In aquatic ecosystems the grazing activity by microzooplankton (Protozoa) has proven to play an crucial role in the flux of carbon in the food web. However the impact of protozoa in the microbial food web can be very variable in different aquatic systems and can depend on e.g. the trophic state of the system. The current data on biomass and production of bacteria and biomass of protozoa in the Westerschelde estuary indicate that the impact of grazing by protozoa may contribute susbstantially to the carbon flux in the microbial food web. Objectives: To optimise experimentally the method (uptake of fluorescent-labelled bacteria) to estimate protozoan grazing rate. To quantify bacterial production and abundance and protozoan abundance and grazing rate in the field.
