Methane is a potent greenhouse gas with approximately 20 times the global warming potential of CO2. The largest reservoirs of methane reside in gas hydrates, located in deep ocean sediments and arctic permafrost. Gas hydrates are structures of lattice ice that trap gas molecules, primarily methane. These gas hydrates form under high pressure and low temperature conditions. Fluctuations in these parameters impact the stability and dissolution rates of hydrates. In addition to temperature and pressure, microbial activity has the potential to impact hydrate dissolution rates. Methanotrophs colonize the area surrounding gas hydrates in nature, and have the potential to oxidize the hydrate containing methane to carbon dioxide. This study explores this potential link between methanotrophs and methane dissolution in gas hydrates. Initial experiments determine the capacity of two species of methanotrophs, Methylococcus capsulatus and Methylosinus trichosporium, to grow under hydrate formation conditions. Growth of these cultures is monitored by measuring concentrations of methane and CO2 present in the culture headspace using gas chromatography. We hypothesize that cultures of these species will grow at a reduced rate under hydrate formation conditions. Once growth under hydrate formation conditions is established, further experiments will monitor changes in carbon stable isotopic composition in an inoculated high pressure chamber containing gas hydrate, using cavity ring-down spectroscopy. We hypothesize that the presence of methanotrophs will increase the carbon stable isotopic composition in the pressure chamber over time. Results of these experiments could provide evidence to suggest that methanotrophs help to mediate the release of methane from gas hydrates through the conversion of released methane to CO2.

Impact of methanotrophy on methane gas hydrate dissolution rates

249th National Meeting (2015)

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