Refining connections between the microbial methane cycle and trace contaminant biotransformations in managed wetland ecosystems

Microbial metabolisms facilitate the production and consumption of methane, contributing significantly to climate change and carbon cycling. At the same time, these dominant metabolisms influence trace contaminant biotransformations, which can have adverse impacts on aquatic ecosystems, human health, and food security.

This seminar highlights recent connections between the microbial methane cycle and trace contaminant biotransformations in two globally significant methane sources: wetlands and flooded rice paddies. The talk will first focus on methane consumption in constructed wetlands, where we combined field and laboratory studies to demonstrate that methane-oxidizing activity, mediated by the particulate methane monooxygenase, was strongly linked with the biotransformation of sulfamethoxazole, an antibiotic commonly observed in the environment.

Next, I will transition to methane production in flooded rice paddies, where we are investigating couplings between methylotrophic methanogenesis and arsenic demethylation, with implications for mitigating straighthead disease in rice. We show that amending soil slurries with trimethylamine promoted a tight but non-specific coupling between dimethylarsinic demethylation and multiple methylotrophic methanogenesis pathways.

In more complex greenhouse growth experiments, we further demonstrated that amending methanol-rich natural organic matter (i.e., dried leaves) to paddy soil favored greater net arsenic demethylation in porewater and resulted in less methylated arsenic accumulation in rice grains, relative to controls without organic matter amendment. Across both ecosystems, our findings illustrate how methane cycling processes can extend beyond greenhouse gas emissions, offering possibilities to harness microbial metabolisms for water quality improvement and sustainable agriculture.

Michael Vega is an applied biogeochemist interested in how microbial communities influence and can potentially be harnessed to solve environmental chemistry problems, with a focus on contamination and greenhouse gas dynamics. He received B.S. degrees in Geology and Chemistry from Kansas State University, then an MS in Hydrologic Science and Engineering and a PhD in Civil and Environmental Engineering, both from the Colorado School of Mines.

Currently, Michael is a Cornell Atkinson Postdoctoral Fellow housed within the School of Civil and Environmental Engineering, working with Dr. Matthew Reid.