Shallow-water mega-epibenthic communities in the high Antarctic (Weddell Sea) and the west coast of the Antarctic Peninsula (Bellingshausen Sea)

Continental shelves around Antarctica are unusual in being deep, and consequently shallow habitats at depths <150 m are scarce. In the Weddell Sea, only two shallow sites with water depths between 55 and 160 m are known (Atka Bay and a shallow bank off Four Seasons Inlet NE of Kapp Norvegia). In contrast, the Antarctic Peninsula has a true coast and thus, true littoral areas are common. This study (1) characterises and describes the distribution and spatial patterns of shallow-water mega-epibenthic fauna in the Antarctic Peninsula (Bellingshausen Sea) and at two sites in the high Antarctic (Weddell Sea), (2) analyses community structures and (3) compares benthic biodiversity in these areas at different spatial scales and with additional data from deep Antarctic shelf sites and corresponding shallow and deep areas in the Arctic. Multivariate analyses revealed significant faunal differences between Marguerite Bay (Bellingshausen Sea) and the Weddell Sea stations, Atka Bay and Four Seasons Bank. Echinoderms, especially ophiuroids, dominated Marguerite Bay, bryozoans and ascidians were abundant at Atka Bay, and hydroids and gorgonians were well represented at Four Seasons Bank. These differences can mainly be explained by the influence of local environmental conditions that are probably the primary factor shaping the Antarctic shallow-water epifauna, and not an intensive exchange with larger depths or limited dispersion due to scarce and isolated shallow areas. Spatial patterns of Antarctic benthic shelf communities were analysed and different patterns are identifiable: a locally limited typical fauna, a patchwork of assemblages as well as continuous faunistic gradients. Combinations of these three scenarios can be considered as the rule in Antarctic mega-epibenthic communities. A faunistic and environmental parallelism with the Arctic in terms of biodiversity was also studied.