LATE WINTER MICROBIAL COMMUNITIES IN THE WESTERN WEDDELL SEA (ANTARCTICA)

Microbial communities in the water column and sea ice were studied dur ing the EPOS-cruise on R/V Polarstern in the western Weddell Sea in la te winter (October-November 1988). Samples were taken from four transe cts from heavy pack-ice to open water. The results indicated the impor tant role of protozoans especially in the ice-edge area. Heterotrophic nanoflagellates, dinoflagellates, ciliates and sarcodines showed sign ificant positive correlations with chlorophyll a. Autotrophic picoplan kton and autotrophic flagellates, which were probably motile zooids of Phaeocystis pouchetii (up to 3 x 10(6) cells 1(-1)), were most abunda nt in the areas of low or medium chlorophyll a concentration. Sea ice contained high numbers of heterotrophic organisms, and the distributio n of the different groups showed distinct vertical zonation. At two si tes, the microbial assembly beneath the ice was clearly influenced by communities from the melting ice.