Coccolithophore fluxes in the Norwegian-Greenland Sea: Seasonality and assemblage alterations

Coccolithophore fluxes were investigated by sediment trap studies at two well separated oceanographic sites in the Norwegian and Greenland seas from 1990 to 1992. Each trap mooring comprised traps at 500 and 1000 m water depth and 300 m above the seafloor. Both sites were characterized by a strong seasonality in coccolithophore fluxes. In the Norwegian Sea fluxes were about 10 to 20 times higher than in the Greenland Sea. Maximum fluxes (13 x 10(6) ind. m(-2) d(-1) for the Norwegian Sea and 2.4 x 10(6) ind. m(-2) d(-1) for the Greenland Sea) were reached during high sedimentation phases in late summer and autumn. The settling assemblages represented already highly altered remnants of the former living communities. Dominant species were Emiliania huxleyi in the Norwegian Sea and Coccolithus pelagicus in the Greenland Sea. Despite severe alterations the coccolithophore assemblages of each site were characterized by a distinct signature reflecting the local oceanography. The settling assemblages underwent only minor alterations during sinking from 500 to 1000 m water depth. By contrast, resuspension and lateral advection within an extensive bottom nepheloid layer strongly influenced the assemblages of the deep sediment traps 300 m above the seafloor, wiping out the distinct seasonality in coccolithophore fluxes and diminishing the differences in assemblage compositions between the two sites.