Quantitative Biological Assessment of the Benthic Fauna in Deep Basins of the Gulf of Maine

The abundance, biomass, and diversity of the macro- and mega-fauna in the deep basins of the Gulf of Maine were estimated from 41 quantitative infaunal samples and 19 visual transects made with the Deep Submergence Research Vessel (DSRV) Alvin. The homogeneous fine silt and clay (66% clay) sediments supported an infaunal abundance and wet preserved biomass which were relatively low for a continental margin (270–297 m deep) with high sediment organic carbon (1.9%). Diversity estimates (H[s]) from Alvin box core samples were lower than Alvin box core sample values from the continental slope, suggesting that the seasonally stable Gulf of Maine basins, because of their short geologic age, do not yet contain an equilibrium assemblage. An additional possibility is that seasonal variations in the production of organic matter, being more pronounced in the Gulf of Maine than offshore in deep water, affect community structure on the bottom.