title: Effects of Age, Colony, and Sex on Mercury Concentrations in California Sea Lions.
abstract: 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 (15)N) and carbon (δ (13)C) 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 (15)N or δ (13)C 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.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, 100 Shaffer Road, Santa Cruz, CA, 95060, USA. emchuron@ucsc.edu.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: McHuron
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, 100 Shaffer Road, Santa Cruz, CA, 95060, USA.
authors.forename: Sarah H
authors.initials: SH
authors.lastname: Peterson
authors.affiliation: U.S. Geological Survey, Western Ecological Research Center, 800 Business Park Drive, Suite D, Dixon, CA, 95620, USA.
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Ackerman
authors.affiliation: National Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 7600 Sand Point Way NE, Seattle, WA, 98155, USA.
authors.forename: Sharon R
authors.initials: SR
authors.lastname: Melin
authors.affiliation: National Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 7600 Sand Point Way NE, Seattle, WA, 98155, USA.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Harris
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, 100 Shaffer Road, Santa Cruz, CA, 95060, USA.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Costa
mesh_terms: D000818:Animals; D002140:California; D004784:Environmental Monitoring; D005260:Female; D006197:Hair / Q000737:chemistry; D008297:Male; D008628:Mercury / Q000032:analysis*; D046070:Sea Lions / Q000378:metabolism*; D012737:Sex Factors; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D008628:Mercury