Published online by Cambridge University Press: 11 May 2009
The macrofauna of the benthic boundary layer (macrozooplankton and suprabenthos) was studied at six stations in May–June 1993 in the English Channel over sediments ranging from medium sand to pebble. The fauna collected consisted of 227 taxa in 30 suprabenthic sledge hauls. Numerically, the macrozooplankton was dominated by euphausids, chaetognaths, the holoplanktonic amphipod Apherusa spp. and fish larvae, and the suprabenthos by mysids (Anchialina agilis, Gastrosaccus spp.), amphipods (Stenothoe marina) and cumaceans at both medium sand stations. Suprabenthos species richness and diversity were significantly higher at western stations, in contrast to the pattern for macrozooplankton. The density of macrozooplankton was significantly higher, and suprabenthos significantly lower, at the western stations. The biomass of macrozooplankton was similar at the six stations, except in the middle of the Dover Strait which had a low biomass. The biomass of the suprabenthos was highest in the eastern part of the Channel. Two main assemblages were distinguished in relation to planktonic production and sediment composition: three western stations with two subgroups (stations 1 and 3 along the coasts of Brittany and station 2 off Plymouth); and the eastern stations also with two subgroups (station 4 in the Bay of Seine and stations 5 and 6 in the Dover Strait). For the macrozooplankton, two types of trophic structures could be distinguished: stations 1 and 4 where suspension-feeders dominated and the other stations (2, 3, 5 and 6) where carnivorous plankton feeders, omnivorous and scavengers predominate. For the suprabenthos, the plankton feeding, omnivorous and carnivorous trophic guilds dominated each station.