Tanaidacea fauna (Peracarida, Crustacea) from the shallow sublittoral zone of Admiralty Bay, King George Island, Antarctica, with new records

The Southern Ocean is a very sensitive ecosystem, with the Antarctic Peninsula being one of the most rapidly warming regions on Earth. Accordingly, studies of its biodiversity are of urgent interest. In this context, taxonomical surveys of Antarctic tanaidacean species become relevant, since it is one of the lesser-known Antarctic macrofaunal groups. The present study aims to elucidate the species composition as well as spatial and vertical distribution of tanaidaceans in the shallow sublittoral zone of Admiralty Bay, one of the Antarctic Specially Managed Areas. Sediment samples were taken in the years 2005 and 2010 from 20 and 50 m depth zones at two sites in each of five chosen stations. Three replicate box-corer samples were taken at each site, and the retained sediment was stratified (0-2, 2-6, and 6-10 cm sediment layers). Nine Tanaidacean species (superfamily Paratanaoidea) were identified, with two new species records for Admiralty Bay: Arhaphuroides parabreviremis and Parakanthophoreus antarcticus. In general, Nototanais antarcticus was the dominant species. Significant abundance differences were found among stations, except at 20 m depth in 2005. The Ullmann Point station stood out by the absence of tanaidaceans. No significant differences were found between depths, although 20 m depth sites exhibited higher abundance than 50 m depth ones, which in turn presented higher species richness. Tanaidaceans were concentrated in the first six cm of sediment. Data suggest that the Tanaidacea assemblages in Admiralty Bay have very heterogeneous spatial distribution, reflecting the variety of habitats present in this region.