Distribution, Export and Alteration of Fossilizable Plankton in the Nordic Seas

The present study gives an overview of recent research results concerning the distribution of living fossilizable plankton groups (coccolithophores, diatoms, dinoflagellate cysts, radiolarians and planktic foraminifers) in the water column of the Nordic Seas. Information is combined with results of sediment trap investigations on fluxes and the species composition of these fossilizable plankton groups in the Nordic Seas and their relation to oceanographic conditions. In order to validate spatial and temporal occurrence patterns of the plankton assemblages, their fluxes were monitored with sediment traps over several years in three different oceanic regions, characterized by the major surface water masses of the Nordic Seas. In addition, the alteration processes on settling plankton assemblages were investigated at three water depths.Oceanographic domains in the Nordic Seas can be clearly distinguished on the basis of the export of different plankton assemblages. The Norwegian Sea is dominated by calcareous plankton and the Greenland Sea and the Jan Mayen Current are dominated by siliceous plankton organisms. All fossilizable plankton groups show a corresponding decrease with low interannual variations in the number of species from the temperate Norwegian Sea to the colder Jan Mayen Current and the Greenland Sea. Dissolution is one of the major alteration processes and alters diatom assemblages significantly during sinking and settling. No quantitative signal of siliceous plankton groups is preserved in the deep traps or in sediments. The second major alteration process is lateral advection. This process influences the investigated sites on different scales.