Benthic foraminifera of surface sediments in the Arctic Ocean

The Recent distribution of living and dead benthic foraminifera of the Arctic Ocean proper has been examined in surface sediments that were sampled during the International Arctic Ocean Expedition 1991 (Arctic 91). The samples represent the Amundsen and Nansen Basins, the Morris Jesup Rise, and the Yermak Plateau from 90°N to 79°42.4'N, 05°15.6'E. Due to the technical difficulties of deep-sea drilling in the Arctic Ocean these areas have, until now, been investigated only in very low density sampling. The Arctic 91 sites of this study cover a water depth range between 552 and 4375 m and represent three sites which are seasonally ice-free, although not yearly, while the other sites are characterized by permanent sea-ice. There is a Recent production of benthic foraminifera in the whole investigation area and all surface samples contain both benthic and planktonic foraminifera. Abyssal assemblages are recorded in the Amundsen and Nansen Basins where Stetsonia arctica dominates with high abundances. It is, however, also possible to distinguish these two basins by the use of diagnostic species. At intermediate water depths (500 to 2000-2500 m) the faunas show higher diversities and higher abundances of Atlantic species than the deep-sea sites. Mixing of North Atlantic water down to approximately 2500 m, is suggested to explain the influx of Atlantic species on the Yermak Plateau and the Morris Jesup Rise. The foraminiferal tests are well preserved within the investigation area and dissolution does not seem to be very obvious in the deeper areas. There is no evidence from the Recent foraminiferal faunas that the bottom waters of the eastern, central Arctic Ocean are undersaturated with respect to calcium carbonate and the deep-sea areas appear, therefore, to lie above the present CCD