Density, biomass and community structure of macrofauna were estimated together with several sediment characteristics at seven stations ranging from 208 m to 4460 m water depth along the OMEX transect in the Goban Spur area (NE Atlantic) during three seasons (October 1993, May 1994, and August 1995), Median grain size decreased with increasing water depth and showed no differences between the seasons. The percentages of organic carbon and total nitrogen were highest at mid-slope depths (similar to 1000 to 1500 m), and were significantly higher in August at the upper part of the slope to a depth of similar to 1500 m. The C:N ratio in the surface layer amounted to similar to 7 to 8 in May, similar to 10 to 12 in August and similar to 14 to 17 in October at all stations (except the deepest at 4460 m, where it was similar to 11 in May and August), indicating arrival of fresh phytodetritus in May, and therefore seasonality in food input to the benthos. Densities of macrofauna decreased exponentially with increasing water depth, Significantly higher densities of macrofauna were found in May at the upper part of the slope to a depth of similar to 1500 m. These differences were mainly due to high numbers of postlarvae of echinoids at the shallowest station and ophiuroids at the deeper stations, Biomass values also decreased with increasing water depth, but biomass was relatively high at the similar to 1000 m station and low at similar to 1500 m, due to relatively high and low mean weights of the individual macrofaunal specimens. No significant differences in biomass were found between the seasons. Respiration was high (15 to 20 mgC . m(- 2). d(-1)) in May at the upper part of the slope to a depth of similar to 1000 m and low (1-3 mg C . m(-2). d(-1)) at the deeper part. At the shallowest stations to a depth of similar to 1000 m respiration was highest in May, at the mid-slope stations (similar to 1400-2200 m) it was highest in August, whereas the deepest stations (similar to 3600 to 4500 m) did not show any differences in respiration rates. In conclusion: seasonal variation in organic input is reflected in density, community structure and activity of the macrofauna along the continental slope in the NE Atlantic. [KEYWORDS: seasonal variation; macrofauna; continental slope; NE Atlantic; C:N ratio Deep-sea floor; rockall trough; northeast atlantic; reproductive-biology; organic material; ocean; phytodetritus; abyssal; program]
Original languageEnglish
Pages (from-to)203-215
JournalJournal of Sea Research
Issue number3-4
StatePublished - 1996

ID: 304970