| The 6:2 chlorinated polyfluoroalkyl ether sulfonic acids(6:2 Cl-PFAES),2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoic acid(HFPO-DA)and perfluoroethylcyclohexane sulfonate(PFECHS)are three kinds of Per-and Polyfluoroalkyl substances(PFASs)that replaces traditional PFASs with high persistence,high bioaccumulation potential and high toxicity.In recent years,these new PFASs compounds have been detected in the estuary and coastal areas and their pollution level is ng/L,which has attracted the attention of many scholars and they pointed out that these short-chain new perfluorinated compounds have become major pollutants in estuarine and coastal waters.In this paper,the long-term exposure effects of the above three emerging PFASs on the growth of typical green algae Chlorella sp.and dinoflagellate Prorocentrum lima were studied under the marine environmentally relevant concentration of 10 ng/L,100 ng/L,1000 ng/L.In addition,we also discussed the response mechanisms of the antioxidant systems of two marine microalgae under the stress of the three emerging PFASs.The main results are as follows:The emerging PFASs compounds at environmentally relevant concentrations have different effects on the growth of two marine single-cell microalgae species.The growth of Chlorella sp.was significantly inhibited compared with the control group(p<0.05),and the inhibition effect was enhanced with the increase of the PFASs concentration.At the last day of the experiment(14 days),the maximum inhibition rates of three emerging PFASs to Chlorella sp.were 63.13%(6:2 Cl-PFAES),63.54%(HFPO-DA)and 46.09%(PFECHS),respectively.It also can be seen that the order of toxicity of three emerging PFASs to Chlorella sp.is HFPO-DA > 6:2 Cl-PFAES >PFECHS.The growth of P.lima showed a "low promotion and high inhibition" characteristics,that is,the lower concentration(10 ng/L,100 ng/L)of the emerging PFASs not only did not inhibit the growth of P.lima,on the contrary,it has a certain stimulating effect on its growth.While the high concentration(1000 ng/L)of three emerging PFASs significantly inhibited the growth of P.lima.In addition,the inhibition rates of P.lima in the 1000 ng/L exposure group were 77.24%(6:2 Cl-PFAES),93.50%(HFPO-DA)and 68.29%(PFECHS),respectively.The order of toxicity of the PFASs to P.lima is consistent with that of Chlorella sp.The emerging PFASs at environmentally relevant concentrations have different effects on the antioxidant system of Chlorella sp.and P.lima.Chlorella sp.showed an increase in SOD activity and a decrease in CAT and POD activity.This effect increased with the increasing concentrations of PFASs.The results indicated that under the stress of three emerging PFASs compounds,Chlorella sp.was subjected to oxidative stress and more active oxygen free radicals were produced in the cells.Although the enhancement of SOD activity plays a positive role in the removal of reactive oxygen species,the excessive intermediates lead to a decrease in CAT and POD activities,leading to an imbalance in the antioxidant system and exacerbating oxidative damage in cells.The activities of three antioxidant enzymes in the cells of P.lima were promoted,but the promotion effect was lower when the concentration of PFASs was higher.At this time,a large amount of superoxide accumulated in the cells,and the P.lima cells were more susceptible to oxidative damage.In addition,the response of the two marine microalgae antioxidant systems was consistent with their cell density.This study found that as the main pollutant in the estuary and coastal waters,these short-chain emerging PFASs have a greater potential risk to the marine environment.Not only do they have a bottom-up serious impact on marine ecosystems,but they also contribute to the outbreak of red tides by promoting red tides in the oceans.Therefore,the emerging PFASs as the contaminant in the marine should be get more attention on their long-term potential influence to ecological and environmental. |
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