Effect of dispersant on the composition of the water-accommodated fraction of crude oil and its toxicity to larval marine fish

Newly hatched mummichog (Fundulus heteroclitus) were exposed in a 96-h static renewal assay to water-accommodated fractions of dispersed crude oil (DWAF) or crude oil (WAF) to evaluate if the dispersant-induced changes in aqueous concentrations of polycyclic aromatic hydrocarbons (PAH) affected larval survival, body length, or ethoxyresorufin-O-deethylase (EROD) activity. Weathered Mesa light crude oil (0.05-1 g/L) and filtered seawater with or without the addition of Corexit 95008 were used to prepare DWAF and WAF At 0.2 g/L, the addition of dispersant caused a two- and fivefold increase in the concentrations of total PAH (Σ PAH) and high-molecular-weight PAH (HMWPAH) with three or more benzene rings. Highest mortality rates (89%) were observed in larvae exposed to DWAF (0.5 g/L; Σ PAH, 479 ng/ml). A reduction in body length was correlated with increased levels of Σ PAH (r(2) = 0.65, p = 0.02) and not with HMWPAH. The EROD activity increased linearly with HMWPAH (r(2) = 0.99, p = 0.001) and not with Σ PAH. Thus, chemical dispersion increased both the Σ PAH concentrations and the proportion of HMWPAH in WAF Dispersed HMWPAH were bioavailable, as indicated by a significantly increased EROD activity in exposed mummichog larvae, and this may represent a significant hazard for larval fish.