BENTHIC MACROFAUNAL COMMUNITY STRUCTURE IN THE NORWEGIAN TRENCH, DEEPSKAGERRAK

Benthic communities were studied at 15 stations along two transects at between 144 and 682 m depth in the Norwegian Trench. Communities of t he deep accumulation bottoms generally exceeding 400 m depth, and 65 n autic miles apart, had a high similarity in species-dominance composit ion (Bray-Curtis index). The faunal composition on the slopes also sho wed high similarities, but was less homogeneous. The average number of species per 0.1 m(2) was significantly higher at the shallow-slope st ations (mean 28.6) than at the deep-trench stations (mean 19.8). Among all stations abundance varied between 455 and 6660 ind . m(-2) and bi omass was generally low, <40 g wet wt . m(-2) (excluding some large in dividuals). Dominant faunal groups were polychaetes and molluscs follo wed by crustaceans. The tube-building polychaete Spiochaetopterus berg ensis was numerically dominant at all deep-trench stations, where the bivalves Thyasira eumyaria and Kelliella miliaris were also abundant. Sediment characteristics, transport and accumulation rates are discuss ed as structuring factors for the benthic communities.