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 studied the megabenthos and macrobenthos biomass and taxonomic composition, measured in situ sediment community oxygen consumption and determined sediment concentrations of particulate organic carbon, phytopigments, and nucleic acids. While the sediment community and activity on the canyon fan was similar to that on the abyssal station near Goban Spur, the sediment within the canyon had relatively enhanced sediment community oxygen consumption rates and higher levels of phytopigments. particulate organic carbon and nucleic acids, particularly towards the canyon head. However, near-bottom sediment traps and transmissometre readings gave no sign of enhanced particle fluxes. Most likely this enrichment is supplied periodically through lateral transport as suggested by increased numbers of filter-feeding macrobenthos. Markedly higher concentrations of sedimentary pigments were found in a second branch of the Whittard Canyon illustrating the complexity of canyon systems and the need for a much more extensive study.