The Ecology of Methanogenic Archaea in a Nutrient-Impacted Wetland

Wetlands are the largest natural sources of methane, and many wetlands are subject to nutrient enrichment due to runoff from adjacent agricultural and urban lands. Methanogenic archaea are responsible for much of the methane produced in terrestrial wetlands and participate in a range of additional activities including nitrogen fixation and mercury methylation. Nutrient enrichment may impact the dominant metabolic groups of methanogens, such that the fundamental activities of methanogens may be associated with the nutrient status of the wetland. Regions of the Everglades, a large marsh in the southern part of Florida, in the USA, are subject to nutrient enrichment and are characterized by a gradient in available phosphorus, organic carbon, and sulfate concentrations. This marsh provides an outstanding system in which to study the impacts of nutrient enrichment on the distribution and activities of methanogens. Competition for acetate with sulfate-reducing prokaryotes plays an important role in structuring methanogenic consortia in nutrient-impacted regions, and the potentials for methanogenic nitrogen fixation and mercury methylation differ along the nutrient gradient.