Tracing basal resource use across sea‐ice, pelagic, and benthic habitats in the early Arctic spring food web with essential amino acid carbon isotopes

A rapidly warming Arctic Ocean and associated sea-ice decline is resulting in changing protist communities, affecting productivity of under-ice, pelagic, benthic fauna. Quantifying such effects hampered by a lack biomarkers suitable for tracing specific basal resources (primary producers microorganisms) through food webs. We investigate the potential δ13C values essential amino acids (EAAs) (δ13CEAA values) to estimate proportional use diverse organisms from under-ice (Apherusa glacialis), pelagic (Calanus hyperboreus) habitats (sponges, sea cucumber), cryo-pelagic fish Boreogadus saida. Two approaches were used: baseline δ13CEAA values, that is, resource fingerprints, or mean-centred values. Substantial sub-ice algae Melosira arctica all studied suggests its role within webs greater than previously recognized. In addition, fingerprints algae-associated bacteria clearly traced sponges, with an individually variable kelp cucumbers. Although A. glacialis, C. hyperboreus, B. saida tissues aligned microalgae resources, they not fully represented filtered pelagic- particulate organic matter constituting spring diatom-dominated algal community. Under-ice could only be differentiated as similar clades occur both habitats. suggest combined are insightful tool assess effect ongoing changes on their organisms.