An estimated 6.9 million liters of dispersant were applied in the Gulf of Mexico in response to the Deepwater Horizon oil spill with approximately 4 million liters deployed to surface waters 2.9 million liters utilized for sub-sea applications. Formulations of COREXIT®, a family of oil dispersants, were the primary agents utilized in this effort. Acute toxicity parameters for these dispersants have been established, but the synergistic effects of weathering and salinity on these oil/dispersant mixtures on aquatic biota are not well known.
A continuing issue facing oil spill responders centers on the decision whether or not to use dispersants during oil spills, and estimating environmental damages of those decisions. Advocates of dispersant use assume that dispersed oil increases toxicity at the site of dispersion (less productive, deeper waters) but reduces toxicity in more productive, inshore habitats by accelerating the biodegradation of dispersed oil such that less oil reaches more productive shallow waters. However, these assumptions do not consider the possible synergistic effects of weathered oil and dispersant in variable saline environments on the bioavailability and toxicity to coastal fish.
The goals of this project are to investigate the effects of dispersant and salinity on the degradation of South Louisiana Crude Oil, and the interactive effects of varying oil degradation on the toxicological, physiological, and genotoxic responses in an estuarine fish common to Louisiana’s coastal marshes. This proposal will assemble an integrated team of researchers to evaluate several hypotheses related to the physical processes of oil degradation and the influence of these processes on the bioavailability and toxicity of these chemicals on the Gulf killifish (Fundulus grandis).
Our team will accomplish this via the following objectives:
- Characterize effects of weathering and dispersion on lethal and sublethal toxicity of oil across a range of salinities. Laboratory experiments will create a range of conditions including un-dispersed and dispersed oil allowed to biodegrade for varying durations at a range of salinities. All water and soil from these manipulations will be collected for analysis and fish exposed to these conditions will be harvested for acute toxicity testing and sublethal endpoint analysis.
- Determine the role of weathered and dispersed oil on fish membrane permeability and whole-animal ion regulation. The gill epithelium of fish is the major site of interaction and uptake of aromatic hydrocarbons in fish. Experiments will characterize the effects that weathered crude and dispersant, at different environmental salinities, exert on this epithelium and physiological processes that are altered by changes in its permeability.
- Determine if weathering or surfactant mediated dispersion alters the genotoxicity of crude oil. A hallmark of many hydrocarbons inherent in crude oil is their ability to form DNA adducts. This aim will determine the amount of DNA damage caused after exposure to crude oil and whether mitigating factors, such as weathering and surfactant dispersion, alter the magnitude of induced DNA damage.
Completion of the aims outlined in this proposal will allow this multi-disciplinary and multi-institutional group of researchers to determine if weathering and/or dispersion of crude oil alters its toxicity in a pivotal Gulf coast species at environmentally relevant salinities.