The plankton community on Sukkertop and Fylla Banks off West Greenland during a spring bloom and post-bloom period: Hydrography, phytoplankton and protozooplankton

The plankton community structure was investigated on Sukkertop and Fylla Banks off West Greenland during the spring bloom in May 2000 and the post-bloom period in June 1999. In May a small change in density, clearly illustrated by the profile of potential energy, was sufficient to support a spring bloom in the upper part of the water column. The spring bloom phytoplankton community displayed high biomass (92 +/- 45 mg C m(-3)) dominated by species of the genera Thalassiosira and Chaetoceros. The phytoplankton species composition, ongoing sedimentation and nutrient depletion indicated late spring- bloom conditions. Spring-bloom heterotrophic biomass (17 +/- 7 mg C m(-3)) was dominated by large heterotrophic dinoflagellates (> 20 mum). In June, low autotrophic biomass was present at post-bloom stations (2 +/- 1 mg C m(-3)) and small autotrophic flagellates (<10 mum), mostly haptophytes, dominated the phytoplankton community. Heterotrophic biomass was low (5 +/- 1 mg C m(-3)) and an important part was comprised by heterotrophic nanoflagellates (24 +/- 1%). Protozooplankters (heterotrophic dinoflagellates and ciliates) were important grazers of the phytoplankton community in the post-bloom period (estimated grazing impact 112 +/- 15% d(-1)) and in the spring bloom (9 +/- 2% d(-1)).