Activity and composition of the benthic fauna in the Whittard Canyon and the adjacent continental slope (NE Atlantic)

We compared the sediment and its community on the Celtic continental slope (Goban Spur) with those in a branch of the nearby Whittard Canyon in search for evidence of canyon mediated transport of (labile) organic matter. We s tudied the megabenthos and macrobenthos biomass and taxonomic composition, measured in situ sediment community oxygen consumption and determined sedim ent concentrations of particulate organic carbon, phytopigments, and nuclei c acids. While the sediment community and activity on the canyon fan was si milar to that on the abyssal station near Goban Spur, the sediment within t he canyon had relatively enhanced sediment community oxygen consumption rat es and higher levels of phytopigments. particulate organic carbon and nucle ic acids, particularly towards the canyon head. However, near-bottom sedime nt traps and transmissometre readings gave no sign of enhanced particle flu xes. Most likely this enrichment is supplied periodically through lateral t ransport as suggested by increased numbers of filter-feeding macrobenthos. Markedly higher concentrations of sedimentary pigments were found in a seco nd branch of the Whittard Canyon illustrating the complexity of canyon syst ems and the need for a much more extensive study. (C) 2001 Ifremer/CNRS/IRD /Editions scientifiques et medicales Elsevier SAS.