Among the responses to the April 2010 Deepwater Horizon oil spill was the spraying of more than 1.8 million gallons of the dispersant Corexit 9500 into the waters of the northern Gulf of Mexico. The effect of the dispersant is to break up subsurface and surface oil slicks into tiny oil globules that are more readily dissolvable sea water. Oil that is dissolved in seawater is more available for degradation by hydrocrabon-eating bacteria. However, persistent concerns have surrounded the use of dispersants, in particular their impact on the marine environment. Recent studies suggest that a Corexit-oil mixture may be substantially more toxic to marine life than the oil alone. Now, SoMAS faculty members Bruce Brownawell and Anne McElroy, along with colleagues at Mississippi State University and Duke University, will be making a thorough examination of the potential environmental effects of dispersant use. With funds provided by the Gulf of Mexico Research Initiative (GOMRI, see below), Brownawell and McElroy will look not just at dispersants themselves—their toxicity, sorption and occurrence in seafood—but also that of the transformation products resulting from the microbial degradation of the dispersants. Most of the analytical methods developed for this type of detective work were designed for hydrophobic compounds, compounds that dissolve poorly or not at all in water. The ability of dispersants to dissolve in sea water makes them more difficult to track. In the planned work, Brownawell will look at how dispersants bind to or interact with sediment and what degradation products are produced in this interaction. McElroy will examine the toxicity of dispersants and their degradation by-products to marine life, in particular various life-stages of sheepshead minnow, a ubiquitous inhabitant of shallow bays, estuaries, marshes and sloughs along the U.S. Atlantic and Gulf coasts.
The primary objective of GoMRI is to investigate the impacts of oil, dispersed oil, and dispersants associated with the Deepwater Horizon spill on the ecosystems of the Gulf of Mexico and affected coastal states in a broad context of improving fundamental understanding of the dynamics of such events and their environmental stresses and public health implications. The GoMRI will also develop improved spill mitigation, oil and gas detection, characterization and remediation technologies. GOMRI is funded by British Petroleum, owner of the Deepwater Horizon well, through a Master Agreement with the Gulf of Mexico Alliance, a partnership involving the five Gulf states. Program and funding decisions under GOMRI are advised by a 20-member blue-ribbon Research Board.