Toxicity of Kuwait crude oil and dispersed oil on selected marine fish species of Kuwait

Abstract

Oil spill is a major source of pollution in Kuwait marine environment and oil dispersants are used as a method to combat oil spill but the adverse effects of either oil or dispersed oil is unknown to fish species local to Kuwait. Therefore, the toxicity of water-accommodated fraction (WAF) of Kuwait crude oil (KCO) and chemically enhanced water-accommodated fraction (CE-WAF) of KCO with three dispersants (Corexit® 9500, Corexit® 9527 and Slickgone® NS) were investigated against selected marine fish species local to Kuwait marine waters such as: sobaity-sea bream (Sparidentex hasta), hamoor-orange-spotted grouper (Ephinephelus coicoides), meidmullet (Liza Klunzingeri), and shea’am-yellow-fin sea bream (Acanthopagrus latus). Prior to exposure chemical characterization of KCO WAF and CE-WAFs was conducted for benzene, toluene, ethylbenzene and xylene (BTEX), polycyclic aromatic hydrocarbons (PAH), aliphatic and total petroleum hydrocarbons (TPH) compounds. Standardization experiments regarding oil loading and mixing duration revealed that 1 g KCO loading and 24 h mixing duration were the most appropriate experimental conditions to obtain a reproducible and stable WAF and CE-WAF solutions. In general, CE-WAF contained higher concentrations of TPH, PAHs and aliphatics compared to KCO WAF. Exposure to KCO WAF and CE-WAF had no adverse effects on hatching success of embryonated eggs of sea bream and orange-spotted grouper exposed but larvae hatched during exposure exhibited a toxic response. Considering larval sensitivity, pre-hatched larvae of four marine fish species were separately exposed to KCO WAF and their sensitivities from the most sensitive to the least sensitive were: sea bream>orangespotted grouper > yellow-fin sea bream > mullet pre-hatched larval stages. The sensitivities of pre-hatched larvae of sea bream and orange-spotted grouper to WAF and CE-WAF were of different degrees. For sea bream the LC50 values were around 0.120 g oil/L for both WAF and CE-WAF indicating that dispersant didn’t increase oil toxicity, whereas for orange-spotted grouper CE-WAF (LC50 0.010 g oil/L) was more toxic than WAF alone (LC50 0.93 g/L). The data obtained in this study showed that most resistant developmental stage of fish to the toxicity of WAF and CE-WAFs was the egg stage > ABSTRACT ©KARAM v larvae hatched during exposure > pre-hatched larvae. Exposure of pre-hatched larvae to KCO WAF induced developmental abnormalities in spinal curvature of larvae and the most prominent deformity types were lordosis, scoliosis and kyphosis compared to that of control larvae were no abnormalities were observed. Relating toxicity data obtained in the present experimental study to actual petroleum hydrocarbon concentrations in Kuwait marine area, it was observed that current contamination level with petroleum hydrocarbons is far less than the LC50 determined in this study suggesting that there isn’t any acute hazard to either fish egg hatching or larva survival.