Deepwater Horizon crude oil deposited on Gulf coast beaches by storm waves was subsequently covered by layers of sand and now is found in inch-thick slabs buried as deep as 60 cm within the supratidal zone of the beaches. Some of the oil-contaminated sand was machine-sifted on site, which produced thick sand layers with a large number of embedded pea-size oil particles. Fate and potential impact of oil layers and oil particles on beach ecology and water quality are not understood. The proposed study investigates degradation of Deepwater Horizon oil embedded in Gulf sandy beaches and the processes that affect this decomposition.
The project will:
1. Produce quantitative data on the degradation rates of oil embedded at different depths ( 0-60 cm) in permeable dry beach sand and assess the changes in oil chemical composition over a time period of one year
2. Quantify oil degradation in sand sediments flushed by pore water for different flow rates and oxygen concentrations in the water
3. Analyze the long-term response of the microbial community associated with the embedded oil
4. Identify microbial species that are indicative of oil degradation in Gulf beach sands
The methods include in-situ experiments at Pensacola Beach on embedded oil degradation, laboratory column reactor experiments addressing oil degradation in beach sands percolated by seawater, identification of microbes extracted from the contaminated sands and culturing of the dominant oil degrading bacteria. Oil will be characterized using a GC-MS and a spectrofluorometer. Changes in microbial community composition and activity will be assessed using a combination of culture-based and cultivation-independent molecular techniques.
The educational component of this project includes training of four undergraduate students and three graduate students and their participation in the listed experimental work, and lectures on the ecological impacts of the oil spill within the courses "Marine Pollution" and "Microbial Ecology" offered by the two PIs. The PIs will continue their outreach activities through public lectures, and through the publication of results in scientific journals, news media and dedicated web pages.
The sandy beaches of the northeastern Gulf of Mexico are biotope, foraging and breeding areas of a large number species, and present a main tourist attraction. Their contamination thus can have severe ecological and economical consequences. The results of this study will improve estimates of the duration of the contamination caused by the embedded oil and the recovery period of the beaches. The data produced in this study will provide information needed for decisions regarding the most effective methods for cleaning the contaminated beaches, e.g. whether sifting accelerates the beach recovery. Our results on microbial indicator species will be used to produce a quantifiable measure for the degree of oil contamination.