DETERMINING GEOCHEMICAL AND INITIAL BIODEGRADATION RESPONSE TO DRILLING FLUID SOUTH MCMURDO SOUND, ANTARCTICA

The Antarctic Drilling Program (ANDRILL) Southern McMurdo Sound Project (SMS) utilized readily biodegradable drilling fluids to recover an 1142 m sedimentary rock core. During the core recovery a total of 5.6×10⁵ liters of drilling fluid were lost to the subsurface. The introduction of an easily biodegradable organic source found in the drilling fluid may cause an increase in microbial activity within the sediments and could alter the in situ microbial ecology and geochemistry. The goal of this research was to determine geochemical and initial biodegradation response to drilling fluid used during the SMS core recovery. This biodegradation experiment utilized drilling fluid samples that were collected onsite during the SMS core recovery. Aliquots were incubated in conditions similar to those of the subsurface for specific time intervals to monitor biodegradation over time. To study the significant chemical changes, data was collected for seven different chemical parameters; dissolved oxygen, pH, conductivity, total carbon, total nitrogen, major anions, and major cations. The anions were analyzed using a High Performance Liquid Chromatograph (HPLC). The cations were analyzed using a High Resolution Inductively Coupled Plasma-Mass Spectrometer (HR-ICP-MS). Two different methods were used to study the microbial population on a community based level. Biolog EcoPlates™ were used to study the metabolic diversity of the viable microbial communities. Polymerase chain reaction (PCR) methods using RAPD (random amplification of polymorphic DNA) primers were used to analyze the bacterial community structure and determine the microbial diversity between samples. To date, results indicate shifts in the microbial population with time along with changes in the geochemistry, both of which are signs that biodegradation is occurring. The results from this study are important to understanding the impact of drilling fluids on pristine environments.