Developmental Toxicity Of Dispersant And Crude Oil On Marine Medaka(Oryzias Melastigma)Embryo

With the vigorous economic development,as the main energy and materials of modern society,the exploitation and transportation of oil is increasing.And oil may enter the ocean through various channels,which seriously threatens marine ecological environment and organisms.To mitigate the effects of oil pollution,oil dispersants are used in the marine oil spill.However,the treatment of oil pollution by oil dispersants may increase the concentration of petroleum hydrocarbons,and then enhance the toxicity on marine organisms.Therefore,the application of oil dispersants is still controversial.In the present study,the developmental toxicity of water-accommodated fraction(WAF),chemically enhanced WAF(CEWAF)and GM-2 dispersant on marine medaka(Oryzias melastigma)embryos at 0-14 day post fertilization(dpf)was investigated.Lethality,hatching,heart rate,movement,general morphological score(GMS)and general teratogenic score(GTS)system of medaka embryos were observed to explore the difference of developmental toxicity of crude oil and dispersants in the early life stage on marine medaka.The specific results are as follows:The results showed that exposure to WAF,CEWAF and GM-2 dispersant caused teratogenicity and delayed development.GMS system indicated that inflated swim bladder,yolk sac resorbed,and hatching were sensitive to the change of exposure concentration.Starting from 10 dpf,results showed that WAF,CEWAF and GM-2 dispersant exposure at low dilution ratios(0%-60%)increased the heart rate of Oryzias melastigma embryo,and inhibited it at high dilution ratios(80%and 100%).The movement of the Oryzias melastigma embryos divided into the tail twisting,pectoral fin swinging,and eye turning.The total of these items showed a trend of low concentration decreased and high concentration increased.Among them,the eye rotation of the embryos was more susceptible to exposure of WAF,CEWAF and GM-2 dispersant than tail twisting and pectoral fin swinging.And GTS system indicated that teratogenic endpoints,yolk sac malabsorption,cranial or cardiac hemorrhage,pericardial edema and yolk sac edema were more severe than other endpoints.At 100%dilution ratio,the teratogenicity of Oryzias melastigma embryos caused by WAF,CEWAF and GM-2 dispersant were 61.89±7.08%,75.17±9.81%and 43.00 ± 3.89%.At 14 dpf,LC20 was 1.80 mg·L-1 of CEWAF and 2.41 mg·L-1 of WAF.Lethality of GM-2 dispersant was less than 20%.The concentration of total petroleum hydrocarbon(TPH)was determined by ultraviolet spectrophotometry,and Sixteen priority-controlled polycyclic aromatic hydrocarbons(PAHs)were detected by gas chromatography-mass spectrometry.Compared with WAF,the concentration of TPH of CEWAF is increased.For example,the content of PAHs in 3-5 rings such as benzoanthracene,benzopyrene and benzofluoranthene increased more significantly.This kind of PAHs has little water-soluble but strong "three induced"effect.The mechanism might be due to the surfactants in the dispersants.Surfactants have stronger solubilization effect on PAHs with higher liposoluble in crude oil.Thus,the biotoxicity of CEWAF was stronger than that of WAF.Our results could provide theoretical reference for toxicity evaluation of oil spill to marine organisms and rational use of dispersants.