Assessment of claw growth-layer groups from ringed seals (<i>Pusa hispida</i>) as biomonitors of inter- and intra-annual Hg, δ¹⁵N, and δ¹³C variation

Abstract

The ringed seal ( Pusa hispida (Schreber, 1775)) is a sentinel species of arctic marine mammals; therefore, methods to monitor its life-history changes are crucial to establish effective conservation strategies. We evaluate the potential use of claws of ringed seals as a proxy for counts of tooth growth-layer groups (age) and a biomonitor of total mercury burden (THg) and diet (stable isotope ratios expressed as δ 15 N and δ 13 C). The count of claw growth-layer groups was indicative of age up to 8 years and we infer differentiation of dark and light annuli as being associated with the spring moult. No differences of THg, δ 15 N, or δ 13 C were observed among flipper digits. The proximal claw annulus representing the most recent growth had δ 13 C values that were correlated to both muscle and liver δ 13 C, supporting the use of claws to monitor visceral δ 13 C. Claw log 10 THg from the proximate annulus was significantly correlated to liver and whisker log 10 THg, while significant interannual THg accumulation was observed in 18 of 32 seals ≥4 years, suggesting the claws receive and disperse Hg from active tissues of the body. Results support the use of claw tissue from ringed seal to provide a chronological record of inter- and intra-annual variations representing seal diet, contaminant load, and life history.