Measuring efficacy of bioremediation of oil spills: Monitoring observations, and lessons from the apex oil spill experience
Bioremediation treatment and monitoring were observed at an oiled marsh in upper Galveston Bay, Texas, August 5 to 8, 1990, during response to the oil spill created by the collision of three Apex barges and the tanker Shinoussa. Samples of oil from treated and untreated sites were collected and independently analyzed for evidence of biodegradation. Required monitoring protocols for water and sediment quality and acquisition of samples for chemical analysis were expertly adhered to. Visual observations indicated that the treated oil experienced color changes. However, after several days there were no significant visual differences in oil appearance in treated and untreated plots. Chemical analyses from samples collected by observers (independent of the required monitoring program) indicated that there were also no apparent chemical differences in petroleum hydrocarbon patterns between treated and untreated plots. Water from one or both of two treated sites was toxic to mysid shrimp; it is possible that micronutrients (trace elements) in the nutrient mix may have contributed to that toxicity, Increased monitoring is needed to demonstrate the efficacy and effects of bioremediation.