Comparative distribution of macrocrustaceans in a north-western Australian mangrove system

Abstract

Species diversity, density and biomass of macromolluscs and macrocrustaceans were investigated in the Bay of Rest (22� 18'S.,114�08'E.), a small mangrove system in north-western Australia. Mollusc species diversity, density and biomass were generally greatest on the seaward mudflat and lower in Avicennia and Rhizophora tree zones; no molluscs were recorded on the landward backflat. Crustaceans were diverse and abundant on the mudflat but the biomass was low. Diversity, density and biomass were high in Avicennia, lower in Rhizophora and the backflat. Filter-feeding molluscs were important on the mudflat, as were deposit feeders which dominated in Avicennia. Surface raspers were most important in Rhizophora. Deposit feeding and omnivorous crustaceans were dominant in all areas. It is suggested that molluscs and crustaceans in the system, both in the tree zones and on the seaward mudflat, are largely dependent on detrital breakdown of the mangroves for their nutrition. They may play a key role in converting primary production by the trees into animal tissue available to higher trophic levels.