Factors Influencing Microbial Gas Production Rates in a Constructed Wetland Ecosystem

Constructed wetlands provide a valuable ecosystem service by sequestering carbon dioxide from the atmosphere and serving as a sink for atmospheric nitrogen export. Unfortunately, carbon sequestration and denitrification in wetlands come with the tradeoff of increased production of methane – another more potent green house gas. Methane is produced by methanogenic archaea that thrive in chemically reduced, anaerobic zones of the wetland. Dinitrogen export, on the other hand, is thought to occur under suboxic conditions by denitrifying bacteria. Few studies have examined the in situ rates of metabolic activity for dominant microorganisms driving these processes or systematically evaluated the key factors controlling their metabolic rates in wetland environments. This research evaluates how three environmental factors: temperature, wetland biome, and redox environment relate to microbial ecology and in situ gas production in a constructed wetland ecosystem located in central Ohio. Microbial measurements provide information about instantaneous fluxes under differing environmental conditions but are not necessarily representative of long-term fluxes that may be quantified using surface chamber measurements or atmospheric eddy-covariance methods. The objective of this research is to develop upper limit estimates for in situ microbial gas production rates under differing environmental conditions so that we may better understand how they relate to spatiotemporal surface and plot-scale emission rates also measured at the site.