Marine cold seeps are natural pipelines connecting the sub-seafloor and seafloor biospheres through upward migration of geofluids and gases. The seabed microbiome in and around cold seeps often has an anomalous community structure consisting of taxa generally observed in deeper subsurface ecosystems. This project will utilize microbial community assessment of a large number of marine sediments from the Eastern Gulf of Mexico to evaluate subsurface taxa associated with hydrocarbon seepage. Concentrations of migrated petroleum hydrocarbons will be monitored in these sediments by geochemical analyses and further correlated with taxa abundance. The findings of this project will determine whether detection of certain subsurface taxa should be integrated in microbial prospection of natural hydrocarbon seeps.