Spatiotemporal variation in foraging ecology and mercury concentrations in ringed seals and bearded seals across a...

Climate change is causing a decrease in Arctic sea ice extent and thickness, leading to alterations in interspecific interactions, food availability, and contaminant exposure for marine organisms, including higher trophic level predators such as ringed seals (Pusa hispida, natsiq) and bearded seals (Erignathus barbatus, ujjuk) who forage in disparate habitats. Despite rapid Arctic ecosystem change, spatiotemporal variability in the foraging behavior and contaminant dynamics of these Arctic seals remains poorly understood. Using stable isotopes (δ¹³C, δ¹⁵N, δ³⁴S) and total mercury (THg) concentrations in claw annuli, we investigated spatiotemporal variability in the foraging ecology and contaminant exposure of ringed and bearded seals in relation to environmental factors at the individual, species, and between-species levels across a latitudinal gradient in the eastern Canadian Arctic. Overall, ringed seals fed more pelagically and had higher THg levels than bearded seals. A latitudinal gradient emerged where seals at lower latitudes had lower δ¹⁵N and THg, and foraged more pelagically than seals at higher latitudes. Bearded seals, and seals at lower latitudes, had higher degrees of individual specialization calculated using individual and population isotope variance analysis, suggesting they are more vulnerable to rapid environmental changes than ringed seals and seals at higher latitudes. Additionally, seals consumed relatively more pelagic prey in years with longer open water periods, supporting evidence of climate-induced shifts in Arctic marine mammal foraging strategies towards pelagic prey. This study provided insight into spatial variation in foraging strategies, habitat use, and contaminant exposure of two Arctic marine predators; information which can be used to inform species management and conservation efforts.