Large-scale faunal characterisation of marine benthic sedimentary habitats around the UK

We present the findings of a large-scale study designed to characterise the benthic faunal assemblages inhabiting soft sedimentary habitats surrounding the British Isles. The number, variety and spatial variability of the organisms encountered are presented and analysed using a suite of standard univariate and multivariate analytical techniques. Triplicate grab sampling at 155 stations arranged in a grid pattern yielded over 68,000 organisms, representing 1123 taxa. Observed variations in faunal assemblage composition were driven predominantly by differences in environmental conditions, such as mean sediment particle size, stratification and tidal stress. Consequently, a similar faunal assemblage occurred wherever the same combination of environmental conditions were present. Despite the high level of variability of the various assemblage metrics observed between sampling stations, some trends in the data could be detected. Most assemblage metrics decreased in value with increasing latitude. Most diversity indices increased at greater depths, yet abundance and biomass decreased with depth. Mean abundance and biomass values per station were higher in the English Channel and in parts of the Irish and North Seas than elsewhere. The number, richness, diversity and evenness of taxa were higher in the South and West than in the North and East. Similarly, assemblage structure was most dissimilar between these two areas, each area harbouring a distinct macrofaunal community.