Hydro-ecological relations in the Delta Waters

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model calculations reveal that a nitrogen loading of approbimately -2 -1 10 g W m y or more unwuples the eutr@hiulti@n controlling processes (Qe Vries, et al, 1988). -2 -1 In the Veerse Meer lagoon, experiencing a N-load of 34 g m y and haaing a long residence time of the water, permanent stratifloation mainly in the eastern section and dear water during considerable parts of the year, obvionsly, the chlorophyl concentration cmot be controlled by the bottom fauna, although a fluctuating but substantfal benthic biomass is available. In the recent literature (Benkema and Cadee, 1986; Cadee. 1956a. h; Cadea and Hegeman, 1966; Nelisseg and Steffels, 1988) a number of biologi~al effects of increasing eutrophioatbn have been mentioned for the Dutch ccoastal waters and the western Wadden Sea: (1) increasing primary prodwtivn; (2) dominance of flagellates cwer diaroms; (3) incrwing biomass of benthic macro-fauna; (4) increasing catches tbimass 7) of demersal fish and shr-S. It ia beymd the diwcussibn of this paper whether or ~ othese t effects of euthropicatlon are proven ~ausnal facts or jusr assumed tendencies. The question arises whether the correlations menrfoned for Dutch coaxtal waters can dso be revealed for the estnaries and lagoons in the Sauth-West Netharlaads. The answer is negative, for several reasons: (1) long terms series. 6uch as published for the Wadden Sea by Beokema and Cadee. 1987, are not available for the Oosterscfielde and Weaterschelde esruarieti; (2) any possible trend in eutrophication of the Delta estuaries has been obscured (except for the Westerscbelde) by the ==cation of the Delta Wsrks, changtng the hgdrography of the area drastically. The Veerse Neer and Grevelingen have their om euthraphicatipn story, starting respectively in 1961 and 1971 when the basins were cloeed off from, the sea (cf. Pig. l). In Figure 6 a restricted dataset on the occurrence of the flagellate Phaeucgstls poucharii in the weecerh part of the Oasterschelde eahtary is compared with data fro= the western Wadden Sea. The Wadden Sea data reveal. a telacian between increasing eutropbicetion and increasing incidence of Phaeocystis blooms. The Oosterscbelde data show a
Phaeocystis pouchetii WADDENZEE OOSTERSCHELDE Figure 6 Duration of the spring$lonm of Phaeocystis pouchecii expressed a5 number of days wit3 cenc%ntratbns of cells above 1000 ml-l, and average concentration of cells, eqressed as nrpnbez of cells ml-l, for the western Waddenaee (tadee and Aegeman. 1986) and the western Oosterschelde (data rrom C. Bakker. DIHO). For the Oosterschelde: rider af deys: y = 819-9.178~~ = 0.94399, P < 0.01; cells ml-l : P > 0.05. significlmr decrease in the lengCh of the petied of the Phaetlcystis bloom, but aa increase in bloom intensity. Thase partly contzadictory results question the asition of Phaeoegatls pouchesli as an indicator for increasing eutrophic*timn of Dutch coastal waters in general. Older records from before the second World War also reveal incidental heavy Phseocysris blooms in the southern North Sea (personal comnlcation S.H.R. hip) which make the position of the flagellate as an indicator oven weaker.
Page 1 and 2:
Netherlands organkation fw applied
Page 4 and 5:
TNO Commlitee on Hydrological Resea
Page 6 and 7:
2 RIVER WATER AM) THE QPALITH OF TB
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B.J.M. Baptist BIJkswaterstaat. Tid
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This approach will put to use what
Page 13 and 14:
Estuaries that have not been influe
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2 CHIWGES XN TEE DELTA The Delta ar
Page 17 and 18: area decltned cnnside~ably, leadins
Page 19 and 20: Plan, then it is apparent tbt the s
Page 21 and 22: Tiddl flats df the Eastem Seheldt v
Page 23 and 24: tracefore possible to convert the a
Page 25 and 26: Figsrlre 7 Changes in the cadrnrum
Page 27 and 28: prevention measures are desirable h
Page 29 and 30: elationships between different spec
Page 31 and 32: Bio-essay Weriments with polluted s
Page 33 and 34: considerable thought to drawing up
Page 35 and 36: ShLOUONS, W. and BYSINK, W.D., 1981
Page 37 and 38: are taken. The first year after the
Page 39 and 40: The Hollands DiepJnaringpllet is pa
Page 41 and 42: In 1976 the determination of chlozo
Page 43 and 44: , 0.66 m 0,s - 0.02 1989 I 0.86 - 0
Page 45 and 46: Table 3 Eutrophication of the Volke
Page 47 and 48: Laks Volkarek ---- Lake Zoom 0.40 0
Page 49 and 50: 4 WAGBEET MEdSIIRaS TO PEEVBT OR LT
Page 51 and 52: Table 5 gives estimtes of the phosp
Page 53 and 54: In principle, two states of equilib
Page 55 and 56: Zooplankton (Alma affinis) Pike (Es
Page 58 and 59: EUTROPHICATION OF ESTUAAIES AND BRA
Page 60 and 61: The average discharge of Xhine and
Page 62 and 63: and only l-2% cows frm the aive Sch
Page 64 and 65: highest trophic potential: nutrient
Page 66 and 67: period 1980-19$3 in an increase of
Page 70 and 71: Table 3 PreUmInary carbon budget of
Page 72 and 73: Water life of Lake Grevelingen
Page 74 and 75: macrophytes livkg on or rooting in
Page 76 and 77: less predictable for water managers
Page 78 and 79: ILWNEWIJK, A.. KEIP, C., 1988. De v
Page 80 and 81: XBE CHANGING TmAL LAMXiCAPE I N TEE
Page 82 and 83: The storm surke of L&Z1 A.D., knorm
Page 84 and 85: osi* rn@8IOIP m .SL 4 Has F~~ULB 3
Page 86 and 87: During the 19th century man starts
Page 88 and 89: mudflats have retreated some 100-20
Page 90 and 91: aq811~33a.e~ pue 3pTatlJS uxaJsafi
Page 92 and 93: Erosion by waves of sandy shoals (c
Page 94 and 95: Lt has been estimated that the sedi
Page 96 and 97: Implementafion of the Delta Project
Page 98 and 99: ECOLOGICAL DEVELOWdENT OF SALT MAKS
Page 100 and 101: fn tidal water systems sedimentatio
Page 102 and 103: hierarchical position. Tn the egtua
Page 104 and 105: Of course. tke environmental change
Page 106 and 107: wind erasson, desaliuation, aeratio
Page 108 and 109: Fonner tirtal flats with saltmarsh
Page 110 and 111: Grevelingen. Lake Veere and Krammer
Page 112 and 113: As mentioned above aa important que
Page 114 and 115: A seaond important perspective for
Page 116: BEEEXNX, W.D. and 80ZBf&. J. L9M. T
Page 119 and 120:
are determining the dfstrlbution af
Page 121 and 122:
this volume or in Duutsaa, et aL, 1
Page 123 and 124:
artificial waterflow was created af
Page 125 and 126:
of waterbirds occur regulsrly. The
Page 127 and 128:
. DISTRIBUXIOBI OF WATEJBIRoS OVER
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small bird$ extludiag them vill net
Page 131 and 132:
In order to lsok for relatiouehips
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Table 3 Biomass of macroroobenthos
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freshwater basins. Clearly the pres
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scmthem bottueary o-f the winter di
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OCLURRENCE AND DIET QF B ~T .tUQ 80
Page 141 and 142:
5.2 H- factors Next to all fartors
Page 143 and 144:
Bewick's Swans (Cygnus columbariusl
Page 145 and 146:
m's activiries do not always have t
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measure affecting food supply or av
Page 149 and 150:
DOQiWT$QS, G. 4 TWISK, F., 1987. De
Page 151 and 152:
MEININGEB, P.L. and HAPEREX, A.M.M.
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PISCIVORES Litfle Grebe Great Crest
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IPYBRO-EGOLOOIOAL BELATIONB ZN THE
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apart from upstream purification; -
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Storm surge barrier Eastern Scheldt
Page 162 and 163:
- In addition to existing managemen
Page 164 and 165:
Nature is pliable. Belattvely young
Page 166 and 167:
Ro. 1. No. 2. SQ. 3. Investigations
Page 168 and 169:
25. The relation between water quan
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Hydro-ecological relations in the Delta Waters

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