Abstract
The goal of this study was to explore the role of non-mercury (Hg) methylating taxa in mercury methylation and to identify potential links between elemental cycles and Hg methylation. Statistical approaches were utilized to investigate the microbial community and biochemical functions in relation to methylmercury (MeHg) concentrations in marine and freshwater sediments. Sediments were collected from the methylation zone (top 15 cm) in four Hg-contaminated sites. Both abiotic (e.g., sulfate, sulfide, iron, salinity, total organic matter, etc.) and biotic factors (e.g., hgcA, abundances of methylating and non-methylating taxa) were quantified. Random forest and stepwise regression were performed to assess whether non-methylating taxa were significantly associated with MeHg concentration. Co-occurrence and functional network analyses were constructed to explore associations between taxa by examining microbial community structure, composition, and biochemical functions across sites. Regression analysis showed that approximately 80% of the variability in sediment MeHg concentration was predicted by total mercury concentration, the abundances of Hg methylating taxa, and the abundances of the non-Hg methylating taxa. The co-occurrence networks identified Paludibacteraceae and Syntrophorhabdaceae as keystone non Hg methylating taxa in multiple sites, indicating the potential for syntrophic interactions with Hg methylators. Strong associations were also observed between methanogens and sulfate-reducing bacteria, which were likely symbiotic associations. The functional network results suggested that non-Hg methylating taxa play important roles in sulfur respiration, nitrogen respiration, and the carbon metabolism-related functions methylotrophy, methanotrophy, and chemoheterotrophy. Interestingly, keystone functions varied by site and did not involve carbon- and sulfur-related functions only. Our findings highlight associations between methylating and non-methylating taxa and sulfur, carbon, and nitrogen cycles in sediment methylation zones, with implications for predicting and understanding the impact of climate and land/sea use changes on Hg methylation.
| Original language | English |
|---|---|
| Article number | 123573 |
| Journal | Environmental Pollution |
| Volume | 346 |
| DOIs | |
| State | Published - Apr 1 2024 |
Funding
The authors wish to acknowledge the Texas Tech University SEED project fund and graduate student research program for providing financial support. Partial funding for this work was also provided by the U.S. Department of Energy, Office of Science, Biological and Environmental Research, Environmental Systems Science Program. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725 . Thanks to Dr. Danny Reible for the South River sediment samples, Michael Vanbuskirk from the Texas Commission on Environmental Quality for Caddo Lake sampling, Dr. Jeremy Bailoo for statistical guidance, and Shubhra Bhattacharjee for guidance on sediment iron analysis. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Disclaimer, not for publication: This manuscript has been authored by UT-Battelle , LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). Disclaimer, not for publication: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).The authors wish to acknowledge the Texas Tech University SEED project fund and graduate student research program for providing financial support. Partial funding for this work was also provided by the U.S. Department of Energy, Office of Science, Biological and Environmental Research, Environmental Systems Science Program. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. Thanks to Dr. Danny Reible for the South River sediment samples, Michael Vanbuskirk from the Texas Commission on Environmental Quality for Caddo Lake sampling, Dr. Jeremy Bailoo for statistical guidance, and Shubhra Bhattacharjee for guidance on sediment iron analysis. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Keywords
- Co-occurrence
- Function
- Methylmercury
- Network
- Non methylating taxa
