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Landfast sea ice–benthic coupling during spring and potential impacts of system changes on food web dynamics in Eclipse Sound, Canadian Arctic

Doreen Kohlbach*, Steven H. Ferguson, Thomas A. Brown, Christine Michel

*Corresponding author:

ABSTRACT: We investigated the role of sea ice-derived carbon in the food web of Eclipse Sound during the spring ice-covered season to understand the potential ecological impact of changes to the sea-ice habitat. Chlorophyll (chl) a concentrations in the bottom of sea ice (438.2 ± 154.2 µg l-1, 19.8 ± 6.6 mg m-2) were more than two orders of magnitude higher than in surface waters (0.9 ± 0.7µg l-1). Fatty acid (FA) composition showed that algal communities in the bottom sea ice comprised higher abundances of diatoms compared to surface waters. Benthic invertebrates (ophiuroids, polychaetes) and sediments had high proportions of diatom-associated FAs in their lipid composition. H-Print estimates of the proportional contributions of sea-ice derived carbon to the carbon pool of the benthic community were substantial, ranging on average between 77% and 85%. High carbon stable isotope values (δ13C) in benthic invertebrates and sediments (δ13C: –19.6 ‰ to –11.6 ‰) further suggests that a large portion of the benthic carbon pool was of sea ice origin, while surface waters were significantly lower (δ13C: –22.32 ± 2.17 ‰). In this ecosystem where landfast ice is present for most of the year, strong sea ice-benthic coupling emphasizes the dependency of the food web to ice productivity. As timing and magnitude of sea ice-derived carbon will change under alterations of climatic conditions and possibly with increased shipping activities in the study region, the adaptive capacity of sea ice-dependent species is anticipated to play a key role in determining future food webs.