Micro-Biogeochemical Interactions in Hydrocarbon Rich Surface and Shallow Aqueous Systems

This research reports recent advances towards understanding the plausible role that microbes play in the biogeochemical interactions that take place in hydrocarbon-rich surface and shallow aqueous systems. The relationship between microbial activity and hydrocarbon production are currently being targeted for natural gas development and environmental remediation. We used geochemical, stable isotope, and membrane lipid analyses to investigate the geochemical changes and microbial community structure associated with hydrocarbon spills in surface and shallow environments. Soil and water samples were collected from springs and wells within the Edwards Aquifer and fractured Eagle Ford Shale near San Antonio, TX. Geochemical analyses were performed on the water samples using the Ion Chromatograph (IC) at the Institute for Water Resources Science and Technology, Texas A&M University-San Antonio; Inductively coupled plasma atomic emission spectroscopy (ICP-OES) and Inductively coupled plasma mass spectrometry (ICP-MS) at the University of Houston. The geochemical measurements in the water samples showed a decrease in sulfate concentration with a corresponding increase in sulfide concentration over sample collection distance. The corresponding decrease in sulfate and increase in sulfide concentration suggest that microbial activity, probably involving thiosulfate reduction, could be responsible for the generation of sulfide in the water samples. On the other hand, microbial membrane lipid and metagenomic analyses will be performed on the water and soil samples at the University of Tennessee to elucidate the microbial community structure and composition. The membrane phospholipid and diglyceride fatty acids (PLFA and DGFA) represent some of the most important proxies for microbial signatures in natural environmental systems. We will use the lipid biomarkers to investigate the possible effects of hydrocarbon on the microbial community composition and biomass. The better we know about the influence of hydrocarbon presence on the microbial community composition of surface and shallow aquifer systems - like the Edwards Aquifer and fractured Eagle Ford Shale near San Antonio, TX - the better we can improve environmental bioremediation in hydrocarbon development and water quality assessment.