Methane Biogeochemistry and Methanogen Communities in Two Northern Peatland Ecosystems, New York State

Rates of methane (CH4) production vary considerably among northern peat-forming wetlands, and it is not clear whether variability is caused by environmental factors affecting CH4 production or differences in methanogen communities. We investigated CH4 production and emission dynamics concomitantly with 16S rRNA gene sequence-based community analysis of Archaea in two contrasting peat-forming northern wetlands, an ombrotrophic bog and a minerotrophic conifer swamp. Individual measurements of CH4 emissions to the atmosphere followed a lognormal distribution pattern in both sites, and mean rates were 30× greater in the bog site. Rates of CH4 production measured in vitro were initially 3× greater in the bog than in the conifer swamp; although, after 30 days of incubation, production rates were similar suggesting that in situ environmental conditions limited production in the conifer swamp. Amplified ribosomal DNA restriction analysis (ARDRA) and rarefaction techniques indicated that both sites had similar levels of archaeal richness, with 27 unique taxa in the bog and 23 taxa in the conifer swamp. However, the bog had more pronounced dominance of a few taxa, whereas the conifer swamp had more even distribution among taxa. A 16S rRNA gene sequence-based phylogenetic analysis indicated high levels of diversity with similarity to known methanogenic families Methanosarcinaceae, Methanosaetaceae, Methanobacteriaceae, and likely Methanomicrobiaceae as well as two additional lineages previously characterized as groups of yet uncultivated Euryarchaeota commonly occurring in flooded rice soils. Therefore, sites with low and high rates of CH4 production supported very diverse methanogenic communities.