PLANKTON SIZE DISTRIBUTIONS AND TROPHIC RELATIONS BEFORE AND AFTER THE CONSTRUCTION OF THE STORM-SURGE BARRIER IN THE OOSTERSCHELDE ESTUARY

Phytoplankton and zooplankton biomass distributions were calculated on a carbon basis for the inland part of the Oosterschelde, in the perio d before (1983), during (1984, 1986) and after (1987, 1988) the constr uction of the storm- surge barrier. In all years studied, both phytopl ankton and zooplankton distributions are very irregular, and little co nsistent patterns emerge. The data were used to test the model of Shel don et al. (1977). The observed standing stock ratios of zooplankton t o phytoplankton agree with the model predictions in 1983, and are slig htly higher during the period 1984-1987. In 1988, the model prediction s are very different from the observed values, because of important ch anges in the zooplankton species abundance occurring in this year.