Geochemical Evidence of Microbial Communities on Carbonate Rocks From the Gulf of Mexico

Science Center, Bent Corridor

Authigenic carbonates from the deep continental shelf and slope of the Gulf of Mexico (GOM) from sites GC600 (1,200 m) and MC118 (1,000 m) were analyzed using trace elemental geochemical signatures for evidence of microbial communities. The continental shelf is characterized by over 10 km of Mesozoic-Cenozoic sediment, which is ideal for the formation and accumulation of large oil and gas reserves (Formolo et al., 2004). Since GOM is affected by both natural petroleum seepage and spilled petroleum, it serves as an ideal environment for various microorganisms.The presence of microbial communities can be detected by measuring rates of denitrification (DNF), sulfate reduction (SR), and aerobic and anaerobic methane oxidation (MO) over time points of 0,2, and 7 days. Microbial activity often drives cold seep ecosystems by first oxidizing methane and other hydrocarbons to produce alkalinity and bicarbonate, leading to the formation of authigenic carbonate precipitation (Joye et al., 2010). These carbonate rock precipitates then provide substrate for large communities of deep sea organisms. Based on the measured rates of DNF, SR and MO, there is evidence that microbial communities are abundant and thriving on these carbonate rocks at hydrocarbon seeps in the Gulf of Mexico.