Methane production in peatlands

Abstract

Methane emissions from peatlands have been researched for decades, although our understanding of methane production at microbial scales is still limited, and this may hamper our ability to predict methane emissions from site-to regional- to global scales. Here, a multi scale approach is used to expand on current knowledge related to the controls and the microbial community responsible for methane production within peatlands. For the first time, an analysis of methane production from a global, coordinated sampling effort was done using a standardized laboratory methodology. Site pH and plant communities were shown to be the best predictors of methane production at the global scale, while peat organic chemical characteristics and abiotic factors including temperature, moisture, and nutrient concentrations, were also shown to be important. Around 5% of samples showed disproportionately high methane emissions compared to CO2. The second research project narrowed focus to a regional scale: peatlands in the Sudbury, ON region were evaluated to assess the role historic and contemporary smelting activities, and subsequent metals and sulfur deposition, have had on the methanogen community composition and methane production. In comparison to most peatland studies, the methanogens present in impacted sites were largely unclassified at the order level and production of methane was dramatically decreased compared to the reference locations. The third research project in the thesis focused even more exclusively at the microbial scale: enrichments of peat were used in an attempt to isolate novel methanogens. While no pure culture isolates were obtained, novel methanogens at the genera and species level where obtained from five of the seven known methanogenic archaeal orders. The case is made that obtaining enrichment (mixed) cultures is an important, underused methodology for discovering and learning about novel methanogens, which have very tight, perhaps inseparable, syntrophic relationships with other anaerobic microbes. Combining culture techniques with modern sequencing technologies was explored as a way forward in obtaining novel species genomes and related growth conditions. Taken together, the overall controls on methane production at global and local scales are commonly peat pH, plant community composition, and peat quality, while the methanogen communities responsible for methane production remain largely unknown and underrepresented in culture collections highlighting the need for further enrichment and isolation work.