Methane Dynamics in Marine Systems

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Laboratory and field experiments were performed to investigate methane (CH4) in marine systems. Laboratory experiments explored the impact of aerobic CH4 oxidizing bacteria on the dissolution process of CH4 hydrate. The pure culture, Methylomicrobium album, grew at high pressure (34 atm), but not at low temperature (15°C). Hydrate was formed in media containing culture, but was not stable to perform dissolution experiments. The culture used was found to be unsuitable for hydrate dissolution experiments. Field experiments were performed in the Chesapeake Bay estuary, where CH4 concentrations were measured in bottom water and sediment pore-water. Results showed that bottom water CH4 concentrations increased to 40μM in mid-July, which coincided with decreasing oxygen concentrations and decreasing CH4 concentrations, which coincided with increasing oxygen concentrations in the fall. These observations supported the hypothesis that estuarine emissions of CH4 are being enhanced by seasonal hypoxia and that estuarine CH4 emissions may be currently underestimated.