Toxicity Effects Of Emerging Pollutant Monochloroacetic Acid To Microcystis Aeruginosa:Cytotoxicity And Mechanisms

Since the spread of novel coronavirus in 2019,the use rate of chlorinated disinfection products has been too high,leading to an increase in the discharge of highly toxic chlorinated disinfection by-products,which poses a potential threat to the ecological environment.At present,the toxicity mechanism of haloacetic acids to algae in the water environment is still unclear.In this study,we used microcystis aeruginosa as a model organism to study the physiological effects of monochloroacetic acid(MCAA)on microcystis aeruginosa,including acute toxicity,oxidative stress,cell apoptosis,production of microcystin-LR(MC-LR)and the effect of transcriptional abundance of microcystin-related gene mcy H,and systematically studied the toxic effects of MCAA in haloacetic acid on microcystis aeruginosa.Exposure to different concentrations of MCAA(1,2,5,10 mg/L)reduced the cell density,protein content and chlorophyll a content of microcystis aeruginosa cells.In addition,the activity of superoxide dismutase(SOD)and peroxidase(POD),malondialdehyde(MDA)content,and reactive oxygen species(ROS)levels increased with the gradient of MCAA concentration,but the activity of catalase(CAT)fluctuated greatly between treatment groups when the concentration of MCAA gradually increased(1,2,5,10 mg/L).Exposure to MCAA resulted in significant changes in the ultrastructure of algal cells,including thylakoid damage,nucleoid disappearance,vacuole formation,increase of starch particles,accumulation of lipid droplets and destruction of cell plasma membrane.At the same time,with the increase of MCAA concentration,the apoptosis rate of microcystis aeruginosa cells increased.Our results show that MCAA has acute toxicity to microcystis aeruginosa,which can cause oxidative damage to algae cells,stimulate the production of MC-LR,and destroy the ultrastructure of algae cells.This study hopes that the relevant departments will intervene in the relevant information of the permitted concentration of MCAA in the drinking water specifications,which is necessary for the safety of aquatic organisms.This study is of great significance to the rational use of chlorine-based disinfectants and the environmental protection and toxicity risk control of surface water.