Skip to main content
U.S. flag

An official website of the United States government

Ecological change drives a decline in mercury concentrations in southern Beaufort Sea polar bears

June 1, 2017

We evaluated total mercury (THg) concentrations and trends in polar bears from the southern Beaufort Sea subpopulation from 2004 to 2011. Hair THg concentrations ranged widely among individuals from 0.6 to 13.3 μg g–1 dry weight (mean: 3.5 ± 0.2 μg g–1). Concentrations differed among sex and age classes: solitary adult females ≈ adult females with cubs ≈ subadults > adult males ≈ yearlings > cubs-of-the-year ≈ 2 year old dependent cubs. No variation was observed between spring and fall samples. For spring-sampled adults, THg concentrations declined by 13% per year, contrasting recent trends observed for other Western Hemispheric Arctic biota. Concentrations also declined by 15% per year considering adult males only, while a slower, nonsignificant decrease of 4.4% per year was found for adult females. Lower THg concentrations were associated with higher body mass index (BMI) and higher proportions of lower trophic position food resources consumed. Because BMI and diet were related, and the relationship to THg was strongest for BMI, trends were re-evaluated adjusting for BMI as the covariate. The adjusted annual decline was not significant. These findings indicate that changes in foraging ecology, not declining environmental concentrations of mercury, are driving short-term declines in THg concentrations in southern Beaufort Sea polar bears.

Publication Year 2017
Title Ecological change drives a decline in mercury concentrations in southern Beaufort Sea polar bears
DOI 10.1021/acs.est.7b00812
Authors Melissa A. McKinney, Todd C. Atwood, Sara Pedro, Elizabeth L. Peacock
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental Science & Technology
Index ID 70193122
Record Source USGS Publications Warehouse
USGS Organization Alaska Science Center Biology MFEB