Casual Observations on DWH Dispersant Effects Expose the Lack of Rigorous Science: Response to Rorick and Colleagues

Robin Rorick, of the American Petroleum Institute (API), and his colleagues question our doubt that subsurface dispersant application was required to prevent Deepwater Horizon (DWH) oil from reaching the sea surface. The photographs provided as support for the need for and efficacy of subsurface dispersant do not allow scientifically rigorous conclusions in the absence of quantitative measurements of subsurface processes and dynamics of materials transport. Despite our close connectivity to industry, government, and academic research, we are unaware of any compelling, peer-reviewed data documenting the efficacy, necessity, and consequences of subsurface dispersant application during the DWH spill. Rorick and his colleagues’ assertions reinforce long-standing concerns that oil spill responses are not based on sufficient science. We expect a higher level of commitment to excellence from an industry capable of so much more.

We questioned the unsupported assumption that the vast majority of hydrocarbon retention at depth is attributable solely to subsurface dispersant use. Rorick and his colleagues’ argument regarding Johansen and colleagues (2003) contradicts our understanding of that experiment. In a review of the study, Adams and Socolofsky (2005) noted that, in the absence of dispersants and under even less favorable conditions (shallower, colder, less turbulent water) for generating natural dispersion than those of the DWH blowout, “most oil was not recovered at the surface, suggesting it was in the form of widely dispersed fine droplets” (p. 1). Even assuming that Rorick and his colleagues are correct, their own calculations suggest as little as 5% of the oil may have reached the surface in that study. By emphasizing the dubious high-end estimate of 90%, they reinforce our argument that unequivocal data are not available and that rigorous, process-oriented study is necessary.

Quantifying the behavior, transport, fate, and effects of hydrocarbons from deepwater blowouts, with and without dispersants at various application rates, is fundamental to the public interest. Because subsurface dispersant application is increasingly touted as a necessary new response method, rigorous scientific answers to questions not only of efficacy but also of the impact of subsurface retention of highly dispersed oil-dispersant droplets on particle feeders and an array of other organisms throughout the water column are urgently needed. Such answers do not come from a few photographs. Rorick and his colleagues’ restricted focus solely on preventing oil from reaching the sea surface reflects a failure to acknowledge the need for a new oil spill model that includes an assessment of risk below the surface following deepwater blowouts. We welcome formal, process-oriented data and urge API to pursue such studies.