Weddell Sea benthic communities under the influence of different ice regimes

Ice in its different forms affects benthic communities in Polar Regions directly and indirectly. In order to recognize effects of ice on benthic communities we analyzed benthos in four regions of the Weddell Sea: a) the southeastern Weddell Sea shelf (SEWSS); b) the Filchner-Rønne Outflow System (FROS); c) the Larsen A/B embayments; and d) the tip of the Antarctic Peninsula. These regions differ considerably in their ice regimes: The SEWSS is a typical high Antarctic habitat, influenced by seasonal sea ice coverage; the FROS is influenced by seasonal ice on its eastern edge, but under heavy year round ice conditions on its western edge; the Larsen A/B embayments were covered for hundreds of years by thick ice shelves, which recently disintegrated providing large areas for recolonization by benthos; and the shelf around the tip of the Antarctic Peninsula which can be considered as being unaffected by ice. Benthos in these four regions revealed distinct differences in abundance, biomass, and production values. Highest abundance values were found at the tip of the Antarctic Peninsula and along the SEWSS (2,767 and 2,535ind.m-2, respectively), whereas the lowest abundance corresponded to the Larsen A/B region (682ind.m-2). In terms of both, biomass and production, the southeastern Weddell Sea region showed the highest values (3,944.2g wet weight.m-2 and 10.3g C.y-1m-2, respectively), whereas the lowest values were found at Larsen A/B (71.08g.m-2 and 1.62g C.y-1.m-2) and FROS regions (71.08g.m-2 and 1.62 g C.y-1.m-2). A PERMANOVA showed the differences among regions to be significant in all three terms: abundance (Pseudo F=7.10; p=0.001), biomass (Pseudo F=6.01; p=0.001), and production (Pseudo F=6.28; p=0.001). These differences were mainly caused by sponges, ophiuroids and polychaetes. This study also shows pronounced differences in the structure, composition of the benthic communities in the four regions. We hypothesize that these differences are primarily due to the different sea-ice regimes in the regions