Abstract
Arctic ecosystem dynamics are shifting in response to warming temperatures and sea ice loss. Such ecosystems may be monitored by examining the diet of upper trophic level species, which varies with prey availability. To assess interannual variation in the Beaufort Sea ecosystem, we examined spatial and temporal trends in ringed seal (Pusa hispida) δ13C and δ15N in claw growth layers grown from 1964 to 2011. Stable isotopes were correlated with climate indices, environmental conditions, seal population productivity, and geographic location. Sex and age did not influence stable isotopes. Enriched 13C was linked to cyclonic circulation regimes, seal productivity, and westward sampling locations. Higher δ15N was linked to lower sea surface temperatures, a higher percentage of pups in the subsistence harvest, and sample locations that were eastward and further from shore. From the 1960s to 2000s, ringed seal niche width expanded, suggesting a diversification of diet due to expansion of prey and/or seal space use. Overall, trends in ringed seal stable isotopes indicate changes within the Beaufort Sea ecosystem affected by water temperatures and circulation regimes. We suggest that continued monitoring of upper trophic level species will yield insights into changing ecosystem structure with climate change.
Highlights
Monitoring of Arctic marine ecosystems can be challenging, due to the region's remoteness, large scale, and complexity
Ecosystem changes in response to shifting environmental conditions within the Arctic may be captured in stable isotopes of ringed seals, as demonstrated in our study
Our sampled seal claws captured up to 12 years of dietary history for an individual, which demonstrates the value in sampling metabolically inactive tissues and allows us to examine the influence of shifting environmental conditions upon ringed seal stable isotopes up to a decade before sampling
Summary
Changes in isotopic values and niche widths over time can reveal changes in diet for an animal if prey isotopic values are distinct (Hobson, Schell, Renouf, & Noseworthy, 1996), which may be due to shifts in foraging behavior or changes in the abundance and distribution of prey Marine predators, such as ringed seals (Pusa hispida; Figure 1), play a role as indicator species, and their stable isotope values can offer insights into shifts in ecological communities (Harwood, Smith, George, et al, 2015; Yurkowski, Hussey, Ferguson, & Fisk, 2018). | 4180 the objective of our study is to examine interannual and spatial trends in δ13C and δ15N of ringed seals based on claw annuli collected from 1974 to 2011 in the Beaufort Sea. As ringed seals are opportunistic feeders, we expected that changes in prey availability driven by environmental variability would be reflected within seal diets and subsequently, their stable isotope values. We did not attempt to infer ringed seal diet contributions because of the numerous possible prey sources within the ringed seal diet and a lack of prey stable isotope data that match our ringed seal data both spatially and temporally
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