Hydro-ecological relations in the Delta Waters

presence of sufficient quantities of another meral hut not in the
absence or at low concentrations of the second metal iRaven and
Richardson. 1986).
Table 2
Etitrogen and cholorcphyl in Dutch coastal waters, eetuies
and bckieh lagoons (data deni~ed fremDe Vries et al, 1988.
and Smoes - Dos+se?rschelde model cdculatloos; E. Schalrea,
personal communication).
load &eez cone. rhlorophyl cm@.
Nor& Seb (coast.)
Wadden Sea
Westersrhelde
0ostersche3.de
Gravelbgenneer
Veerse Seer
Table 2 shovs a large variatiw in tohd nitwgen loads (4 - 235 g N
-2 -1
m y ) in Dutch coastd waters, estuaries ad brackish lagwns,
whereas N-edncencratims only &a4 a rwe of 0.5-4.6
Obtrioustg, a nitrogen load of 40-200 g N m-'T-'
mg 1-l.
does not giae rise to
extremely high chlurophgl conkentrations during summer, usifher in
North Sea coastal water, nor in the Wadden Sea and the WssCerscheLde
e s t q . It is assumed that l&ght availability is the limiting factor
in these turbid c-tax
and estuarine waters, end not nitrogen,
explaining the relatively low phptoplankton tchlarophyl) biomass in
smer. Contrary, in the clear water of the Veerae Weer lagoan a N-lead
-2 -1
of 34 g m p results in high ~hlorophyl concentrations (l00 mg CB1
m-' or even higher; Table 2). This large productien of phytgplanktm
bioaass ip the Veerse Meer lagoon, and soasequent de~sition of
particulate or!&anic cnrbon on the bottom sedimenfs, resale& during the