Macrobenthic community structure over the continental margin of Crete (South Aegean Sea, NE Mediterranean)

Macrobenthic faunal composition, abundance, biomass and diversity together with a suite of sedimentary environmental parameters were investigated on a seasonal basis in order to determine factors regulating faunal distributio n over the oligotrophic continental margin of the island of Crete (South Ae gean Sea, North Eastern Mediterranean). Macrofaunal species composition was similar to that of the western Mediterranean and the neighboring Atlantic having several common dominant species. Mean benthic biomass, abundance and diversity decreased with depth, with a major transition zone occurring at 540 m, beyond which values declined sharply. At comparable depths biomass a nd abundance values were considerably lower to those found in the Atlantic, high-lighting the extreme oligotrophy of the area. The continental margin of Crete was characterised by a high diversity upper continental shelf envi ronment (dominated by surface deposit feeding polychaetes) and a very low d iversity slope and deep-basin environment (dominated by carnivorous and fil ter feeding polychaetes). Classification and ordination analyses revealed t he existence of four principle clusters divided by a faunal boundary betwee n 200 and 540 m, as well as beyond 940 m depth. Significant correlations be tween macrofauna and sediment parameters led to the conclusion that besides depth, food availability (as manifested by the concentration of chloroplas tic pigments) is the principle regulating factor in the system. Such being the case, the prevailing hydrographic features that structure the pelagic f ood web and are directly responsible for the propagation of organic matter to the benthos also affect its community structure. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.