Dynamic sulfur pools as a control on methane flux in freshwater Prairie Pothole lacustrine sediments
EMSL Project ID
48837
Abstract
Inland waters (wetlands, lakes) play a poorly constrained role in regional and global carbon cycling, and may account for much of the uncertainty in climate change models. Although lake sediments are generally thought to efficiently sequester organic carbon (OC), the formation of methane (CH4) and carbon dioxide (CO2) by microbial activity contributes significantly to greenhouse gas emissions. The prairie pothole region (PPR) of North America spans five US states, and two Canadian provinces, and is characterized by millions of small lakes that contain some of the highest dissolved organic carbon (DOC) concentrations ever measured in freshwater systems, in addition to elevated abundances of sulfur species from the weathering of glacial till. While abundant DOC inputs may represent labile substrates for microbial activity (such as methanogenesis), sulfur species in lacustrine pore waters may constrain methane generation, in a similar manner to marine continental shelf sediments where methane emissions are an order of magnitude smaller than those from rice paddies or terrestrial wetlands. We hypothesize that seasonal inputs of labile DOC to prairie pothole lake sediments will drive reduction of the aqueous and solid-phase sulfur pool, thus affecting constraints on methanogenesis and sulfate-dependent anaerobic oxidation of methane (AOM). We are currently investigating these concepts at the Cottonwood Lakes research site near Jamestown, ND, where we have performed preliminary microbiology and geochemistry analyses through the collection of sediment cores. We plan to further these analyses through a series of research aims that enable testing of specific hypotheses. Our approach will use complementary cutting-edge geochemical and microbiological analyses including assembly-based community (meta)genomics and radiotracer rate measurements for sulfate-reduction and AOM. We will investigate CH4 concentrations and fluxes through sediment columns, and determine the microbial drivers behind production and consumption of this key greenhouse gas. Rate measurements for AOM will be used to determine spatial and temporal ‘hotspots’ of CH4 consumption. Characterizing carbon inputs to sediment pore waters is a key component of this research, and we are requesting EMSL resources (nuclear magnetic resonance (NMR) and fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)) to perform this aspect of the work. FT-ICR-MS will be used to characterize the pool of carbon compounds in DOC, while proton and carbon-based NMR will be used to measure labile substrates (e.g. acetate, lactate) that likely drive microbial metabolism. Further, we are requesting transcriptomic RNA-Seq analyses at EMSL to identify the activity of key microbial species within this ecosystem. The combination of sequence-based analyses, rate measurements for key biogeochemical processes, and high-resolution geochemical characterization of carbon pools will enable a greater understanding of coupled carbon and sulfur cycling in this critical eco-region of North America that may play an underappreciated role in regional greenhouse gas emissions.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2015-10-01
End Date
2017-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Dalcin Martins P, DW Hoyt, S Bansal, C Mills, MM Tfaily, BA Tangen, RG Fincchiaro, MD Johnston, BC Mcadams, MJ Solensky, GJ Smith, YP Chin, and MJ Wilkins. 2017. "Abundant carbon substrates drive extremely high sulfate reduction rates and methane fluxes in Prairie Pothole Wetlands." Global Change Biology 23(8):3107–3120. doi:10.1111/gcb.13633
Dalcin Martins P, Frank J, Mitchell H, Markillie LM, and Wilkins MJ (2019) Wetland sediments host diverse microbial taxa capable of cycling alcohols. Applied and Environmental Microbiology. doi: 10.1128/AEM.00189-19