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Arctic benthic organisms of various taxa (Anthozoa, Polychaeta, Pantopoda, Crustacea, Echinodermata) were collected on the shelves off northeast Greenland, Spitsbergen and the western Barents Sea. Their fatty acid compositions were generally characterised by the predominance of the polyunsaturated fatty acids 20:5(n-3) and 22:6(n-3) together with the saturated fatty acid 16:0, which reflect the dominance of phospholipids. The fatty acid compositions of most benthic specimens were influenced by fatty acids of dietary origin.

Analysis of seabed video-strips on the Weddell Sea shelf provided evidence that the effects of iceberg scouring on megabenthic assemblages differ, depending on spatial scale. At a local scale (1 to 100 m), undisturbed glass sponge-associated habitats were significantly more diverse than disturbed ones; at a regional scale (1 to 100 km), increased habitat heterogeneity caused by iceberg scouring enhanced species diversity. The pace and succession of the recolonization exhibits high variability and is difficult to predict. The results not only underpin the concept that disturbance events are essential factors in the regulation of ecosystem dynamics, but also emphasize the relevance of scale in the evaluation and explanation of diversity patterns.

22Although knowledge of Arctic seas has increased tremendously in the past decade, benthic 23 diversity was investigated at regional scales only, and no attempt had been made to examine it 24 across the entire Arctic. We present a first pan-Arctic account of the species diversity of the