COMPOSITION AND DISTRIBUTION OF ZOOPLANKTON IN THE LAPTEV SEA AND ADJACENT NANSEN BASIN DURING SUMMER, 1993

Zooplankton composition and distribution were investigated on the Lapt ev Sea shelf, over the continental slope and in the adjacent deep Nans en Basin during the joint German-Russian expedition ''Arctic 93'' with RV Polarstern and Ivan Kireyev in August/September 1993. In the shelf area biomass decreased from west to east with the lowest values in th e area influenced by the Lena river runoff. A gradual increase of biom ass from the shallow to the deep area correlated with water depth. Tot al biomass ranged between 0.1 and 1.5 g m(-2) on the shelf and 4.7 and 7.9 g m(-2) in the adjacent Nansen Basin. On the shelf Calanus glacia lis/finmarchicus dominated overall. The contribution of brackish-water taxa was low in the west, where high salinity and southward currents from the Arctic Basin supported a marine neritic community, but on the southern and eastern Laptev shelf, in the areas of freshwater influen ce, brackish-water taxa contributed up to 27% of the total biomass. On the slope and in deep areas a few large Arctic copepod species, Calan us glacialis, C. hyperboreus and Metridia longa, composed the bulk of biomass and determined the pattern of its vertical distribution. The e xport of Calanus species from the Nansen Basin onto the Laptev shelf a ppears to be of great importance for the shelf communities. In turn, t he eastern outer shelf and slope area of the Laptev Sea are thought to have a pronounced effect on the deep basin, modifying the populations entering the central Arctic.