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Research article - Peer-reviewed, 2022

The Influence of the Degree of Forest Management on Methylmercury and the Composition of Microbial Communities in the Sediments of Boreal Drainage Ditches

Bitenieks, Kriss; Bardule, Arta; Eklof, Karin; Espenberg, Mikk; Rungis, Dainis Edgars; Klavina, Zane; Klavins, Ivars; Hu, Haiyan; Libiete, Zane


Inorganic mercury (Hg) can be methylated to the highly toxic and bioavailable methylmercury (MeHg) by microorganisms in anaerobic environments. The Hg methylation rate may be affected by forest management activities, which can influence the catchment soils, water, and sediments. Here, we investigate the influence of forest management in the form of ditch cleaning and beaver dam removal, as well as the seasonal variations, on sediment chemistry and microbiota. The relationships between MeHg concentrations in sediment samples and archaeal and bacterial communities assessed by 16S rRNA gene amplicon sequencing were investigated to determine the microbial conditions that facilitated the formation of MeHg. Concentrations of MeHg were highest in undisturbed catchments compared to disturbed or slightly disturbed sites. The undisturbed sites also had the highest microbial diversity, which may have facilitated the formation of MeHg. Low MeHg concentrations and microbial diversity were observed in disturbed sites, which may be due to the removal of organic sediment layers during ditch cleaning and beaver dam removal, resulting in more homogenous, mineral-rich environments with less microbial activity. MeHg concentrations were higher in summer and autumn compared to winter and spring, but the temporal variation in the composition and diversity of the microbial community was less than the spatial variation between sites. Beta diversity was more affected by the environment than alpha diversity. The MeHg concentrations in the sediment were positively correlated to several taxa, including Cyanobacteria, Proteobacteria, Desulfobacterota, Chloroflexi, and Bacteroidota, which could represent either Hg-methylating microbes or the growth substrates of Hg-methylating microbes.


Hg; freshwater sediment; water catchment area; sediment microbiome; bacterial community; archaeal community; amplicon-based next-generation sequencing

Published in

2022, volume: 10, number: 10, article number: 1981
Publisher: MDPI

Authors' information

Bitenieks, Kriss
Latvian State Forest Res Inst Silava LSFRI Silava
Bardule, Arta
Latvian State Forest Res Inst Silava LSFRI Silava
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Espenberg, Mikk
University of Tartu
Rungis, Dainis Edgars
Latvian State Forest Res Inst Silava LSFRI Silava
Klavina, Zane
Univ Latvia
Klavina, Zane
Latvian State Forest Res Inst Silava LSFRI Silava
Klavins, Ivars
Latvian State Forest Res Inst Silava LSFRI Silava
Klavins, Ivars
Univ Latvia
Hu, Haiyan
Chinese Academy of Sciences
Libiete, Zane
Latvian State Forest Res Inst Silava LSFRI Silava

Associated SLU-program

SLU Network Plant Protection

UKÄ Subject classification

Environmental Sciences related to Agriculture and Land-use

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