Biomass of the invertebrate megabenthos from 500 to 4100 m in the northeast Atlantic Ocean
- Cite this article as:
- Lampitt, R.S., Billett, D.S.M. & Rice, A.L. Marine Biology (1986) 93: 69. doi:10.1007/BF00428656
Data are presented on the biomass of the invertebrate megafauna at 22 stations on the continental slope in the Porcupine Seabight (PSB) (northeast Atlantic Ocean). Samples were collected between 1980 and 1982. Several units of biomass are used, all of which illustrate a decrease by a factor of about 30 from 500 to 4100 m. Lognormal curves were fitted to the data, the gradients of which were very similar for all biomass units and similar to the value for a transect down the continental slope in the western Atlantic. Biomass levels in the PSB are compared with those from other deep-sea environments. Some published values are more than ten times higher than the values reported here, while others are less than a tenth. The reasons for these differences and trends are discussed in terms of food supply. Sampling variability was examined at two stations, but by chance one (at 1300 m) appeared to encompass a sharp faunal discontinuity of the dominant fauna and the other (at 4000 m) contained very small numbers of large animals. For these reasons, sample variability was high at the repeat stations. Suspension-feeders and crustaceans dominated the biomass at upper-slope depths, while echinoderms were dominant on the middle and lower slope. As a result of this phyletic change, there was a small but insignificant decrease in mean body weight with increasing depth. Within phyla there was also a small but insignificant decrease with depth. If large species are excluded from the biomass/depth regression, the gradient changes considerably, demonstrating the increasing importance of small species at greater depths. The size distribution of megafaunal biomass was examined at several stations. This indicated that the megafauna form a functional group distinct from the macrofauna, just as the macrofauna are distinct from the meiofauna.