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Title: Oligotrophic wetland sediments susceptible to shifts in microbiomes and mercury cycling with dissolved organic matter addition

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 HgCl 2) 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. Altogether, 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.
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [4]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. The Ohio State Univ., Columbus, OH (United States)
  3. Lake Superior National Estuarine Research Reserve, Superior, WI (United States)
  4. Univ. of Colorado, Boulder, CO (United States)
  5. Univ. of Colorado, Boulder, CO (United States); Duke Univ., Durham, NC (United States)
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Additional Journal Information:
Journal Volume: 6; Journal ID: ISSN 2167-8359
PeerJ Inc.
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
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Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES; Mercury methylation; Fermentation; Carbon; Microbial community structure; Sediment microbiome; Mercury contamination; Freshwater microbiology; Wild rice; Fluorescence spectroscopy; Organic matter chemistry
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