Future oil exploration and marine navigation may well extend into the Arctic Ocean, and government agencies and responders need to plan for accidental oil spills. We argue that dispersants should play an important role in these plans, since they have substantial logistical benefits, work effectively under Arctic conditions, and stimulate the rapid biodegradation of spilled oil. They also minimize the risk of surface slicks to birds and mammals, the stranding of oil on fragile shorelines and minimize the need for large work crews to be exposed to Arctic conditions.

Integrating Dispersants in Oil Spill Response in Arctic and Other Icy Environments.

Toxicity of oil and dispersant on the deep water gorgonian octocoral Swiftia exserta, with implications for the effects of the Deepwater Horizon oil spill.

https://escholarship.org/content/qt8zj652f5/qt8zj652f5.pdf?t=ptol7x

Effects of corexit 9500A and Corexit-crude oil mixtures on transcriptomic pathways and developmental toxicity in early life stage mahi-mahi (Coryphaena hippurus).

Dispersants are among a number of options available to oil spill responders. The goals of this technique are to remove oil from surface waters in order to reduce exposure of surfacedwelling organisms, to keep oil slicks from impacting sensitive shorelines, and to protect responders from volatile organic compounds. During the Deepwater Horizon response, unprecedented volumes of dispersants (Corexit 9500 and 9527) were both sprayed on surface slicks from airplanes and applied directly at the wellhead (~1,500 m water depth). A decade of research followed, leading to a deeper understanding of dispersant effectiveness, fate, and effects. These studies resulted in new knowledge regarding dispersant formulations, efficacy, and effects on organisms and processes at a broad range of exposure levels, and about potential environmental and human impacts. Future studies should focus on the application of high volumes of dispersants subsea and the long-term fate and effects of dispersants and dispersed oil. In considering effects, the research and applications of the knowledge gained should go beyond concerns for acute toxicity and consider sublethal impacts at all levels of biological organization. Contingency planning for the use of dispersants during oil spill response should consider more deeply the temporal duration, effectiveness (especially of subsurface applications), spatial reach, and volume applied. By Antonietta Quigg,

/pdf/a-decade-of-gomri-dispersant-science-lessons-learned-and-1f36jn5syk.pdf

A Decade of GoMRI Dispersant Science: Lessons Learned and Recommendations for the Future

Toxicity of oil spill response agents and crude oils to five aquatic test species.

Chemical dispersants can be a useful tool to mitigate oil spills. This study examined potential risks to sensitive estuarine species by comparing the toxicity of two dispersants (Corexit® EC9500A and Finasol® OSR 52) individually and in chemically enhanced water-accommodated fractions (CEWAFs) of Louisiana Sweet Crude oil. Acute toxicity thresholds and sublethal biomarker responses were determined in seven species (sheepshead minnow, grass shrimp, mysid, amphipod, polychaete, hard clam, mud snail). Comparing median lethal (LC50) values for the dispersants, Finasol was generally more toxic than Corexit and had greater sublethal toxicity (impaired embryonic hatching, increased lipid peroxidation, decreased acetylcholinesterase activity). The nominal concentration-based mean LC50 for all species tested with Corexit was 150.31 mg/L compared with 43.27 mg/L with Finasol. Comparing the toxicity of the CEWAFs using the nominal concentrations (% CEWAF), Corexit-CEWAFs appeared more toxic than Finasol-CEWAFs; however, when LC50 values were calculated using measured hydrocarbon concentrations, the Finasol-CEWAFs were more toxic. There was greater dispersion efficiency leading to greater hydrocarbon concentrations measured in the Corexit-CEWAF solutions than in equivalent Finasol-CEWAF solutions. The measured concentration-based mean LC50 values for all species tested with Corexit-CEWAF were 261.96 mg/L total extractable hydrocarbons (TEH) and 2.95 mg/L total polycyclic aromatic hydrocarbons (PAH), whereas the mean LC50 values for all species tested with Finasol-CEWAF were 23.19 mg/L TEH and 0.49 mg/L total PAH. Larval life stages were generally more sensitive to dispersants and dispersed oil than adult life stages within a species. These results will help to inform management decisions regarding the use of oil-spill dispersants.

M. Franco

Papers

Comparative Toxicity of Two Chemical Dispersants and Dispersed Oil in Estuarine Organisms.