Multi-decadal trends in mercury and methylmercury concentrations in the brown watersnake (Nerodia taxispilota)

David L Haskins; M Kyle Brown; Chongyang Qin; Xiaoyu Xu; Melissa A Pilgrim; Tracey D Tuberville

doi:10.1016/j.envpol.2021.116722

Multi-decadal trends in mercury and methylmercury concentrations in the brown watersnake (Nerodia taxispilota)

Environ Pollut. 2021 May 1:276:116722. doi: 10.1016/j.envpol.2021.116722. Epub 2021 Feb 15.

Authors

David L Haskins¹, M Kyle Brown², Chongyang Qin³, Xiaoyu Xu³, Melissa A Pilgrim⁴, Tracey D Tuberville³

Affiliations

¹ Interdisciplinary Toxicology Program, University of Georgia, Athens, GA, 30605, USA; Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30605, USA; Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, 29802, USA. Electronic address: davidhaskins44@att.net.
² Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30605, USA; Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, 29802, USA.
³ Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, 29802, USA.
⁴ Division of Natural Sciences and Engineering, University of South Carolina Upstate, Spartanburg, SC, 29303, USA.

PMID: 33640654
DOI: 10.1016/j.envpol.2021.116722

Abstract

Mercury (Hg) is an environmental contaminant that poses a threat to aquatic systems globally. Temporal evaluations of Hg contamination have increased in recent years, with studies focusing on how anthropogenic activities impact Hg bioavailability in a variety of aquatic systems. While it is common for these studies and ecological risk assessments to evaluate Hg bioaccumulation and effects in wildlife, there is a paucity of information regarding Hg dynamics in reptiles. The goal of this study was to investigate temporal patterns in total mercury (THg) and methylmercury (MeHg) concentrations across a 36-year period, as well as evaluate relationships among and between destructive (kidney, liver, muscle) and non-destructive (blood, tail) tissue types in a common watersnake species. To accomplish this, we measured THg and MeHg concentrations in multiple tissues from brown watersnakes (Nerodia taxispilota) collected from Steel Creek on the Savannah River Site (SRS; Aiken, SC, USA) from two time periods (1983-1986 and 2019). We found significant and positive relationships between tail tips and destructive tissues. In both time periods, THg concentrations varied significantly by tissue type, and destructive tissues exhibited higher but predictable THg values relative to tail tissue. Methylmercury concentrations did not differ among tissues from the 1980s but was significantly higher in muscle compared to other tissues from snakes collected in 2019. Percent MeHg of THg in N. taxispilota tissues mirrored patterns reported in other reptiles, although the range of % MeHg in liver and kidney differed between time periods. Both THg and MeHg concentrations in N. taxispilota declined significantly from the 1980s to 2019, with average values 1.6 to 4-fold lower in contemporary samples. Overall, our data add further evidence to the utility of watersnakes to monitor Hg pollution in aquatic environments and suggest attenuation of this contaminant in watersnakes in our study system.

Keywords: Heavy metal; Natricinae; Pollution; Reptile; Squamate.

MeSH terms

Environmental Monitoring
Mercury* / analysis
Methylmercury Compounds*
Rivers
Water Pollutants, Chemical* / analysis

Substances

Methylmercury Compounds
Water Pollutants, Chemical
Mercury