontl,+rtrasr scat diet specific to <strong>estuarine</strong>chnfit~thl hdbttat~ wl thln <strong>the</strong> Strsi ts <strong>of</strong>,lurli? clc lt~fa irnd tinuryfe and lbuyet Sound,Interrtnatdon documented traca this region(St.ttc?ltcr atra Spcrry 19331; Fisher 1952;Catdmb~kidtb et al. 1978; Sirnenstad et61. tQ79a; Everltl ct &I. 1980) indicatesctst~slclerable overlap in prey taxa, indicatlng that tt~tuarine channel tauna conktttute& wjor element <strong>of</strong> RarbOr sealFcrurl rurource tn fnland waters. anlytrbytt\et~tb~+y ditta fs available on tneirtoatf RbOlts and llttle originates tronrtnts rciyion; prey am assumed to beyr-tnclpal ly dmcrsill fish, and pelagicft$ti and CP~R~~OCJOCIS (Stmenstad et at,191Ya; Antunel 1s snd Flscus 1980; Everittet a!. l!&B.l).frrter~rttaion ot <strong>the</strong>se tood web relatronbnrpsr~suits in a coml~osite food webtor P$EUI~~IICP channel comun t t ies (fig.G.1) which is at least quatftativelyartentea more toward aetrltus util lzalionand heter~tr0yfitt pr~duction than towardpelaylc auCutrayntr production. If Stand-Iny stock <strong>of</strong> detfltlvares and tneir yredatarsr?; lndiedtlve, <strong>the</strong> food webs arequa1 't tatively dmrnatett by detrital car-%ran, As idenertrea ~?y de Sylva (1975).Udm! and Maa~ld (197s). and Northcote etat. (23731, insst Gtstuartne rood webs fallinto two cateyorles: 1) relativelyclear, deep systerns where organic caraonis derived prlmarl ly frorrl phytoplanhtonproduction, and 2) compdrdtlvely turbld,snal low estuaries wnere <strong>the</strong> cdrbonoriginates trom a cornbinatton <strong>of</strong>macrophyf lc production (both exoyenOuSand endogenous), wn iCh I s degrdded todetritus and utlllred by mlcr<strong>of</strong>tord, anaperipnyte productlon. Very tew estudrtesin <strong>the</strong> Paclfic <strong>Northwest</strong> fall Into tnefirst cateyory, especial ly tf we lncludethose estuarres which, althougn seldomturbid, may nave tood webs based upondynamic, short-tenn recycl 1 ny ot endoyenouscarbon exuded ay any 1 ospernts, Inac roalgae,and eplynytes (Wlssrl~ar an0 Slfnenstad,Fish. Kes. Inst., Uniw. Wash.,unpubl. aata; see Sectlon 4.1). Thus,direct (pelagic) autotrovnic productlunIs only maryinal\y supportive <strong>of</strong> <strong>estuarine</strong>tood WDS In tne reylon dnd is yrnerallyrestricted to tne larye codstalestuarle~ wnere treshwa ter dnd estur lnephytoplanktrrs are entrained in a conf1 ned euvhot I c zone.A~nony <strong>the</strong>se yeneral ized food wea1 inkayes $re several dl st 1 nct modules(Palfle 1980) which typi ty estuar~ne cndnnelco~rmunities, not only in structurebut <strong>of</strong>teri In cotirnon consunrer taxa. 'fhrsoorrest, least-conlpartmented food web(it is still a "web" due to conSlderabiepredator-prey interaction within dcoqartm@nt such as tot! benthic lntduna)is that Northcote et a]. (1979) descrlbeaBS :detrft~s~benthos~benttto~ndyous f t sneswhen tertiary Consumers included, <strong>the</strong>archetyptcal food webs in this cdrrgurywould rnclude both "cfetritus:benthrc1nfauna:obl iyate ~entnlvore: tunctrondepibentnic cdrnivore" iirodules ds wel 1 as"artri tus :@pibenthic zoop t ankton: tuneti~naleyibenthlc plarrkt~vores :tunctlont~1eprarntnlc carnivore" modules such as:More con~ylexr ty is evident in detrl tusbased,eyibenthic ntodules which involve
PRODUCERFig. 9.1. Representative food web <strong>of</strong> <strong>estuarine</strong> channel habitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>;sizes <strong>of</strong> linkage arrows illustrate relative biomass transfer.mei<strong>of</strong>auna carnivores such as Crangon spp.or benthic carnivores such as Cancerspp., resul tiny in "detritus :detritivorouseyi benthic zooplankton: benthiclepi benthiccarnivore (2') :facultative epibenthiccarnivore (3")" modules such as:Planktonic food webs are characteristicallyshorter, as represented by <strong>the</strong>phytopl ankton: herbivorous pelagic zooplankton:obl igate planktivore: obl igatepiscivore module, a1 though <strong>the</strong>y can becomplicated by <strong>the</strong> inclusion <strong>of</strong> carnivorouszooplankton such as Acartia spp.,where:<strong>The</strong> ul tirnate compl exi ty is represented bymodules including species ~hich are ei<strong>the</strong>rextre~liely plastic (facul tative) in <strong>the</strong>feediny behavior or incorporate or growthrough several feeding strategies over<strong>the</strong> period <strong>of</strong> residence in <strong>the</strong> estuary.This is particularly evident in <strong>the</strong> case<strong>of</strong> juvenile salmonids, vrhich utilize bo<strong>the</strong>ndogenous and exogenous (to <strong>the</strong> habitatand, <strong>of</strong>ten <strong>the</strong> estuary) detritivores andherbivores. <strong>The</strong> resulting modules can beambi yuously described as detri tus/phytoplankton:detritivorous epibenthic zooplankton/herbivorous pel ay ic zoopl ankton:epibenthiccarnivore: facul tative epibenthiclpelagicp1anktivore:obligatepiscivore such as shown on <strong>the</strong> fol lollringpage. Of course, this complexity seldomexists to this extent within any channelclass, order, or configuration, or anysize class <strong>of</strong> consumer (e.g., juvenilesalmonid) at any one time, but variesuniquely as a function <strong>of</strong> all <strong>the</strong>se variables.
Classically, <strong>the</strong> diversity (i.e.,nul-iber <strong>of</strong> connecttons ar "connectence" )and strength <strong>of</strong> <strong>the</strong>se interactions havebeen correlated wllth <strong>the</strong> stability (i.e.,its inherent susceptlbf 1 t ty to collapse toa JJfferent, usually less dlverse structurewhen perturbed by removal <strong>of</strong> 1 f nkagesor nodes); this poses <strong>the</strong> question <strong>of</strong>dhekher food webs are "structured" or"unstructured" (MacArthur 1955; Watt 1964;Paine 1966, 1969; Sardner and Ashby 1370;lsadcr; 1972, 1973; May 1972, 1973; DeAncjelis 1975), Thc imp1 icatfons <strong>of</strong> mutatirricrrlalfonships have also been recentlyitlclrrpor~ted into <strong>the</strong>se models (Vance19183. Onfartunately, <strong>the</strong> functionalr.;rilience <strong>of</strong> <strong>the</strong>se mdules, <strong>the</strong>lr linkages,and <strong>the</strong>lr dependence upon externalevents; has seldom been tnvesttgated frm<strong>the</strong> s tat~dpoint af <strong>the</strong> processes genera tinytilei r structure and, until that resolut tonuf rvrearch is appl led to <strong>estuarine</strong> chantrrleun~rtuni tics, <strong>the</strong> ques tlon <strong>of</strong> food webstdbi l "ry wJll reinah unresolved,We can,hoii~ever, set ec t f vlely examine ercempl ars <strong>of</strong>pratnJnent predator-prey or competitionintersctfons far clues to <strong>the</strong> strength <strong>of</strong>I inkages within representative mcxiules or00 <strong>the</strong> potential stabi? ity <strong>of</strong> <strong>the</strong> slrnplerisvdul es & &I&,41.2 ROLES OF PREDATION RNO COMPETI-IIW lNTEri4CTlONS If4 SPRUCTURIK COM-MVOUNITIES AhtD PO00 MfDS<strong>The</strong>re are, among <strong>the</strong> modules dencrtbedIn <strong>the</strong> prev fous section, i 1 lustratjons <strong>of</strong> strong predator-prey and cwnpetitlvninteractlcrns wherein <strong>the</strong> distrlbutqonand slbundance <strong>of</strong> <strong>estuarine</strong> channel organlsrzlr,and thus <strong>the</strong> structure <strong>of</strong> <strong>the</strong>cornauni ty, a* canetagant upon <strong>the</strong> presenceand myna tude <strong>of</strong> <strong>the</strong>se 1 inkages.A1 though fw <strong>of</strong> <strong>the</strong>se examples originatefratn <strong>Pacific</strong> Horthwes t estuaries, <strong>the</strong>y aresufficiently close analogues that reasanableinferences to <strong>the</strong> region's <strong>estuarine</strong>channel cawunities might be inade.One <strong>of</strong> <strong>the</strong> strongest linkages suggestedis that between <strong>the</strong> cdlanoid &- tia spp. which could represent an importantpredator upon <strong>the</strong> larvae <strong>of</strong> <strong>the</strong>dominant <strong>estuarine</strong> calanoid in <strong>the</strong> region,and Rippingale's<strong>of</strong> Cronin et al.and Jeffrles (1967) accounts <strong>of</strong>zooplankton in North Aerican estuariesindicated that Acartia, by its carnivoryupon crf tfcal l h i s t o r ~ stages <strong>of</strong> <strong>the</strong>cs tuari es' Eur te~nora populations, mayprevent r i g a 4 ~ r e c r utment i to <strong>the</strong>adult population, Cocnparable AcartiaJElr temora data sets also exist m a -&a Bay (Frolander et al. 1913). <strong>the</strong>Columbia River estuary (Haertel and 0s terbery1967). Netarts Bay (Ziminerman 1972),and Grays Harbor (Simenstad and Eggers1981). Fur<strong>the</strong>r testing and verification<strong>of</strong> this hypo<strong>the</strong>sis mst depend upon fur<strong>the</strong>rdetailed analysis <strong>of</strong> <strong>the</strong>se datasets.<strong>The</strong> potential for predation structuring<strong>of</strong> epiknthic harpacticoid copepaddssefnblages 4n shal low sub1 i ttoral habttats<strong>of</strong> Hood Canal by juvenile chum salmonwas suggested by Simenstad et al. (1980)and Sitenstad and Salo (1982). Given <strong>the</strong>intensive, selective foraging pressurethat juveni Ie saltwnids exert upon epibenthicharpacticoid copepod (e.g Nargamnaridanphlpod 'it?=,M A j * and cumacean (e.g.. Cumella)& t is highly probable that p-dforaging upon <strong>the</strong>se epibenthic preyresources by high deqsi ties <strong>of</strong> juvenilesaltnon could resul t in dratna tic res tructurlny<strong>of</strong> that assetnblage. This is evenmore probable gfven <strong>the</strong> high density,pulse releases <strong>of</strong> juvenile salmon fromhatcheries which may result in mf 11 ions <strong>of</strong>fish entering estuaries at one time.A1 though <strong>the</strong>re has been no comprehensive,estuary-ride exdrnfnatian <strong>of</strong> such arelatianship, <strong>the</strong> same situation may existin <strong>the</strong> pelagic environs uf those estuarieswhich experience high densities <strong>of</strong> larval
and juvenile plankti vorous fish. YaquinaBay, <strong>the</strong> Columbia River estuary, and GraysHarbor have we1 1-documented concentrations<strong>of</strong> Paci f ic herring, nor<strong>the</strong>rn anchovy, andsmelts (particularly surf and longfin)which are both temporally and spatiallyabundant duri ng certain seasons (see Section6.2). But Johnson's (1981) analysis<strong>of</strong> <strong>the</strong> Acartia cal i forniensis populationin Yaquina Bay (see Section 5.4) providesample 'evi den& that such selecti ve predationcan effectively control abundancecycles, and ul tiinately production, <strong>of</strong> <strong>the</strong>prorilinent members <strong>of</strong> <strong>the</strong>se zoopl anktonassemblages. Under such intense andselective foraging pressure on pelagiczooplankton, predominantly <strong>the</strong>se calanoidcopepod taxa, <strong>the</strong>se obl igate pl ankt ivoresmay we1 1 structure <strong>the</strong> composition, diversity, and standing stock <strong>of</strong> <strong>the</strong> <strong>estuarine</strong>channel zooplankton assemblage.Si tts and Knight (1979) and o<strong>the</strong>rs(C. Simenstad, Fish. Res. Inst., Univ,Wash., unpubl. data) have produced evidencethat <strong>the</strong> crangonid shrimp Cran onfranci scorum <strong>of</strong> ten feeds extensive I-- y upon<strong>the</strong> mysid Neoniysis mercedis. Si tts andKnight in fact, estimated that C. franciscoruniremoved between 0.1% and 5 . 0 m e- N. mercedis biomass daily from <strong>the</strong> Sacramento-SanJoaquin River estuary, and that,by preying selectively upon intermediatesized (4-7 mm) mysids, <strong>the</strong> shrimp aresignificantly affecting <strong>the</strong> mysid populationstructure. <strong>The</strong> persistence <strong>of</strong> such aCrangon-Neomysi s interact ion in <strong>the</strong> Paci f-ic <strong>Northwest</strong>, particularly in <strong>the</strong> large<strong>coast</strong>al estuaries which maintain largepopulations <strong>of</strong> both taxa, is highly probableand fur<strong>the</strong>r il lustrates <strong>the</strong> importance<strong>of</strong> <strong>the</strong> detritus-based module involving <strong>the</strong>e ~ benthic i zoopl ankton prey <strong>of</strong> inysids (l.iercedi s) and ' shrimp (c.- franci scorum~,and <strong>the</strong> ~rominent predators on <strong>the</strong> shrimp(starry 'flounder and harbor seal). <strong>The</strong>relative importance <strong>of</strong> this particularmodule may be evaluated in final syn<strong>the</strong>sis<strong>of</strong> <strong>the</strong> CREDDP studies (Col. Riv. Est.Study Team, pers. comm.), which includedquatti tative assessment <strong>of</strong> <strong>the</strong>se taxa in<strong>the</strong> Colurnbia River estuary in 1980-1981.9.3 ESTUARINE CHANNELS AS CRITICAL REPRO-DUCT1 VE, NURSERY , FORAGING, AND REFU-GIA HABITATSEstabl ishment <strong>of</strong> uti 1 i zation patternsand food web \nodules involving <strong>estuarine</strong>organisms carries iinp1 ici t assumptions <strong>of</strong>dependence upon <strong>the</strong>se re1 a tionships most<strong>of</strong> which, however, are co~npl etely unverifiable.Uhe<strong>the</strong>r <strong>the</strong> loss or major disruption<strong>of</strong> a food web linkage or microhabitatwould actually result in <strong>the</strong> subsequentdecl ine in <strong>the</strong> population remains conjectureunless control 1 ed rnanipul ationexperiinents can he conducted. Out, unlikethose which have been successfully conductedin marine rocky 1 i ttoral (see Paine1977, a~nany rnany) and shal low sub1 i ttoralsand- or mudfl at habi tats (Vi rnstein 1977;and Aoodin 1951; among not so many; hutsee Hurlberg and 01 iver 1980 for discussion<strong>of</strong> interpretive 1 irni tations), effec-tive manipulations within <strong>the</strong> dynamic<strong>estuarine</strong> channel habi tats have seldombeen attempted and would be even inoredifficult to interpret due to extremevariation in uncontrollable physiochernicalconditions. <strong>The</strong> fol lowi ng il lustrations<strong>of</strong> potentially "critical" habitat associationsare, <strong>the</strong>refore, only descriptivehypo<strong>the</strong>ses which relnai n to be effectivelytested.Compared wi ttl o<strong>the</strong>r habitats, <strong>estuarine</strong><strong>channels</strong> appear to be limited inproviding optimum condi ti ons for reproduction<strong>of</strong> most fauna. Except in <strong>the</strong> case <strong>of</strong>blind (e.g., tidal) <strong>channels</strong>, high watervelocities and uns tab1 e bottom sedimentsin most channel habitats inhibit manyinvertebrates and vertebrates from establishingnesting sites; even <strong>the</strong> suitability<strong>of</strong> <strong>the</strong> tidal <strong>channels</strong> is <strong>of</strong>ten limitedby tidal dewatering, Fauna which dospawn in <strong>channels</strong> typi cal ly depos it adhesiveeggs (gastropods, 1 i ngcod) , bury<strong>the</strong>ir eggs (salmon), or carry and brood<strong>the</strong> eggs and 1 arvae/ juveni les (gammari damphipods, i .e., Eogammarus spp. ;Dungeness crab). But, except for <strong>the</strong>spawniny immigration <strong>of</strong> salmon (typicallychum and pink salmon) into <strong>the</strong> <strong>channels</strong><strong>of</strong> estuaries' upper reaches, most repraductiveactivities are confined to residentfauna which undergo <strong>the</strong>ir entire life
cycle within <strong>the</strong> estuary. Many <strong>estuarine</strong>residents, however, mi grate from channelto o<strong>the</strong>r habitats to reproduce. Estuarinebirds, <strong>of</strong> course, are <strong>the</strong> extremecase, as none actually nest within <strong>the</strong>habitat. But resident fishes such assturgeons, smet ts, gobies, stickelbacks,and many sculplns move to ei<strong>the</strong>r channelboundaries or o<strong>the</strong>r esturf ne habitats(e.y., shat low sublittoral or littoralsand- or mudflats; saltmarshes) to spawn.whe<strong>the</strong>r from resident or exoyenouspopulations, both f nvertebrate and vertebratelarvae and juveni 1 es can residewithin <strong>estuarine</strong> <strong>channels</strong> for extendedperiods <strong>of</strong> time, essentially utilf zing<strong>the</strong> habitat as a "nursery" until settl inyout into benthic, epibenthfc, or demersalassemblages ar moving out <strong>of</strong> <strong>the</strong> habitat.<strong>The</strong> net outlfow circulation pattern <strong>of</strong><strong>the</strong> estuaries, however, represents a majorinhibitor to prolonged entrainment <strong>of</strong>yldnktonic larvae. Assuming neutral buoyancyand passive behavior, <strong>the</strong> minimumrate <strong>of</strong> reproduction reqtlired for an endm1c zooplankton popul at Ion to maintainitself in an estuary is detern~ined by <strong>the</strong>rate ot circulation, such that reproductionmust be higher than <strong>the</strong> tidal exchangetoss rate (Ketchurn 1951, 1954).But <strong>the</strong> organisms' behavior is not passiveand yartjcular li te history patternsand behaviors <strong>of</strong> such organisms haveevolved to oytimfze <strong>the</strong>lr <strong>estuarine</strong> residencetfrne. Carriker (1951). Bousfield( 1955). Pearcy (1962)" Wood and Haryis(1971), Graham (1972), de Woiff (1974),Sandlfer (1915), Wheeler and Epifanlo(1978). Cronin and Forward (1979), andCronin (1982) have a1 1 described behavioralretention mechani smS exhibited by1 arvae in two-l ayered estuaries havjnynet landward flow along <strong>the</strong> bottom duringperiods when larvae arc? abundant, <strong>The</strong>irstudles i 1 lustrated that larvae can prolong<strong>the</strong>ir resjdence in <strong>the</strong> estuary byact1 vely nrigrating into <strong>the</strong> landward-f lowingsurtace water on flood Cfdes. Slmilarretention mechani sins have a1 so been postulatedto account for <strong>the</strong> maintenance <strong>of</strong>resident mop1 ankton (e.9.. 1populations in estuarjes (KO ,Hurl ber t 1957; Wooldridge and Erasmus1980). Carri ker (1959) , Sandifer (1975),and Johnson and Gonor ( 1982) , however,have i 1 lustrated situations where s m<strong>estuarine</strong> larvae are flushed out <strong>of</strong> <strong>the</strong>estuary <strong>of</strong> origin, only to be transportedback into o<strong>the</strong>r, adjacent estuaries aslater larvae, post-larvae, or juveniles*Johnson and Gonor (1982), in fact, estimatedthat 88% <strong>of</strong> <strong>the</strong> total abundance <strong>of</strong>Call ianassa cal iforniensis stage I zoeawere carried out <strong>of</strong> <strong>the</strong> Salmon River estuaryon <strong>the</strong> ebbing tide; this would resultin a "leap-frog" transport and metamorphosis<strong>of</strong> larvae in and out <strong>of</strong> estuariesalong <strong>the</strong> <strong>coast</strong> until <strong>the</strong>y settled out in<strong>the</strong> benthic form. Johnson and Gonor (1982)suggested that <strong>the</strong> concentration <strong>of</strong> Call i --- anassa larvae in <strong>the</strong> <strong>coast</strong>al n m cwaters and successful recruitment to<strong>coast</strong>al estuaries was enhanced by <strong>the</strong>alternation <strong>of</strong> active upwelling and relaxationperiods which Huyer (1976) described<strong>of</strong>f Oregon. Thus, <strong>the</strong> extent and importance<strong>of</strong> <strong>estuarine</strong> retention <strong>of</strong> larvae maydepend upon both <strong>the</strong> position <strong>of</strong> <strong>the</strong> repraducingpopulation, since maximum retentionwill occur with populations in <strong>the</strong>upper reaches <strong>of</strong> <strong>the</strong> estuary (Dayton andOliver 1980), as well as <strong>the</strong> evolved behavforal repertalre and seasonal periodic-Ity <strong>of</strong> <strong>the</strong> reproductive and early lifehistory events.Pearcy and Myers (1974) provide one<strong>of</strong> <strong>the</strong> few comprehensive assessments <strong>of</strong><strong>the</strong> value <strong>of</strong> a <strong>Pacific</strong> <strong>Northwest</strong> estuaryas a nursery habitat for larval fishes,excludiny McHuyh's (19b7) suggestion thatPactffc <strong>coast</strong> estuaries are less importantthan eastern seaboard estuaries.<strong>The</strong>y established that, indeed, larvae <strong>of</strong>most species were Inore common <strong>of</strong>f shorethan wlthin <strong>the</strong> estuary and that <strong>Pacific</strong>herring larvae were <strong>the</strong> only commerciallyimportantspecies to utilize <strong>the</strong> estuaryas a nursery habitat. O<strong>the</strong>r, lessnetarious species whlch were also identifiedto utilize Yaqulna Bay were baygoby, prickly sculpfn, buffalo sculpin,and <strong>Pacific</strong> staynorn sculpin (see Table6.21; o<strong>the</strong>r studies also suqqested thatposiiarval and juvenile embiotocids (P.furcatus, R, vacca, and E, IateraliT)no-G$ pr%mini(8eardsl@ 1969; WaresIYtlf. Later studies <strong>of</strong> <strong>the</strong> zoo- and ichthyoplankton<strong>of</strong> <strong>the</strong> Columbia River and
Grays Harbor estuaries suggest that larvaland juvenile nor<strong>the</strong>rn anchovy, surfand longfin smelt, and eulachon shouldalso be considered as nursery residentsin <strong>the</strong> <strong>coast</strong>al estuaries (see Sections6.2.1-6.2.3.).Although <strong>the</strong>ir larvae are not <strong>of</strong>tendocumented as abundant components <strong>of</strong> <strong>the</strong>ichthyopl ankton, juvenile pleuronectids(prominently starry flounder, Englishsole, and speckled and <strong>Pacific</strong> sanddab)are abundant in demersal f i sh assemblages,particularly those which occupy shallowsubl i ttoral regions <strong>of</strong> <strong>estuarine</strong> channeland adjacent tideflat habitats (Westrheim1955; Beardsley 1969; 01sen and Pratt1973; as well as those cited in Section6.1). <strong>The</strong>se species <strong>of</strong>ten i 1 lustrateincreasingly deeper depth di stri bu tionsrelative to increasing fish size, suchthat <strong>the</strong>y appear to move <strong>of</strong>f <strong>the</strong> tideflatsand fur<strong>the</strong>r into <strong>the</strong> <strong>channels</strong> as <strong>the</strong>y growlarger. This depth-size relationship hasnot been well-documented, nor have <strong>the</strong>causal mechani s~ns been evaluated, a1 thoughboth predator avoidance and foraying onoptimal prey resources could explain thistransition.Juvenile salmonids illustrate one <strong>of</strong><strong>the</strong> better example <strong>of</strong> active retention in<strong>estuarine</strong> <strong>channels</strong> over a critical periodin <strong>the</strong>ir early life history. <strong>The</strong> fivespecies show varying durations <strong>of</strong> <strong>estuarine</strong>residence (Table 6.3), with markedintraspecific variation resulting fromrespectively variable times and sizes atentry into <strong>the</strong> estuary. Within <strong>the</strong> estuaryare a diverse array <strong>of</strong> prey resources,<strong>of</strong>ten in extremely high density(e.9, , harpacticoid copepods, Coro hiumamphi pods, chi ronomi d 1 arvae, decapod -7 anfish larvae), which allow <strong>the</strong> juvenilesalmon to sustain high growth rates (ashigh as 6% body weight per day) whileoccupying a relative refugia from predation(Simenstad et al. 1982b); whe<strong>the</strong>rthrough schooling in shal low subl i ttoral ,eelgrass habitats (i e., juvenile chumsalmon) or turbid pelagic waters (i.e.,chinook smolts), <strong>the</strong>se systems may benarrowi ng <strong>the</strong> "wi ndow <strong>of</strong> vul nerabi 1 i ty"to predation outside <strong>the</strong> estuary by "growingout" <strong>of</strong> it while in <strong>the</strong> estudry.This relationship between <strong>estuarine</strong>residence time and foraging success, and<strong>the</strong> implications to <strong>the</strong> total marinesurvival rate, suggests that <strong>the</strong> distributionand dbundancu <strong>of</strong> <strong>the</strong> principalpreferred prey (Table 9.1) ultimatelydetermine <strong>the</strong> production <strong>of</strong> <strong>the</strong> salmonpopulations migrating through <strong>the</strong> system(Northcote et al. 1979; Simenstad andSal o 1982; Simenstad et a1 . 1982a, b).9.4 INTEKKELATIONSHIPS AMONG ESTUARINECHANNEL HABlTATS AND RIVEKINE, WET-LAND, OCEANIC, AND OTHER ESTUARINEHABITATSFood web and o<strong>the</strong>r ecological interactionsamong channel and o<strong>the</strong>r <strong>estuarine</strong>habitats as well as with habitats outside<strong>the</strong> estuary are manifold. <strong>The</strong>y rangefroin simple transport <strong>of</strong> pelagic phytoplanktonand zooplankton into and out <strong>of</strong><strong>the</strong> channel community from and to riverineand oceanic sources, to <strong>the</strong> complexexchange and entrainment <strong>of</strong> exogenousdetritus. <strong>The</strong>se, like <strong>the</strong> transport <strong>of</strong>larval fish and invertebrates into <strong>the</strong>habitat, are relatively passive actionswhich result from physical (e.g., tidal)influences. O<strong>the</strong>r transfers, such as <strong>the</strong>migrations <strong>of</strong> anadromous fishes and birds,can occur on a seasonal scale, whereas<strong>the</strong> movement <strong>of</strong> fishes from <strong>the</strong> shallowsublittoral flat habitats into <strong>the</strong> channelhabitats with tidal dewatering occurapproximately every six hours, invol veactive movements <strong>of</strong> organisms but may beequally predictable.At <strong>the</strong> base <strong>of</strong> <strong>the</strong> <strong>estuarine</strong> channelfood web, detritus constitutes <strong>the</strong> mostcritical material originating from outside<strong>the</strong> community. Alteration <strong>of</strong> <strong>the</strong>detritus resource--its supply, timing, orcharacter--to <strong>estuarine</strong> <strong>channels</strong> posesdirect impacts upon <strong>the</strong> structure andstanding stock <strong>of</strong> all consumer organismsin those food web modules based upondetritivores. Whe<strong>the</strong>r originating fromriverine sources completely outside <strong>the</strong>estuary (e.9.. DOC; Naiman and Sibert1978) or from within adjacent habitats(vascular sal tmarsh plants; Kistritz andYesaki 1979), <strong>the</strong> accumulation and retention<strong>of</strong> detritus is dependent upon <strong>the</strong>
compl ex factors effecting ci rcul at ion andsal i nity intrusion. <strong>The</strong> endogenous sources<strong>of</strong> trophic energy, autotrophic producerssuch as phytoplankton and algae, donot, on <strong>the</strong> o<strong>the</strong>r hand, provide an equivalentproportion <strong>of</strong> <strong>the</strong> total carbon budgetcycling through <strong>the</strong> community.Primary consumers are typically endemic populations. Benthic 1 nf auna andsessi le epifauna are 0bvi0u~ly residentassemblayes but <strong>the</strong> organisms recruitinyto <strong>the</strong>se populations oriyinate from parentassemblayes outside that particul arestuary, perhaps even from o<strong>the</strong>r, adjacentestuaries (see Section 9.3). Extremeexamples <strong>of</strong> primary consumers (orprey resources <strong>of</strong> secondary consumerssuch as juvenile salmonids) which origi -nate from outside <strong>the</strong> community are <strong>the</strong>terrestrial insects which are transportedinto <strong>the</strong> neuston assemblage from <strong>the</strong>watershed upriver or are blown in frornwet1 and and up1 and habitats bordering <strong>the</strong>estuary.More motile secondary and tertiaryconsumers include progressively more non-endemi c popul ati ons, which ei<strong>the</strong>r derive<strong>the</strong>ir recruitment from outside <strong>the</strong> community (e.g., <strong>Pacific</strong> herring, nor<strong>the</strong>rnanchovy) or intermi ttently occupy <strong>the</strong>habitat for important functions (e.g.,foraging by harbor seals; roosting by migratoryseabirds ). Accordingly , many <strong>of</strong><strong>the</strong>se immigrants are critical components<strong>of</strong> prominent food web modules and through<strong>the</strong>se roles are largely responsible for<strong>the</strong> structure <strong>of</strong> <strong>the</strong>ir prey assemblages.<strong>The</strong> community a1 so exports considerablebiomass, both passively through <strong>the</strong>net flow out <strong>of</strong> <strong>the</strong> system, carrying varying proport ions <strong>of</strong> <strong>the</strong> pel agi c phytopl anktonand zooplankton to oceanic habitats,and actively through <strong>the</strong> emmigration <strong>of</strong>secondary and tertiary consumers. <strong>The</strong>end result <strong>of</strong> <strong>the</strong> nursery process involvinglarval and juvenile fishes discussedearlier provides <strong>the</strong> best example <strong>of</strong> thisexport: almost a1 1 bai tfi sn--herring,smelts, anchovies, eul achon--whi ch residein <strong>estuarine</strong> <strong>channels</strong> during <strong>the</strong>ir early1 i fe hi story eventual ly mi grate out <strong>of</strong><strong>the</strong> estuary after consuming a large portion<strong>of</strong> several year's pelagic zooplanktonproduction.
CHAPTER 10SUMMARY - THE ROLE OF CHANNEL HABITATS IN ESTUARINEECOSYSTEMS AND MANAGEMENT IMPLICATIONSIn essence, <strong>the</strong> role <strong>of</strong> channel habitatscan metaphorically be equated to that<strong>of</strong> any 1 i vi ng organi sm' s circulatory systemin that transport <strong>of</strong> energy, nutrients,wastes, and <strong>the</strong> living products <strong>of</strong>an <strong>estuarine</strong> ecosystem flow within <strong>the</strong>sepassages. Similarly, as <strong>the</strong> loss <strong>of</strong>peripheral appendages or organs may notnecessarily affect <strong>the</strong> ultimate function<strong>of</strong> circulation, loss <strong>of</strong> adjacent <strong>estuarine</strong>habitats may not depreciate this transportrole <strong>of</strong> <strong>channels</strong> ; however, <strong>the</strong> carryingcapacity and production <strong>of</strong> <strong>the</strong> overallsystem (i.e., it's quality) will undoubtedlydecline. On <strong>the</strong> o<strong>the</strong>r hand, significantinhibition <strong>of</strong> channel habitats' capacitiesto function, 1 i ke arteriosclerosis,will ultimately result in deterioration<strong>of</strong> <strong>the</strong> whole estuary as a healthy, productiveecosystem. It is difficult to understand,<strong>the</strong>n, why <strong>channels</strong> have typicallybeen some <strong>of</strong> <strong>the</strong> most highly impactedhabitats but typically <strong>the</strong> most ignoredestua~i,ne envi rons when management goalsand priorities are set. Presumably, <strong>the</strong>dynamics <strong>of</strong> continuous riverine and marineinfusion <strong>of</strong> high quality water andorganisms are assumed to naturally mediate<strong>the</strong> insults occurring within <strong>the</strong> estuaryitself or those interjected into <strong>the</strong> systemfrom upriver or from <strong>the</strong> ocean. But,as a result, several estuaries in <strong>the</strong><strong>Pacific</strong> <strong>Northwest</strong> have become burdenedwith supposedly innocuous modificationsto <strong>the</strong> point <strong>of</strong> disfunction.Of a1 1 <strong>estuarine</strong> habitats, <strong>channels</strong>have undoubtedly been diminished quanti tatively<strong>the</strong> least. Bortleson et al. (1980)have illustrated some <strong>of</strong> <strong>the</strong> dramaticlosses <strong>of</strong> subaeri a1 wet1 and habitat (100%in Puyallup River, 99.2% in Duwamish Kiver,and 96.4% in Samish River estuaries)but indicated no losses in channel habi-tat. Thomas' (1982) exhaustive analysis<strong>of</strong> habitat changes in <strong>the</strong> Columbia Riverestuary2since 1868 provided an estimate <strong>of</strong>10.4 km <strong>of</strong> deep water (>6 m below MLLW)habitat lost since that time. Over <strong>the</strong>entire estuary, this is a change <strong>of</strong> only7.3%, as compared to losses as high as76.8% for o<strong>the</strong>r habitats (e., tidalswamps). This relatively minor loss <strong>of</strong>habitat applies, however, only to mai nstemand subsidiary <strong>channels</strong>. Losses <strong>of</strong> blindor tidal channel habitat are much more extensivebut unfortunately unestimated.Thyas (1982) estimated a 43.2% loss (28.3km ) <strong>of</strong> tidal marshes in <strong>the</strong> Columbia River*estuary and Levy (1980a) a 39% (0.23km ) loss <strong>of</strong> <strong>estuarine</strong> marshes in <strong>the</strong>Fraser River estuary, but it is impossibleto estimate what portion <strong>of</strong> <strong>the</strong>se lossesinvolved channel habitats.Qua1 i tati ve changes in <strong>estuarine</strong><strong>channels</strong>, however, have been rampantsince "civilized" man arrived in <strong>the</strong> region.Some <strong>of</strong> <strong>the</strong>se are <strong>the</strong>, result <strong>of</strong>accretion and erosion unrelated to man'sinfluence, but are symptomatic <strong>of</strong> <strong>the</strong>natural "aging" processes in <strong>the</strong> evolution<strong>of</strong> an estuary. In <strong>the</strong> more than 100years since <strong>the</strong> Columbia River estuary wasfirst mapped in entirety, this relativelyundeveloped estuary has undergone somedramatic changes in channel configuration(Fig. 10.1). Certainly changes over <strong>the</strong>last forty years can be attributed partially to anthropogenetic a1 terations suchas dredging and dredge spoil disposalwithin <strong>the</strong> estuary and hydroelectric powerdam construction (and resulting river di s-charge a1 teration) outside <strong>the</strong> estuary.But it must be remembered that <strong>the</strong>se processesare characteristic <strong>of</strong> <strong>the</strong> normalphysical dynamics <strong>of</strong> an estuary and, although<strong>the</strong>y can be modified by man's
Fig. 10.1. Configuration <strong>of</strong> channel habitats (>6 m below MLLW) in <strong>the</strong> Columbia Riverestuary in 1868-1875 (A) and recent time (6); maps modified from Columbia River EstuaryStudy Taskforce (unpubl .) maps prepared for Thomas (1982).118
structures and o<strong>the</strong>r manipulations areseldom el iminated. For example, during<strong>the</strong> last 100 years <strong>the</strong> volume <strong>of</strong> <strong>the</strong> MerseyRiver, England, estuary has declinedabou8 10% despite dredging <strong>of</strong> over 500 x106m <strong>of</strong> material (Price and Kendrick1963).Physiochemi ca1 attributes such assalinity and <strong>the</strong>ir influence upon <strong>the</strong>estuary's communities have also been alteredover time as a result <strong>of</strong> <strong>the</strong> effect<strong>of</strong> ba<strong>the</strong>metry upon <strong>estuarine</strong> mixing andsalinity intrusion. Thomas (1982) <strong>the</strong>orizedthat more extreme flow fluctuations,extensive shoaling, and a measurablydifferent geomorphology <strong>of</strong> <strong>the</strong> entranceto <strong>the</strong> Columbia River estuary formerlyproduced more temporal ly and spati a1 lyextreme salinity regimes than now exist.<strong>The</strong> result was probably an essentiallyfreshwater system at all stages <strong>of</strong> tideduring large spring freshets and increasedsalinity intrusion during periods <strong>of</strong> lowdischarge; this may have been substantiatedby <strong>the</strong> reports <strong>of</strong> significantly brackishwater near Gray's Point in 1805(Thwaites 1959) ; see Fig. 10.1.Qualitative change in <strong>estuarine</strong> channelmorphology has also changed <strong>the</strong> demography<strong>of</strong> man's exploitation <strong>of</strong> <strong>estuarine</strong>fish fauna. This is best illustrated by<strong>the</strong> changes in commercial salmon fishingstrategies in <strong>the</strong> Columbia and FraserRivers estuaries, wherein dredged navi -gation <strong>channels</strong> can now be fished muchmore effectively by certain net (driftgi 1 lnet, purse seine) fisheries.So man's influence is superimposedupon a natural ly evolving, dynamicsystem. <strong>The</strong> difference is in <strong>the</strong>short-term, intense perturbations mancontinues to impose upon estuaries.10.1 SOURCES AND MECHANISMS OF IMPACTA suite <strong>of</strong> impacts result from man'sdevelopment <strong>of</strong> estuaries and <strong>the</strong>ir contributingwatersheds. Among <strong>the</strong> majorperturbations occurring within <strong>the</strong> channelwhich can produce deleterious impacts to<strong>the</strong> <strong>estuarine</strong> ecosystem are:1) Dredgi ng and dredge-spoi 1 disposal ;2) Filling and o<strong>the</strong>r so-called landreclamation;3) Jetty, training wall, and o<strong>the</strong>rconstruction;4) Urban and industrial effluentdischarge;5) Log dumping and storage;6) Commercial or recreational exploitation<strong>of</strong> fauna and its artificialenhancement; and7) Upstream water diversions and storagereservoi rs.In addition to <strong>the</strong>se, alterations to adjacent<strong>estuarine</strong> or exogenous riverine orup1 and habitats which indirectly insult<strong>estuarine</strong> <strong>channels</strong> i ncl ude:1) Logging;2) Hydroelectric power development;3) Agriculture; and4) Mining.Only <strong>the</strong> endogenous impacts wi 11 be discussedin this syn<strong>the</strong>sis.Dredging and dredge-spoi 1 disposalhas been probably <strong>the</strong> most extensive, and<strong>of</strong>ten <strong>the</strong> most blatant, modification imposedupon channel habitats (Fig. 10.2).Just <strong>the</strong> magnitude <strong>of</strong> sediment removal isastoundiny. In <strong>the</strong> Columbia River estuaryalone, including <strong>the</strong> mouth and bar, over4.6 x 106m3 <strong>of</strong> bottom sediment is dredgedannually (based on most recent 5-yeardata, L. Smith, U.S. Army Corps <strong>of</strong> Engineers,Portland, OR, pers. comm.) or over25% <strong>of</strong> <strong>the</strong> estimated annual deposition(Gross 1972). Elsewhere along <strong>the</strong> <strong>coast</strong>,1.6 x 106m3 is dredged annually in Oregonestuaries, principally in Coos Bay, <strong>the</strong>Umpqua River estuary, Yaquina Bay, andSui slaw River e tuary (Smith, pers. comm.) ;about 2.3 x 102m3 is dredged annually inWashinyton State, over half <strong>of</strong> that inGrays Harbor (Simenstad et a1 . 1982b) ; and0.4 x 106m3 is dredged annually along <strong>the</strong>nor<strong>the</strong>rn <strong>coast</strong> <strong>of</strong> California, almost entirelyin Humboldt Bay (B. Dixon, U.S.Army Corps Enyineers, San Francisco, CA,pers. comm. ).Genera1 1 iterature on envi ronmentaleffects <strong>of</strong> dredging is extensive (see
Tiq. 10.7. Late It3iiO'
dation <strong>of</strong> <strong>the</strong> biological community, althouyh<strong>the</strong>y are usually manifested overlonger time periods and are Inore effectiveupon communi ty structure due to speciesspecificinteractions. <strong>The</strong>se effects include:1) sublethal decline in waterqual ity (e. g., dissolved oxyyen, turbidity,nutrients, heavy metals, pesticides)or sediment qual i ty (e.y., particle sizedistribution, % volatile solids, depthdistribution and magnitude <strong>of</strong> redox potential,heavy metals) ; and 2) modification<strong>of</strong> current patterns and sal i ni ty intrusionas a result <strong>of</strong> changes in <strong>estuarine</strong>bathymet ry.Evaluation <strong>of</strong> behavioral responses<strong>of</strong> aquatic organisms to dredging and <strong>the</strong>imp1 ications to <strong>the</strong>ir ultimate survivalhas seldom been attempted, however. Evenin <strong>the</strong> absence <strong>of</strong> any sublethal effectsto dredge-suspended sediment (i.e., Kehoe1982), organi scns such as juvenile <strong>Pacific</strong>salmon, which depend upon channel habi -tats as migration corridors, may activelyavoid certain turbidity levels (Bissonand Bilby 1982) to <strong>the</strong> detriment <strong>of</strong> <strong>the</strong>irability to feed effectively or to avoidpredators.Fi 11 ing and diking have obvious directeffects by removal <strong>of</strong> blind (tidal)<strong>channels</strong> which characterize tidal marshand swamp habitats. This has been apervasive modification <strong>of</strong> many <strong>Pacific</strong><strong>Northwest</strong> estuaries (Fig. 10.3) and, given<strong>the</strong> apparent dependence upon <strong>the</strong>se shallowchannel systems by certain juvenilesalmonids (see Sect ion 6.2; Levy et dl.1979; Anderson et al. 1981; Levy andNorthcote 1981; Congleton et al. 1982;Levy and Northcote 1982; Levy et al.1982), <strong>the</strong> removal <strong>of</strong> such optimal habitatsmay be a major contributor to <strong>the</strong>decline <strong>of</strong> many native salmon runsthroughout <strong>the</strong> region.In addition to <strong>the</strong> direct el imination<strong>of</strong> channel habitat, <strong>the</strong> construction<strong>of</strong> structures such as dikes, jetties, andtraining walls in or adjacent to <strong>channels</strong><strong>of</strong>ten impose far-reachiny effects upon<strong>estuarine</strong> ci rculation. Current velocitiesand salinity intrusion are commonlyaltered as a result <strong>of</strong> flow constrictionOr inhibition, resulting in direct modification<strong>of</strong> <strong>the</strong> behavior <strong>of</strong> organi s~ns andcommunities lirni ted to specific currentvelocity and sa l inity regisles or i ndi rectimpact by loss <strong>of</strong> food resources or refugia.Levinys and Chang (1977) comparedCurrent velocities in a "back channel"(Wi 1 liamson slough; 60 cat S~C-I),withininfluence <strong>of</strong> a winy darn (Steveston Is1 and;75 cm sec-I), in mid-channel (LadnerReach; YO cm sec-I), and adjacent to atraining wall (Woodward; 104 cm sec-1) in<strong>the</strong> Fraser River estuary dnd found significantdifferences due to <strong>the</strong> influence <strong>of</strong><strong>the</strong> training wall althouyh not <strong>of</strong> <strong>the</strong> wingdam. Interpretation <strong>of</strong> Brett's (1970) andBrett and Glass' (1973) response surfacesfor critical swimming speed <strong>of</strong> juveni lesockeye salmon would suggest that feedingactivities under temperatures expectedduring <strong>estuarine</strong> outmi gration i nvol ve sustainedswimming speeds <strong>of</strong> under threelengths sec-1. Extrapolating <strong>the</strong>ir relationshipsto <strong>the</strong> expected lengths <strong>of</strong> o<strong>the</strong>routrni yratiny salmon species, it wouldappear that normal feeding behavior wouldbe disrupted at water velocities yreaterthan 40 cm sec-1. Levinys and Chang(1977) also suggested that important prey<strong>of</strong> juvenile salmon. such as <strong>the</strong> qamrnaridconfervi c<strong>of</strong> us, wouldremaininq on <strong>the</strong> bottomor attach& to algae at cirrent velocitiesgredtzr than 10 crn sec-1; Levings(1973) found that much higher, sustainedvelocities (a250 cm sec-I) woul d actual lyflush A. conferivicolus out <strong>of</strong> <strong>the</strong> innersquamiTh River estuary. This il lustrateswhat may be an element <strong>of</strong> <strong>the</strong> functionalrelationships between water velocities,prey avai 1 abi 1 i ty , and foraging behavior<strong>of</strong> juvenile salmon. <strong>The</strong> fact that juvenile salmon do, indeed, feed predorninantlyin subsidiary and blind <strong>channels</strong> where<strong>the</strong> highest standing Stock <strong>of</strong> benthic,epibenthic, and drift prey are found, i l-lustrates <strong>the</strong> potential deleterious ef feet<strong>of</strong> increasing channel water velocities in<strong>the</strong>se habitats.~odi fication <strong>of</strong> current velocitiesalong <strong>the</strong> bottom and <strong>the</strong> resulting restructuring<strong>of</strong> bottom sediments can alsolead to shifts in trophic associations <strong>of</strong>benthic infauna. Mildish (1977) and
Fig. 10.3. Example<strong>of</strong>wheredikingand filling have removed (blindor tidal) channelhabitat in Fraser River estuary; (A) illustrates diking <strong>of</strong> subsidiary (entering fromlower right) channel and blind <strong>channels</strong> in saltmarsh, and (8) shows historical channelpatterns still evident in existing fields (photos courtesy <strong>of</strong> David Levy, WestwaterResearch Centre, Universi ty <strong>of</strong> British Columbia, ~anada) .
Wildish and Kristiqanson (1979) hypo<strong>the</strong>sizedthat <strong>the</strong> magnitude <strong>of</strong> turbulent liasstransfer fro111 <strong>the</strong> water co1u:nn to <strong>the</strong>sediment surface determines <strong>the</strong> proportion<strong>of</strong> filter feeders to deposit feeders.<strong>The</strong>y suggest that, at least under food1 imi ted situations, deposit feeders predominatein low current speeds and filterfeeders are benefited by moderate to hiyhcurrents and bottom roughness. Such inducedchanges in water velocities andsalinity intrusion probably also affect<strong>the</strong> rate and distribution <strong>of</strong> detritusaccumulation or processing. <strong>The</strong> end result<strong>of</strong> this perturbation would bedisplaced, if not reduced, sources <strong>of</strong>food for detritivorous organisms in <strong>the</strong>channel habitat.Estuarine <strong>channels</strong> have traditional -ly been looked upon as opportune receptaclesfor urban and industrial wastes dueto <strong>the</strong>ir usually close proximity to effluentsources and rapid mixing potential.A1 though <strong>the</strong>re is some consequenti a1urban and rural drainage into subsidiaryand blind <strong>channels</strong>, most <strong>of</strong> <strong>the</strong> massivewaste discharges occur in mainstem <strong>channels</strong>.But even <strong>the</strong>se dynamic habitatshave a threshold to <strong>the</strong> amount <strong>of</strong> wasteswhich can be accommodated without changesto biological structure. Two categories<strong>of</strong> comnon wastes--organic and toxicant--ref1 ect <strong>the</strong> mechani sms <strong>of</strong> impact uponchannel habitats and associated biota.Organic pol lution is manifested primarilythrough increased chemical or biologi c.31oxygen demand within <strong>the</strong> water columnand, with settlement <strong>of</strong> organic particles,on and within bottom sediments.Since dissolved oxygen is a criticalrequisite for <strong>estuarine</strong> oryanisms' (excludingsome mi cr<strong>of</strong>l ora) rnetabol i sm (seeVernberg and Vernberg 1972 for review),even minor short-term depressions cana1 ter animal behavior and major, 1 ong-termdeclines can result in major communityshifts toward a reduced number <strong>of</strong> moretolerant species. At sufficient concentrations,toxicants such as petroleumhydrocarbons, heavy metal s, radioactiveisotopes, pesticides, acids, and o<strong>the</strong>rchemicals have <strong>the</strong> potential to directlyki 11 aquatic organisms (i e., acutelytoxic); but more <strong>of</strong>ten than not <strong>the</strong>y arepresent in chronic sub1 ethal concentrationswhich still influence <strong>the</strong> distributionand abundance <strong>of</strong> organisms throughdegradation <strong>of</strong> longevity , reproduction,growth, metabol ism, and behavior.Fur<strong>the</strong>r, more detai led examinations<strong>of</strong> pollutant effects upon aquatic organismsand communities can be found inreviews such as Bryan (1971) and Warren(1971). Felice (1959) also described aclassic case <strong>of</strong> <strong>the</strong> influence <strong>of</strong> domesticand industrial wastes upon <strong>the</strong> benthiccommunity <strong>of</strong> San Francisco Bay, an estuarywith many para1 lel features to <strong>Pacific</strong><strong>Northwest</strong> estuaries. Anderson et a1 .Is(1981) examination <strong>of</strong> <strong>the</strong> envi ronmentaleffects <strong>of</strong> harbor construction at Steveston,Hritish Columbia, also indicates <strong>the</strong>synergistic influences <strong>of</strong> normal envi ronmentalperturbation, organic pollution,and dredging and jetty construction onendemic channel communities.Log transportation ("booming"), dumping,and storage has been a traditionaluse <strong>of</strong> estuaries in this region. Forexample, logs from all along <strong>the</strong> BritishColumbia <strong>coast</strong> are transported to <strong>the</strong>Fraser River estuary, where almost 5 km2<strong>of</strong> <strong>estuarine</strong> habitat, most <strong>of</strong> its shallowreaches <strong>of</strong> mainstem <strong>channels</strong>, are developedas "booming grounds" to hold a sixweeksupply <strong>of</strong> logs for <strong>the</strong> local saw andpul mills (Levy et al. 1982). Approximately1.2 km2 <strong>of</strong> <strong>the</strong> Columbia Riverestuary is presently utilized for logstorage (Pac. NW Riv. Basins. Comm.1980).Many studies <strong>of</strong> <strong>the</strong> envi ronmentaleffects <strong>of</strong> log handling and storaye inestuaries have been conducted within <strong>the</strong>region (Schaumberg 1973; Schuytema andShankland 1976; Smith 1977; Conlan andEllis 1979; Sibert and Harpham 1979;Zegers 1979; Levy et al. 1982) and inAlaskan estuaries (Ellis 1970; Pease1974; Buchanan et al. 1976; Schultz andBerg 1976), while many <strong>of</strong> <strong>the</strong> negativeimpacts documented were particularlyassociated with 1 i ttoral habitats, wheredirect benthic disturbance was caused bygrounding logs, log dumping, rafting, andstorage in subsidiary and shallow regions
<strong>of</strong> mainstem <strong>channels</strong> can also produce significaritirnpacts if water exchange fromtainly played a role in most cases. Given<strong>the</strong> important role which <strong>the</strong>se consumerriver and tidal currents was low. <strong>The</strong>se organisms (typically upper trophic levelwere primarily due to <strong>the</strong> accumulation <strong>of</strong> carnivores) have upon <strong>the</strong> structure <strong>of</strong>bark and log debris on <strong>the</strong> bottom, caus- channel communities, it may be valid toing smo<strong>the</strong>ring <strong>of</strong> benthic organisms and assume that ecol ogical accommodation hasmeasurable increases in biochemical oxy- resulted in somewhat di fferent producergen demand in <strong>the</strong> water overlying <strong>the</strong> and primary consumer assemblages thandebris. Leachates from stored logs and occurred historically. <strong>Pacific</strong> salmon,bark deposits may also locally degrade nor<strong>the</strong>rn anchovy, <strong>Pacific</strong> herring, andwater qual i ty through ei<strong>the</strong>r direct Dungeness crab are examples <strong>of</strong> exploitedtoxicity or via biological and chemical species which are suspected to structureoxygen demand (Pease 1974; Buchanan et <strong>the</strong>ir prey assemblages (see Secfion 9.2);al. 1976; Peters et al. 1976), factors and it must also be concluded that assowhichmay be intensified by intermediate ciated pelagic, epibenthic, and benthicsalinities (Pease 1974).assembl ayes have a1 so responded indirect-1y to man's exploitation <strong>of</strong> <strong>the</strong>se preda-Prolonged impacts upon benthic com- tors. <strong>The</strong> consequence <strong>of</strong> <strong>the</strong> recent enmunitiesresulting from loy rafting is hancement efforts upon some <strong>of</strong> <strong>the</strong>se spe<strong>of</strong>tenmanifested in reduced standing crop cies, i.e., <strong>Pacific</strong> salmon, or <strong>the</strong> protecanddiversity and tends to be restricted tion <strong>of</strong> o<strong>the</strong>r, previously-harvested predatobenthic infauna ra<strong>the</strong>r than epibenthic tors, i.e., seals and sea 1 ions can alsoorganisms except under extreme situations. be predicted to induce measurable changesFor example, Smith (1977) illustrated in <strong>the</strong> community because <strong>of</strong> increased prethat<strong>the</strong> abundances <strong>of</strong> three polychaete dation upon <strong>the</strong>ir preferred food organannelidspecies (Mana unkia aestuarina, isms. This has been suggested for hatch-Pseudoam hicteis Ca itella ery releases <strong>of</strong> juvenile salmon in Hood&ubiferous a m p h i p o h Canal (Sinenstad et al. 1980) and night7ie- p ium salmonis), and oligochaetes were also be applied to increased seal and seareducedinraft areas <strong>of</strong> <strong>the</strong> Snohomish lion predation upon crabs and fishes inRiver estuary, but <strong>the</strong> epibenthic amphi- <strong>the</strong> Columbia River estuary (Beach et al.pod Eoyammarus confervicolus was unaffect- 1981). Such holistic food web interaced.Levy et al. (1982) indicated that tions must be equally considered synerepibenthicqysids (Neom sis mercedis) and gistic with man's o<strong>the</strong>r impacts in estuaramphipods(E. confervlco -5- us and Corophium ine <strong>channels</strong> and, ultimately, within hissp. ) were er<strong>the</strong>r more or equal ly abundant management strategies for <strong>the</strong> maintenanceand isopods (Gnorimosphaeroma ore onensi s) or restorat ion <strong>of</strong> a speci f i c <strong>estuarine</strong>less abundant in <strong>the</strong> Point G r e h -age area as compared to <strong>the</strong> Musqueam Marsachannel community.control area; environmental conditions, 10.2 UTILIZATION OF AND DEPENDENCE ONt~owever, were responsible for some <strong>of</strong> CHANNELS BY ECONOMICALLY - AND ECO<strong>the</strong>sedifferences, and no si gni f i cant con-LOGICALLY-IMPORTANT SPECIEStrasts in growth <strong>of</strong> chinook salmon frywere evident between <strong>the</strong> two study areas As illustrated throughout this syndespitequal i tati ve differences in <strong>the</strong> <strong>the</strong>sis, many organisms <strong>of</strong> economic importfishes'diets.ance to man or <strong>of</strong> ecological importanceto <strong>the</strong> <strong>estuarine</strong> ecosystem can be foundA final, seldom-considered and even1 ess-evaluated impact upon channel communutilizingchannel habitats. But in <strong>the</strong>context <strong>of</strong> <strong>estuarine</strong> management, <strong>the</strong> cri t-ities is that <strong>of</strong> extensive exploitation ical question is dependence upon <strong>channels</strong><strong>of</strong> economical iy-important species. Whi le to sustain popul ati ons <strong>of</strong> <strong>the</strong>se organismshabitat reduction or alteration has cer- by providing ample food resources, optitainlycontributed to <strong>the</strong> decline <strong>of</strong> many mum conditions for growth and/or reproduc<strong>of</strong>our cornnmercial or sport fish and in- tion, and refugia from predation. Such avertebrate stocks, overharvesting has cer- definition <strong>of</strong> uti 1 ization in terms <strong>of</strong>124
<strong>estuarine</strong> <strong>channels</strong> as "critical " habitatsrequires more knowledge <strong>of</strong> <strong>the</strong> functionalrelationships regulating populations thanis usually available.Util ization <strong>of</strong> <strong>estuarine</strong> channel s isobvious for many econmical ly- and ecol ogi -cal ly-important species <strong>of</strong> fishes. But,among <strong>the</strong>se, only a few can be illustratedto be potentially limited by <strong>the</strong> availabilityor quality <strong>of</strong> <strong>estuarine</strong> channelhabitat. Juvenile salmon such as chinookand chum may provide <strong>the</strong> best example <strong>of</strong>such a positive functional relationshipbetween <strong>estuarine</strong> residence and popul a-tion production (see Section 6.2.2). Thismay also be <strong>the</strong> case for <strong>Pacific</strong> herring(Pearcy and Myers 1974), American shad,and striped bass. 8ut <strong>the</strong>re is some evidencethat many species "utilize" <strong>of</strong>fshoreenvirons to a yreater extent thanestuaries and, as such, occurrence in<strong>estuarine</strong> channel s is merely a product <strong>of</strong>current transport <strong>of</strong> planktonic larvaefrom a large <strong>of</strong>fshore population into <strong>the</strong>estuary; this may be true <strong>of</strong> nor<strong>the</strong>rnanchovy, surf perch, <strong>Pacific</strong> sand lance,lingcod, English sole, butter sole, andsand sole (Pearcy and Myers 1974). And,while <strong>the</strong> ecological ly-important Crangonspp. shrimps may be highly dependent upon<strong>estuarine</strong> channel habitats, <strong>the</strong>re is noevidence i 1 lustrating that <strong>channels</strong> providecritical habitats for economical lyimportantDungeness crab as juveni 1 es,which may be equally or more abundant<strong>of</strong>fshore.A number <strong>of</strong> ecological ly-importanttop carnivores such as seals, sea lions,and many <strong>of</strong> <strong>the</strong> surface and diving waterbirdsare seasonal migrants which behavioral1y immigrate to <strong>estuarine</strong> channel sfor specific periods <strong>of</strong> <strong>the</strong> year. Since<strong>the</strong>re is good evidence that this is associatedwith optimum foraging and/or reproductionconditions, <strong>the</strong>ir population levelsmay also depend upon this utilizationpattern.10.3 RATES AND PATHWAYS OF RECOVERY FROMSHORT-TERM IMPACTSA1 though some manipulations <strong>of</strong> <strong>channels</strong>such as extensive dredging can bedramatic in <strong>the</strong>ir initial impact, if sustainedfor only a short interval, biologicalrecovery may also involve only a relativelyshort time period. Although unverified,it may be assumed that, due torapid mixing and immigration <strong>of</strong> pelagicorganisms, impact to water column assemblageswill be relatively short-1 ived.Benthic and epibenthic assemblages, on<strong>the</strong> o<strong>the</strong>r hand, wi 11 require longer recoverytimes and may pass throuyh a number<strong>of</strong> successional stages before attaininypre-impact status. McCauley et al.(1977) documented a readjustment in benthicinfauna within a dredged area <strong>of</strong>Coos Bay, Oregon, after 28 days and withinimpacted, adjacent areas after 14days; similarly, infauna at <strong>the</strong> site <strong>of</strong>dredye spoi 1 disposal had a1 so recoveredfrom depletion within 14 days. Andersonet al. (1981) described recovery <strong>of</strong> <strong>the</strong>benthic community in Steveston Harbor in<strong>the</strong> Fraser River estuary within one monthafter dredging. McCauley et al. (1976)also followed <strong>the</strong> recolonization patterns<strong>of</strong> four species <strong>of</strong> polychaete annelids inCoos Bay, Oregon, for eight weeks aftermaintenance dredyi ng. <strong>The</strong>y found thatCapi tell a capi tata -domi nate-d <strong>the</strong> assemblaqein recently de~osi ted sediments butnot- under si tuition; <strong>of</strong> rapid sedimentturnover; Polydora liyni, on <strong>the</strong> o<strong>the</strong>rhand, pervaded where sediments were overturnedfrequently and where sawdust andwood debris occirred. Steblospio benedicti and Pseudoool . " vdora kemoi are commonunder ei<strong>the</strong>r recent sedimeaon or sedimentoverturning, perhaps because bothcan readily vacate <strong>the</strong>ir tubes to rebuildnew ones quickly. Thus, <strong>the</strong> rate and pattern<strong>of</strong> recolonization will proceed as afunction <strong>of</strong> <strong>the</strong> rate <strong>of</strong> sediment resuspensionor sedimentation as well as <strong>the</strong> organiccontent (Be1 la and W i 11 iamson 1979-1980; see also Section 2.5.2). Pequegnat(1975) suggested that mei <strong>of</strong>aunal consti tuents<strong>of</strong> <strong>the</strong> benthos may be even more sensitiveto sediment disruption, as evidencedby changes in generation time,standing stock, and diversity. A1 though
<strong>the</strong>y may be <strong>the</strong> first colonizers, <strong>the</strong>iri ntirnate re1 atiotiships with sediment propertiesand intrinsic short populationcycles would dictate that succession <strong>of</strong>mei<strong>of</strong>auna assemblages would be prolongedas long as abnormal sedimentation (orremoval ) persisted.Unfortunately, such successionalpatterns have not been well documented indredgi ng-impact studies in this region.Oliver et al. (1977), however, providedan excellent illustration <strong>of</strong> benthicsuccession in a s<strong>of</strong>t-bottom assemblage <strong>of</strong>small crustaceans and polychaete annelidsin Monterey Bay, California. Two phaseswere evidenced after dredging ceased.<strong>The</strong> first involved immediate immigration<strong>of</strong> peracarid crustaceans and settlement<strong>of</strong> larvae <strong>of</strong> opportunistic polychaetespecies, i.e., relatively small-sizedtaxa with short generation times, lowfecundity, and high larval avai labi lity.<strong>The</strong> later phase included gradual reestab-1 ishment by less motile crustacenas andless opportunistic polychaete species.One important thing to remember inconsiderf ng succession rates and patternsin <strong>the</strong> temperature waters <strong>of</strong> <strong>the</strong> <strong>Pacific</strong><strong>Northwest</strong> is <strong>the</strong> highly seasonal reproductiveschedules <strong>of</strong> most fauna. As a result,succession is going to be highlymediated by <strong>the</strong> seasonal availability <strong>of</strong>propagules <strong>of</strong> <strong>the</strong>se opportunistic and latersuccessional stage taxa. In addition,benthic asse~nblages in central regions <strong>of</strong>large estuaries like <strong>the</strong> Columbia and FraserRivers may never naturally progressbeyond <strong>the</strong> opportunistic species successionalstage. Due to <strong>the</strong> frequent .and<strong>of</strong>ten extreme fluctuations in salinityregimes, <strong>the</strong>se benthic assemblages aretypically limited to species which areto1 erant <strong>of</strong> such random environmentalperturbations and persist by being small,capable <strong>of</strong> wide dispersal and rapidreproduction, and extremely euryhal ine.10.4 METHODS OF CHANNEL RESTORATION ANDREHABILITATIONUnlike <strong>the</strong> recent support for <strong>estuarine</strong>marsh restoration (Josselyn 1982; butsee Race and Christie 1982 for caveats),restoration and rehabi l i tation <strong>of</strong> <strong>channels</strong>is seldom considered among available optionsin <strong>estuarine</strong> habitat management.Dorcey et al. 's (in press) analysis <strong>of</strong><strong>the</strong> history, status, and managementoptions <strong>of</strong> <strong>estuarine</strong> sloughs, specificallyTilbury Slough in <strong>the</strong> Fraser Riverestuary, presents one <strong>of</strong> <strong>the</strong> few discussions<strong>of</strong> restoration and enhancementstrategies applicable to such <strong>estuarine</strong>channel and associated habitats (e.g.,marshes). Among <strong>the</strong> rehabi 1 i tationoptions specific to <strong>the</strong> area's <strong>channels</strong>were: 1) breaching <strong>of</strong> remnant dykes toincrease flushing and passage <strong>of</strong> juvenilesalmon; 2) dredging <strong>of</strong> <strong>the</strong> mouth and channelto arrest infilling and maintain circulation;3) dredging <strong>of</strong> side (blind)<strong>channels</strong> to increase juvenile salmon utilization;and, 4) stabilization <strong>of</strong> waterlevels through flow control structuresand selected channel creation.In addition to <strong>the</strong>se means <strong>of</strong> restoring<strong>the</strong> habitat to a viable, productiveenvi ronment , management must i nvol ve removalor mediation <strong>of</strong> <strong>the</strong> sources <strong>of</strong> degradationand protection <strong>of</strong> <strong>the</strong> selfcleansingmechanisms. In <strong>the</strong> case <strong>of</strong>Tilbury Slough, as in many similarlydeveloped<strong>estuarine</strong> <strong>channels</strong> in <strong>the</strong><strong>Pacific</strong> <strong>Northwest</strong>, exogenous influencessuch as pollutant sources eliminate some<strong>of</strong> <strong>the</strong> more viable options (i.e.,openingup flow from <strong>the</strong> former, upriver end <strong>of</strong><strong>the</strong> channel), In all cases, however, restoration- must be accompanied by changesin those uses which led or contributed to<strong>the</strong> channel's deterioration. Pollutantsources must be eliminated or diverted.Structures (i.e., docks, training walls,wharves) and practices (i.e. , log dumpingand storage) which promote abnormal sedi -mentation and scouring must bediscouraged.<strong>The</strong>re are presently active managementpolicies promoting or practicingmitigation as a means <strong>of</strong> compatibly incorporatingnecessary <strong>estuarine</strong> developmentinto <strong>the</strong> natural environment withoutprecluding such activity (Ashe 1982). Assuch, mitigation can take on two goals:1) <strong>the</strong> creation, restoration, or enhancement<strong>of</strong> an <strong>estuarine</strong> area to maintain <strong>the</strong>
functional characteristics and processes<strong>of</strong> <strong>the</strong> estuary; and, 2) <strong>the</strong> creation orrestoration <strong>of</strong> ano<strong>the</strong>r area <strong>of</strong> similarbiological potential to ensure that <strong>the</strong>integrity <strong>of</strong> <strong>the</strong> <strong>estuarine</strong> ecosystem ismaintained. While <strong>the</strong> first goal iscompatible with maintenance <strong>of</strong> a viablyfunctioning<strong>estuarine</strong> channel community ,<strong>the</strong> second yoal should be approachedjudiciously. Destruction or debi 1 itativemodification <strong>of</strong> any natural habitat,particularly <strong>channels</strong> so integral to anestuary's circulation, by creation <strong>of</strong> asupposedly equivalent habitat cannot bejustified with <strong>the</strong> existing technology.This approach to mi tigation originatedfrom relatively successful salt marshrestoration projects in east <strong>coast</strong> estuaries,but man-made marshes in west <strong>coast</strong>estuaries have yet to be proven comparablereplacements for natural marshes (Raceand Christie 1982). A1 though restoration<strong>of</strong> diked, filled, or modified <strong>channels</strong> isa worthwhile objective <strong>of</strong> contemporary<strong>estuarine</strong> manayement, devaluing existing<strong>channels</strong> in exchange for <strong>the</strong> unpredictableresults <strong>of</strong> <strong>the</strong>se projects is still adubious strategy.10.5 RESEARCH GAPS AND PRIORITIESDespite <strong>the</strong> pr<strong>of</strong>usion <strong>of</strong> knowledge<strong>of</strong> <strong>estuarine</strong> <strong>channels</strong> in <strong>the</strong> <strong>Pacific</strong><strong>Northwest</strong>, i 1 lustrated by <strong>the</strong> bulk <strong>of</strong> <strong>the</strong>Literature Cited section, we find our understanding<strong>of</strong> <strong>the</strong> role <strong>of</strong> <strong>the</strong>se habitatsin <strong>the</strong> <strong>estuarine</strong> ecosystem to be limited.In most cases this is because this vastaccumulation <strong>of</strong> data is predominantly descriptiveand qua1 itative. That which isquantitative is typical 1 y oriented towarda particular taxa and seldom <strong>of</strong> a scopeencompassing o<strong>the</strong>r organisms <strong>of</strong> <strong>the</strong> community,environmental conditions, or functionalre1 ationshi ps among <strong>the</strong>m. Futureresearch must address this lack <strong>of</strong> holisticapproaches, particul arly when evaluating<strong>the</strong> dependence <strong>of</strong> important biotaupon key functional processes. Despite<strong>the</strong> intent <strong>of</strong> this syn<strong>the</strong>sis to identify<strong>the</strong> role <strong>of</strong> <strong>estuarine</strong> ci rcul ation, sal initygradients, nutrient and material fluxes,and sediment structure in determi ni ng<strong>the</strong> composition, distribution, and standingstock <strong>of</strong> <strong>estuarine</strong> biota (Section1.1), few such functional relationshipshave been verified though many have beenhypo<strong>the</strong>sized. <strong>The</strong> fol 1 owing research proposalsare designed to elucidate, test,and quantify <strong>the</strong>se "conceptual hypo<strong>the</strong>sismodels" in terms <strong>of</strong> <strong>the</strong> functioning <strong>of</strong><strong>estuarine</strong> channel systems, <strong>the</strong>ir relationshipto overall <strong>estuarine</strong> processes, and<strong>the</strong> imp1 i cations <strong>of</strong> estuari ne manayementoptions.1. Prepare comprehensive analysis <strong>of</strong>hi storical trends in channel habitatdemography (extent and morphology)for all major <strong>Pacific</strong> <strong>Northwest</strong> estuarieswhere data exists; i nterpretdocumented changes re1 ati ve tonatural and anthropogeni c processes.Vertical 1~-strati fied, three-dimensionalma<strong>the</strong>matical modeling <strong>of</strong> ci r-cul ation in a prominent, representative<strong>Pacific</strong> <strong>Northwest</strong> estuary shouldbe conducted with considerable fieldcalibration in order to better understand<strong>the</strong> effect <strong>of</strong> river dischargeand estuary bathymetry upon salinityintrusion and sedimentation. Variousdevelopment scenarios affecting parameterssuch as riverine discharge(i.e., dams), ba<strong>the</strong>metry (i.e. ,dredging), or geomorphology (i .e. ,jetty construction) could be simul atedfor optimum assessment <strong>of</strong> effectsupon circulation.3. Conduct intensive, vertical ly-strati -fied sampling <strong>of</strong> pelagic and epibenthiczooplankton over diel periodsat representative channel 1 ocationsthrough <strong>the</strong> <strong>estuarine</strong> gradient. Ifperformed concurrently with fieldcalibration <strong>of</strong> <strong>the</strong> three-dimensionalcirculation model (#2 above), <strong>the</strong> re-sul ting documentation <strong>of</strong> diel patternsin zooplankton distribution andstanding stock could be correlatedwith cycles in tidal and current velocity,salinity distributions, andmi xi ng processes.4. As in Healey's (1982) estimation <strong>of</strong><strong>the</strong> ultimate (i.e.,to adult return)survivorship <strong>of</strong> chum salmon uti 1 izing<strong>the</strong> Nanaimo River estuary, <strong>the</strong>
e1 ati ve importance <strong>of</strong> <strong>estuarine</strong>channel attributes must be evaluatedin terms <strong>of</strong> <strong>the</strong> total cost to <strong>the</strong>salmon population. Similarly, differentpatterns <strong>of</strong> channel uti 1 izationby juvenile salmon (e,g., extendedresidence, inshore/<strong>of</strong>fshoremovements) must be examined relativeto <strong>the</strong>se attributes. A1 though <strong>the</strong>reis <strong>of</strong>ten opportunity for "natural 'Iexperiments, <strong>the</strong> lack <strong>of</strong> control overdependent variables <strong>of</strong>ten inhibitsinterpretation. For this reason,manipulation experiments should beundertaken to isolate independentvariables affecting patterns <strong>of</strong> channelutilization. Examples includeequal releases <strong>of</strong> marked groups <strong>of</strong>fish at different points along <strong>the</strong><strong>estuarine</strong> gradient or differentdensity or fish-size releases justupstream <strong>of</strong> <strong>the</strong> estuary and recapture<strong>of</strong> <strong>the</strong> marked Fish at <strong>the</strong> mouthor just outside <strong>the</strong> estuary.Uespi ti? strony evidence that foodwebs <strong>of</strong> <strong>estuarine</strong> channel comtnunitiesare based yredomi nantly upon detritus,<strong>the</strong>re is 1 i ttle data substantiatinythis hypo<strong>the</strong>sis (see Section9.1). Techniques such as stable carbonisotope analysis should be appliedto primary producers, inputs<strong>of</strong> dissolved and particulate organicand dl ssol ved inorganic carbon fromexogenous sources, detritus accumulations, and dominant consumer organismsin <strong>estuarine</strong> <strong>channels</strong> in orderto evaluate <strong>the</strong> sources and pathways<strong>of</strong> organic carbon leading to <strong>the</strong>endemic food web.Siini l ar to determining causal mechanis111~<strong>of</strong> utilization <strong>of</strong> <strong>estuarine</strong><strong>channels</strong> by juvenile salmon (#4above), <strong>the</strong> factors influencingstructure, distribution, and standingstock <strong>of</strong> benthic and epibenthicassernbl ages cannot be easily eluci -dated from highly variable fieldmeasurements ; separation <strong>of</strong> confoundingeffects <strong>of</strong> natural physical andcnerni cal influences from those <strong>of</strong>pol lution are also usually intractable.Functional relationships be-tween physiocherni cal variables andlarval settlement, feeding and o<strong>the</strong>rcritical behavior, reproduction, andsurvival can be resolved only throughexperimental means. Organisms suchas polychaete annelids, harpacticoidcopepods, gammarid amphi pods, mysids,and crangonid shrimps should be testedunder control led rep1 icatable conditions indicative <strong>of</strong> <strong>estuarine</strong> channelbenthic environs, both as individualspecies and 1 ife historystages as well as characteristicmixed-taxa assemblages. This approachachieves i ts ul timate appl i-cabil ity in <strong>the</strong> form <strong>of</strong> ecosystem~~iicrocosms which, dl though subject toa nunber <strong>of</strong> shortcwings (Harte etal. 1980; Silierlstad et al. 1982) canbe a very effective method <strong>of</strong> environmentdlilnpdct assessnent and ecologicalelucidation (T.P. Smith1980).7. <strong>The</strong> importance <strong>of</strong> <strong>the</strong> null zone in<strong>the</strong> concentration <strong>of</strong> detritus hasbeen suggested by studies <strong>of</strong> watercolumn primary production and bothpelagic and epi benthic zoopl ankton(see Chap. 5). But <strong>the</strong> processesaccounting for detritus entrainmentand processing in <strong>the</strong> nu1 1 zone <strong>of</strong><strong>the</strong> region's estuaries are littleunderstood. Both vertical and hori -zontal distributions <strong>of</strong> detritus particlesand associated water chemistrycharacteristics (i.e., DOC, DON, ATP)should be sampled seasonally in relationto circulation parameters in anestuary with a we1 1 -defined nu1 1zone. As in documenting zooplanktondistribution processes (#3 above),coup1 ing with <strong>the</strong> three-dimensionalci rcul at ion model (#2 above) wouldalso expand <strong>the</strong> potential <strong>of</strong> similarlyexplaining detritus cyclingand utilization by physical ci rculationprocesses.Appendix D provides a list <strong>of</strong> researchgroups/organi zati ons currentlyconducting research in <strong>estuarine</strong> channelhabitats in <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>.
10.6 SUMMARYAlthough <strong>the</strong>y are classical ly avoidedin most research, due to <strong>the</strong> complexityand dynamic nature <strong>of</strong> <strong>the</strong> physiochemi calenvironment, channel habitats in <strong>Pacific</strong><strong>Northwest</strong> estuaries obviously supportunique populations <strong>of</strong> economical ly- andecological ly-important biota. This bondingtakes form as routes for organismmovement and migration, conduits <strong>of</strong>material transport, and sources <strong>of</strong>rep1 eni shment for sediments, nutrients,food particles, and organism recruits.A1 1 <strong>estuarine</strong> habitats are integratedthrough <strong>the</strong> estuary's articulated system<strong>of</strong> mainstem, subsidiary, and blind <strong>channels</strong>,and <strong>the</strong> principal linkages withterrestrial and marine ecosystems occurthrough <strong>the</strong> mainstem <strong>channels</strong>. Inaddition to this critical role as <strong>the</strong>estuary 's ci rculatory system, <strong>channels</strong>act as critical nursery habitats fororganisms such as juvenile <strong>Pacific</strong> salmonand <strong>Pacific</strong> herring; as opportune f6ragingand resting habitats for migrantbirds and marine mammals; and as <strong>the</strong>focal point <strong>of</strong> detritus entrai nment,accumulation, and processing in <strong>the</strong>estuary.Management <strong>of</strong> any <strong>estuarine</strong> resourceor exogenous resources which derivebenefit from a we1 1-functioning estuarycannot occur without consideration andmanagement <strong>of</strong> <strong>estuarine</strong> <strong>channels</strong>. But<strong>the</strong> state <strong>of</strong> our knowledge <strong>of</strong> <strong>estuarine</strong>channel communities and processes and <strong>of</strong><strong>the</strong>ir management is lagging far behindthat <strong>of</strong> <strong>the</strong> o<strong>the</strong>r major <strong>estuarine</strong> habitats.This document describes whatDorcey ahd Hall (1981) would define as<strong>the</strong> "descriptive knowl edge" necessary forinput into management decisions. Unfortunately,<strong>the</strong>re is also a second category<strong>of</strong> requisite information, that <strong>of</strong> <strong>the</strong>"functional knowledge" <strong>of</strong> how <strong>the</strong> channel'sbiotic and abiotic processes operateand interact, which we have barelybegun to develop. Essentially all <strong>the</strong>studies described herein have beenderived from inventorying or monitoringtypes <strong>of</strong> investigative activities. Anyinterpretation <strong>of</strong> system processes hasmerely been <strong>the</strong> result <strong>of</strong> deductive analyses.Genuine functional knowl edye requiresa different approach, that <strong>of</strong> generating testable hypo<strong>the</strong>ses and experi -rnents. Such experimental research <strong>of</strong>fersour only view <strong>of</strong> causal mechanisms, and<strong>the</strong> process <strong>of</strong> sequential ly testing a1 ternativehypo<strong>the</strong>ses is our only means <strong>of</strong>'exploring <strong>the</strong> complex interrelationshipsaffecting channel communities. Effectivemanagement decisions require this functionalknowledge and, as advocated byDorcey and Hal 1 , experimental managementand research are <strong>the</strong> only source <strong>of</strong> functionalknowledge. It is hoped. that, inaddition to syn<strong>the</strong>sizing our descriptiveknowl edge <strong>of</strong> <strong>estuarine</strong> channel communitiesin <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong>, this' communitypr<strong>of</strong>ile might provide <strong>the</strong> impetus for<strong>the</strong> necessary steps to <strong>the</strong> experilnentswhich are ultimately necessary for effectivemanagement <strong>of</strong> our region's estuaries.
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APPENIX AGlossary 9f Terms
Advection - Local change in a property <strong>of</strong>a system that takes place as a result<strong>of</strong> a current, as <strong>of</strong> air or water;inc 1 udes transport <strong>of</strong> water vapor,heat, sediment load, salinity(Proctor et al . 1980).Alkal inlty - <strong>The</strong> capacity <strong>of</strong> a water massto accept protons, i.e., hydrogenions.Anadror~ious - Mi grating up rivers from <strong>the</strong>sea to breed in fresh water.GLOSSARY OF TERMSBenthic - Relating to <strong>the</strong> bottom <strong>of</strong> <strong>the</strong>body <strong>of</strong> water, i.e. animals, livingwithin or directly upon <strong>the</strong> substrate.Benthivore - Oryanism which feeds onbenthic flora and fauna.Bight - A bend, curve, or indentation in<strong>the</strong> shore <strong>of</strong> a sea, including <strong>the</strong>body <strong>of</strong> water bounded by such a<strong>coast</strong>al form.tomoos ng Branching , Boulder - Rock fragment wi di ameaerinterco~;r;runicating, <strong>the</strong>reby producing larger than 60.4 cm (Cowardin et al.a nctlike or braided appearance. 1979).Anyul ar - A roundness yrade showing verylittle or no evidence <strong>of</strong> wear, wi<strong>the</strong>dges and corners sharp (Am. Geol.Inst. 1976).Autotrophic - Self-nourisning; referringto organisms that are capable <strong>of</strong> constructingorganic matter with hi yhenergybonds frodl inorganic substancesfor <strong>the</strong>ir food supply by photosyn<strong>the</strong>sisor ct~emosyn<strong>the</strong>si s.Uar - An elongated landform generated bywaves and currents, usual ly runningpara1 1 el to shore, composed predomi -nant ly <strong>of</strong> unconsol idated sand,grave 1, cobbles, stones and rubbleand with Mdter on two sides.Bed - Bottom <strong>of</strong> <strong>the</strong> channel.Cavitation - Corrasive and corrosive effect<strong>of</strong> collapsing <strong>of</strong> bubbles producedby a decrease <strong>of</strong> pressure toincrease <strong>of</strong> water velocity (Bernouli ieffect) at point where pressure isincreased to decrease <strong>of</strong> velocity(Am. Geol. Inst. 1976)Channel - An open conduit ei<strong>the</strong>r naturallyor artificially created whichperiodical ly or continuously containsrnovlng water, or which forms a connectinglink between two bodies <strong>of</strong>Water (Langbein and Iseri 1960).Channel Bank - <strong>The</strong> sloping land borderinga channel, which typically has asteeper slope than ei<strong>the</strong>r <strong>the</strong> bottom<strong>of</strong> <strong>the</strong> channel or <strong>the</strong> adjacent land(Cowardin et al. 1979).Bed Load - Sediment particles and o<strong>the</strong>r Cobble - Rock fragments with diametersdebris rolled alony <strong>the</strong> bottom by between 7.6 cm and 25.4 cm (Cowardinrnovlng water. et al. 1979).
Competence - Maximum size <strong>of</strong> particles <strong>of</strong> iletritds - Finely divided naterial <strong>of</strong> orgivenspecific gravity which a water ganic 3r inorganic origin which ismass will move at a given velocity. ei<strong>the</strong>r suspended in <strong>the</strong> water coluriln or,in <strong>the</strong> case <strong>of</strong> large particles, accurnu-Consumer - Heterotrophlc orqani - sm, chief lv lated on <strong>the</strong> hotton.animals, which ingest o<strong>the</strong>r organismsor particulate organic matter.Diffusion - <strong>The</strong> spreading out <strong>of</strong> molecules,atoms, or ions in a waterCoriolis Effect - <strong>The</strong> effect <strong>of</strong> <strong>the</strong>mass in directions tending to equalearth'srotation to deflect waterize concentrations in all parts <strong>of</strong>masses to <strong>the</strong> right in <strong>the</strong> nor<strong>the</strong>rn<strong>the</strong> system.'phere and to <strong>the</strong> left in <strong>the</strong>nor<strong>the</strong>rn hemisphere.Diversity - Term or lneasure used to describe <strong>the</strong> species-abundance di s-Corrasion - Mechani cal erosion performedtribution <strong>of</strong> a biotic assemblage orby moving agents, generally by <strong>the</strong>community; both <strong>the</strong> number <strong>of</strong> speciesand tne evenness <strong>of</strong> <strong>the</strong>ir abunirrlpactor grinding action <strong>of</strong> partidancescontribute to <strong>the</strong> termcles in water.(Pielou 1977).Corrosion - Chemical erosion which resul tsfrom <strong>the</strong> reaction <strong>of</strong> water and rockson <strong>the</strong> surface <strong>of</strong> <strong>the</strong> land.Critical Erosion Velocity - Lowest velocityat which grains <strong>of</strong> a given size,loose on <strong>the</strong> bed <strong>of</strong> a channel, wi 11move.Decomposer - An organism that breaks downdead organic matter into simpler constituents for its nutrition.Uernersal - Nektonic fauna living on orclosely associated with <strong>the</strong> bottom;typical ly refers to fishes, whereepi benthic refers to invertebratefauna.Dendri tic - A drainage pattern chardcterizedby irregular branching in alldirections with <strong>the</strong> tributaries joining<strong>the</strong> main channel at all angles(An. Geol . Inst. 1976).Density - Abundance <strong>of</strong> organisms per unitarea or volume.Deposit Feeder - Organism, typically benthic,which is ei<strong>the</strong>r somewhat selectiveor almost completely unselectivein feeding; includes organisms whichsweep <strong>the</strong> surface or use ciliarytracts along extensile tentacles.Elutriate - Tne fluid product <strong>of</strong> mixingwater, or a water acid solution, withsediment, a1 lowi ng settl iny over avarying amount <strong>of</strong> time and decantiny<strong>the</strong> resultiny solution,Epibenthic - Associated primarily with<strong>the</strong> surface <strong>of</strong> <strong>the</strong> bottom but alsowith <strong>the</strong> water column directly above<strong>the</strong> bottom.Euhaline - Associated with nrouth Or extremesalinity, i.e., 30-40 ppt,region <strong>of</strong> estuary (Symp. Class.Brack. Mat. 1959).Facultative (Feeder) - An orgarlisln wnichis not functional ly constrained t<strong>of</strong>eeding on one yeneral type <strong>of</strong> plantor animal but may feed on diverseprey from several trophic levels.Flocculation - Aggregation <strong>of</strong> small suspendedparticles due to ionicchanges brouyht on by contact withseawater.Fluviatile - Belonging to a river orproduced Dy river action (An. Geol .inst. 1976).Flow Ratio - Ratio <strong>of</strong> volume <strong>of</strong> uplandwater entering <strong>the</strong> estuary during atidal cycle to its tidal prism.
Fluvial - Of, or pertaining to, rivers. Obligate (Feeder) - Organism const rainedby moryholoyy or behavior to feedingFood Web - <strong>The</strong> pattern and sequence <strong>of</strong> on one general type <strong>of</strong> plant orfeeding interrelationships among <strong>the</strong>animal.organisms <strong>of</strong> a community , from reducerand producer organisms to <strong>the</strong> Omnivore - Organism which feeds on bothhighest carnivores.plant and animal matter.Food Web Linkage - <strong>The</strong> trophic connectionbetween food web node.Food Web Module - Interacting species thatseem dependent upon specific prey resources,yi ve evidence for evolvedmodification for use <strong>of</strong>, or associationwith, <strong>the</strong>se resources, and thatdisappear upon removal <strong>of</strong> a stronglyinteracting species {or appear withits addition) constitute a module(Paine 1980).Oliyohaline - Associated with head or lowsalinity, i.e., 0.5-5 lpt, reyion <strong>of</strong>estuary (Symy. Class. Brack. Wat.1959).Pelayic - Characteristic <strong>of</strong> <strong>the</strong> water columnand not in association with <strong>the</strong>bottom.PhiUnits - Units <strong>of</strong> particle or grainsize where @I = -1092 dia (mm).Food Web Node - Species, taxon, or func- Planktivore - Organism which feeds ontional feeding group constituting asuspended zooplankton and nekton.unique prey or predator compartmentin a food web.Polyhal ine - Associated with middle andGravel - Hock fragments with diameters belowerreaches <strong>of</strong> estuary, typicallywith salinities between 18-30 ppttween 2 mm and 7.6 cm (Cowardin et (Symp. Class. Brack. Water 1959).al. 1979).Littoral - Pertaining to <strong>the</strong> shore zone Primary Production a ate) - ~easure <strong>of</strong>between extreme high and low tide carbon fixed per unit area per unitlevels during spring tides. time by photosyn<strong>the</strong>tic organisms(producers). usual ly expressed asMeropl ankton - Planktonic stages (eggs andy C m-2 hr'i.larvae) <strong>of</strong> organisms which in later1 ife wi 11 become members <strong>of</strong> <strong>the</strong> hen- Kheotaxis - Movement <strong>of</strong> an organism inthos or nekton.which a water stream or current is<strong>the</strong> directive stimulus.Mesohaline - Associated with upper reachesor intermediate salinities, i.e., 5- Saline - Possessiny a hiyh deyree <strong>of</strong> sa-18 pyt, region <strong>of</strong> estuary (Symp. linity, i.e., more than 3°/00 (Am.Class. Brack. Mat. 1959). Geol. Inst. 1976).Nektonic - Capable <strong>of</strong> swirnrning againstnormal wave and current action,i .e., sel f-propel led.Neritic - Shallow surface water zone extendingfrom <strong>the</strong> high-tide mark to<strong>the</strong> edye <strong>of</strong> <strong>the</strong> continental shelf.Neuston - Organisms associated with <strong>the</strong>surface film <strong>of</strong> <strong>the</strong> water.Salinity - <strong>The</strong> total amount ot dissolvedsol id material (in grams) containedin one kilogram <strong>of</strong> water, expressedas O/, (ppt). For this measurementall organic matter is oxidized, allcarbonate converted to oxide, and allbromide and iodide replaced by chloride(Sverdrup et al. 1942; colloquial- <strong>the</strong> saltiness <strong>of</strong> a body <strong>of</strong>water).
Sand- Coarse-grai ned mineral sedimentswith diameters between 74 pm and2 mln (Cowardin et al. 1979).Spring Tides - <strong>The</strong> highest high and lowestlow tides during <strong>the</strong> lunar month.Standing crop - Term applied to biomass <strong>of</strong>oryanisms per unit area or volume.Standing stock - Term used to describecombined concept <strong>of</strong> density andstanding crop.Stone - Hock fragments with diameters between25.4 cm and 60.9 cm (Cowardinet al. 1979).Subaerial wet1 ands - Wetland habitatswhich lie between mean low water andmean high water.Sublittoral - Pertaining to <strong>the</strong> marinezone between extreme lowest 1 ow tidallevel and <strong>the</strong> margin <strong>of</strong> <strong>the</strong> continentalshelf.Subrounded - A roundness grade in whichconsiderable wear is evident, wi<strong>the</strong>dges and corners rounded to smoothcurves and <strong>the</strong> area <strong>of</strong> <strong>the</strong> originalfaces considerably reduced (An. Geol .Suspension feeder - Organism which processeswater for food, ei<strong>the</strong>r passively(benthic) or actively (pelayic) entraining phytoplankton ando<strong>the</strong>r microscopic organisms and suspendeddetritus.Thigmotaxis - Movement <strong>of</strong> an organism inwhich contact with a solid body(i e., a1 gae, bottom sediments,rocks, pilings) is <strong>the</strong> directivestimulis; also called stereotaxis.Tidal amplification (factor) - Local tidalrange as a function (divided by) <strong>the</strong>tidal range at or near <strong>the</strong> mouth <strong>of</strong><strong>the</strong> estuary.Trophic - Related to food, feeding, andnutrition.Trophic level - A group <strong>of</strong> oryanisms in afood web that secures food in <strong>the</strong>same general manner.Volatile solids - Products, exclusive <strong>of</strong>moisture, given <strong>of</strong>f as gas and vaporas determined by definite prescribedmethod01 ogy ; measure <strong>of</strong> organiccontent.
APPENDIX I3Sedinent Classification Schtmcs
Appendix fable 0-1. Various schemes <strong>of</strong> unconsolidated sediment particleclassification (Source: U.S. Army Corps Engineers 1973).Wentworth Scale(size description)PhiUnitsd*GrainDiameterd (mm)U.S.StandardSieveSizeUnifiedSoi 1Classification(USC)Bou 1 derCobble- 8256.0Cobble
APPENDIX CTidal Channel Characteristics Measurements(from Levy and Northcote 1981)
Measured Tidal Channel (TC) Characteristics1. TC mouth width (m)2. Width <strong>of</strong> TC at sampling station ( m)3. Distance from sampling site to mouth <strong>of</strong> TC (m)4. TC depth (m)5. Trough depth (cm)6. TC length (m)7. Average sedge height (m)8. Average szdiment particle size (microns)9. Distance to nearest subtidal refuge (m)10. Angular deflection to prevailing flowing tide (degrees)II. Channel order12. Sub- channel length (m)13. Angle <strong>of</strong> sedge bank (degrees)14. Slope <strong>of</strong> <strong>the</strong> tidal change (m/hr)15. Height <strong>of</strong> <strong>the</strong> high tide (m)16, Turbidity <strong>of</strong> <strong>the</strong> water at low tide (NTU)17. Area <strong>of</strong> <strong>the</strong> TC (m2)18. Compass heading <strong>of</strong> main axis <strong>of</strong> TC (degrees)19. Relative elevation <strong>of</strong> TC bottom (m)20. Elevation <strong>of</strong> surrounding bank (m)2 1 . Area <strong>of</strong> refugia at low tide (m2)22. Length <strong>of</strong> time TC submerged (hr )cross-sectionA1.LSLOUGH
Measurement <strong>of</strong> Tidal Channel tlabi tat CharacteristicsFish catch results from <strong>the</strong> May 10-17 surveys were comparedstatistically with habitat characteristics <strong>of</strong> tidal <strong>channels</strong> to assess hichcharacteristics were associated with high numbers <strong>of</strong> fish in different tidal<strong>channels</strong>. <strong>The</strong> characteristics used in <strong>the</strong> analysis were chosen to be easilymeasurable ei<strong>the</strong>r directly at <strong>the</strong> sampling site or in <strong>the</strong> laboratory, orindirectly from Fraser River Delta Project Maps. Figure 5 shows several <strong>of</strong><strong>the</strong> tidal channel characteristics and Table 13 supplies numerical values.<strong>The</strong> fol lowing measurements were taken and included in statistical analyses:1. Width <strong>of</strong> <strong>the</strong> tidal channel mouth in meters (MTHWDTH) - measured in<strong>the</strong> field from one tidal channel bank to <strong>the</strong> o<strong>the</strong>r perpendicular to<strong>the</strong> axis <strong>of</strong> <strong>the</strong> channel.2. Width at <strong>the</strong> sampling site in meters (STNWDTH) - measured in <strong>the</strong>field from one tidal channel bank to <strong>the</strong> o<strong>the</strong>r perpendicular to <strong>the</strong>axis <strong>of</strong> <strong>the</strong> channel.3. Distance from <strong>the</strong> sampling site to <strong>the</strong> tidal channel mouth in meters(MTHDIST) - measured with a map measure from <strong>the</strong> Fraser River DeltaSeries Maps.4. Tidal channel depth in metres (CHNDPTH) - measured in <strong>the</strong> field atlow tide. A rope was stretched between <strong>the</strong> stakes at <strong>the</strong> level <strong>of</strong><strong>the</strong> bank and a 3-meter pole, graduated at 5 cm intervals, waspositioned vertically in <strong>the</strong> deepest part <strong>of</strong> <strong>the</strong> tidal channel. <strong>The</strong>height at which <strong>the</strong> rope bisected <strong>the</strong> pole was recorded as <strong>the</strong>tidal channel depth.5. Trough depth in centimeters (TRODPTH) - <strong>the</strong> residual tidal f l o ~ nearlow tide frequently scoured a trough in <strong>the</strong> bottom <strong>of</strong> <strong>the</strong> tidal,channel which varied in depth between sampling sites.This depth was measured with a ruler during periods <strong>of</strong> low slacktide between June 7-13, 1979.6. Length <strong>of</strong> <strong>the</strong> tidal channel in ~neters (TCLNGTH) - measured witha map measure from <strong>the</strong> Fraser River Delta Series Maps. <strong>The</strong>length was defined from <strong>the</strong> position <strong>of</strong> <strong>the</strong> sampling site to <strong>the</strong>fur<strong>the</strong>st point on <strong>the</strong> 0 foot geodetic perimeter <strong>of</strong> <strong>the</strong> tidalchannel.7. Height <strong>of</strong> surrounding niarsh plants in ineters (IITSEDCC) -measured in <strong>the</strong> field during a one week period at <strong>the</strong> beginning<strong>of</strong> June, 1979 using a 3-meter pole graduated in 5 cnl intervals.
8. Mean sediment particle size (SFDSIZE) - replicate sediment sampleswere obtained on June 12, 1973 at all 18 tidal channel samplingsites. Samples <strong>of</strong> <strong>the</strong> upper 1 cm <strong>of</strong> sediment were collected with atrowel close to <strong>the</strong> center trough <strong>of</strong> <strong>the</strong> tidal <strong>channels</strong> andtransported to <strong>the</strong> Geochemistry Lab, U.B.C., in Whirl Pak Bags. <strong>The</strong>samples were dried in an oven in drying bags and <strong>the</strong>n broken up witha mortar and pestlc. Individual samples were <strong>the</strong>n placed on <strong>the</strong>uppermost (coarsest) <strong>of</strong> a series <strong>of</strong> 6 sieves and shaken for 5minutes. <strong>The</strong> fractions <strong>of</strong> sediment were weighed and <strong>the</strong> proportion<strong>of</strong> sediment in a given size range calculated as a fraction <strong>of</strong> <strong>the</strong>total sample weight. <strong>The</strong> average particle size in a given fractionwas asst~med to be half-way between <strong>the</strong> surrounding sieve sizes. <strong>The</strong>proportion <strong>of</strong> sediment in a given fraction was multiplied by <strong>the</strong>average particle size to obtain weighted proportions <strong>of</strong> sedimentwhich were <strong>the</strong>n summed to give an estimate <strong>of</strong> <strong>the</strong> mean particlesize. <strong>The</strong> average value <strong>of</strong> 2 replicates was used in <strong>the</strong> statisticalanalyses and is shown in Table 13.9. Distance to nearest sub-tidal refuge in meters (REFDIST) -determined as <strong>the</strong> distance from <strong>the</strong> sampling site to <strong>the</strong> nearestslough (sub-tidal) habitat capable <strong>of</strong> maintaining juvenile salmon at1 ow tide when no water occurred in <strong>the</strong> tidal <strong>channels</strong>. Thisdistance was measured <strong>of</strong>f Fraser River Delta Maps with a mapmeasure.10. Angular deflection to prevailing flowing tide in degrees(ANGDEFL) - <strong>the</strong> angle <strong>of</strong> <strong>the</strong> axis <strong>of</strong> <strong>the</strong> tidal channel at <strong>the</strong> mouthto <strong>the</strong> direction <strong>of</strong> <strong>the</strong> flooding tide in <strong>the</strong> slough (Figure 5) wasmeasured <strong>of</strong>f <strong>the</strong> Fraser River Delta Maps with a protractor.11. Tidal channel order (TCORDER) - tidal <strong>channels</strong> were classifiedaccording to <strong>the</strong> following characteristics:ORDERCHARACTER I ST I CS1 large sub-tidal slough or reach which never dewatersat low tide.2 large channel which experiences high velocity tidalflows and usually does not dewater at low tide.3 inter-tidal channel which branches <strong>of</strong>f a 2nd orderchannel or slough and usually dewaters completcly atlow tide.small inter-tidal channel hich branches <strong>of</strong>f a 2ndor 3rd order channel and always dewaters at low tide.
12. Total sub-channel length in rneters (SUBCHNL) - <strong>the</strong> length <strong>of</strong> a1 ltributaries flowing into <strong>the</strong> tidal <strong>channels</strong> was measured with a napmeasure. Only those tributaries deeper than <strong>the</strong> 0-foot contour wereincl uded.13. Average angle <strong>of</strong> <strong>the</strong> sedge bank in degrees (ANGBANK) - determined in<strong>the</strong> field indirectly through measurement <strong>of</strong> parameter: A, B and C(shown on Figure 5) and calculation <strong>of</strong> angles r* and o( wl~ere o(=tan'l A/B and d = tdn-' A/C. <strong>The</strong> mean value for <strong>the</strong>se 2angles was used to give a measure <strong>of</strong> <strong>the</strong> relative slope <strong>of</strong> <strong>the</strong> tidalchannel banks.14. Slope <strong>of</strong> <strong>the</strong> tidal change in meters per hour (TIDSLOP) - <strong>the</strong>difference between <strong>the</strong> height <strong>of</strong> <strong>the</strong> predicted high and 10v~ tides atPoint Atkinscn was divided by <strong>the</strong> length <strong>of</strong> time between <strong>the</strong>se twotides to give a measure <strong>of</strong> <strong>the</strong> rate <strong>of</strong> tidal flow for <strong>the</strong> datessampl i ng took place.15. Height <strong>of</strong> <strong>the</strong> high tide in meters (HTHTIDE) - <strong>the</strong> predicted levels<strong>of</strong> <strong>the</strong> high tide at Point Atkinson for <strong>the</strong> dates sampling took placewere obtained from tide tables.16. Turbidity <strong>of</strong> <strong>the</strong> trough water at low tide in nephelometric turbidityunits (WATURB) - water sampling took place at low tide on June 12,1979 at a1 1 18 tidal channel sampling sites. Sub-surface sampleswere obtained from <strong>the</strong> trough <strong>of</strong> <strong>the</strong> tidal channel in 250 m1 plasticsample jars. Care was taken to avoid disturbing <strong>the</strong> sedimentupstream <strong>of</strong> <strong>the</strong> sampling site. Turbidity levels were laterdetermined in <strong>the</strong> laboratory with a tlach Turbidimeter.17. Area <strong>of</strong> <strong>the</strong> tidal channel in square meters (TCARCA) - measured byplanimetry from <strong>the</strong> Fraser River Delta Series maps. <strong>The</strong> margitis <strong>of</strong><strong>the</strong> tidal <strong>channels</strong> were defined by <strong>the</strong> 0-foot geodetic contour.18. Compass heading <strong>of</strong> <strong>the</strong> main axis <strong>of</strong> <strong>the</strong> tidal channel in degrees(COMPASS) - <strong>the</strong> main axis <strong>of</strong> <strong>the</strong> tidal channel was drawn onto FraserRiver Delta maps and <strong>the</strong> difference between this line and <strong>the</strong>North axis was measured with a protractor.19. Elevation <strong>of</strong> <strong>the</strong> tidal channel bottom in meters (TCELEV) - <strong>the</strong> depth<strong>of</strong> water in <strong>the</strong> tidal <strong>channels</strong> was measured with a 3-meter graduatedstaff gauge at all eighteen sites over a 40 minute period near hightide on June 14, 1979. <strong>The</strong> location <strong>of</strong> <strong>the</strong> deepest part <strong>of</strong> <strong>the</strong>channel was marked with a previously deposited anchor and float.Since all measurements were conducted at a time when <strong>the</strong> water levelwas static, measured differences reflected variations in bottom
elevation. <strong>The</strong> measured water depths were subtracted froin <strong>the</strong> level<strong>of</strong> <strong>the</strong> predicted high tide at Point Atkinson to give a measure <strong>of</strong><strong>the</strong> absolute elevation <strong>of</strong> <strong>the</strong> tidal channel bottom. <strong>The</strong>measurements were repeatl?d on two consecutive high tides to compareresults. Since <strong>the</strong> relative ranking <strong>of</strong> bottom elevation wasconsistent, only <strong>the</strong> June 14 results are shown in Tahle 13.20. Elevation <strong>of</strong> <strong>the</strong> surrounding bank in meters (BNKELEV) - <strong>the</strong> average<strong>of</strong> two spot heights nearest <strong>the</strong> sampling site was determined from<strong>the</strong> Fraser River Celta Series maps. This served to give a measure<strong>of</strong> <strong>the</strong> absolute elevation <strong>of</strong> <strong>the</strong> surrounding marsh habitat above 0foot geodetic elevation.21. Area <strong>of</strong> low elevation refuges in square meters (AREAREF) - <strong>the</strong> area<strong>of</strong> sub-tidal pools in <strong>the</strong> tidal <strong>channels</strong> bras planimetered fram <strong>the</strong>Fraser River Delta Series maps. <strong>The</strong>se areas were bounded by dashedlines and indicated low elevation depressions in <strong>the</strong> tidal <strong>channels</strong>which contained water at low tide.22. Time <strong>of</strong> submergence prior to sampling in hours (TIMESUB) -calculated by plotting tidal curves (predicted tide height at PointAtkinson vs. time) and defining <strong>the</strong> period <strong>of</strong> tidal <strong>channels</strong>ubmergence prior to sampling based on <strong>the</strong> measured tidal channelbottom elevations (no. 19 on p. 13). <strong>The</strong> number <strong>of</strong> hours at which<strong>the</strong> predicted tide level was greater than <strong>the</strong> measured elevationswas extrapolated <strong>of</strong>f <strong>the</strong> tidal curves.
Appendix Table C-1. Measured tidal channel habitat characteristics. For explanation <strong>of</strong> terms and tinits <strong>of</strong>measurement, see text.TldalSAWPLlNG SITESChannel Woodward Island Barber I s l end Lsdner Marsh Robsrts Be*Chwecterlst lcsW 1 Y2 W3 W4 W5 W6 81 82 83 84 85 Dl D2 03 04 05 FI F2MlHWDM 17.0 29.0 135 4.5 14.5 21.5 15.0 130 10.5 115 6.0 13.0 195 9.5 11.5 115 10.5 5.5STNWDTH 9.9 28.0 12.9 7.9 8.3 12.1 11.8 10.8 11.3 12.3 3.9 9.7 11.6 6.9 8.7 0 4 7.2 7.7MmD IST 192 53 85 30 35 1128 55 65 165 132 4 9 282 28 90 98 40 65CWTH 1.75 I 1.38 1.19 174 3 1 1-69 I.% 1.68 213 1-51 2-16 2.05 1.90 1.77 2.27 1.18 1.88lRODPTH 9.0 15.0 5.0 5.0 6.0 5.0 6.5 3.5 17.5 8.0 3.0 6.0 145 7.0 9.0 24.5 6.0 6.0TCLMiTH 495 870 480 391 566 234 352 370 891 315 346 770 463 215 376 480 414 533HT SEDGE 0.95 1-05 1.10 1.15 0.s 1.05 0.85 0.82, 0.96 O.R 0.90 1.10 1.0 0.95 1.35 1.40 o.n 0.60SEOS I ZE 192 I08 98 75 155 89 79 83 77 105 87 72 96 84 100 80 80 143REFDl ST 219 63 489 522 45 1143 70 189 108 216 1U 11 291 49 217 228 416 290ANGDEFL 79 56 57 57 46 57 % 79 20 78 65 102 31 111 0 0 60 77TCQIDER 3 2 3 3 3 2 3 3 3 3 4 3 3 3 3 2 3 3SUBCHNL 474 2210 838 31 1 476 492 659 N I229 495 75 200 495 78 252 221 983 4%ANOBAK 19.4 8.6 12.5 17.0 263 12.6 16.3 20.2 164 19.8 38.8 24.1 24.2 29-0 22.5 13.4 19.0 26.8" TIOSLW 0.44 0.44 0.44 0.44 0.44 0.44 0.49 0.49 0.49 0.49 0.49 0.48 0.48 0.48 0-48 0.48 0.46 0.46May 10-13T lOSL6 0.49 0.49 0.49 0.49 0.49 0.49 0.X 0.36 0.36 0.36 0.36 00.4 0.44 0.44 0.44 0.44 0.49 0.49Mey 14-17HTHT l DE 4.2 4.2 4.2 4.2 4.2 4.2 4.1 4.1 4 1 4.1 4.1 4.1 4.1 4.1 4.1 4.1 4.2 4.2May 10-13HTHT l C€ 4.1 4.1 4.1 4.1 4.1 4 1 3.7 3.7 3.7 3.7 3.7 1.9 3.9 3.9 3.9 3.9 4.1 4.1Way 14-17WATURB 110 77 2s 50 1 130 160 22 100 120 52 67 46 23 36 76 80 57TCAREA 4608 24071 6197 U)84 4097 2778 3855 4x15 9950 4311 1laO 393 2694 2044 2323 8240 4617 3214WASS 197 95 103 99 263 121 40 114 85 328 122 8 84 143 33 79 144 266TCELEV 1.6 1.41 1-95 2.09 1-68 2.19 1.67 1.91 1.62 1-66 1-96 1.81 1 2.12 1.94 1.58 2-34 2.21WKELE V 0.2 0.3 0.2 0.3 0.4 0.6 0.6 0.8 0.9 0.5 1.1 0.9 1.2 0.9 1.0 1.2 0.0 0.6AREAREF 37 2183 632 74 74 9 46 0 1623 37 0 0 46 56 0 1208 418 0T I MSUB 17.43 17.67 16.49 16.10 17.24 15.83 16.02 15.55 16.12 16.00 15.45 15.86 15.76 15.22 15.59 16.34 15.02 15.32Mey 10-13T IKSVB 15.75 16.13 15.12 14.86 15.62 14.68 1605 15.57 15.15 15.51 16.21 15.56 15-46 14-96 15-31 16.00 14.47 14.71Mey 14-17
APPENOIX DSumnary <strong>of</strong> Current Research andResearch Groups/Centers AddressingEstuarine Channel Ecology orEffects <strong>of</strong> A1 teration <strong>of</strong> Channel Habitats
Estuarine Channel Research in <strong>Pacific</strong> <strong>Northwest</strong>Organization:Oregon Institute <strong>of</strong> Marine BiologyUni vers i ty <strong>of</strong> OregonAddress:Contact(s) :Oregon Insti tute <strong>of</strong> Marine BiologyUni versi ty <strong>of</strong> OreaonCharleston, Oregon 97420Daniel Varoujean, Paul Rudy Jr.Type <strong>of</strong> Research : general es tuari ne <strong>ecology</strong>Location :Coos Baygrganizatiun: Oregon Department <strong>of</strong> Fish and Wild? ifeAddress: Oregon Department <strong>of</strong> Fish and Wild1 ifeOregon State Universi tyExtension Hal 1 303Corval 1 is , Oregon 97331Contact(s):Daniel Bottom, James Lichatowich, Kim Jones, Peggy HerringType <strong>of</strong> Research:<strong>estuarine</strong> utilization by juvenile salmonidsLocation: Oregon <strong>coast</strong>al estuaries , Coos BayOrganization:Department <strong>of</strong> Botany and Plant PathologyOregon State Uni vers i t yAddress:Department <strong>of</strong> Botany and Plant PathologyOregon State UniversityCorvallis, Oregon 97331Contact(s): C. David McIntireType <strong>of</strong> Research: benthic primary production; eelgrass production andphysiology; structure and production <strong>of</strong> epiphytic algaeLocation(s):Columbia River estuary; Netarts Bay
Organization: Department <strong>of</strong> General ScienceOregon State UniversityAddress : Department <strong>of</strong> General Science and, Marine Science CenterOregon State University Newport, Oregon 97365Corval 7 is, Oregon 97331Contact(s) : Robert Worrest,Dani 1 HancockType <strong>of</strong> Research: <strong>ecology</strong> <strong>of</strong> <strong>estuarine</strong> diatomsLocation:Yaqui na BayOrganization: Department <strong>of</strong> GeographyOregon State UniversityAddress : Department <strong>of</strong> OceanographyOregon State UniversityCorval 1 is, Oregon 97331Contact(s) : Robert Frenkel , <strong>The</strong>odore BossType <strong>of</strong> Research:sal tmarsh comuni ty <strong>ecology</strong>; introduced species <strong>of</strong> <strong>estuarine</strong>macrophytesLocation:Siuslaw River estuaryOrganization: School <strong>of</strong> OceanographyOregon State UniversityAddress : School <strong>of</strong> Oceanography and, Marine Science CenterOregon State University Newport, Oregon 97365Corvall is, OregonContact(s): Lawrence Small, Charles Miller, Robert Hol ton, Jefferson GonorJames GoodType <strong>of</strong> Research: water column primary production; phytoplanktonassemblage structure; zooplankton grazing on<strong>estuarine</strong> phytoplankton; pelagic zooplanktonassemblage structure and dynamics; benthicinfauna assemblage distribution and structureLocation (s):Columbia River estuary, Yaquina Bay, Coos Bay
Organization:Hammond LaboratoryNational Marine Fisheries ServiceAddress : Hammond LaboratoryNational Marine Fisheries ServiceP.O. Box 155Hammond, Oregon 971 21Contact(s) :Robert McConnell , George McCabe, Robert EmmettType <strong>of</strong> Research:fisheries <strong>ecology</strong>; distribution, abundance, and food habits <strong>of</strong>juvenile salmonids and Dungeness crabLoca ti on :Columbia River estuaryOrganization:Battelle Marine Research LaboratoryBattelle Memorial Institute <strong>Northwest</strong>Address : Battel le Marine Research Laboratory439 West Sequim Bay RoadSeqbim, Washington 98382Contact(s) : James Young, Walter Pearson, Jack Anderson, Charles GibsonType <strong>of</strong> Research:<strong>estuarine</strong> <strong>ecology</strong> <strong>of</strong> benthic infauna, pelagic zooplanktonand f.ishes; effects <strong>of</strong> oil pollution on <strong>estuarine</strong> communitiesLocation :Strait <strong>of</strong> Juan de Fuca and nor<strong>the</strong>rn Puget SoundBrganization: Fisheries Research Insti tuteUniversity <strong>of</strong> Washington .Address: Fisheries Research Institute WH-10College <strong>of</strong> Ocean and Fishery SciencesUniversity <strong>of</strong> WashingtonSeattle, Washington 98195Contact(S): Charles Simenstad, Robert Wissmar, Ernest Salo, Quentin Stober,Bruce MillerType <strong>of</strong> Research: <strong>estuarine</strong> utilization by juvenile salmonids; food webstructure <strong>of</strong> <strong>Pacific</strong> <strong>Northwest</strong> estuaries; structureand dynamics <strong>of</strong> epi benthic and neri tic zooplanktoncomnuni ties in estuaries; <strong>estuarine</strong> fish assemblagestructureLocation :Hood Cana 1, Puget Sound and component estuaries , Grays Harbor,Columbia River estuary
Organization: School <strong>of</strong> FisheriesUniversity <strong>of</strong> WashingtonAddress : School <strong>of</strong> Fisheries WH-10Col lege <strong>of</strong> Ocean and Fishery SciencesUniversity <strong>of</strong> WashingtonSeattle, Washington 98195Contact(s) : David Armstrong, Kenneth Chew, Ronald Thorn, Jack WordType <strong>of</strong> Research:basic biology and <strong>ecology</strong> <strong>of</strong> <strong>estuarine</strong> crustaceansand molluscs; early life history (larval) <strong>of</strong> economical IYimportant crustaceans; maricul ture <strong>of</strong> <strong>estuarine</strong> organi SmsLocation :Grays Harbor, Puget Sound and associated estuariesOrganization: Department <strong>of</strong> OceanographyUniversity <strong>of</strong> WashingtonAddress: School <strong>of</strong> Oceanography WE-10Col 1 ege <strong>of</strong> Ocean and Fisheries SciencesUniversity <strong>of</strong> WashingtonSeattle, Washington 98195Contact(s) : Joe Creager, Chris Sherwood, David Jay, T. Saunders Engl i sh,Peter Jumars, Arthur Nowel 1Type <strong>of</strong> Research: <strong>estuarine</strong> sedimentology and circulation; <strong>estuarine</strong> zooplanktonand larval fish distribution, abundance, and<strong>ecology</strong>; benthic infauna and epi fauna <strong>ecology</strong>Location: Columbia River estuary, Puget Sound and associated estuari esOrganization: Huxley College <strong>of</strong> Environmental StudiesWestern Washington UniversityAddress : Huxley College <strong>of</strong> Environmental StudiesWestern Washington UniversityBe1 1 i ngham, Washington 98225Contact(s) : Wi 11 jam Summers, Bert WebberType <strong>of</strong> Research:ecolow <strong>of</strong> <strong>estuarine</strong> and nearshore marine algae andbenthic. invertebrate comuni tiesLocation: nor<strong>the</strong>rn Puget Sound estuaries
Organization : Department <strong>of</strong> OceanographyUniversity <strong>of</strong> British ColumbiaAddress : Department <strong>of</strong> OceanographyUniversity <strong>of</strong> British ColumbiaVancouver, British Columbia V6T 281CanadaContact(s) : Brenda HarrisonType <strong>of</strong> Research:Location: Fraser Ri ver estuary<strong>ecology</strong> <strong>of</strong> <strong>estuarine</strong> benthic and epibenthic invertebratecomnuni ti esOrganization: Department <strong>of</strong> BotanyUniversity <strong>of</strong> British ColumbiaAddress: Department <strong>of</strong> BotanyUniversity <strong>of</strong> British ColumbiaVancouver, Britich Columbia V6T 2B1CanadaContact(s) : Paul Harrison, Richard BigleyType <strong>of</strong> Research : seagrass (Zos tera spp. ) cormuni ty <strong>ecology</strong>Location:Strait <strong>of</strong> Georgia estuaries, nor<strong>the</strong>rn Puget SoundOrganization : Wes twa ter Research CentreUniversity <strong>of</strong> British ColumbiaAddress: Westwater Research CentreUniversity <strong>of</strong> British ColumbiaVancouver, British Columbia V6T 1W5CanadaContact(s) : Thomas Northcote, David Levy, Anthony Dorcey, Kenneth Ha1 1Type <strong>of</strong> Research:<strong>estuarine</strong> utilization by juvenile salmonids; management<strong>of</strong> <strong>estuarine</strong> habitats; effects <strong>of</strong> log rafting, dikingand filling, and construction <strong>of</strong> training wallsLocation:Fraser River estuary
Organization : Department <strong>of</strong> Biological SciencesSimon Fraser UniversityAddress:Contact (s):Department <strong>of</strong> Biological SciencesSimon Fraser Un iverst iyBurnaby, British Columbia V5A 1S6CanadaMichael St anhopeType <strong>of</strong> Research:<strong>estuarine</strong> <strong>ecology</strong> <strong>of</strong> gammarid amphipods with referenceto log storage effectsLocation:Squami sh and Fraser River estuariesOrganization:Address:Contact(s):Fisheries Research Branch,Salmon Habitat Research Sect ionl~est Vancouver Laboratory,z~acif ic Biological Stat ion,4160 Marin eDrive, Departure Bay Road.West Vancouver, B.C. V7V IN6 Nanaimo, R.C. V9R 5K6Canada9Colin ~evin~sl, Mich el ~aldichukl Me1 ~ o t ~ k lT.J. ~rown~, B. Kask , I. ~irtwelyl, G. ~reer~.C. MCA~1 ister2,Type <strong>of</strong> Research:Locat ion:<strong>ecology</strong> <strong>of</strong> gammarid amphipods in <strong>estuarine</strong> habitats; feeding<strong>ecology</strong> <strong>of</strong> juvenile salmonids; survivorship <strong>of</strong> chinookreleased in <strong>estuarine</strong> and alternate habitats; effects <strong>of</strong>domestic waste on juvenile salmonids in estuariesFraser River, Campbell River, Nanaimo River estuariesOrganization: <strong>Pacific</strong> Biological StationAddress: <strong>Pacific</strong> Biological StationDepartment <strong>of</strong> <strong>the</strong> EnvironmentP.O. Drawer 100Nanairno, British Columbia V9R 5K6CanadaContact(s) : John Sibert, Robin LeBrasseur, Michael Healey, Brent HargreavesType <strong>of</strong> Research:<strong>estuarine</strong> utilization by juvenile salmonids; <strong>ecology</strong> <strong>of</strong>epibenthic zooplankton; <strong>estuarine</strong> feeding <strong>ecology</strong> <strong>of</strong> juve~ilefishesLoca ti on :Nanairno River estuary, o<strong>the</strong>r Vancouver Island estuaries
--50272 -101'REPORTPAGE-- --4. Title and SubtntleTHE ECOLOGY OFA COMMUNITY PROFILE ---- -- - - - - - - - - -- -9. Performing Organlzatlon Name and AddressFisheries Research InstituteCollege <strong>of</strong> Ocean and Fishery SciencesUniversity <strong>of</strong> WashingtonSeattle, WA 98195- -3. Rectplent's Accession No- ---- -8. Perform~ng Organlzatlon Rep:. No.I- . - -- -10. Pro~ectlTaskIWork Unit No1.- . -11. Contract(C) or Grant(G) No.--- -- -.-- -- ---- --- -- --p Organ~zatton Name and AddressFish and Wild1 ife ServiceDivision <strong>of</strong> Biological Services--- - --U.S. Department <strong>of</strong> <strong>the</strong> Interior li4 ' --Washington, DC 20240- -IS. Supplementary Notes--16. Abstract (Ltrnlt: 200 word$)This report on <strong>the</strong> <strong>estuarine</strong> channel habitats <strong>of</strong> <strong>the</strong> <strong>Pacific</strong> <strong>Northwest</strong> is one <strong>of</strong> a series <strong>of</strong>community pr<strong>of</strong>iles that syn<strong>the</strong>size useful information about specific natural <strong>coast</strong>al habitats.This pr<strong>of</strong>ile will assist environmental scientists and biologists and <strong>coast</strong>al plannersand managers who are interested in <strong>the</strong> open-water <strong>channels</strong> <strong>of</strong> <strong>coast</strong>al estuaries from <strong>the</strong>Straits <strong>of</strong> Juan de Fuca in Washington, south to Cape Mendocino, California.<strong>The</strong> pr<strong>of</strong>ile describes <strong>the</strong> geomorphological , hvdrological , chemical, and biological componentsand natural processes <strong>of</strong> <strong>the</strong> <strong>channels</strong>, <strong>the</strong>ir energy interchange, and interactionsamong adjacent habitats. In combination <strong>the</strong>se habitat components and <strong>the</strong>ir interactionsdictate <strong>the</strong> ecological structures and functions <strong>of</strong> <strong>the</strong> <strong>channels</strong>. <strong>The</strong> subject materials <strong>of</strong><strong>the</strong> various chapters are integrated and summarized in <strong>the</strong> last chapter, and considerationsfor habitat management are identified.117. Oocument Analysis a. Oescriptors1ChannelsHydro1 ogyEcology<strong>Pacific</strong> <strong>Northwest</strong>Estuariesb Identlflers/Open Ended Terms_, __._______I__.^_ _ _- _ _ __ . _ --c COSATI F8eldIGroup-18. Avatlab~laty Statement ; 19. Securtty Class (Ths Reporf)(See ANSI-239.18;Unl imi ted ! . ~ ] fieh-- ~ ~ jUnclassified120. Secur~ty Class (Ths Page) 22. PrjceIOPTIONAL FORM 272 (4-77)(Formeriv NTIS-35)Department ol Commerce* U.S. GOVERNMENT PRINTING OFFICE: 1984-772-308