DISTRIBUTION, BIOMASS AND COMMUNITY STRUCTURE OF MEGABENTHOS OF THE GULF-OF-CARPENTARIA, AUSTRALIA

To describe the megabenthos communities in the Gulf of Carpentaria, Au stralia, beam trawls were taken from a systematic grid of 107 stations sampled during November and December 1990. Over 476500 individuals we re collected, weighing over 1700 kg and representing more than 840 spe cies from 150 families. The mean biomass was 15.9 kg trawl(-1), the av erage number of species was 59.8 trawl(-1) and the average number of i ndividuals was 4405 trawl(-1). The main taxa in terms of biomass were spatangoida (60.5%), porifera (13.7%), zoantharia (7.3%), bivalvia (2. 8%), and decapoda (2.8%); they included 12, 102, 10 and 198 species re spectively. The megabenthos species were mainly scavengers/carnivores (345), suspension-feeders (331), deposit-feeders (121) and a few herbi vores (37). Most species were classed as mobile (496) with lesser numb ers classed as sessile species (334). Two deposit-feeding spatangoids accounted for 59% of the biomass but were sampled at only 9 stations. Classification and ordination using species presence or absence data i ndicated that there were 2 main communities in the Gulf: a community l ocated in predominantly sandy sediments along the eastern and southeas tern margins of the Gulf that comprised mainly sessile suspension-feed ing sponges, zoantharians, pennatulaceans, bivalve molluscs and ascidi ans; and a community located in the muddier sediments in the central a nd western Gulf that comprised mainly deposit-feeding spatangoids and sand dollars. However, sessile suspension-feeders were also found in t he central Gulf wherever suitable substrata were present.