Circalittoral suprabenthic coarse sand community from the western English Channel

Abstract

A first quantitative description of the suprabenthic fauna in a coarse sand community from the western English Channel is provided. One hundred and twenty species of Crustacea were collected in 22 suprabenthic sledge hauls collected throughout the year (1988–1989). Mysids and Amphipods dominated the fauna, among them Anchialina agilis (Sars), Gastrosaccus spp., Apherusa spp., Eusirus longipes Boeck, and Stenothoe marina (Bate) were the dominant species. Although most dominant species showed a vertically decreasing gradient of density from the lower net to the upper level of the sledge, the most abundant species, Apherusa spp., showed similar density at all four levels. The mean density at the four levels of the sledge did not differ significantly with the distance above the sediment. Species performed nocturnal vertical migrations: the densities of mysids were higher during the day than at night; conversely, the densities of amphipods and decapods were higher at night than during the day. The density and species richness showed high seasonal variation, from low values at the end of autumn and winter to high values in summer and the beginning of autumn. The results are compared with the available data on suprabenthic communities from the North Atlantic; this highlights (1) the lack of concentration of suprabenthic fauna towards the sediment on coarse sand, and (2) the highest abundance of the suprabenthic fauna from muddy substrata.