Microbial changes, including methanogens, influenced by arsenic speciation in anaerobic wetland environments

Methylated and inorganic arsenic species are frequently detected in natural water systems due to anthropogenic activities and geological origins. However, the impact of arsenic species on microbial activity, particularly on methanogens responsible for methane production, remains underexplored. This study investigates the effects of arsenic on methanogenesis by adding iAs(V) and DMA(V) to wetland sediment batches and monitoring arsenic speciation in the supernatant and methane production over time. Changes in arsenic behavior in the sediment were analyzed using X-ray Absorption Fine Structure (XAFS). Microbial diversity analysis revealed that while iAs(V) acted as an electron acceptor and its reduction to iAs(III) inhibited methanogen activity due to its toxicity, DMA showed minimal effects on methane production. These findings demonstrate that arsenic dynamics in wetlands influence methane-producing microorganisms, with inorganic form of arsenic species posing significant inhibitory effects, whereas less toxic DMA(V) appears to have limited impact. This might shed light on the potential for regulating methane emissions in arsenic-contaminated wetlands.