MEPS 557:161-175 (2016)  -  DOI: https://doi.org/10.3354/meps11863

ABSTRACT: We characterized the feeding ecologies of common bivalves Macoma calcarea, Nuculana radiata, and Ennucula tenuis, and polychaetes Leitoscoloplos pugettensis and Nephtys spp. from the Bering Sea using relative proportions of fatty acids (FA profiles), FAs indicative of distinct organic matter sources (FA markers), and stable carbon isotope values of FA markers. We measured FAs from these invertebrates and from surface sediment scrapes collected during March to July in 2009 and 2010. The bivalve species had indistinguishable trophic signatures, as inferred by overlapping FA profiles and δ¹³C values for algal marker FAs, and similar proportions of FA markers. FA δ¹³C values from bivalve taxa were most similar to FA δ¹³C values from particulate organic matter (POM) from surface sediments. In contrast, δ¹³C values for the algal marker eicosapentaenoic acid in the polychaetes were higher relative to those from the bivalves and sediment from the same locations (mean difference of 3.6‰), suggesting low direct dietary contributions of benthic POM from surface sediments. L. pugettensis, a head-down deposit-feeding polychaete, had a higher contribution from bacterial sources to its total FA pool relative to the bivalves and to Nephtys spp., a predatory polychaete, based on a bacterial FA marker. Distinct FA profiles between the polychaetes imply different proportional contributions of dietary FA sources, including greater contribution of microbially altered FAs to L. pugettensis and greater contribution of ice algal FAs to Nephtys spp. Our findings revealed resource partitioning among select benthic invertebrates and suggest that responses to climate-induced changes in sub-Arctic production may be species specific.

KEY WORDS: Arctic benthos · Trophic markers · Bacteria · Sea ice algae · Phytoplankton · Microphytobenthos