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Accumulation of Methylmercury in Invertebrates and Masked Shrews (Sorex cinereus) at an Upland Forest–Peatland Interface in Northern Minnesota, USA

Abstract

Mercury (Hg) methylation is often elevated at the terrestrial–peatland interface, but methylmercury (MeHg) production at this “hot spot” has not been linked with in situ biotic accumulation. We examined total Hg and MeHg levels in peat, invertebrates and tissues of the insectivore Sorex cinereus (masked shrew), inhabiting a terrestrial–peatland ecotone in northern Minnesota, USA. Mean MeHg concentrations in S. cinereus (71 ng g−1) fell between concentrations measured in spiders (mean 70–140 ng g−1), and ground beetles and millipedes (mean 29–42 ng g−1). Methylmercury concentrations in S. cinereus increased with age and differed among tissues, with highest concentrations in kidneys and muscle, followed by liver and brain. Nearly all Hg in S. cinereus was in the methylated form. Overall, the high proportional accumulation of MeHg in peat at the site (3.5% total Hg as MeHg) did not lead to particularly elevated concentrations in invertebrates or shrews, which are below values considered a toxicological risk.

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Acknowledgements

We thank Planck Huang for his help with lab analysis and staff at the Marcell Experimental Forest Research Station and the USFS Northern Research Station. Funding was provided by a NSERC Discovery grant and a Great Lakes Air Deposition Program grant to CPJM. Rachel Strickman and Planck Huang provided useful comments on the manuscript.

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Correspondence to Carl P. J. Mitchell.

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All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures and protocols were approved by the University of Toronto-Scarborough’s Animal Care Committee.

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Tavshunsky, I., Eggert, S.L. & Mitchell, C.P.J. Accumulation of Methylmercury in Invertebrates and Masked Shrews (Sorex cinereus) at an Upland Forest–Peatland Interface in Northern Minnesota, USA. Bull Environ Contam Toxicol 99, 673–678 (2017). https://doi.org/10.1007/s00128-017-2198-z

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Keywords

  • Small mammal
  • Spider
  • Mercury
  • Methylmercury
  • Bioaccumulation
  • Wetland
  • Ecotone