Effects of Age, Colony, and Sex on Mercury Concentrations in California Sea Lions

• Published in: Archives of environmental contamination and toxicology 2016-01, Vol.70 (1), p.46-55
• Main Authors: McHuron, Elizabeth A, Peterson, Sarah H, Ackerman, Joshua T, Melin, Sharon R, Harris, Jeffrey D, Costa, Daniel P
• Format: Article
• Language: English
• Subjects: adults; Age; Animals; Aquatic mammals; Bats; Benchmarks; Blood; California; carbon; Contamination; diet; Earth and Environmental Science; Ecology; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental Monitoring; Environmental studies; Female; Females; Fisheries; Food chains; foraging; habitats; Hair; Hair - chemistry; intraspecific variation; Islands; juveniles; Laboratories; Male; Marine; Marine mammals; Mercury; Mercury - analysis; Monitoring/Environmental Analysis; nitrogen; Pollution; Sea lions; Sea Lions - metabolism; Sex Factors; Soil Science & Conservation; Stable isotopes; Statistical analysis; Toxicity; Toxicology; Trophic levels; trophic relationships; Water Pollutants, Chemical - analysis; Wildlife; Zalophus californianus
• ISSN: 0090-4341; 1432-0703
• DOI: 10.1007/s00244-015-0201-4

We measured total mercury (THg) concentrations in California sea lions (Zalophus californianus) and examined how concentrations varied with age class, colony, and sex. Because Hg exposure is primarily via diet, we used nitrogen (δ ¹⁵N) and carbon (δ ¹³C) stable isotopes to determine if intraspecific differences in THg concentrations could be explained by feeding ecology. Blood and hair were collected from 21 adult females and 57 juveniles from three colonies in central and southern California (San Nicolas, San Miguel, and Año Nuevo Islands). Total Hg concentrations ranged from 0.01 to 0.31 μg g⁻¹ wet weight (ww) in blood and 0.74 to 21.00 μg g⁻¹ dry weight (dw) in hair. Adult females had greater mean THg concentrations than juveniles in blood (0.15 vs. 0.03 μg⁻¹ ww) and hair (10.10 vs. 3.25 μg⁻¹ dw). Age class differences in THg concentrations did not appear to be driven by trophic level or habitat type because there were no differences in δ ¹⁵N or δ ¹³C values between adults and juveniles. Total Hg concentrations in adult females were 54 % (blood) and 24 % (hair) greater in females from San Miguel than females from San Nicolas Island, which may have been because sea lions from the two islands foraged in different areas. For juveniles, we detected some differences in THg concentrations with colony and sex, although these were likely due to sampling effects and not ecological differences. Overall, THg concentrations in California sea lions were within the range documented for other marine mammals and were generally below toxicity benchmarks for fish-eating wildlife.