Transgenerational Effects And Mechanisms Of Sunken Heavy Fuel Oil Pollution On The Sea Urchin

In recent years,most oil spillages from tank vessels involve heavy fuel oil(HFO).HFO has a high density and a high viscosity.HFO in the environment after a spill tends to sink and becomes sunken oil.Sunken HFO is resistant to evaporation and degradation,which is unlikely to be recoverable.HFO is characterized by high concentrations of toxic polycyclic aromatic hydrocarbons(PAHs).Therefore,sunken HFO may result in a long-term and great damage to marine environment.Benthic habitats are at increased risks from sunken HFO.In the present study,flow-through oiled gravel columns are prepared in the laboratory to provide closer field approximation of sunken HFO.The sea urchin Strongylocentrotus intermedius is selected as a model system.On the clue of 'adult sea urchin-gamete-offspring',the bioconcentration and parental transfer of the PAHs released from sunken HFO are investigated.The effects of parental exposure on the reproduction and the early development of the offspring in the sea urchins are also investigated,as well as the effects of parental exposure to sunken HFO on the macromolecular damage and the total antioxidant capacity of gonad tissues,eggs,sperm and offspring.These results provide information related to the transgenerational effects and mechanisms of sunken HFO on the sea urchins.The results of the present study will be especially useful in the implementation of ecological risk assessments and natural resource damage assessments of sunken HFO.The results obtained are as follows:(1)During the exposure period(21 d),chemical characterizations of the interstitial water from flow-through oiled gravel columns simulating field sunken HFO at a range of oil loadings(500,1000,2000,4000 and 8000 ?g oil/g gravel)are analyzed every 24 h.The results demonstrate that concentrations of total petroleum hydrocarbons and PAHs in the interstitial water decrease exponentially with the time,with the ranges of 44.2-752.9 ?g/L and 0.564-5.978 ?g/L,respectively.The composition of PAHs in the interstitial water is dominated by naphthalene and phenanthrene.Throughout the experiment,the relative abundances of aqueous PAHs change,such that phenanthrene becomes more prominent as naphthalene volatilized.The concentrations of total petroleum hydrocarbons and PAHs in the interstitial water from oiled gravel columns are consistent with realistic exposure conditions in marine environment,suggesting that the flow-through oiled gravel column is effective to provide better approximations for sunken HFO in marine environment.(2)The effects of PAHs concentrations in the interstitial water from the flow-through oiled gravel columns and the gender of the sea urchins on the bioconcentration and parental transfer of PAHs are investigated.The sea urchins are exposed to the interstitial water from the oil gravel columns at a range of oil loadings for 21 days.The sea urchins are induced to spawn for the collection of eggs and sperm.The PAHs concentrations in female and male gonad tissues,eggs and sperm are measured.The results show that the concentrations of PAHs in gonads,eggs and sperm are positively correlated with the concentrations of PAHs in the interstitial water.The maximum concentrations of PAHs in the gonads of female and male sea urchins are 1079.5 and 921.0 ng/g dry weight(DW),respectively.The maximum concentrations of PAHs in eggs and sperm are 350.0 and 170.4 ng/g DW,respectively.The concentrations of PAHs are significantly lower in the sperm than in the eggs.The concentration of individual PAH in the gonads,eggs and sperm of the sea urchins is different.For PAHs with a logKOW(octanol-water partition coefficient)less than 5.6,the logBCF(bioconcentration factor)of the PAHs is linearly positively correlated with the logKOW.The results suggest that the sea urchins can bioconcentrate PAHs and transfer them to their offspring through eggs and sperm.The parental transfer of PAHs in the sea urchins is gender specific.(3)The transgenerational effects of sunken HFO on sea urchins are investigated through measuring the life-history traits,which include the gonad index,fecundity,egg size,fertilization success and the abnormality and body length in the offspring.Furthermore,the gender specificity and the stage specificity of the offspring are considered.After exposure to the interstitial water from the oil gravel columns at a range of oil loadings for 21 days,the gonad weight,gonad index and fecundity of the sea urchins are significantly reduced.The fecundity is more sensitive to sunken HFO.The egg size and the fertilization success are not significantly affected.The offspring development at 24 hpf is mainly negatively affected by the paternal exposure,while the offspring development and body length at 48 hpf are negatively affected by the maternal exposure.The EC50 values of the offspring at 48 hpf derived from both exposed parents,exposed mothers and exposed fathers are 646.3,879.4 and 1179.5 ng/g DW,respect-ively(expressed as PAHs concentrations in gonads of adult sea urchins).When expressed as PAHs concentrations in gametes,the EC50 values of the said offspring are 190.2,305.5 and 201.3 ng/g DW,respectively.(4)After exposure to the interstitial water from the oil gravel columns at a range of oil loadings for 21 days,the macromolecular damage(lipid peroxidation,protein carbonyls and DNA damage)and the total antioxidant capacity of gonad tissues,eggs,sperm and offspring are determined.Together with the concentrations of PAHs in the sea urchins and the changes of the life-history traits,the mechanisms related to transgenerational effects of sunken HFO on the sea urchins are investigated.The results show that the levels of macromolecular damage of gonad tissues significantly increase,whereas the total antioxidant capacity decreases.Parental exposure to sunken HFO increases the level of DNA damage in the eggs and sperm,with the former significantly lower that the latter.The levels of total antioxidant capacity and lipid peroxidation of eggs are higher than those of sperm.The offspring at 24 hpf derived from exposedmothers have a higher level of total antioxidant capacity but a lower level of DNA damage,compared to those derived from exposed fathers.At 48 hpf,the offspring derived from exposed mothers demonstrate similar levels of DNA damage with the offspring from exposed fathers,which are higher that the control offspring.These results suggest that paternal exposure to sunken HFO induces the DNA damage of sperm,thus leading to the abnormality of the 24 hpf offspring.The negative effects of maternal exposure on 48 hpf offspring are related to the levels of DNA damage of the eggs and maternally inherited PAHs.