MARINE MOLLUSCA FROM EXPEDITION FJORD, WESTERN AXEL-HEIBERG ISLAND, NORTHWEST-TERRITORIES, CANADA

Marine molluscs, including bivalves, gastropods and scaphopods, were r ecovered by dredging at depths of 3-82 m in Expedition Fiord, Axel Hei berg Island, Canada. Cluster analysis, based on presence/absence data at 27 stations, defined two mollusc associations within the fiord. A P ortlandia-Thyasira association, characterized by the abundance of Port landia arctica and Thyasira gouldi, inhabits silty clay substrates at depths of 32-82 m throughout the fiord. An Astarte association, charac terized by the abundance of Astarte borealis and Astarte warhami, inha bits sandy mud substrates at depths of 3-32 m in the middle and outer fiord. The absence of this mollusc association at the fiord head sugge sts that the suspension-feeding molluscs that constitute this associat ion, such as Astarte, Hiatella, Mya and Trichotropis, are intolerant o f the lowered salinities and high suspended-sediment concentrations cr eated by the discharge of Expedition River into the fiord-head environ ment. The Expedition Fiord molluscan fauna is compared to the mollusca n fauna recorded in Jorgen Bronlund Fjord, Greenland. In the latter fi ord, shallow-water (5-19 m) molluscan faunas are characterized by the abundance of Portlandia arctica and Hiatella arctica, while deep-water (22-48 m) faunas are characterized by the abundance of Thyasira dunba ri. Molluscs recovered live in both of these fiords are distributed wi dely in high-latitude fiord and continental shelf environments.