title: Influence of carbon and lipid sources on variation of mercury and other trace elements in polar bears (Ursus maritimus).
abstract: In the present study, the authors investigated the influence of carbon and lipid sources on regional differences in liver trace element (As, Cd, Cu, total Hg, Mn, Pb, Rb, Se, and Zn) concentrations measured in polar bears (Ursus maritimus) (n = 121) from 10 Alaskan, Canadian Arctic, and East Greenland subpopulations. Carbon and lipid sources were assessed using δ(13) C in muscle tissue and fatty acid (FA) profiles in subcutaneous adipose tissue as chemical tracers. A negative relationship between total Hg and δ(13) C suggested that polar bears feeding in areas with higher riverine inputs of terrestrial carbon accumulate more Hg than bears feeding in areas with lower freshwater input. Mercury concentrations were also positively related to the FA 20:1n-9, which is biosynthesized in large amounts in Calanus copepods. This result raises the hypothesis that Calanus glacialis are an important link in the uptake of Hg in the marine food web and ultimately in polar bears. Unadjusted total Hg, Se, and As concentrations showed greater geographical variation among polar bear subpopulations compared with concentrations adjusted for carbon and lipid sources. The Hg concentrations adjusted for carbon and lipid sources in Bering-Chukchi Sea polar bear liver tissue remained the lowest among subpopulations. Based on these findings, the authors suggest that carbon and lipid sources for polar bears should be taken into account when one is assessing spatial and temporal trends of long-range transported trace elements.
authors.affiliation: Ecotoxicology and Wildlife Health Division, Science and Technology Branch, Environment Canada, National Wildlife Research Centre, Carleton University, Ottawa, Ontario.
authors.forename: Heli
authors.initials: H
authors.lastname: Routti
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Letcher
authors.forename: Erik W
authors.initials: EW
authors.lastname: Born
authors.forename: Marsha
authors.initials: M
authors.lastname: Branigan
authors.forename: Rune
authors.initials: R
authors.lastname: Dietz
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Evans
authors.forename: Melissa A
authors.initials: MA
authors.lastname: McKinney
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Peacock
authors.forename: Christian
authors.initials: C
authors.lastname: Sonne
mesh_terms: D000413:Alaska; D000818:Animals; D001110:Arctic Regions; D002170:Canada; D002244:Carbon / Q000737:chemistry / Q000378:metabolism*; D004785:Environmental Pollutants / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D020387:Food Chain; D006116:Greenland; D008099:Liver / Q000378:metabolism; D008297:Male; D008628:Mercury / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D014131:Trace Elements / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D001503:Ursidae / Q000378:metabolism*
chemical_list: D004785:Environmental Pollutants; D014131:Trace Elements; D002244:Carbon; D008628:Mercury