, Volume 375-376, Issue 0, pp 265-285

Do physical and chemical factors structure the macrobenthic community at a continental slope in the NE Atlantic?

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Abstract

Macrofauna density, biomass and community structure together with several characteristics of the sediment and flow velocity were estimated in May 1994 and August 1995 at seven stations ranging from 208 m to 4470 m water depth along the OMEX-transect in the Goban Spur area (NE Atlantic). In 1994 four additional stations were sampled at a parallel transect about 40 km SSE of the OMEX-transect. In 1995 two additional transects were sampled, one in the Porcupine Seabight ∼ 100 km NNW and one along the slope at ∼ 3500 m water depth situated ∼ 200 km SSE of the OMEX-transect. An overall trend in decrease in density and biomass with increasing water depth was found, but no depth related pattern in mean individual weight could be observed. Mean individual weight, however, did show a negative relationship with flow velocities. Correspondence-analyses and single linkage clustering of the community structure showed three more or less depth related clusters, representing a shelf community, an upper-slope and a lower-slope community. These clusters coincided with differences in grain-size, % organic C and total N within the sediment and differences in flow velocities. However, some of the stations at similar depths were not clustered together. Grain-size did not differ at stations with similar depth, but the % of C and N and flow velocities could differ markedly. Stations at similar depth, but with different physical and/or chemical conditions showed differences in density, biomass, mean individual weight and in macrobenthic community structure. More filter-feeding taxa were observed at stations with higher flow velocities, whereas more subsurface deposit-feeders were found at stations with higher sedimentation rates. Thus, besides the effects of water depth on macrobenthic community structure, other physical and chemical factors (such as flow velocities and organic matter supply) can be important structuring factors as well.

This revised version was published online in August 2006 with corrections to the Cover Date.