The mean density and mean biomass of macrobenthis invertebrates on the U.S. continental shelf off Martha's Vineyard, Mass., were 3,008/m¹ and 245.7 g/m², respectively. The latter estimate was considerably higher than values from the North Sea, Scotian Shelf, and Middle-Atlantic Bight. Molluscs (pelecypods and gastropods) and echinoderms (echinoids and ophiuroids) greatly influenced patterns of total biomass distribution. The ocean quahog, Arctica islandica, was the dominant species in terms of biomass. Total density was dominated by crustaceans (amphipods), polychaetous annelids, molluscs, (small pelecypods), and echinoderms (ophiuroids).

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