Physiological Toxicity Of Phenoxypropionic Acid Herbicides On Toxigenic Cyanobacteria

Extensive use of phenoxy acid(AOPP)herbicides was bound to be residual,the ecological behavior and physiological toxicity of drug and its metabolites in the environment is worth attention.Cyanobacteria breakout frequently in the world was difficult to control,the release of microcystins to aquatic organisms poses a serious threat to human safety.The purpose of this article is to study biological toxicity to cyanobacteria of two representative fluorophenoxy propionic acid herbicide fenoxaprop-p-ethyl and quizalofop-p-ethyl,including the effect on algae growth,chlorophyll a and protein content and the influence on the microcystins released of two herbicides at different environmental concentration,and further studyed the antioxidant system damage and apoptosis of algae cell to evaluate ecological toxicity of them.Results showed that Microcystis viridis was more sensitive to fenoxaprop-p-ethyl,while Microcystis aeruginosa was more sensitive to quizalofop-p-ethyl from the point of growth,chlorophyll a and protein.Low concentration of fenoxaprop-p-ethyl posed slight apparent stimulationmicrocystin algae.With the increase of drug concentration and processing time,patina of the growth of Microcystis aeruginosa began to be suppressed.Fenoxaprop-p-ethyl inhibited the growth of Microcystis viridis at different experiments concentrations and showed concentration effect.Due to stimulation effect at low concentrations,quizalofop-p-ethyl into the water environment may promote the outbreak of the "water bloom".From the release of microcystins,the microcystins content of two microcystis increased and show the concentration effect on day 3.6 days,Extracellular microcystins content increased on day 6,illustrating the release of microcystins into the water through the cell membrane.Considering the change of the growth,chlorophyll a and protein content,the release of microcystin from two microcystis caused by high concentrations of fenoxaprop-p-ethyl maybe because the cell membrane was destroyed.Under the treatment of quizalofop-p-ethyl,the increase of extracellular microcystins content may be due to activate response to external environment,is a defense mechanism.From the point of oxidative damage,the oxidative mechanisms of Microcystis viridis were damaged only at highest concentration of fenoxaprop-p-ethyl damage.Microcystis aeruginosa were forced under the action of two drugs,but there was no serious damage.At experimental concentrations of quizalofop-p-ethyl,algal cell antioxidant system have played a very good protection role.Apoptosis have taken place in different degrees in two microcystis,and show the concentration effect.Cells in From the electron microscope photo,we analysised that cell damage is cell apoptosis under high levels of drugs treatment.