Feeding types of the benthic community and particle transport across the slope of the NW European Continental Margin (Goban Spur)

Densities and biomass of feeding guilds of benthic foraminifera, macrofauna and megafauna were estimated at seven stations ranging from 208 m to 4460 m water depth along the OMEX-transect at the continental margin of the Goban Spur N.E. Atlantic. At the same stations flow velocities in the Bottom Boundary Layer (BBL) were measured at 30 cm height above the bottom. Overall densities of all three faunal groups decreased with increasing water depth, but a peak in density and biomass of suspension-feeding taxa was observed in all groups at similar to 1000-1500 m water depth. At these depths the highest how velocities were measured in all seasons of the year. At station II at 1470 m flow velocities of similar to 35 cm s(-1) were measured during autumn/winter, but in spring/summer flow velocities did not exceed 10 cm s(-1), but were still highest at this station. At this station a very high biomass of suspension feeders was found within the megafauna (mainly sponges), high densities of Astrorhizid foraminifera and high densities of hydrozoids, sponges and tunicates within the macrofauna. At all other stations deposit feeders predominate and much lower flow velocities occurred. It was concluded that a high load of (re)suspended material at similar to 1470 m water depth provide good feeding conditions for suspension feeders and hence that flow velocities are important in structuring the benthic community. These high numbers of suspension feeders, on the other hand, actively capture particles that would otherwise have been transported past this highly energetic region and the relative high numbers of surface- and interface-feeding infauna then bury them in the sediment. Feeding and tube structures seen on the sediment surface can locally change the flow velocities and cause resuspension and passive biodeposition of particles. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.