Annual succession of marine pelagic protozoans in Disko Bay, West Greenland, with emphasis on winter dynamics

The succession of pelagic ciliates and heterotrophic dinoflagellates was in vestigated in Disko Bay, West Greenland, from April 1996 to June 1997. In t erms of biomass they contributed equally. Their annual distribution was bim odal with maxima in May/June and August. Summer levels were similar to thos e reported at lower latitudes. Winter dynamics were different. Due to 2 mo of polar darkness, food concentrations for ciliates and heterotrophic dinof lagellates were below threshold concentrations for growth. Nonetheless, sma ll populations persisted throughout the winter. Both protozoan groups had a concentration of similar to0.25 x 10(3) cells l(-1). The succession patter ns showed that all individual species peaked at different times during the summer months. However, diversity of the winter community was not different from that observed during summer. Even in the polar winter, the autotrophi c ciliate Myrionecta rubra and the obligate mixotrophic ciliate Laboea stro bila were recorded. Different strategies for winter survival of protozoans are discussed.