Microbial Degradation of Refractory Organic Carbon During Rock Weathering

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AbstractMicrobial Degradation of Refractory Organic Carbon during Rock WeatheringByK.J. Edwards, T.I. Eglinton, S.T. PetschDepartment of Marine Chemistry and GeochemistryWoods Hole Oceanographic InstitutionWoods Hole, MA 02543An important component of the carbon cycle is transfer of organic carbon from ancient sedimentary rocks to the oceans and atmosphere. Oxidation of ancient sedimentary organic matter during rock weathering and soil formation consumes O2 and releases CO2, thus providing a strong control on the composition of Earth's atmosphere over geologic time scales. This study investigates the role of microbial activity in the degradation and oxidation of sedimentary organic matter during rock weathering. We have determined that there are microorganisms living within shallow-subsurface sedimentary rocks. Compound-specific 14C analysis of cell membrane lipids was used to establish that in culture, these organisms are assimilating refractory, rock-derived organic carbon as their carbon source. Future investigations of this study include: Compound-specific 13C and 14C analysis of microbial lipids from environmental samples to determine carbon pathways in nature environments of rock weathering. Phylogenetic analysis of microorganisms in field samples and lab cultures to establish community structure and comparison with known organisms. Fluorescent in-situ hybridizations of microbial cells with iteratively more specific probes to examine spatial relationships between microorganisms, organic matter and minerals in weathering environmentsArray-detector infrared spectroscopy to provide microscale description of organic matter composition within sedimentary rocks and correlations with microbial growth patterns.Analysis of abundance and composition of dissolved organic compounds released through microbial activity compared with sterile controls to contrast rates of oxidation versus dissolution of ancient sedimentary organic matter.From this study will emerge an unprecedented description of the influence microbial activity has on oxidation of ancient sedimentary organic matter during rock weathering, with direct applicability towards understanding of global scale carbon cycling and controls on the composition of Earth's atmosphere.