Samenvatting

This study shows that the main predation pressure in the Dutch Wadden Sea is found to be on calanoid copepods, being the main prey item of C. harengus, A. tobianus, C. edulis, A. aurita and M. leidyi. Bivalve veligers are also found to be widely ingested by predator species, with the main predators being M. edulis, C. edule and M. leidyi. This is followed by predation on mysids, mainly by A. tobianus and C. crangon, as well as harpacticoid copepods predated by A. tobianus and M. edulis. In order to investigate zooplankton ingestion by those predator species microscopically, the dissecting method is shown to be the most successful. In addition, the ‘flushing’ method is another effective way to obtain gut contents of small pelagic fish and ctenophores. For further microscopic as well as DNA analysis of gut contents, the preservation of samples in 96 % ethanol is the preferred method. The results of this research underpin the important role of zooplankton in the marine trophic food web as well as the need for additional research to eliminate the still existing knowledge gaps on those predator-prey-interactions. Zooplankton needs to be recognized as a key component in the marine ecosystem and should therefore be monitored on a regular basis in order to provide the scientific foundation for adequate management and protection of the Wadden Sea area.