| Summary: | Climate change is causing the poleward redistribution of species linked to abiotic factors such as temperature. The Arctic is warming three times faster than the global average and causing a rapid climate-driven recession of sea ice, which is an added stressor to Arctic species and ecosystems. As a mobile, generalist predator, ringed seals integrate resources spatially and trophically up the Arctic marine food web, which makes them a model indicator of how the Arctic marine ecosystem will respond to environmental change. Ringed seals are also vulnerable to loss of the sea-ice habitat they depend on for pupping, nursing, moulting, and prey from sea-ice derived food webs but experience a broad range of sea-ice conditions from the southern to northern edge of their range. The objectives of this thesis were to determine how the (1) density and (2) diet of ringed seals varied over the vastly different icescapes within their latitudinal range. Our results indicated latitudinal variation in ringed seal density potentially increased with availability of preferred first-year ice habitat. We also found a shift in ringed seals diets from primarily phytoplanktonic carbon in the low Arctic to a high proportion of ice-algal carbon in the high Arctic. The observed change in the base of food webs contributing to ringed seal diets may also have implications for trophic dynamics in these food webs. Overall, we show the potential of ringed seal density and diet to indicate large scale changes to the Arctic environment and Arctic food webs. We also provide insight into the potential responses to continued sea-ice recession of a key species for Arctic ecosystems and communities, important information for cooperative management of Arctic resources. February 2022
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