Benthic Megafaunal Community Structure and Biodiversity Along a Sea Ice Gradient on the Western Antarctic Peninsula:

The Western Antarctic Peninsula (WAP) is experiencing some of the fastest rates of regional warming in the world, resulting in the collapse of ice shelves, warming ocean temperatures, and increased melt and retreat of glaciers. Winter sea ice coverage in the waters off the WAP has decreased in duration and extent over the last half century. The significant changes observed off the WAP are extremely important in studying the effects that global climate change may have on marine ecosystems. Observed changes in sea ice may have negative effects on benthic ecosystems due to interactions between sea ice, primary production, and pelagic-benthic coupling. The effects of sea ice duration on deep benthic community structure (550-650 m depth) along the WAP continental shelf are not well understood. We evaluated megafaunal abundance, species richness, and community structure at five physically similar midshelf stations along a strong latitudinal sea ice gradient from Smith Island (63S) to Marguerite Bay (68S). Data collection included replicate towed “Yoyo Camera” transects (i.e. quantitative photographic surveys) of the seafloor at each station. Our most northern station (Sta. AA) experiences ~1 month of sea ice per year and our most southern station (Sta. G) sees >7 months of sea ice cover per year. This study found that both megafaunal abundance and community structure varied latitudinally along our north-south transect on the WAP in concert with sea ice duration. Interestingly, species richness showed no general patterns or trends as a result of sea ice extent. These results suggest that sea ice