oa Biogeophysical Monitoring of the Microbial Degradation of Crude Oil from the BP Deep Horizon Oil Spill

The BP Deep Horizon oil spill, although an unfortunate incident, presents a unique opportunity to utilize geophysical methods to investigate at the physical, chemical, and biological transformation of fresh crude oil in a highly saline environment and specifically investigate if the biotransformation of the oil will cause the electrical signature of the sediment to change over time. Based on the depictions of the contaminate concentration on the shores of the Gulf of Mexico, the island Grand Terra 1, located off of Louisiana was selected as the location of the survey site. <br>We are performing geophysical, geochemical and microbiological measurements. We have deployed an autonomous resistivity monitoring system that addressed thirty-two stainless steel electrodes at a half-meter spacing. This automated system was created to monitor and acquire electrical resistivity in the form of time-lapse geophysical measurements. Soil samples were collected at predefined time intervals for microbiological and geochemical analysis. Our aim is to determine the microbial community structure and dynamics in response to the crude oil spill, to capture the biodegradation of the crude oil, and link time evolving electrical geophysical signatures to biodegradation of the oil spill.<br>Initial data acquired from GT1 during a reconnaissance trip included electrical resistivity data and soil samples for microbial analyses. Post acquisition processing of the collected data produced a 2D resistivity model of the subsurface, which demonstrates that the electrical geophysical technique is not just able to detect the presence of hydrocarbons in the subsurface as a relatively small but still distinctive resistive anomaly, as would be expected of a fresh oil spill which has not yet undergone extensive biodegradation, but could also be utilized to delineate the oil-impacted sediments. This result suggests that electrical resistivity may be a useful technique in both the short term for characterizing the full extent of the oil impacted zones as well for the long term monitoring the biodegradation of the oil.