Little is known about the history of heavy metal pollution of Russia's Lake Baikal, one of the world's largest lakes and a home to numerous endemic species, including the Baikal Seal, Pusa sibirica. We investigated the history of heavy metal (V, Cu, Zn, Cd, Hg, Tl, Pb, U) pollution in Lake Baikal seals over the past 8 decades. C and N stable isotope analysis (SIA) and laser-ablation ICP-MS of seal teeth were used to examine changes in feeding ecology, heavy metal levels associated with life history events and long-term variation in metal exposure. SIA did not suggest large changes in the feeding ecology of Baikal seals over the past 80 years. LA-ICP-MS analyses revealed element-specific ontogenetic variability in metal concentrations, likely related to maternal transfer, changes in food sources and starvation. Hg and Cd levels in seals varied significantly across the time series, with concentrations peaking in the 1960s - 1970s but then declining to contemporary levels similar to those observed in the 1930s and 1940s. Trends in atmospheric emissions of Hg suggest that local sources as well as emissions from eastern Russia and Europe may be important contributors of Hg to Lake Baikal and that, despite the size of Lake Baikal, its food web appears to respond rapidly to changing inputs of contaminants.
Bibliographical noteFunding Information:
The pioneering research and scientific collections of Baikal seals conducted by Vladimir Pastukhov made this study possible and warrant special recognition. We thank Kate Corcoran, Abby Duck, Jenna Disch, Graham Durovich, Amanda Gardner, Gabi Guzman, Julia Halbur, Diana Lee, Iris Lin, Kirill Shchapov, and Melaina Wright for help with sample processing and analysis. We acknowledge the use of the NSF-supported WHOI ICPMS facility and thank Scott Birdwhistle for his assistance. We also thank David Hawkins, Steve Katz and Simon Thorrold for help and suggestions on sample processing, data and LA-ICP-MS analyses. Comments by three anonymous reviewers helped to substantially improve this manuscript. This work was supported by a Brachman-Hoffman Fellowship, a Brachman-Hoffman Small Grant, and a Fiske grant from Wellesley College in addition to the Dimensions of Biodiversity Program of the US National Science Foundation (DEB-1136657).