Factors influencing mercury levels in Leach's storm-petrels at northwest Atlantic colonies

• Published in: The Science of the total environment 2023-02, Vol.860, p.160464, Article 160464
• Main Authors: Pollet, Ingrid L., McFarlane-Tranquilla, Laura, Burgess, Neil M., Diamond, Antony W., Gjerdrum, Carina, Hedd, April, Hoeg, Rielle, Jones, Patricia L., Mauck, Robert A., Montevecchi, William A., Pratte, Isabeau, Ronconi, Robert A., Shutler, Dave, Wilhelm, Sabina I., Mallory, Mark L.
• Format: Article
• Language: English
• Subjects: Animals; Animals, Wild; Birds; Canada; Contamination; Environmental Monitoring; Humans; Hydrobates leucorhous; Mercury - analysis; Methylmercury; Methylmercury Compounds; Seabirds
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.160464

Mercury (Hg) is a globally distributed heavy metal, with negative effects on wildlife. Its most toxic form, methylmercury (MeHg), predominates in aquatic systems. Levels of MeHg in marine predators can vary widely among individuals and populations. Leach's storm-petrels (Hydrobates leucorhous) have elevated levels of Hg but the role of Hg in storm-petrel population declines is unknown. In this study, we used egg and blood samples to study variation in Hg exposure among several northwest Atlantic colonies during breeding seasons, thereby evaluating relative toxicity risk within and among colonies. Total mercury (THg) concentrations were higher with increasing colony latitude, and were more pronounced in blood than in eggs. THg concentrations in blood were mostly associated with low toxicity risk in birds from the southern colonies and moderate risks in birds from the northern colonies; however, those values did not affect hatching or fledging success. THg concentrations in both eggs and blood were positively correlated with δ34S, emphasizing the role of sulfate-reducing bacteria in methylation of THg acquired through marine food webs, which is consistent with enriched δ34S profiles. By associating tracking data from foraging trips with THg from blood, we determined that blood THg levels were higher when storm-petrel's intensive search locations were over deeper waters. We conclude that spatial variation in THg concentrations in Leach's storm-petrels is attributable to differences in ocean depth at foraging locations, both at individual and colony levels. Differences in diet among colonies observed previously are the most likely cause for observed blood THg differences. As one of the few pelagic seabird species breeding in Atlantic Canada, with limited overlap in core foraging areas among colonies, Leach's storm-petrels can be used as biomonitors for less sampled offshore pelagic regions. The global trend in Hg emissions combined with legacy levels warrant continued monitoring for toxicity effects in seabirds. [Display omitted] •Potential role of mercury in contributing to population declines of Leach’s storm-petrels is not fully understood•We analyzed associations among geotracking, stable isotope, and mercury concentration data•Blood mercury levels were higher with increasing foraging depth, trophic level, and latitude•Leach’s storm-petrels can be biomonitors of pelagic marine food webs•Effects of mercury on the species should be further investigated