Relationships between dinoflagellate cyst assemblages in surface sediment and hydrographic conditions in the Bering and Chukchi seas

Palynological analyses were performed on 52 surface sediment samples from the eastern part of the Bering Sea and Chukchi Sea in order to document the regional distribution of dinoflagellate cyst assemblages and their relationship with sea-surface conditions. The assemblages present a relatively high species diversity (20 taxa are recovered routinely), especially in the Bering Sea, where they are dominated by Operculodinium centrocarpum and the cyst of Pentapharsodinium dalei accompanied mainly by Spiniferites elongatus s.l., Spiniferites ramosus, Impagidinium pallidum, Brigantedinium spp., Islandinium minutum, Selenopemphix quanta, Selenopemphix nephroides, Quinquecuspis concreta and the cyst of Polykrikos kofoidii. The percentages of the main taxa vary with latitude, and principal component analysis shows that the distribution of assemblages is closely related to hydrographic conditions, notably the seasonal duration of sea-ice cover and the sea-surface temperature in February. The dinoflagellate cyst assemblages from the Bering Sea differ significantly from those of subarctic seas of the North Atlantic, with respect to their species composition and relationships with sea-surface conditions. In particular, the occurrence of the cyst of Polykrikos kofoidii and Quinquecuspis concreta and the positive correlation between the percentages of Operculodinium centrocarpum and the extent of sea-ice, constitute peculiar features in the Bering Sea assemblages. Copyright (C) 2001 John Wiley & Sons, Ltd.