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Graham EB, Gabor RS, Schooler S, McKnight DM, Nemergut DR, Knelman JE. Oligotrophic wetland sediments susceptible to shifts in microbiomes and mercury cycling with dissolved organic matter addition. PeerJ 2018; 6:e4575. [PMID: 29632744 PMCID: PMC5888151 DOI: 10.7717/peerj.4575] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 03/15/2018] [Indexed: 12/26/2022] Open
Abstract
Recent advances have allowed for greater investigation into microbial regulation of mercury toxicity in the environment. In wetlands in particular, dissolved organic matter (DOM) may influence methylmercury (MeHg) production both through chemical interactions and through substrate effects on microbiomes. We conducted microcosm experiments in two disparate wetland environments (oligotrophic unvegetated and high-C vegetated sediments) to examine the impacts of plant leachate and inorganic mercury loadings (20 mg/L HgCl2) on microbiomes and MeHg production in the St. Louis River Estuary. Our research reveals the greater relative capacity for mercury methylation in vegetated over unvegetated sediments. Further, our work shows how mercury cycling in oligotrophic unvegetated sediments may be susceptible to DOM inputs in the St. Louis River Estuary: unvegetated microcosms receiving leachate produced substantially more MeHg than unamended microcosms. We also demonstrate (1) changes in microbiome structure towards Clostridia, (2) metagenomic shifts toward fermentation, and (3) degradation of complex DOM; all of which coincide with elevated net MeHg production in unvegetated microcosms receiving leachate. Together, our work shows the influence of wetland vegetation in controlling MeHg production in the Great Lakes region and provides evidence that this may be due to both enhanced microbial activity as well as differences in microbiome composition.
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Affiliation(s)
- Emily B Graham
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Rachel S Gabor
- School of Environment and Natural Resources, Ohio State University, Columbus, OH, United States of America
| | - Shon Schooler
- Lake Superior National Estuarine Research Reserve, Superior, WI, United States of America
| | - Diane M McKnight
- Institute for Arctic and Alpine Research, University of Colorado at Boulder, Boulder, CO, United States of America.,Civil Engineering Department, University of Colorado at Boulder, Boulder, CO, United States of America.,Environmental Studies Program, University of Colorado at Boulder, Boulder, CO, United States of America
| | - Diana R Nemergut
- Institute for Arctic and Alpine Research, University of Colorado at Boulder, Boulder, CO, United States of America.,Biology Department, Duke University, Durham, NC, United States of America
| | - Joseph E Knelman
- Institute for Arctic and Alpine Research, University of Colorado at Boulder, Boulder, CO, United States of America
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Lewis AS, Huntington TG, Marvin-DiPasquale MC, Amirbahman A. Mercury remediation in wetland sediment using zero-valent iron and granular activated carbon. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2016; 212:366-373. [PMID: 26874318 DOI: 10.1016/j.envpol.2015.11.047] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 11/25/2015] [Accepted: 11/26/2015] [Indexed: 06/05/2023]
Abstract
Wetlands are hotspots for production of toxic methylmercury (MeHg) that can bioaccumulate in the food web. The objective of this study was to determine whether the application of zero-valent iron (ZVI) or granular activated carbon (GAC) to wetland sediment could reduce MeHg production and bioavailability to benthic organisms. Field mesocosms were installed in a wetland fringing Hodgdon Pond (Maine, USA), and ZVI and GAC were applied. Pore-water MeHg concentrations were lower in treated compared with untreated mesocosms; however, sediment MeHg, as well as total Hg (THg), concentrations were not significantly different between treated and untreated mesocosms, suggesting that smaller pore-water MeHg concentrations in treated sediment were likely due to adsorption to ZVI and GAC, rather than inhibition of MeHg production. In laboratory experiments with intact vegetated sediment clumps, amendments did not significantly change sediment THg and MeHg concentrations; however, the mean pore-water MeHg and MeHg:THg ratios were lower in the amended sediment than the control. In the laboratory microcosms, snails (Lymnaea stagnalis) accumulated less MeHg in sediment treated with ZVI or GAC. The study results suggest that both GAC and ZVI have potential for reducing MeHg bioaccumulation in wetland sediment.
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Affiliation(s)
- Ariel S Lewis
- Department of Civil and Environmental Engineering, University of Maine, Orono, ME, USA
| | | | | | - Aria Amirbahman
- Department of Civil and Environmental Engineering, University of Maine, Orono, ME, USA.
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Keller RH, Xie L, Buchwalter DB, Franzreb KE, Simons TR. Mercury bioaccumulation in Southern Appalachian birds, assessed through feather concentrations. ECOTOXICOLOGY (LONDON, ENGLAND) 2014; 23:304-316. [PMID: 24420618 DOI: 10.1007/s10646-013-1174-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/31/2013] [Indexed: 06/03/2023]
Abstract
Mercury contamination in wildlife has rarely been studied in the Southern Appalachians despite high deposition rates in the region. From 2006 to 2008 we sampled feathers from 458 birds representing 32 species in the Southern Appalachians for total mercury and stable isotope δ (15)N. Mercury concentrations (mean ± SE) averaged 0.46 ± 0.02 μg g(-1) (range 0.01-3.74 μg g(-1)). Twelve of 32 species had individuals (7 % of all birds sampled) with mercury concentrations higher than 1 μg g(-1). Mercury concentrations were 17 % higher in juveniles compared to adults (n = 454). In adults, invertivores has higher mercury levels compared to omnivores. Mercury was highest at low-elevation sites near water, however mercury was detected in all birds, including those in the high elevations (1,000-2,000 m). Relative trophic position, calculated from δ (15)N, ranged from 2.13 to 4.87 across all birds. We fitted linear mixed-effects models to the data separately for juveniles and year-round resident adults. In adults, mercury concentrations were 2.4 times higher in invertivores compared to omnivores. Trophic position was the main effect explaining mercury levels in juveniles, with an estimated 0.18 ± 0.08 μg g(-1) increase in feather mercury for each one unit rise in trophic position. Our research demonstrates that mercury is biomagnifying in birds within this terrestrial mountainous system, and further research is warranted for animals foraging at higher trophic levels, particularly those associated with aquatic environments downslope from montane areas receiving high mercury deposition.
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Affiliation(s)
- Rebecca Hylton Keller
- Appalachian Mountains Joint Venture, American Bird Conservancy, 1900 Kraft Drive, Suite 250, Blacksburg, VA, 24061, USA,
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Moberly JG, Miller CL, Brown SD, Biswas A, Brandt CC, Palumbo AV, Elias DA. Role of morphological growth state and gene expression in Desulfovibrio africanus strain Walvis Bay mercury methylation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:4926-4932. [PMID: 22500779 DOI: 10.1021/es3000933] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The biogeochemical transformations of mercury are a complex process, with the production of methylmercury, a potent human neurotoxin, repeatedly demonstrated in sulfate- and Fe(III)-reducing as well as methanogenic bacteria. However, little is known regarding the morphology, genes, or proteins involved in methylmercury generation. Desulfovibrio africanus strain Walvis Bay is a Hg-methylating δ-proteobacterium with a sequenced genome and has unusual pleomorphic forms. In this study, a relationship between the pleomorphism and Hg methylation was investigated. Proportional increases in the sigmoidal (regular) cell form corresponded with increased net MeHg production but decreased when the pinched cocci (persister) form became the major morphotype. D. africanus microarrays indicated that the ferrous iron transport genes (feoAB), as well as ribosomal genes and several genes whose products are predicted to have metal binding domains (CxxC), were up-regulated during exposure to Hg in the exponential phase. Whereas no specific methylation pathways were identified, the finding that Hg may interfere with iron transport and the correlation of growth-phase-dependent morphology with MeHg production are notable. The identification of these relationships between differential gene expression, morphology, and the growth-phase dependence of Hg transformations suggests that actively growing cells are primarily responsible for methylation, and so areas with ample carbon and electron-acceptor concentrations may also generate a higher proportion of methylmercury than more oligotrophic environments. The observation of increased iron transporter expression also suggests that Hg methylation may interfere with iron biogeochemical cycles.
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Affiliation(s)
- James G Moberly
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Mercury and other heavy metals influence bacterial community structure in contaminated Tennessee streams. Appl Environ Microbiol 2010; 77:302-11. [PMID: 21057024 DOI: 10.1128/aem.01715-10] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
High concentrations of uranium, inorganic mercury [Hg(II)], and methylmercury (MeHg) have been detected in streams located in the Department of Energy reservation in Oak Ridge, TN. To determine the potential effects of the surface water contamination on the microbial community composition, surface stream sediments were collected 7 times during the year, from 5 contaminated locations and 1 control stream. Fifty-nine samples were analyzed for bacterial community composition and geochemistry. Community characterization was based on GS 454 FLX pyrosequencing with 235 Mb of 16S rRNA gene sequence targeting the V4 region. Sorting and filtering of the raw reads resulted in 588,699 high-quality sequences with lengths of >200 bp. The bacterial community consisted of 23 phyla, including Proteobacteria (ranging from 22.9 to 58.5% per sample), Cyanobacteria (0.2 to 32.0%), Acidobacteria (1.6 to 30.6%), Verrucomicrobia (3.4 to 31.0%), and unclassified bacteria. Redundancy analysis indicated no significant differences in the bacterial community structure between midchannel and near-bank samples. Significant correlations were found between the bacterial community and seasonal as well as geochemical factors. Furthermore, several community members within the Proteobacteria group that includes sulfate-reducing bacteria and within the Verrucomicrobia group appeared to be associated positively with Hg and MeHg. This study is the first to indicate an influence of MeHg on the in situ microbial community and suggests possible roles of these bacteria in the Hg/MeHg cycle.
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Qin Y, Yang Z, Yang W. A Novel Index System for Assessing Ecological Risk under Water Stress in the Yellow River Delta Wetland. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/j.proenv.2010.10.058] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Gabriel MC, Kolka R, Wickman T, Nater E, Woodruff L. Evaluating the spatial variation of total mercury in young-of-year yellow perch (Perca flavescens), surface water and upland soil for watershed-lake systems within the southern Boreal Shield. THE SCIENCE OF THE TOTAL ENVIRONMENT 2009; 407:4117-26. [PMID: 19349066 DOI: 10.1016/j.scitotenv.2009.03.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 03/09/2009] [Accepted: 03/11/2009] [Indexed: 05/17/2023]
Abstract
The primary objective of this research is to investigate relationships between mercury in upland soil, lake water and fish tissue and explore the cause for the observed spatial variation of THg in age one yellow perch (Perca flavescens) for ten lakes within the Superior National Forest. Spatial relationships between yellow perch THg tissue concentration and a total of 45 watershed and water chemistry parameters were evaluated for two separate years: 2005 and 2006. Results show agreement with other studies where watershed area, lake water pH, nutrient levels (specifically dissolved NO(3)(-)-N) and dissolved iron are important factors controlling and/or predicting fish THg level. Exceeding all was the strong dependence of yellow perch THg level on soil A-horizon THg and, in particular, soil O-horizon THg concentrations (Spearman rho=0.81). Soil B-horizon THg concentration was significantly correlated (Pearson r=0.75) with lake water THg concentration. Lakes surrounded by a greater percentage of shrub wetlands (peatlands) had higher fish tissue THg levels, thus it is highly possible that these wetlands are main locations for mercury methylation. Stepwise regression was used to develop empirical models for the purpose of predicting the spatial variation in yellow perch THg over the studied region. The 2005 regression model demonstrates it is possible to obtain good prediction (up to 60% variance description) of resident yellow perch THg level using upland soil O-horizon THg as the only independent variable. The 2006 model shows even greater prediction (r(2)=0.73, with an overall 10 ng/g [tissue, wet weight] margin of error), using lake water dissolved iron and watershed area as the only model independent variables. The developed regression models in this study can help with interpreting THg concentrations in low trophic level fish species for untested lakes of the greater Superior National Forest and surrounding Boreal ecosystem.
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Affiliation(s)
- Mark C Gabriel
- The University of Minnesota, Department of Soil Water and Climate, 1991 Upper Buford Circle, St. Paul, MN 55108, USA.
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Harmon SM, King JK, Gladden JB, Newman LA. Using sulfate-amended sediment slurry batch reactors to evaluate mercury methylation. ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2007; 52:326-31. [PMID: 17384981 DOI: 10.1007/s00244-006-0071-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2006] [Accepted: 09/04/2006] [Indexed: 05/14/2023]
Abstract
In the methylated form, mercury represents a concern to public health primarily through the consumption of contaminated fish tissue. Research conducted on the methylation of mercury strongly suggests that the process is microbial in nature and facilitated principally by sulfate-reducing bacteria. This study addressed the potential for mercury methylation by varying sulfate treatments and wetland-based soil in microbial slurry reactors with available inorganic mercury. Under anoxic laboratory conditions conducive to the growth of naturally occurring sulfate-reducing bacteria in the soil, it was possible to evaluate how various sulfate additions influenced the methylation of inorganic mercury added to overlying water as well as the sequestration of dissolved copper. Treatments included sulfate amendments ranging from 25 to 500 mg/L (0.26 to 5.2 mM) above the soil's natural sulfate level. Mercury methylation in sulfate treatments did not exceed that of the nonamended control during a 35-day incubation period. However, increases in methylmercury concentration were linked to bacterial growth and sulfate reduction. A time lag in methylation in the highest treatment correlated with an equivalent lag in bacterial growth. The decrease in dissolved copper ranged from 72.7% in the control to 99.7% in the highest sulfate treatment. It was determined that experimental systems such as these can provide some useful information but that they also have severe limitations once sulfate is depleted or if sulfate is used in excess.
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Affiliation(s)
- S M Harmon
- Department of Environmental Health Sciences, University of South Carolina, Arnold School of Public Health, Columbia, South Carolina 29208, USA.
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