MEGAFAUNA ASSOCIATED WITH HYDROTHERMAL VENTS IN THE MANUS BACK-ARC BASIN (BISMARCK SEA)

The vent fauna of Manus Back-Arc Basin were investigated during the 21 st cruise of the Akademik Mstislav Keldysh in May-June 1990. Communiti es associated with three active hydrothermal fields were explored duri ng a series of dives by the DSRV Mir. At least sixteen vent species we re collected; some of them are new. Material for physiological and bio chemical analyses was collected as well. Special attention was paid to the exploration of spatial distribution of animals. Distributional in formation is combined with our knowledge on the biology of animals to construct a food web of the community. Species composition of the comm unities investigated is similar but relative abundance varies. These d ifferences seem to be a result of temporal changes in the communities. Early stages of the cycle of the Manus Basin vents are hypothetically dominated by vestimentiferans but mesogastropods will replace them wi th lime. Faunal composition and community structure of the Manus Basin reinforce the likelihood that the hydrothermal vents of western Pacif ic spreading centres have been in communication with each other. The M anus Basin vent fauna displays close affinity with the communities of the North Fiji and Lau Basins as compared with the Mariana Trough vent region. (C) 1997 Elsevier Science B.V.