ABSTRACT: This study used fatty acid trophic markers (FATMs) to assess carbon sources of the bivalve Bathyarca glacialis and describe the pelagic–benthic coupling in the Canadian Arctic Archipelago. Four regions characterized by contrasting trophic environments were investigated: Southeastern Beaufort Sea, Victoria Strait, Lancaster Sound and Northern Baffin Bay. Our results suggest that B. glacialis is a non-selective filter feeder, feeding on microalgae, zooplankton, and bacteria. Diet was based mainly on microalgae, especially for coastal populations of the Southeastern Beaufort Sea. However, zooplankton and bacteria contributed more significantly to the diet of B. glacialis in bathyal populations than the coastal populations. Local and seasonal environmental conditions likely explain these differences in diet between populations. Furthermore, non-methylene-interrupted (NMI) fatty acids were present in the polar lipids of B. glacialis, which could be produced de novo when access to essential fatty acids (EFAs), required for maintaining membrane structure and function, is limited. This physiological response could help the bivalve to modulate its membrane fluidity in the face of constraints of the deep-sea environment such as low temperatures, high pressure, and when EFAs are less available in its diet. This bivalve species thus has certain attributes that could help it to cope with expected strong modifications in primary production dynamics due to climate-induced changes in the Arctic marine system.