Hydro-ecological relations in the Delta Waters

less predictable for water managers; the Veerse Meex is an eraple of
phase 11.
Relative dorninonce
l SALT WATER I /
I
n
I II m
EutPophlccltion phase
Figure 8 Tentative model for the relation between primary producers
and nutriats and the snccessive stages in the eutmphication
proce6s. Explanation see text.
In hypereutrophicated systems (phase 111) heavy uncontrolled
phytoplilnkton blooms alternate with mass growth of macro-algae.
Nutrient concentrations are continuously high. Rooting waterplants hwe
completely disappeared. Bottom sediments suffer from permanent anoxia.
The lagoon of Venice is an example of phase 111, where E bimass
-2
reaches values of 1.5 kg dry weight m (Sfriso, et al. 1987; Sfriso,
et al. 1988) which is 6 times higher as in the Veerse Meer.