DISTRIBUTION PATTERN OF BIOGENIC COMPONENTS IN SURFACE SEDIMENTS OF THE NORTHERN BERING SEA AND THEIR PALEOCEANOGRAPHIC IMPLICATIONS

Biogenic components in total 29 surface sediments, which were taken from the northern Bering Sea during the First and Third Chinese National Arctic Expedition cruises, are analyzed for probing into the relationship between surface primary productivity, chlorophyll and nutrient conditions in this area. The results show that the highest TOC percentages appear on the outer-middle shelf, with the higher in the basin, and the lowest in the area from the inner shelf to the Bering Strait; the highest biogenic opal percentages appear in the basin and slope, with the higher on the outer-middle shelf, and the lowest in the area from the inner shelf to the Bering Strait. On the contrary, the highest CaCO₃ percentages are found on the inner-middle shelf, and the lowest on the outer shelf and slope and in the basin. High TOC and opal percentages on the outer-middle shelf are related to high chlorophyll and nutrient levels in the upper water column, suggesting that this area has the seasonal phytoplankton bloom and high primary productivity. Relative high CaCO₃ on the outer-middle shelf are associated with the long-term bloom of phytoplankton coccolithophore Emiliania huxleyi, and low CaCO₃ in the area from the outer shelf to the basin are linked with calcium carbonate dissolution. Phytoplankton bloom and organic carbon input are responsible for increasing organic carbon and opal percentages on the outer to middle shelf. Corg/N ratio in surface sediments ranges dominantly in 6~9, implying that the organic carbon is originated mainly from marine source and controlled by biological pump process. High correlative coefficient (0.71) between organic carbon and biogenic opal shows a closer relationship between organic carbon and diatom. Primary productivity of diatom and other phytoplankton can control the absorption and release of carbon by the biological pump.