Hydro-ecological relations in the Delta Waters

Crucial here is the presence of extensive, protected shallows.
Manageability of fish stocka should be lrentral to policy. Simply
granting fishing rights to anglers and fishermen, frustrate
atzeqts to combat eutropkieation directly by means of active
biological oiutagEment. Suceess is conditional on the management of
fish stocks being incgrporated into water quality management.
Salwte* entraphication in different frotn freshwater wtrophication,
althongk closed, stagnant salt waters also have a greater
susceptibility to eutrophication. One of the main differences is that
in the case of salt water often nitrogen is the limiting factor and
nitrification is the key process. In response to this the Eollowing
managewant measures can be taken:
- Excessive levels of nutrients in stagnant, saline systems are
chiefly regional in origin. In p~ineiple this provides scppe f ~ r
gearing nlltrient levels to the individual eapacity of a system. At
its present level, the channelling of nutrient-rich polder water
into the tidal systems does not lead to undesirable affects
associated with wtmphicat-lon. The channelling to ttre Ea6tern
Scheldt of the polder water currently teleased into the Veerse
Wer, for example, i4 even expected to hring about a slighr rise in
productivity. The main objective, incidentaliy, continues to be the
improvement af polder water quality, not in the Least because of
present pollution levels;
- Besides adaptirrg nutrient levels to the system, it is necessary to
create sufficient scope for intermingling with salt tidal waters if
stagnant, saline systems are to develop. Besides the significance
of salinity as euch aa m ecological determinant, this approach
permits regulation of the nutrient balance. Surplus nutrients and
organic matter ean be &rained
off and the likelihood of
stratification can be reduced. That this latter phenomenon is
rmportant is illustrated by the Veerse Meer. where srratitiaatien
has been Eamd to exacerbate the current prablenns of
eutropllication;