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

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Abstract
The taxonomic composition and spatial distribution of pelagic algae were studied in the south-western Kara Sea in August-September 1981. In the north-western and easternmost regions of the study area the phytoplankton community, dominated by neritic diatoms and autotrophic dinoflagellates, was at the late spring bloom stage of the seasonal succession. In the central deep-water zone of the sea, there was a predominance of heterotrophic dinoflagellates from the genera Protoperidinium and Dinophysis, and the autotrophic compartment of the algal community was clearly in a stage of decline. The distribution of the phytoplankton assemblages followed closely the major routes of receding marginal ice zones. Three stages of the seasonal succession were established for the area of interest: (1) early spring (ice edge) bloom of arcto-boreal neritic diatoms; (2) late spring bloom of neritic diatoms and autotrophic dinoflagellates, fuelled by continental run-off; and (3) summer minimum with a predominance of heterotrophic dinoflagellates, followed by autumnal decline of the phytoplankton community.