A comparative study on the effect of dispersed and undispersed Kuwait crude oil on egg hatching and larval survival of Epinephelus coioides

ABSTRACT

Aim: The objective of the present study was to investigate the effects of dispersed and undispersed Kuwait crude oil on egg hatching and larval survival of Epinephelus coioides. Methodology: In the present study, the toxic effects of crude and dispersed oil using three formulations of oil dispersants against multiple life stages of Epinephelus coioides was assessed. The lethal concentration was calculated by ToxCal® software developed by Tidepool Scientific, LLC. Results: Specifically, the following life stages were investigated embryonated eggs (EE), larvae hatched during exposure (LHE) and hatched larvae (HL). Chemical analysis showed that Total Petroleum Hydrocarbon (TPH) concentrations were higher in dispersed than undispersed oil solutions, indicating accommodation of more petroleum hydrocarbons in the aqueous phase. Acute static toxicity tests produced variable LC50 values for all chemical preparations and all fish life stages. Crude oil dispersed with both Corexit® EC 9500A and Corexit® EC 9527A separately was more toxic to both EE and LHE stages than undispersed oil, but crude oil dispersed with Slickgone® NS resulted in lower toxicity. Furthermore, all three types of dispersed oil exerted higher toxicity than undispersed oil at HL stage. Interpretation: A life stage dependent effect demonstrated variation in the toxicity of both dispersed and undispersed crude oil to fish. Few life stages were more sensitive than others to either dispersed or undispersed crude oil toxicity. While dispersion of an oil slick with oil dispersant has proved to be an effective tool in the oil response strategy, the fate of dispersed oil can exert lethal effects on embryo-larval stages of marine fish present near the spill.