Hydro-ecological relations in the Delta Waters

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macrophytes livkg on or rooting in sediment, respectively macro-algae (mainly green algae) and aeagrasaes, offer a significant share to the carbon budget. In the Orwelingenmeer the seagrass Zostera marina dominates, coverkg 30% of the surface area of the lagacm, but contributing only 14% to the annual carbon bu&et, owing to the low P/B ratio of 3. Coverage 1%) 80 GREVELINGEN seagrass Losfera marina GoveraQe 1% 1 90- VEERSE MEER Sigure 7 Percentage coverage in vertical projection on the sediment of Zostera marina and mcro-algae in permanent sample plocs in the Grevelingen and Veerse Meer. She of sample plot is 15 x 15 ma, waterdepth 14 both localitaties is 1.25 m (data bsrrowed from F. Van Lent, DIEO). The Veerse Meer &Ears a &ifFerent picture. Seagrassee csver only 3% of the surface area of the lagoon (IhnewFjk, 1988) and have to compete with epp~rtunistic green algae (mainlp E) for space and light. The lagoon is dominated by plva during the smer season, showFng a roughly
estimated primary production of 500 g C mdZy-l in shallow are-. The contribution to the annual carbon budget of the Veerse Meer is roughly -E -1 120 g C m y , which is 27X of the lagow' budget. The higb nitrogen load not only leads to a relatively high production of phytoplanktou, but also to intensive and undesirable mass growth of =in areas. shallow Figure 7 reveals the inareae and decrease in biomass, eapressed as perrentage wvezage, in a permaaent saaple plot In the Grevelingeu and in the Vwse Fleet!. In the Grevelingemeer the annual cycle of cbaagerr in biomass of seagrass is not disturbed by macro-algae. which have only a low presence. In the Veezse Meer the seagraes plot becomes cmpletely damindted by quickly growing-, suppressing the growth of zostera. Table 3 shows that the eutrophicated Veerse Meer has the highest tmtal -2 -1 primary production (roughly 4-50 g C m y ) and that the nutrient limited Oosterschelde estuary has the lowest values (rdu@ly -P -1 240gCrn y 1. For Ereshwater ecosystems a tentative model has beau developed, descrihlng the relation berween the relative domtuanca of primary producers wmected to the availability of nutrients. and the successive phase$ in the process of %acreasin% eutrophicatton (Phillips. et al. 1978; Van Vierssen, et al. 1985; De Nfe. 1987: Fig. 8, upper panel). The model for esruarine and lagoonal situations Rig. 8, loaez panel) is adapted, based on data from the Qrevelinpn and Veerse &er. The model is odly applicable to stagnant brackish lagoons and extremely sheltered parts of tidal estuaries. In "healthy" saline waters, waterplants - such as seagrasses - dominate. Nitrogen load and concentrations are lm and the relative importance of phytoplanktm in the shallow seagrassbeds is iusigniEicant; the Grevelisgeumeer is an example of phase I. Zn brack3sh waters where eutropbiearim increases, revealed by higher nitrogen loads and concentrations and lower, instable salinities, waterpLants am outcompeted by macto-algae. Epiphyte gowth gn seagrass- increa~es considerably together with the relative dsmtnanee of pbytoplankfou. The resilience of the aquatic cmumnitied decreases, which makes the system less constant in time end
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Netherlands organkation fw applied
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TNO Commlitee on Hydrological Resea
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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
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Estuaries that have not been influe
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2 CHIWGES XN TEE DELTA The Delta ar
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area decltned cnnside~ably, leadins
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Plan, then it is apparent tbt the s
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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$3 in an increase of
Page 68 and 69: model calculations reveal that a ni
Page 70 and 71: Table 3 PreUmInary carbon budget of
Page 72 and 73: Water life of Lake Grevelingen
Page 76 and 77: less predictable for water managers
Page 78 and 79: ILWNEWIJK, A.. KEIP, C., 1988. De v
Page 80 and 81: XBE CHANGING TmAL LAMXiCAPE I N TEE
Page 82 and 83: The storm surke of L&Z1 A.D., knorm
Page 84 and 85: osi* rn@8IOIP m .SL 4 Has F~~ULB 3
Page 86 and 87: During the 19th century man starts
Page 88 and 89: mudflats have retreated some 100-20
Page 90 and 91: aq811~33a.e~ pue 3pTatlJS uxaJsafi
Page 92 and 93: Erosion by waves of sandy shoals (c
Page 94 and 95: Lt has been estimated that the sedi
Page 96 and 97: Implementafion of the Delta Project
Page 98 and 99: ECOLOGICAL DEVELOWdENT OF SALT MAKS
Page 100 and 101: fn tidal water systems sedimentatio
Page 102 and 103: hierarchical position. Tn the egtua
Page 104 and 105: Of course. tke environmental change
Page 106 and 107: wind erasson, desaliuation, aeratio
Page 108 and 109: Fonner tirtal flats with saltmarsh
Page 110 and 111: Grevelingen. Lake Veere and Krammer
Page 112 and 113: As mentioned above aa important que
Page 114 and 115: A seaond important perspective for
Page 116: BEEEXNX, W.D. and 80ZBf&. J. L9M. T
Page 119 and 120: are determining the dfstrlbution af
Page 121 and 122: this volume or in Duutsaa, et aL, 1
Page 123 and 124: artificial waterflow was created af
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of waterbirds occur regulsrly. The
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. DISTRIBUXIOBI OF WATEJBIRoS OVER
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small bird$ extludiag them vill net
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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
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5.2 H- factors Next to all fartors
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Bewick's Swans (Cygnus columbariusl
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m's activiries do not always have t
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measure affecting food supply or av
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DOQiWT$QS, G. 4 TWISK, F., 1987. De
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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
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- In addition to existing managemen
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Nature is pliable. Belattvely young
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Ro. 1. No. 2. SQ. 3. Investigations
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25. The relation between water quan
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Hydro-ecological relations in the Delta Waters

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