Toxicological Effects Of Chiral Pesticide Acetochlor On Microcystis Flos-aquae

The racemic form of chiral pesticides is widely used in agriculture and forestry,and different enantiomers may have completely different toxicological effects on target organisms.Therefore,it is particularly important to study the effects of chiral pesticides on environmental organisms from the enantiomer level.In this study,the effects of acetochlor(ACT)on photosynthesis of Microcystis flos-aquae were analyzed using chlorophyll fluorescence parameters,algal protein,and phycobiliprotein.Enantiomeric separation and preparation of ACT were performed by High Performance Liquid Chromatography.We also investigated the enantioselective effects of ACT on the population phenomenon,ultrastructure,oxidative stress,and production and release of microcystin on Microcystis flos-aquae.The detail conclusions were listed as follows.(1)According to the photosynthetic physiology experiments of Microcystis flos-aquae,under the stress of low concentration(0.01?1 mg/L)of ACT,photosynthesis is not affected;while under the high concentration(10 and 50mg/L),Fv/Fm,Y(II),Rapid Light Curve and other parameteret were significantly reduced(P<0.05),and photosynthesis was suppressed.ACT also inhibits algal protein and phycobiliprotein.(2)Enantiomeric separation and preparation of the ACT were achieved by High Performance Liquid Chromatography.Baseline resolution was achieved.The first peak was ?R-ACT and the second peak was ?S-ACT.(3)According to the algal cell population phenomenon and ultrastructure experiment,with the increase of the concentration of ACT and its enantiomers,Microcystis flos-aquae will agglomerate,and the effect of population phenomenon will be more obvious;ACT and its enantiomers also cause different degrees of damage to the ultrastructure of Microcystis flos-aquae,such as cell deformation,asymmetry of division,cell wall damage and so on.The effect order of ACT and its enantiomers on the population phenomenon and ultrastructure of Microcystis flos-aquae was: ?S-ACT >Rac-ACT > ?R-ACT.There were enantioselective effects on algal cell population phenomenon and ultrastructure.(4)The results about oxidative stress of ACT on Microcystis flos-aquae showed as follows: for ?S-ACT,the SOD activity and MDA content decreased,and GSH content decreased first and then increased.However,the ?R-ACT concentration groups had no effect on the oxidative stress of Microcystis flos-aquae.The effect order of ACT and its enantiomers on the oxidative stress of Microcystis flos-aquae was: ?S-ACT > Rac-ACT > ?R-ACT.There were enantioselective effects on algal cell oxidative stress.(5)Microcystin LR(MC-LR)enzyme-linked immunoassay was used to determine the content of extracelluar,intracellular,and total MC-LR.ACT promoted the increase of MC-LR production of Microcystis flos-aquae,and the longer the exposure time,the more MC-LR production.But due to the different degrees of damage of ACT and its enantiomers to the cell wall of Microcystis flos-aquae,a large amount of MC-LR was released into the culture medium which lead to the intracellular MC-LR content reducing,and the extracelluar MC-LR content increasing.The effect order of ACT and its enantiomers on the production and release of microcystin of Microcystis flos-aquae was: ?S-ACT > Rac-ACT > ?R-ACT.There were enantioselective effects on algal cell production and release of microcystin.