The Macrobenthic Infauna Of The Offshore Northern North Sea  <B>The Macrobenthic Infauna Of The Offshore Northern North Sea</B><P>A. ELEFTHERIOU</B><I><P> Department of Biology, University of Crete, PO Box 1470, Heraklion 71110, Crete, Greece</I><B><P> AND D.J. BASFORD</B><I><BR> Marine Laboratory, PO Box 101, Victoria Road, Aberdeen, AB9 8DB</I><P> Between 1980 and 1985 ninety-seven stations were sampled by Smith-McIntyre grab from the offshore northern section of the North Sea. Four hundred and nine infaunal species were identified from the 76 selected macrofaunal stations. The number of species per station varied from 25 to 80 with a maximum abundance of 9,600 individuals m- 2 . The biomass ranged from 0. 13 to 18.86 g dry weight m- 2. At most stations, however, biomass varied between 1 and 4 g dry weight m- 2. Diversity and abundance were highest in the 120-140 m zone, characterised by fine sand containing variable amounts of silt. The highest biomasses were recorded in two areas; firstly where stronger currents predominate and the sediments are coarser (east of Shetland and west of the Norwegian Trough), and secondly in the fine sandy deposits of the centrally located area. In the silty sediments (Fladen Ground and smaller depressions) there was a predominantly subsurface deposit-feeding community, whereas in the coarser area east of the Shetlands carnivores predominated. Over the remaining area surface deposit feeders were dominant.<BR> The faunal data were analysed using multivariate techniques. Axes from detrended correspondence analysis were correlated with the environmental parameters. Depth, sediment granulometry and organic carbon content were found to be the major parameters governing the faunal distribution.<BR> Two way indicator species analysis indicated two major groups of stations, one characterised by low organic carbon and plant pigments, having less than 20% silt and containing Aonides paucibranchiata, Aricidea wassi, Exogone verugera, Bathyporeia elegans and Urothoe elegans; a second,where the deeper siltier stations were characterised by Heteromastus sp., Lumbrineris gracilis, Phylo norvegica, Eriopisa elongata and the Thyasira complex. These groups were subdivided into four subgroups according to the depth and sediment granulometry at the stations, and their geographic distribution is mapped. The distribution of these major groups and subgroups modifies existing ideas concerning the structure of the communities in the northern North Sea.<P> J. mar. biol. Ass. U.K. (1989), 69,123-143<P>