Phytoplankton in the south-western Kara Sea: composition and distribution

The taxonomic composition and spatial distribution of pelagic algae were st udied in the south-western Kara Sea in August-September 1981. In the north- western and easternmost regions of the study area the phytoplankton communi ty, dominated by neritic diatoms and autotrophic dinoflagellates, was at th e late spring bloom stage of the seasonal succession. In the central deep-w ater zone of the sea, there was a predominance of heterotrophic dinoflagell ates from the genera Protoperidinium and Dinophysis, and the autotrophic co mpartment of the algal community was clearly in a stage of decline. The dis tribution of the phytoplankton assemblages followed closely the major route s of receding marginal ice zones, Three stages of the seasonal succession w ere established for the area of interest: (1) early spring lice edge) bloom of arcto-boreal neritic diatoms; (2) late spring bloom of neritic diatoms and autotrophic dinoflagellates, fuelled by continental run-off; and (3) su mmer minimum with a predominance of heterotrophic dinoflagellates, followed by autumnal decline of the phytoplankton community.