Toxicity of Three Dispersants Alone and in Combination with Crude Oil on Blue CrabCallinectes sapidusMegalopae

Abstract

Abstract During the Deepwater Horizon incident in 2010, ∼1.8 million gallons of Corexit® dispersants were approved for use directly onto the released oil. Callinectes sapidus (Blue Crab) megalopae are pelagic and, therefore, likely to be one of the first organisms exposed to spilled oil and applied dispersants in open-ocean and nearshore waters. In this study, we examined acute toxicity of Corexit 9500, Corexit 9527, and MicroBlaze® (a microbial surfactant) alone and in combination with crude oil. We adapted methods from the established 48-h copepod toxicological assay and exposed Blue Crab megalopae for 48 h to varying dosages of each treatment. Oil treated with dispersant was more toxic than either oil or dispersant alone (48-h LC50 = 29.8 mg/L vs. 55.9 mg/L and 37.5–59.1 mg/L, respectively), and MicroBlaze was essentially non-toxic (48-h LC50: 7643 mg/L). Corexit 9527 was more toxic than Corexit 9500 both in solutions with oil and alone (48-h LC50 = 37.5 mg/L vs. 51.8 mg/L and 59.1 mg/L, respectively)....