HR: 1340h
AN: B53A-0933    [Abstracts]
TI: Methanotrophic Bacteria Maintaining and Coexisting With a Methanogenic Consortium in Soils at Man-Made Natural gas Seeps at Petroleum Well Sites in Western Canada
AU: * Arkadakskiy, S
EM: serguey.arkadakskiy@isobrine.com
AF: Isobrine Solutions Inc., Suite 3060, 8308-114 St., Edmonton, AB T6G 2V2, Canada
AU: Muehlenbachs, K
AF: University of Alberta, 3-22 ESB, Department of Earth and Atmospheric Sciences, Edmonton, AB T6G 2E3, Canada
AB: Unwanted leakage of natural gas (>90% vol. CH₄) in soil is ubiquitous at petroleum well sites in western Canada. Long term monitoring at several of those man-made seeps demonstrates that aerobic methanotrophy is the most important microbially mediated process in the soil. Bacterial oxidation of methane is severely impeded by soil freezing in winter and also in soils contaminated with liquid hydrocarbons. Soil gas compositions and carbon stable isotope data demonstrate that bacterial methanogenesis also occurs in deeper sections of the soil column at a number of the seeps. While methanogenic activity is common in soil contaminated with liquid hydrocarbons, it is also detected in soils where no evidence of oil contamination has been found (i.e., in "clean" soils). Methanogenic activity in "clean" soils occurs in the summer when soil temperature and moisture are comparatively high. Results also demonstrate that at this time of the year metanotrophic bacteria move upwards in the soil column whereby consuming nearly all available oxygen methanotrops are, thus, providing a habitat for the methane producing microorganisms. The concentrations of electron acceptors other than CO₂ (HCO₂) in soil moisture are very low or below detection, hence, indicating that methanogenesis is the energetically favorable terminal electron acceptor process in this environment. Conspicuous lack of soil biomass of methanotrophic origin evident from the low concentrations of soil organic matter (SOM) and the comparatively high carbon stable isotope composition of SOM, suggests that fermenting bacteria from the methanogenic consortium metabolize lysed cells and polysaccharide film left over from the demise of methanotrophic bacteria in winter, therefore practically feeding of the latter. Methane generated by the methanogens mixes with leaking gas and it is, sometimes, completely consumed by the methanotrophs. The seasonal interplay of methanogenic and methanotrophic bacteria at the man-made natural gas seeps in western Canada is a remarkable example of the ability of the soil microorganisms involved in the methane cycle to coexist and rapidly adapt to diverse environmental conditions.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0428 Carbon cycling (4806)
DE: 0448 Geomicrobiology
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0490 Trace gases
SC: Biogeosciences [B]
MN: 2007 Fall Meeting