Mega-epibenthic communities in Arctic and Antarctic shelf areas

Mega-epibenthic shelf assemblages were investigated off Northeast Greenland and in the Weddell, Bellingshausen and Amundsen Seas in the Antarctic usin g underwater video. In the Arctic a total of 94 taxa represented by more th an 100 000 individuals were identified. Echinoderms, particularly brittle s tars, were the most important elements of the mega-epibenthic fauna on the shelf off Northeast Greenland. Multivariate analyses of the species distrib ution revealed a conspicuous depth zonation in which an assemblage on the s hallow banks can be clearly distinguished from that in the troughs. Between these a transitional zone with a heterogeneous benthic fauna was found. Ph ysical disturbances are supposed to be responsible for the pronounced domin ance patterns observed on the shallow banks. The fauna in the troughs, whic h consists of more than 50% suspension feeders, is diverse but low in numbe rs of individuals. In the Antarctic more than 115 000 individuals belonging to 169 taxa were analyzed. Obvious faunal differences exist between the st ations in the Weddell Sea and the Bellingshausen/Amundsen Seas. Assemblages of suspension feeders dominated by sponges and bryozoans are prevalent on the shelf of the eastern Weddell Sea, but almost absent in the Bellingshaus en and Amundsen Seas. These assemblages seem to be restricted to areas wher e bottom currents provide favourable feeding conditions. However, motile de posit feeders are more abundant in both regions where there is a soft botto m substrate with presumably slow bottom currents and reduced horizontal tra nsport of organic particles.