Preliminary data on the composition and distribution of polychaetes in the deep-water areas of the north-western part of the Sea of Japan

During the SoJaBio expedition, the deep sea fauna of the north-western Sea of Japan was sampled in August–September 2010. From this study, 11 epibenthic sledge stations are analyzed, with a focus on species composition, diversity and distribution patterns of polychaetes. A total of 92 polychaete taxa belonging to 70 genera and 28 families and 3 indeterminate species were found. Twelve species and eight genera have not been reported from the Sea of Japan before, but were registered from other deep-sea basins. Calculation of diversity (Shannon–Wiener Index, Pielou's Evenness) showed that the upper bathyal of the Sea of Japan is an area of higher polychaete diversity than the abyssal plain. The increased richness and diversity here could possibly be explained by a zoogeographic overlapping with the shallower species' assemblages of the shelf. At a higher taxonomic level the polychaete fauna of the deep Sea of Japan does not seem to differ from that of other deep-sea regions world-wide. In depths below 2000 m about 30% polychaete species have wide distributional ranges.