The effect of the Siberian Tundra on the environment of the shelf seas andthe Arctic Ocean

The Tundra Ecology -94 expedition investigated inflow of inorganic and orga nic carbon to the shelf seas by river runoff, and its transformation by bio chemical processes in seawater and sediment. In addition, anthropogenic rad ionuclides, Cs-137, Sr-90, and Pu-239,Pu-240, Were studied in water and sed iments. The distribution of dissolved inorganic carbon indicates that the m ajority of the Ob and Yenisey discharges flow into the Laptev Sea before en tering the central Arctic Ocean. The sediment study shows that there is a m arked difference in benthic oxygen uptake, efflux of dissolved inorganic ca rbon and nutrients between localities. Cs-137 activity from the Chernobyl a ccident is 30% in the Barents, Kara, and Laptev Seas. Cs-137 increased from 5-8 Bq m(-3) in Barents Sea, 5-13 Bq m(-3) in the Kara Sea to 8-15 Bq m(-3 ) in the Laptev Sea, but with locally low concentrations at the river mouth s. Corresponding values for Sr-90 were 2.5, 3, and 4 Bq m(-3) respectively.