The megabenthic fauna in the deep sea south of New England,USA

Data from 105 benthic trawls made in an area south of New England, USA between 40 and 5000 m show the fauna to be zoned with depth, areas of rapid faunal change separating regions of relative faunal homogeneity. Distinct faunal assemblages with characteristic catch rates, diversity, and dominant species are found on the shelf (40 to 264 m), upper continental slope (283 to 650 m), middle continental slope (653 to 1290 m), lower continental slope (1380 to 1947 m), the transitional region from slope to rise (2116 to 2481 m), the upper continental (2504 to 3113 m), the middle continental rise (3244 to 3470 m), and lower continental rise to abyssal plain (3879 to 4986 m). Catch rates and diversity are greatest on the lower continental slope and transition to the upper rise, and are lowest at the greatest depths. Dominance, particularly by echinoderms, is an important aspect of community structure. The 3 major taxa represented (decapod crustaccean, echinoderms, and fishes) do not always display the same patterns within and between assemblages. Generalities derived from study of a single group need not apply to all segments of the deep-ocean community. Overall patterns in the megafauna are similar to those described in other groups and areas, but species assemblages are not the same everywhere and perhaps too much has been made of the horizontal extent of zones. Trophic level is related to degree of zonation, but where predators are generalists their ranges may be wide rather than restricted. Diversity patterns can be understood in terms of the interrelationships of predation, competition, environmental heterogeneity, and trophic level. Faunal zones are of importance as the geographical units within which evolution, community development, and diversification take place.This research was supported by the National Science Foundation under Grant OCE76-21878, the Office of Naval Research under Contract N00014-74-C0262, and, in part, by the United States Department of Energy under Contract No. EY-76-C-02-0016 and the Canadian Natural Sciences and Engineering Research Cancil under Grant A-7230