Role of organic matter and microbial communities in mercury retention and methylation in sediments near run-of-river hydroelectric dams

Ferriz, Lise Millera; Ponton, Dominic E.; Storck, Véronika; Leclerc, Maxime; Bilodeau, François; Walsh, David A.; Amyot, Marc

doi:10.1016/j.scitotenv.2021.145686

Cited by 19 publications

(44 citation statements)

References 93 publications

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“…Given the high MMHg concentration detected in the constructed wetland water compared to the MMHg concentration found in the biofilms ( Table 1 ), it is likely that periphyton plays some role as a source of MMHg for the surrounding water of this site rather than a sink. Moreover, a parallel study conducted in the same river area did not find a high abundance of hgcA nor a high concentration of MMHg in the sediments (0.31 ± 0.20 ng g −1 of DW, representing 1.59% ± 0.58% of THg) of the constructed wetland site compared to the flooded and natural sites ( 58 ). This does not detract from the likely implications of sediments in the production and export of MMHg in the wetland site.…”

Section: Resultsmentioning

confidence: 87%

Microbial Diversity and Mercury Methylation Activity in Periphytic Biofilms at a Run-of-River Hydroelectric Dam and Constructed Wetlands

Leclerc

Harrison

Storck

et al. 2021

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Periphytic biofilms have the potential to greatly influence the microbial production of the neurotoxicant monomethylmercury in freshwaters although few studies have simultaneously assessed periphyton mercury methylation and demethylation rates and the microbial communities associated with these transformations. We performed a field study on periphyton from a river affected by run-of-river power plants and artificial wetlands in a boreal landscape (Québec, Canada). In situ incubations were performed on three sites using environmental concentrations of isotopically enriched monomethylmercury (MM198Hg) and inorganic mercury (200Hg) for demethylation and methylation rate measurements. Periphytic microbial communities were investigated through 16S rRNA gene analyses and metagenomic screenings for the hgcA gene, involved in mercury methylation. Positive mercury methylation rates ([5.9 ± 3.4] × 10−3 day−1) were observed only in the wetlands, and demethylation rates averaged 1.78 ± 0.21 day−1 for the three studied sites. The 16S rRNA gene analyses revealed Proteobacteria as the most abundant phylum across all sites (36.3% ± 1.4%), from which families associated with mercury methylation were mostly found in the wetland site. Metagenome screening for HgcA identified 24 different hgcA sequences in the constructed wetland site only, associated with 8 known families, where the iron-reducing Geobacteraceae were the most abundant. This work brings new information on mercury methylation in periphyton from habitats of impacted rivers, associating it mostly with putative iron-reducing bacteria. IMPORTANCE Monomethylmercury (MMHg) is a biomagnifiable neurotoxin of global concern with risks to human health mostly associated with fish consumption. Hydroelectric reservoirs are known to be sources of MMHg many years after their impoundment. Little is known, however, on run-of-river dams flooding smaller terrestrial areas, although their numbers are expected to increase considerably worldwide in decades to come. Production of MMHg is associated mostly with anaerobic processes, but Hg methylation has been shown to occur in periphytic biofilms located in oxic zones of the water column. Therefore, in this study, we investigated in situ production of MMHg by periphytic communities in habitats impacted by the construction of a run-of-river dam by combining transformation rate measurements with genomic approaches targeting hgcAB genes, responsible for mercury methylation. These results provide extended knowledge on mercury methylators in river ecosystems impacted by run-of-river dams in temperate habitats.

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Section: Resultsmentioning

confidence: 87%

Microbial Diversity and Mercury Methylation Activity in Periphytic Biofilms at a Run-of-River Hydroelectric Dam and Constructed Wetlands

Leclerc

Harrison

Storck

et al. 2021

mSphere

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“…Methylmercury (methylHg) is an extremely toxic contaminant that can be highly damaging to people (Budnik and Casteleyn, 2019; Ceccatelli et al, 2010) and aquatic organisms including turtles (Barraza et al, 2021; Di Marzio et al, 2019; Green et al, 2010; Hopkins et al, 2013; Schneider and Vogt, 2018; Slimani et al, 2018). Patterns of mercury contamination have been intensely studied around dams (Budnik and Casteleyn, 2019; Millera Ferriz et al, 2021; Pestana et al, 2019; Wang et al, 2004). Few ecotoxicological studies focused on freshwater turtles exist [(Thompson et al, 2018) but see (Lu et al, 2019; Tada et al, 2007)], with most focusing on fish due to their economic importance and use as a food resource (Duponchelle et al, 2021; Moran et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

Impacts of dams on freshwater turtles: a global review to identify conservation solutions

Bárcenas-García

Michalski

Morgan

et al. 2021

Preprint

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Dams create many impacts on freshwater ecosystems and biodiversity. Freshwater turtles are at direct and indirect risk due to changes caused by damming including the loss of terrestrial and aquatic nesting and feeding habitats, changes to resource availability and reduced dispersal. We reviewed the global scientific literature that evaluated the impact of dams on freshwater turtles, and carried out additional searches of literature published in seventeen languages for studies evaluating actions to mitigate the impact of dams. The search produced 43 published articles documenting dam impacts on 29 freshwater turtle species from seven families (Chelidae, Chelydridae, Emydidae, Geoemydidae, Kinosternidae, Podocnemididae and Trionychidae) in 13 countries. More than a third of studies (41.9%, n = 18) focused on nine North American species of the Emydidae. Few studies were found from Europe and Asia and none from Africa. The number of studies, life-history stage studied and threat status differed significantly between temperate and tropical latitudes. Most studies were from temperate latitudes, where studies focused more on adults and less threatened species compared with tropical latitudes. Studies evaluated dam impacts as barriers and changes to water flow and quality, but no studies were found that assessed turtles and changes to land cover or mercury caused by dams. More than half of the studies (59%, n = 24) suggested actions to help mitigate dam impacts. Yet, only four studies on three temperate and one tropical species documented the effect of interventions (dam removal, flow management, artificial pond maintenance and community-based action). These findings demonstrate a lack of documented evidence evaluating dam impacts on freshwater turtles particularly in tropical regions. This lack of evidence reinforces the importance of strengthening and maintaining robust long-term studies of freshwater turtles needed to develop effective conservation actions for this group of vertebrates.

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“…Water samples were collected at these anoxic depths. Five metagenomes (RES5S) were obtained from reservoir sediments from the St. Maurice River near Wemotaci, Canada in 2017 and 2018 (Millera-Ferriz et al, 2021, GOLD-JGI Ga0393614 Ga0393582, Ga0393617, Ga0393586, Ga0393589). The studied river section has been affected by the construction of two run-of-river power plant dams and its watershed has been disturbed by a forest fire, logging, and the construction of wetlands.…”

Section: Methodsmentioning

confidence: 99%

“…We apply this pipeline to metagenomes collected from paddy soils, brackish and lake waters, as well as sediments from reservoirs and lakes in which hgc genes have been previously detected (Liu et al, 2018;Jones et al, 2019;Capo et al, 2020;Millera Ferriz et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, we present marky-coco (https://github.com/ericcapo/marky-coco), a ready-to-use bioinformatic pipeline to detect, identify and count hgc genes from metagenomes ( Fig 2 ). We apply this pipeline to metagenomes collected from paddy soils, brackish and lake waters, as well as sediments from reservoirs and lakes in which hgc genes have been previously detected (Liu et al, 2018; Jones et al, 2019; Capo et al, 2020; Millera Ferriz et al, 2021). Further, we specifically compared the reliability of (i) applying the marky-coco pipeline based on de novo single assembly approach from single metagenomes with (ii) co-assembling of multiple metagenomes (co-assembly) prior to mapping and identification.…”

Section: Introductionmentioning

confidence: 99%

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A consensus protocol for the recovery of mercury methylation genes from metagenomes

Capo

Peterson

Kim

et al. 2022

Preprint

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Mercury methylation genes (hgcAB) mediate the formation of the toxic methylmercury and have been identified from diverse environments, including freshwater and marine ecosystems, Arctic permafrost, forest and paddy soils, coal-ash amended sediments, chlor-alkali plants discharges and geothermal springs. Here we present the first attempt at a standardized protocol for the detection, identification and quantification of hgc genes from metagenomes. Our Hg-MATE (Hg-cycling Microorganisms in Aquatic and Terrestrial Ecosystems) database, a catalogue of hgc genes, provides the most accurate information to date on the taxonomic identity and functional/metabolic attributes of microorganisms responsible for Hg methylation in the environment. Furthermore, we introduce 'marky-coco', a ready-to-use bioinformatic pipeline based on de novo single-metagenome assembly, for easy and accurate characterization of hgc genes from environmental samples. We compared the recovery of hgc genes from environmental metagenomes using the marky-coco pipeline with an approach based on co-assembly of multiple metagenomes. Our data show similar efficiency in both approaches for most environments except those with high diversity (i.e., paddy soils) for which a co-assembly approach was preferred. Finally, we discuss the definition of true hgc genes and methods to normalize hgc gene counts from metagenomes.

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Role of organic matter and microbial communities in mercury retention and methylation in sediments near run-of-river hydroelectric dams

Cited by 19 publications

References 93 publications

Microbial Diversity and Mercury Methylation Activity in Periphytic Biofilms at a Run-of-River Hydroelectric Dam and Constructed Wetlands

Microbial Diversity and Mercury Methylation Activity in Periphytic Biofilms at a Run-of-River Hydroelectric Dam and Constructed Wetlands

Impacts of dams on freshwater turtles: a global review to identify conservation solutions

A consensus protocol for the recovery of mercury methylation genes from metagenomes

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