The infauna and epifauna of the northern North Sea

Abstract This paper compares the infaunal and epifaunal assemblages from surveys encompassing 121 grab stations and 152 Agassiz trawl samples respectively, collected between 1980 and 1985. The area surveyed is delimited by the Scottish, Norwegian and Danish coasts lying between 56°15'N and 60°45'N. Samples for infauna and environmental parameters were collected by Smith-McIntyre grab and Craib corer. The epifaunal and infaunal assemblages were analysed separately by ordination techniques (DECORANA and TWINSPAN) to detect the major environmental gradients underlying the distribution and abundance of the fauna and to indicate which taxa were characteristic of different zones within the survey area. The major determinant of infaunal community composition was sediment granulometry, with depth being of secondary importance. For the epibenthos, depth was the major factor and the sediment composition seemed less significant. Assemblages identified by TWINSPAN were characterised by particular species, but these ‘community types’ were seen to grade into one another along continuous environmental gradients. These findings are discussed in relation to previous North Sea benthic classification schemes.