Description: Seventeen surface sediment samples from the North Atlantic Ocean off NE-Greenland between 76° and 81°N, and nine samples from the South Atlantic Ocean close to Bouvet Island between 48° and 55°S were taken with the aid of a Multiple Corer and investigated for their live (Rose Bengal stained) benthic foraminiferal content within the upper 15 cm of sediment. Preferentially endobenthic Melonis barleeanum, M. zaandami, and Bulimina aculeata as well as preferentially epibenthic Lobatula lobatula were counted from 1-cm-thick sediment slices each and analyzed for stable carbon and oxygen isotopic compositions of their calcareous tests. Live and dead specimens were counted and measured separately. The carbon isotopic composition of the foraminifera was compared to that of the dissolved inorganic carbon (DIC) of simultaneously sampled bottom water. During a period of one month one station off NE-Greenland was replicately sampled once every week and samples were processed as above.Live specimens of Lobatula lobatula are confined to the uppermost two centimeters of sediment. Live specimens of Melonis spp. are found down to eight centimeters within the sediment but with a distinct sub-surface maximum between two and five centimeters. The down-core distribution of live Bulimina aculeata shows a distinct surface maximum in the top centimeter and constant but low numbers down to 11 cm subbottom depth.The average stable carbon isotopic composition (d13C per mil VPDB) of live L. lobatula off NE-Greenland is by 0.4 ± 0.1 per mil higher than the d13CDIC of the ambient bottom water at the time of sampling. There is evidence that this species calcify before the ice-free season, when bottom water d13CDIC is supposed to be higher. This would reconfirm the one-to-one relationship between d13C of ambient water DIC and cibicids, widely used by paleoceanographers. Live M. barleeanum show a negative offset from bottom water DIC of -1.7 ± 0.6 per mil in the uppermost sediment and of -2.2 ± 0.5 per mil in three to four centimeters subbottom depth. All d13C values of live Melonis spp. decrease within the upper four centimeters, regardless of the time of sampling and site investigated. The offset of live B. aculeata from bottom water d13CDIC values of eight stations rather constantly amounts -0.6 ± 0.1 per mil, no matter what subbottom depth the specimens are from. At one station however, where is strong indication of elevated organic carbon flux, the negative offset averaged over all sub-bottom depths increases to -1.5 ± 0.2 per mil. Buliminids actively move within the sediment and by this either record an average isotope signal of the pore water or the signal of one specific calcification depth. The recorded signal, however, depends on the organic carbon flux and reflects general but site specific pore water d13CDIC values. If compared with epibenthic d13C values from the same site, not influenced by pore water and related phytodetritus layer effects, Bulimina d13C values bear some potential as a paleoproductivity proxy. Specimens of Melonis spp. seem to prefer a more static way of life and calcify at different but individually fix depths within the sediment. Although live specimens thus record a stratified pore water d13C signal, there is no means yet to correct for bioturbational and early diagenetic effects in fossil faunas.

Description: During the Arctic Expedition ARK VIII/3 (August to September 1991) with RV Polarstern, the macrofauna, meiofauna, foraminifera, bacteria were sampled and sediment chemistry was determined at 13 stations along a transect from the Barents Sea slope across the deep Arctic Eurasian Basins towards the Lomonosov Ridge. Water depths ranged from 258 to 4427 m. In general, higher values for all benthic compartments as well as total organic carbon (TOC) and total hydrolysable amino acids (THAA) were recorded for the Barents Sea slope than for the deeper stations in the basins and the ridge slopes. The only significant correlation found was between macrofaunal abundance and depth. Bacterial and all faunal abundances as well as bacterial and macrofaunal biomass decreased significantly with increasing latitude. Although correlations between food items such as TOC and THAA and the fauna were weak, significant relationships between the bacterial and faunal size-classes reflected a distinct food chain typical of oligotrophic systems. The smallest compartments bacteria, meiofauna and foraminifera were more abundant than the macrofauna in the central Arctic Ocean. Macrofauna biomass dominated the biomass on the Barent Sea shelf and slope and on the Lomonosov Ridge, but bacterial biomass was equally or even more important on the Gakkel Ridge and in the deep basins. The results reveal the Eurasian Basin as one of the most oligotrophic regions in the World Ocean. Although primary production is low, recent foraminiferal investigations have revealed that benthic communities in the central Arctic Ocean are driven by the sedimentation of fresh organic material. Lateral transport of organic material from the Siberian shelf may provide additional food. The various benthic compartments compete either for fresh organic matter or for refractory material that is transferred to higher levels of the food chain by bacterial mineralisation.

Description: The formation of bottom water in the southern Weddell Sea is strongly controlled by the flow of Ice Shelf Water (ISW) out of the Filchner-Ronne Ice Shelf cavity. The breakout of three giant icebergs in 1986 and their grounding on the shallow Berkner Bank modified the circulation and water mass formation in the Filchner Trough and the adjacent sea areas. Hydrographic measurements along the Filchner Ice Shelf front, carried out with RV Polarstern in 1995, show significant changes in the water mass characteristics and flow patterns in the Filchner Trough in comparison to measurements from the early 1980s. Changes in the trough will affect the flow over the sill to the deep Weddell Abyssal Plain. We combine a three-dimensional ocean circulation model with CTD and stable isotope measurements to investigate the details of the circulation in front of and beneath the Filchner Ice Shelf. We asserss the impact of stranded icebergs and a more southerly ice shelf front position caused by a 1986 iceberg calving event on the circulation and observed water mass properties. Results indicate variations of the flow pattern in the Filchner Trough and on Berkner Bank, where High Salinity Shelf Water, the feedstock for ISW, is produced. The calving and grounding impacts illustrate the sensitivity of the ice-shelf/ocean system to perturbations in local bathymetric settings.