Abundance of megafauna based on OFOS photographic survey during POLARSTERN cruise PS80 (ARK-XXVII/3, IceArc)

A photographic survey was carried out during the expedition ARK-XXVII/3 to the Nansen and Amundsen basins. The seafloor was photographed using a towed Ocean Floor Observation System (OFOS). Nine transects were performed: four in the Nansen Basin between 83-84°N and 18-110°E at depths 3571-4066 m, and five in the Amundsen Basin between 83-89°N and 56-131°E at depths 4041-4384 m. All images were analysed and stored using the image analysis program and database BIIGLE (www.BIIGLE.de). The laser points were used for calculation of the seafloor surface area on images. Visible megafauna was counted and identified to the lowest possible taxonomic level. Taxonomic identifications were made with the assistance of experts. The following taxa/organisms were excluded from statistical analyses: infauna represented only by surface traces, gelatinous zooplankton, small-size organisms (< 1 cm) and organisms that could not be identified at least to the phylum level.