Abstract:
Toxicity assays of the oil dispersant Corexit 9500, and fresh and weathered Alaska North Slope (ANS) crude oil were conducted on Alaskan tanner crab larvae (Chionoecetes bairdi) under cold-region conditions, the reference species, Mysidopsis bahia and Menidia beryllina, and Vibrio fischeri (Microtox bioassay). Acute 96-hour toxicity data for C. bairdi were calculated using the response 'affected' (decreased phototactic response and ability to swim). C. bairdi were most sensitive to non-dispersed weathered oil (EC₅₀=0.4 mg/L), least to dispersant-only solutions (EC₅₀=1,267 mg/L), and were typically more sensitive than the reference species. Dispersant-only solutions were consistently least toxic for all species tested. Dispersed fresh oil was frequently more toxic than non-dispersed oil. Weathered oil data are greatly influenced by aqueous solubilities, indicating non-dispersed weathered oil was most toxic, although those solutions required the highest oil loading (25 g/L). Interpretations of toxicity data are dependent upon expression of solution concentrations.
