Influence of Ni, Co, Fe, and Na additions on methane production in Sphagnum-dominated Northern American peatlands

Although Sphagnum (moss)-dominated, northern peatland ecosystems harbor methane (CH4)-producing microorganisms (methanogens) and are a significant source of atmospheric CH4, rates of CH4 production vary widely among different systems. Very little work has been done to examine whether concentrations of cations and metal elements may account for the variability. We examined rates of CH4 production in peat from five geographically and functionally disparate Sphagnum-dominated peatlands by incubating peat samples in vitro with and without additions of trace metals (Fe, Ni, Co) and base cations (Ca, Li, Na). In peat from the most mineral poor sites, the addition of metals and Na enhanced CH4 production beyond that observed in controls. The same treatments in mineral rich sites yielded no effect or an inhibition of CH4 production. None of the treatments affected anaerobic respiration, measured as CO2 production, in the in vitro incubations of peat, except added citrate, suggesting that methanogens, and not the entire anaerobic community, can be limited by the availability of metal elements and cations.