Spatial distribution patterns of the mega-epibenthos on the continental shelves off the northern Antarctic Peninsula studied from OFOS seabed images taken during POLARSTERN cruise ANT-XXIX/3 (PS81) 2013

The epibenthos of the Southern Ocean shelves plays a significant role in marine ecosystem functioning, including biodiversity processes, but information on its composition, distribution and ecological drivers is still scarce. Here, we report results of a first study on the relationship between the spatial patterns of 18 systematic or functional groups and environmental factors, conducted in the waters off the northern Antarctic Peninsula during RV Polarstern cruise XXIX/3 (PS81) in January-March 2013. To comparatively address this issue at three nested spatial scales, seabed imaging surveys were performed along 28 photographic transects of 2 km length each at water depths from 70 to 770 m in three ecoregions (northwestern Weddell Sea, southern Bransfield Strait and southern Drake Passage), which differ in general environmental setting, primarily oceanographic characteristics and sea-ice dynamics. At a regional (100-km) scale, epibenthic assemblages differed significantly from each other in all three ecoregions, whereas at an intermediate 10-km scale, differences among depth-related habitat types (bank, upper slope, lower slope, deep/canyon) were less pronounced. These regional and intermediate spatial patterns were superimposed by a marked small-scale (10-m) patchiness of epibenthic distribution within the 2-km transects. Obvious correlation between mega-epibenthos and environmental factors (e.g., temperature, salinity, oxygen, sea-ice cover, seabed ruggedness) was found especially for large scales of >2 km.