Food resources of the bivalve Astarte elliptica in a sub-Arctic fjord: a multi-biomarker approach

ABSTRACT: It is generally agreed that pelagic-benthic coupling is tight on Arctic shelves, i.e. that organic matter produced in the surface layers supports the seafloor and benthos. However, this paradigm is mainly based on the assumption that phytoplankton and ice algae are the main sources of carbon for the benthic communities. Climate change is expected to alter the relative contribution of food sources for benthic organisms. Macroalgal biomass is predicted to increase in near-shore systems in response to increased temperature and reduced sea ice cover. Thus, a better understanding of the relative contribution of benthic and pelagic components in benthic food webs in the Arctic is needed. In this study, a multi-biomarker approach (stable isotopes, fatty acid trophic markers, and compound-specific stable isotope analysis) was applied to link potential sources of carbon, including particulate organic matter from subsurface and bottom waters, sediment organic matter, and 6 macroalgal species to the diet of the bivalve Astarte elliptica collected below the euphotic zone in a sub-Arctic fjord (Kobbefjord, Greenland). Results showed that A. elliptica feeds on particulate and sediment organic matter and that brown macroalgae significantly support the Arctic benthic food web. Multi-biomarker approaches can be used to determine the diet of benthic organisms and track temporal variability in sources of food. It therefore appears to be an interesting method to study food regime strategies in response to changing primary production dynamics.