Dinocyst distribution in surface sediments from the northeastern Pacific margin (40–60°N) in relation to hydrographic conditions, productivity and upwelling

Abstract

Seventy-six surface marine sediment samples from the northwest margin of North America, between 40°N and 60°N, were analysed for their palynological content in order to document the regional distribution of dinocyst assemblages and their relationships with environmental conditions (sea-surface temperature and salinity, productivity and upwelling). The results illustrate a high concentration of dinocysts, notably in the neritic area (up to 34 000 cysts cm −3) and a relatively high species diversity with 32 taxa identified. The assemblages include cysts of both autotrophic and heterotrophic species. Brigantedinium spp. accompanied by other heterotrophic taxa such as Votadinium spp., Quinquecuspis concreta, Trinovantedinium variabile and Lejeunecysta spp. dominate in the nearshore areas influenced by seasonal upwelling. The offshore sites are dominated by autotrophic taxa represented mainly by Operculodinium centrocarpum, Pyxidinopsis reticulata, Nematosphaeropsis labyrinthus and Impagidinium aculeatum in the south, and by O. centrocarpum, Pentapharsodinium dalei, Spiniferites ramosus and Spiniferites elongatus in the Gulf of Alaska. Principal component analysis demonstrates that the regional distribution of dinocyst assemblages is controlled by the primary productivity and upwelling, and by the winter temperature gradient.