Proceedings of the Royal Society of Edinburgh. S8B, 281-290, 1986 An investigation into the causes of small scale variation in sediment community oxygen consumption in the Rockall Trough* J. W. Patching and R. C. T. Raine Department of Microbiology, School of Marine Sciences, University College, Galway, Ireland and P. R. O. Barnett Scottish Marine Biological Association, Dunstaffnage Marine Research Laboratory, P.O. Box 3, Oban, Argyll PA34 4AD, Scotland Synopsis An attempt was made to interpret the core to core variation in oxygen uptake observed during an in situ determination of sediment community oxygen consumption (SCOC) at a station in the Rockall Trough using the "suspended core" technique. No direct relationships between macrofaunal abundance or biomass and SCOC were observed. The results obtained suggested that the use of experimental chambers of small cross-sectional area (26-2cm 2 ) allow for greater influence on SCOC of the activity of individual organisms which would otherwise be averaged out by larger, grab-type enclosures. The possible significance of other components of the benthos is discussed. Introduction Deep-sea sediments are believed to play a significant role in the overall scheme of carbon cycling within the oceanic biosphere, principally as receivers of sedimenting organic material which may either accumulate or be metabolised with the subsequent release of inorganic nutrients. Although various methods of assessing benthic metabolism have been described in the literature (Pamatmat 1977; Patching & Raine 1983), the in situ flux of dissolved oxygen across the benthic boundary layer has, so far, proved best suited to studies of carbon cycling within abyssal sediments. Unfortunately, such studies typically require the use of sophisticated free fall respirometer systems (Smith & Baldwin 1983). Because of this, few measurements at depths greater than 1000 m have been carried out. The bulk of such investigations have been restricted to those carried out by Smith and his associates (Smith & Hinga 1983), who have obtained results for areas within the northwest Atlantic and eastern Pacific oceans. Sediment community oxygen consumption (SCOC) has been found to vary between sites. By applying multiple regression analyses, attempts were made to generate equations describing these changes in terms of environmental factors. Initial results, dominated by a transect from Gay Head to Bermuda, provided an This is contribution no. 249 of the School of Marine Sciences, University College, Galway.