Comparative Acute Toxicity of Eight Oil Spill Dispersants, Louisiana Crude Oil and Chemically Dispersed Oil to Two Gulf of Mexico Aquatic Species

Abstract

Abstract Approximately two million gallons of oil dispersants were applied in response to the Deepwater Horizon spill. This study determined the acute toxicity of eight commercial oil dispersants, South Louisiana crude oil (SLC), and chemically dispersed SLC using each of the eight oil dispersants. The approach utilized consistent test methodologies within a single laboratory in assessing the relative acute toxicity of the eight dispersants, including Corexit 9500A, the dispersant applied offshore to surface waters and directly to the leak source. Static acute toxicity tests were performed with two Gulf of Mexico estuarine test species to determine 48-hr LC50 values for mysid shrimp (Americamysis bahia) and 96-hr LC50 values for inland silversides (Menidia berylina). Dispersant-only test solutions were prepared with high energy mixing, whereas water accommodated fractions of SLC and chemically dispersed SLC were prepared with moderate energy followed by settling and testing of the aqueous phase. For all e...