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

• Published in: Limnology and Oceanography
• Main Authors: Vane, Kim, Cobain, Matthew R. D., Trueman, Clive N., Vonnahme, Tobias R., Rokitta, Sebastian, Polunin, Nicholas V. C., Flores, Hauke
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: Arctic; Arctic Ocean; Boreogadus saida; Calanus hyperboreus; ice algae; Sea ice
• Online Access: https://hdl.handle.net/10037/30151; https://doi.org/10.1002/lno.12315

A rapidly warming Arctic Ocean and associated sea-ice decline is resulting in changing sea-ice protist communities, affecting productivity of under-ice, pelagic, and benthic fauna. Quantifying such effects is hampered by a lack of biomarkers suitable for tracing specific basal resources (primary producers and microorganisms) through food webs. We investigate the potential of δ 13 C values of essential amino acids (EAAs) (δ 13 C EAA values) to estimate the proportional use of diverse basal resources by organisms from the under-ice (Apherusa glacialis), pelagic (Calanus hyperboreus) and benthic habitats (sponges, sea cucumber), and the cryo-pelagic fish Boreogadus saida. Two approaches were used: baseline δ 13 C EAA values, that is, the basal resource specific δ 13 C EAA values, and δ 13 C EAA fingerprints, or mean-centred baseline δ 13 C EAA values. Substantial use of sub-ice algae Melosira arctica by all studied organisms suggests that its role within Arctic food webs is greater than previously recognized. In addition, δ 13 C EAA fingerprints from algae-associated bacteria were clearly traced to the sponges, with an individually variable kelp use by sea cucumbers. Although mean-centred δ 13 C EAA values in A. glacialis, C. hyperboreus, and B. saida tissues were aligned with microalgae resources, they were not fully represented by the filtered pelagic- and sea-ice particulate organic matter constituting the spring diatom-dominated algal community. Under-ice and pelagic microalgae use could only be differentiated with baseline δ13C EAA values as similar microalgae clades occur in both habitats. We suggest that δ 13 C EAA fingerprints combined with microalgae baseline δ 13 C EAA values are an insightful tool to assess the effect of ongoing changes in Arctic basal resources on their use by organisms.