Microbes Drive Methane Release from Wetlands
Study reveals how shallow wetlands act as hotspots for greenhouse gas generation.
Inland waters and wetlands are increasingly recognized as critical sites of methane emissions to the atmosphere, but little is known about the biological and geochemical processes driving the release of this powerful greenhouse gas from these ecosystems. A new study of microbial and geochemical processes in shallow wetlands known as “potholes” reveals that these wetlands are biogeochemical hot spots for some of the highest methane fluxes to the atmosphere ever reported.
The study’s findings reveal high concentrations of carbon and sulfur compounds in the Prairie Pothole Region wetlands of North America and that these wetlands support microorganisms that generate high levels of methane. Moreover, the results show that this region is a hot spot of geochemical and microbial activity and plays an important role in regional elemental cycling—the flow of chemical elements and compounds between living organisms and the physical environment.
Small ponds and lakes recently have been found to play an oversized role in degrading carbon and catalyzing fluxes of greenhouse gases such as methane and carbon dioxide to the atmosphere. The Prairie Pothole Region is a huge wetland ecosystem containing thousands of shallow wetlands that span five states in the United States and two provinces in Canada. This region’s wetland sediments contain some of the highest concentrations of dissolved organic carbon and sulfur compounds ever recorded in terrestrial aquatic environments. The observations suggest that these wetlands likely support high levels of microbial activity, which, in turn, could account for substantial greenhouse gas emissions from this ecosystem. To explore this possibility, researchers from The Ohio State University; Environmental Molecular Sciences Laboratory (EMSL), a Department of Energy Office of Science user facility; and the U.S. Geological Survey conducted one of the first studies of coupled geochemical and microbial processes driving methane emissions from Prairie Pothole Region wetlands. They collected sediment and pore water samples from these wetlands; used chemical analysis techniques to measure the concentrations of carbon, sulfur and methane; and conducted gene sequencing to identify members of the microbial community. They also performed in-depth chemical analysis of the dissolved carbon pools using 600-MHz nuclear magnetic resonance (NMR) spectrometers and the 12 Tesla Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer at EMSL. The findings suggest that conversion of abundant carbon pools into methane in the Prairie Pothole Region results in some of the highest fluxes of this greenhouse gas to the atmosphere ever reported. Moreover, high levels of carbon and sulfur compounds support some of the highest sulfate reduction rates ever measured in terrestrial aquatic environments. Taken together, the findings reveal a significant and previously underappreciated role for this ecosystem in supporting extremely high levels of microbial activity that directly impact terrestrial elemental cycling. As such, the results offer novel insights into how Prairie Pothole Region wetlands and other small inland waters act as hot spots for greenhouse gas generation.
Michael J. Wilkins
Ohio State University
This work was supported by the U.S. Department of Energy’s Office of Science (Office of Biological and Environmental Research), including support of the Environmental Molecular Sciences Laboratory (EMSL) and the DOE Joint Genome Institute, both DOE Office of Science User Facilities; U.S. Geological Survey Climate and Land Use Change R&D Program; and National Science Foundation.
P. Dalcin Martins, D.W. Hoyt, S. Bansal, C.T. Mills, M. Tfaily, B.A. Tangen, R.G. Finocchiaro, M.D. Johnston, B.C. McAdams, M.J. Solensky, G.J. Smith, Y-P Chin, and M.J. Wilkins, “Abundant carbon substrates drive extremely high sulfate reduction rates and methane fluxes in Prairie Pothole Wetlands.” Global Change Biology (2017). [DOI: 10.1111/gcb.13633]