Hydro-ecological relations in the Delta Waters

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The herbivores form a rather beterogenous group of swans, geese apd ducks. Some species like the Brent Geese feed nrainly on Eelgrass and salt marshes, although in inoinrer semizkatural grasslands and cereal crops form an important part of phe diet (Ebbinge, er 81, 1987). Mute Bwens are strongly attached to water for feeding, whereas other species like the Mallard feed mainly on adjacent wetlands and agricultural land and use the basins mainly for resting, d~inking and preenins. Ad the food source used by these birds is so variable (@.g. agrimitural wastes and crops) it is impossible to estimate the wailable food supply. Therefore in Table 4 only the biomass of macroalgae (mainly Ulva sp. and Zosrera 8p.) and the denaity of herbivores are given. With the exception of the Voordelta the average density of herbivoree is quite similar in the different hasins, although somewhat hisher in the Tahle 4 Occurrence of macrqphyta (tong ash free dry weight at martmum stwding stock) and herbivores CbirdsIlOO ha) in the different aquatic system of the Delta atea. (Souree of macrophyta datat (1) Craeymeersch (pers. cm.) L2) De Jong (pers. corn.) (3) Nienhnis (pers. corm.) (L) Hannewijk, 1B88.) For abbreviations see Tahle 3. System 'Lotal Gran algae Source Density of biomass macrohyta herbivores W smell 0 mall 1 87 KV 360 80 280 2 199 OS 1833 S67 1457 3 334 ws smdl 0 sncg21 2 399 QV ? 1110-3300 ? 3 302 W 630 9.6 680 4 562 W small 0 0 415 BD small 0 0 418 BB small
freshwater basins. Clearly the presenoe of these macrophyta haw no influence on the density af all herbivores as they form only a 4 1 part of the diet pf only some species. Notwithstanding the huge differences in food supply it is rewkable no larger diffexenees in densities exist. Table 5 Comparison between the consumption (C) (kg ash free dry weight/lQO ha3 and deqsity CD3 (birds/lQD ha) of different bird groups in the tidal areas, the saline and t&e freshwater l&s (far further explanation see tm). TIDAL WINE FKESH Herbivores C D Diving ducks C D Waders In Table 5 the dara on densities are summarized together with estimates of the food emsumption a£ the different bird gzoups. This was obtained by standard methods (see e.g. Nienhuis and Groenendijk, 1986). It i8 obvious that the densities of herbivores are high in cwtpsrisun with those of other groups, their consumption even mueh higher. This is what we expect from primary consumers. Waders and diving ducks are secondary omsumess and their densities as well as their oonsmptian are much lewer. The on17 exception are waders in the tidal areas. It is obvious
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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
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tracefore possible to convert the a
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Figsrlre 7 Changes in the cadrnrum
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prevention measures are desirable h
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elationships between different spec
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Bio-essay Weriments with polluted s
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considerable thought to drawing up
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ShLOUONS, W. and BYSINK, W.D., 1981
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are taken. The first year after the
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The Hollands DiepJnaringpllet is pa
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In 1976 the determination of chlozo
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, 0.66 m 0,s - 0.02 1989 I 0.86 - 0
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Table 3 Eutrophication of the Volke
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Laks Volkarek ---- Lake Zoom 0.40 0
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4 WAGBEET MEdSIIRaS TO PEEVBT OR LT
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Table 5 gives estimtes of the phosp
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In principle, two states of equilib
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Zooplankton (Alma affinis) Pike (Es
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EUTROPHICATION OF ESTUAAIES AND BRA
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The average discharge of Xhine and
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and only l-2% cows frm the aive Sch
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highest trophic potential: nutrient
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period 1980-19$3 in an increase of
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model calculations reveal that a ni
Page 70 and 71:
Table 3 PreUmInary carbon budget of
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Water life of Lake Grevelingen
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macrophytes livkg on or rooting in
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less predictable for water managers
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ILWNEWIJK, A.. KEIP, C., 1988. De v
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XBE CHANGING TmAL LAMXiCAPE I N TEE
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The storm surke of L&Z1 A.D., knorm
Page 84 and 85: osi* rn@8IOIP m .SL 4 Has F~~ULB 3
Page 86 and 87: During the 19th century man starts
Page 88 and 89: mudflats have retreated some 100-20
Page 90 and 91: aq811~33a.e~ pue 3pTatlJS uxaJsafi
Page 92 and 93: Erosion by waves of sandy shoals (c
Page 94 and 95: Lt has been estimated that the sedi
Page 96 and 97: Implementafion of the Delta Project
Page 98 and 99: ECOLOGICAL DEVELOWdENT OF SALT MAKS
Page 100 and 101: fn tidal water systems sedimentatio
Page 102 and 103: hierarchical position. Tn the egtua
Page 104 and 105: Of course. tke environmental change
Page 106 and 107: wind erasson, desaliuation, aeratio
Page 108 and 109: Fonner tirtal flats with saltmarsh
Page 110 and 111: Grevelingen. Lake Veere and Krammer
Page 112 and 113: As mentioned above aa important que
Page 114 and 115: A seaond important perspective for
Page 116: BEEEXNX, W.D. and 80ZBf&. J. L9M. T
Page 119 and 120: are determining the dfstrlbution af
Page 121 and 122: this volume or in Duutsaa, et aL, 1
Page 123 and 124: artificial waterflow was created af
Page 125 and 126: of waterbirds occur regulsrly. The
Page 127 and 128: . DISTRIBUXIOBI OF WATEJBIRoS OVER
Page 129 and 130: small bird$ extludiag them vill net
Page 131 and 132: In order to lsok for relatiouehips
Page 133: Table 3 Biomass of macroroobenthos
Page 137 and 138: scmthem bottueary o-f the winter di
Page 139 and 140: 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
Page 147 and 148: 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.
Page 153 and 154: PISCIVORES Litfle Grebe Great Crest
Page 156 and 157: IPYBRO-EGOLOOIOAL BELATIONB ZN THE
Page 158 and 159: apart from upstream purification; -
Page 160 and 161: 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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