Different benthic size-compartments and their relationship to sediment chemistry in the deep Eurasian Arctic Ocean

During the Arctic Expedition ARK VIII/3 (August to September 1991) with RV 'Polarstern', the macrofauna, meiofauna, foraminifera, bacteria were sample d and sediment chemistry was determined at 13 stations along a transect fro m 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 d epth. Bacterial and all faunal abundances as well as bacterial and macrofau nal biomass decreased significantly with increasing latitude. Although corr elations between food items such as TOC and THAA and the fauna were weak, s ignificant relationships between the bacterial and faunal size-classes refl ected a distinct food chain typical of oligotrophic systems. The smallest c ompartments-bacteria, meiofauna and foraminifera-were more abundant than th e macrofauna in the central Arctic Ocean. Macrofauna biomass dominated the biomass on the Barent Sea shelf and slope and on the Lomonosov Ridge, but b acterial 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 mo st oligotrophic regions in the World Ocean. Although primary production is low, recent foraminiferal investigations have revealed that benthic communi ties in the central Arctic Ocean are driven by the sedimentation of fresh o rganic material. Lateral transport of organic material from the Siberian sh elf may provide additional food. The various benthic compartments compete e ither for fresh organic matter or for refractory material that is transferr ed to higher levels of the food chain by bacterial mineralisation.