Investigations on uptake and utilization ofPhaeocystis globosa colonies by the blue musselMytilus edulis

The poster gives main results of a study on the relevance ofPhaeocystis globosa (Haptophyceae) as a food source forM. edulis (Ökosytemforschung Niedersächsisches Wattenmeer, TP A 3.1). DensePhaeocystis blooms were suspected to be one reason for the observed decrease of the mussel population of the Wadden Sea of Lower Saxony within the last decade. During the same period density and duration ofPhaeocystis blooms increased in the coastal regions of the North Sea. These blooms are dominated by the colony form ofPhaeocystis (diameter of colonies: some urn up to 2 mm; max. observed density 100,000 colonies 1−1). It was suggested, that mussels would not be able to feed on the gelatinous colonies ofP. globosa due to inhibition of filtration. Therefore, mussels would suffer from starvation during bloom time, leading to growth reduction.