Macrobenthic ecology of the West Shetland Slope

Abstract

An unusual and complex hydrographic regime in the Faeroe-Shetland Channel makes it one of the best-studied oceanographic provinces in the world. However, few benthic ecological studies of the region have been undertaken since the early 1880s. The present study examines the influence of a number of environmental variables on macrobenthic faunal distribution on the West Shetland Slope. Macrobenthic samples were collected by corer and grab along a depth transect in 1996 and 1998. The macrofauna studied were retained on 500 m and 250 m sieves enabling comparisons to be made between samples taken using these two sieve sizes. The addition of the 250 m-to-500 m size fraction to the >500 m size fraction resulted in an increase in species diversity (31% at the 150 m station) and species richness (38% at the 800 m station). Faunal abundance was also seen to increase by an average of 40% per station when combining the smaller size fraction. The results also illustrated that water temperature appears to be the major environmental variable controlling benthic macrofaunal distribution (especially in terms of standing stock), polychaete species diversity, feeding modes and restriction of polychaete species to specific temperature bands. Other environmental variables such as sediment grain size and total organic carbon also influenced macrofaunal distribution although to a lesser degree. The level of taxonomic resolution required was investigated and the conclusion drawn was that to achieve adequate discrimination between stations for this area, the macrofauna should be identified to species level.

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