Peatlands that soak up methane??

Northern peatlands store huge carbon stocks, but warming can cause them to decompose, releasing methane (CH₄) and carbon dioxide (CO₂). Methane traps heat far more efficiently than CO₂, so processes that control its release strongly affect climate feedbacks. Researchers thought CH₄ oxidation in peatlands was limited because few electron acceptors are available. A new study combined peat incubations, field‑based models of CH₄ and CO₂ concentrations, and stable‑isotope profiles to quantify CH₄ cycling in an inundated fen. Potential CH₄ oxidation rates reached almost 50 % of CH₄ production rates, even though the fen stayed waterlogged. Multi‑omic analyses (16S rRNA genes, metagenomics, and metatranscriptomics) showed that the methanotroph community was dominated by aerobic Methylobacter_C taxa with genomic potential for alternative electron acceptors. Methylobacter_C were actively expressing nirB and narG, consistent with respiration of nitrogen compounds. In contrast, anaerobic methanogenic ANME were detected only at the deepest depth and at very low abundance (0.026 %). CH₄ oxidation potential also remained high with depth, contrary to predictions from current ecosystem models, suggesting that deep‑peat and microaerophilic CH₄ oxidation may be underrepresented in peatland CH₄ budgets.

The study employed an integrated approach combining in‑situ incubations, field‑based modelling of CH₄ and CO₂ concentrations, and multi‑omic analyses to quantify methane cycling in a northern fen. Measurements of CH₄ and CO₂ levels, together with stable‑isotope profiles, allowed estimation of production and oxidation rates at different peat depths. Metagenomic data revealed abundant genes for methane oxidation, predominantly from Methylobacter_C, which also carry genes for nitrate and nitrite reduction. Metatranscriptomic profiling confirmed active expression of these genes, indicating functional metabolism even under low‑oxygen conditions. Anaerobic methanotrophic ANME were found only in the deepest layers and at trace levels, highlighting their niche role. Traditional ecosystem models often overlook deep‑peat CH₄ oxidation, where microaerophilic conditions can support aerobic methanotrophs. Incorporating these findings into climate models could refine predictions of peatland methane feedbacks and improve mitigation strategies.