Beyond the usual suspects: methanogenic communities in eastern North American peatlands are also influenced by nickel and copper concentrations

Abstract

Peatlands both accumulate carbon and release methane, but their broad range in environmental conditions means that the diversity of microorganisms responsible for carbon cycling is still uncertain. Here we describe a community analysis of methanogenic archaea responsible for methane production in 17 peatlands from 36 to 53 N latitude across the eastern half of North America, including three metal-contaminated sites. Methanogenic community structure was analyzed through Illumina amplicon sequencing of the mcrA gene. Whether metal-contaminated sites were included or not, metal concentrations in peat were a primary driver of methanogenic community composition, particularly nickel, a trace element required in the F430 cofactor in methyl-coenzyme M reductase that is also toxic at high concentrations. Copper was also a strong predictor, likely due to inhibition at toxic levels and/or to cooccurrence with nickel, since copper enzymes are not known to be present in anaerobic archaea. The methanogenic groups Methanocellales and Methanosarcinales were prevalent in peatlands with low nickel concentrations, while Methanomicrobiales and Methanomassiliicoccales were abundant in peatlands with higher nickel concentrations. Results suggest that peat-associated trace metals are predictors of methanogenic communities in peatlands.

Global Patterns of Metal and Other Element Enrichment in Bog and Fen Peatlands

“…Additionally, metal enrichment in surface peat may not be solely caused by atmospheric deposition because biogeochemical processes in peatlands may lead to enrichment of metals in surface soil horizons (Reimann and De Caritat 2000). Metal in peatlands also serve as key enzyme cofactors (e.g., Ni, Cu, Fe, Mb) and low levels can constrain microbial activity (Glass and Orphan 2012; Bear et al 2021). On the other hand, high concentrations of metals can be toxic to plants and microbes, reducing their abundance and productivity (Glass and (smelters, metal processing).…”