Differences in Mercury Bioaccumulation between Polar Bears (Ursus maritimus) from the Canadian high- and sub-Arctic

Polar bears (Ursus maritimus) are being impacted by climate change and increased exposure to pollutants throughout their northern circumpolar range. In this study, we quantified concentrations of total mercury (THg) in the hair of polar bears from Canadian high- (southern Beaufort Sea, SBS) and sub-...

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Bibliographic Details
Published in:	Environmental science & technology Vol. 45; no. 14; pp. 5922 - 5928
Main Authors:	St. Louis, Vincent L, Derocher, Andrew E, Stirling, Ian, Graydon, Jennifer A, Lee, Caroline, Jocksch, Erin, Richardson, Evan, Ghorpade, Sarah, Kwan, Alvin K, Kirk, Jane L, Lehnherr, Igor, Swanson, Heidi K
Format:	Journal Article
Language:	English
Published:	Washington, DC American Chemical Society 15-07-2011
Subjects:	Animals Arctic Regions Bioaccumulation Biological and medical sciences Canada Carbon Isotopes - analysis Characterization of Natural and Affected Environments Climate change Environmental Pollutants - analysis Environmental Pollutants - pharmacokinetics Fluorescence Food Chain Food chains Fundamental and applied biological sciences. Psychology Geography Hair - chemistry Mammalia Mass Spectrometry Mercury Mercury - analysis Mercury - pharmacokinetics Nitrogen Isotopes - analysis Polar bears Pollutants Ursidae - metabolism Ursus maritimus Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution Canada Arctic Regions Beaufort Sea Hudson Bay PNW, Beaufort Sea PN, Arctic PNW, Canada, Hudson Bay PNW, Canada, Arctic Archipelago Trace element Fissipedia Carnivora Vertebrata Mammalia Subpolar zone Biological accumulation Mercury Ursus maritimus Heavy metal
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Summary:	Polar bears (Ursus maritimus) are being impacted by climate change and increased exposure to pollutants throughout their northern circumpolar range. In this study, we quantified concentrations of total mercury (THg) in the hair of polar bears from Canadian high- (southern Beaufort Sea, SBS) and sub- (western Hudson Bay, WHB) Arctic populations. Concentrations of THg in polar bears from the SBS population (14.8 ± 6.6 μg g–1) were significantly higher than in polar bears from WHB (4.1 ± 1.0 μg g–1). On the basis of δ15N signatures in hair, in conjunction with published δ15N signatures in particulate organic matter and sediments, we estimated that the pelagic and benthic food webs in the SBS are ∼4.7 and ∼4.0 trophic levels long, whereas in WHB they are only ∼3.6 and ∼3.3 trophic levels long. Furthermore, the more depleted δ13C ratios in hair from SBS polar bears relative to those from WHB suggests that SBS polar bears feed on food webs that are relatively more pelagic (and longer), whereas polar bears from WHB feed on those that are relatively more benthic (and shorter). Food web length and structure accounted for ∼67% of the variation we found in THg concentrations among all polar bears across both populations. The regional difference in polar bear hair THg concentrations was also likely due to regional differences in water-column concentrations of methyl Hg (the toxic form of Hg that biomagnifies through food webs) available for bioaccumulation at the base of the food webs. For example, concentrations of methylated Hg at mid-depths in the marine water column of the northern Canadian Arctic Archipelago were 79.8 ± 37.3 pg L–1, whereas, in HB, they averaged only 38.3 ± 16.6 pg L–1. We conclude that a longer food web and higher pelagic concentrations of methylated Hg available to initiate bioaccumulation in the BS resulted in higher concentrations of THg in polar bears from the SBS region compared to those inhabiting the western coast of HB.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0013-936X 1520-5851
DOI:	10.1021/es2000672