(Table 2) Species density and composition of an inshore and offshore station in Kongsfjord, Svalbard

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Megafauna plays an important role in benthic ecosystems and contributes significantly to benthic biomass in the Arctic. The distribution is mostly studied using towed cameras. Here, we compare the megafauna from two sites located at different distances from the Kongsfjord: one station at the entrance to the fjord, another on the outer shelf. Although they are only located 25 km apart and at comparable depth, there were significant differences in their species composition. While the inshore station was characterized by shrimps (2.57 +/- 2.18 ind./m2) and brittlestars (3.21 +/- 3.21 ind./m2), the offshore site harboured even higher brittlestar densities (15.23 +/- 9.32 ind./m2) and high numbers of the sea urchin Strongylocentrotus pallidus (1.23 +/- 1.09 ind./m2). Phytodetrital concentrations of the upper sediment centimetres were significantly higher inshore compared with offshore. At a smaller scale, there were also differences in the composition of different transect sections. Several taxa were characterized by a patchy distribution along transects. We conclude that these differences were caused primarily by habitat characteristics. The seafloor inshore was characterized by glacial soft sediments, whereas the station offshore harboured large quantities of stones. Although the use of a new web-2.0-based tool, BIIGLE (http://www.BIIGLE.de), allowed us to analyse more images (~90) than could have been achieved by hand, taxon area curves indicated that the number of images analysed was not sufficient to capture the species inventory fully. New automated image analysis tools would enable a rapid analysis of larger quantities of camera footage.

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