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

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

doi:10.1016/j.envpol.2021.116722

Cited by 11 publications

(10 citation statements)

References 62 publications

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“…Similar to prior research (Brisbin et al, 1974; Burger et al, 2006; Haskins, Brown, Bringolf, et al, 2021; Haskins, Brown, Qin, et al, 2021), our results lend further credence to the use of aquatic snakes, such as N. floridana , as effective bioindicators for monitoring spatial and temporal trends of contamination in aquatic habitats. Nerodia floridana readily accumulate Hg and 137 Cs that can be measured through nonlethal techniques.…”

Section: Discussionsupporting

confidence: 90%

“…As expected, concentrations of THg in tail tips increased with increasing SVL in N. floridana from the three Savannah River Site reservoirs sampled. Similar trends of a strong positive relationship between body size and THg have been observed for northern watersnakes ( N. sipedon ) in Virginia (Drewett et al, 2013), cottonmouths ( A. piscivorus ) in Texas (Rainwater et al, 2005), Burmese pythons ( Python bivitattus ) in Florida (Rumbold & Bartoszek, 2019), viperine snakes ( Natrix maura ) in Europe (Lemaire et al, 2018), and brown watersnakes ( N. taxispilota ) in the Savannah River adjacent to the Savannah River Site (Haskins, Brown, Bringolf, et al, 2021; Haskins, Brown, Qin, et al, 2021). A pattern of increasing THg burdens with increasing body size does provide support for bioaccumulation (Wolfe et al, 1998).…”

Section: Discussionmentioning

confidence: 99%

“…Effects of acute exposure, particularly to high doses of a contaminant, have been documented for both 137 Cs (e.g., radiation sickness and death; Djomina & Barilyak, 2010) and Hg (e.g., neurotoxicity and death; Heinz, 1996; Wren et al, 1987); however, chronic, low‐dose exposure has also been associated with sublethal effects in a broad array of taxa ( 137 Cs: Shugart et al, 1989; Stark et al, 2004; Hg: Evers, 2018; Wolfe et al, 1998). Several studies have quantified contaminant levels, including 137 Cs and Hg, in reptiles (Brisbin et al, 1974; Burger et al, 2006; Haskins, Brown, Qin, et al, 2021; W. A. Hopkins et al, 1999; Lemaire et al, 2018). However, potential sublethal effects in reptiles—particularly snakes—have received scant attention.…”

Section: Introductionmentioning

confidence: 99%

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Mercury and Radiocesium Accumulation and Associations With Sublethal Endpoints in the Florida Green Watersnake (Nerodia floridana)

Brown

Haskins

Russell

et al. 2022

Enviro Toxic and Chemistry

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Mercury (Hg) and radiocesium (137Cs) are well‐known environmental contaminants with the potential to impact the health of humans and wildlife. Snakes have several characteristics conducive to studying environmental contamination but have rarely been included in the monitoring of polluted sites. We investigated the bioaccumulation of Hg and 137Cs and associations with sublethal effects (standard metabolic rate [SMR] and hemoparasite infections) in Florida green watersnakes (Nerodia floridana). We captured 78 snakes from three former nuclear cooling reservoirs on the US Department of Energy's Savannah River Site in South Carolina (USA). For captured snakes, we (1) determined whole‐body 137Cs, (2) quantified total Hg (THg) using snake tail clips, (3) conducted hemoparasite counts, and (4) measured the SMR. We used multiple regression models to determine associations among snake body size, capture location, sex, tail THg, whole‐body 137Cs, Hepatozoon spp. prevalence and parasitemia, and SMR. Average whole‐body 137Cs (0.23 ± 0.08 Becquerels [Bq]/g; range: 0.00–1.02 Bq/g) was correlated with snake body size and differed significantly by capture site (Pond B: 0.67 ± 0.05 Bq/g; Par Pond: 0.10 ± 0.02 Bq/g; Pond 2: 0.03 ± 0.02 Bq/g). Tail THg (0.33 ± 0.03 mg/kg dry wt; range: 0.16–2.10 mg/kg) was significantly correlated with snake body size but did not differ by capture site. We found no clear relationship between SMR and contaminant burdens. However, models indicated that the prevalence of Hepatozoon spp. in snakes was inversely related to increasing whole‐body 137Cs burdens. Our results indicate the bioaccumulation of Hg and 137Cs in N. floridana and further demonstrate the utility of aquatic snakes as bioindicators. Our results also suggest a decrease in Hepatozoon spp. prevalence related to increased burdens of 137Cs. Although the results are intriguing, further research is needed to understand the dynamics between 137Cs and Hepatozoon spp. infections in semiaquatic snakes. Environ Toxicol Chem 2022;41:758–770. © 2022 SETAC

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mercury and Radiocesium Accumulation and Associations With Sublethal Endpoints in the Florida Green Watersnake (Nerodia floridana)

Brown

Haskins

Russell

et al. 2022

Enviro Toxic and Chemistry

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“…The watersheds of the Savannah River Site (SRS, Aiken, SC, USA) showed elevated Hg concentrations in the sediment and biota due to the legacy contamination from upstream industrial activities such as the Olin Corporation Chlor-Alkali Plant (Augusta, GA, USA), the historical agricultural runoff, and the SRS seepage basins that received liquid effluents containing Hg before the 1980s [23,[47][48][49][50]. The Fourmile Branch (Figure 1) is a contaminated water body on the Savannah River Site; it received Hg release from multiple sources in different portions of the stream, with the two major sources having seeped through two basins-the F-area and H-area seepage basins [23,51,52].…”

Section: Sampling Sitementioning

confidence: 99%

Mercury Accumulation in a Stream Ecosystem: Linking Labile Mercury in Sediment Porewaters to Bioaccumulative Mercury in Trophic Webs

Bryan

Parks

et al. 2022

Water

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Mercury (Hg) deposition and accumulation in the abiotic and biotic environments of a stream ecosystem were studied. This study aimed to link labile Hg in porewater to bioaccumulative Hg in biota. Sediment cores, porewaters, and biota were sampled from four sites along the Fourmile Branch (SC, USA) and measured for total Hg (THg) and methyl-Hg (MHg) concentrations. Water quality parameters were also measured at the sediment–water interface (SWI) to model the Hg speciation. In general, Hg concentrations in porewaters and bulk sediment were relatively high, and most of the sediment Hg was in the solid phase as non-labile species. Surface sediment presented higher Hg concentrations than the medium and bottom layers. Mercury methylation and MHg production in the sediment was primarily influenced by sulfate levels, since positive correlations were observed between sulfate and Hg in the porewaters. The majority of Hg species at the SWI were in non-labile form, and the dominant labile Hg species was complexed with dissolved organic carbon. MHg concentrations in the aquatic food web biomagnified with trophic levels (biofilm, invertebrates, and fish), increasing by 3.31 times per trophic level. Based on the derived data, a modified MHg magnification model was established to estimate the Hg bioaccumulation at any trophic level using Hg concentrations in the abiotic environment (i.e., porewater).

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“…Many reptiles are long‐lived, exhibit limited vagility and feed at high trophic levels, all of which make them susceptible to the accumulation of high concentrations of Hg (Rowe, 2008; Schneider et al, 2013). Several studies have demonstrated that reptiles readily accumulate (Chumchal et al, 2011; Drewett et al, 2013; Haskins, Brown, Qin, et al, 2021; Heaton‐Jones et al, 1997) and may be negatively impacted by Hg exposure (Chin et al, 2013a; Day et al, 2007; Hopkins, Willson, & Hopkins, 2013; Wang et al, 2013). Although snakes are known to accumulate high levels of Hg, only one study has evaluated snake immunity in relation to Hg exposure.…”

Section: Introductionmentioning

confidence: 99%

Mercury immunotoxicity in the brown watersnake (Nerodia taxispilota): An in vitro study

Haskins

Brown

Meichner

et al. 2021

J of Applied Toxicology

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Mercury (Hg) is a heavy metal that enters the environment through natural and anthropogenic means. Once in the environment, Hg can biomagnify in food webs and is known to cause immunotoxic effects to wildlife. Compared with other vertebrates, knowledge of the reptilian immune system is lacking, especially in snakes. Further, even less is known about the impact of environmental contaminants on snake immunity. This gap in knowledge is largely due to an absence of established immune‐based assays or specific reagents for these species. In this study, brown watersnakes (Nerodia taxispilota; n = 23) were captured on the Savannah River (Augusta, Georgia, USA), weighed, measured, bled, and released. Peripheral blood leukocytes (24 h old) were enriched and evaluated with an established mammalian in vitro lymphocyte proliferation assay. Enriched leukocytes were then exposed to mercury chloride (HgCl2) at 3.75, 37.5, and 75 μM. Total mercury (THg) in whole blood was also quantified. Snake peripheral blood leukocyte enrichment yielded >90% lymphocytes with viabilities averaging >70%. Exposure to HgCl2 resulted in significant dose‐dependent suppression of proliferative responses relative to spontaneous proliferation at 37.5 and 75 μM (both p ≤ 0.01) but not 3.75 μM (p = 0.99). Mean ± 1 SE concentration of THg in whole blood was 0.127 ± 0.027 mg/kg (wet weight). Based on the in vitro findings with HgCl2, snakes in systems with heavy Hg pollution may be at risk of immunosuppression, but N. taxispilota at the site in this study appear to be at low risk.

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

Cited by 11 publications

References 62 publications

Mercury and Radiocesium Accumulation and Associations With Sublethal Endpoints in the Florida Green Watersnake (Nerodia floridana)

Mercury and Radiocesium Accumulation and Associations With Sublethal Endpoints in the Florida Green Watersnake (Nerodia floridana)

Mercury Accumulation in a Stream Ecosystem: Linking Labile Mercury in Sediment Porewaters to Bioaccumulative Mercury in Trophic Webs

Mercury immunotoxicity in the brown watersnake (Nerodia taxispilota): An in vitro study

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