Effects Of Herbicide Fenoxaprop-p-ethyl On Physiological Processes In Microcystis Aeruginosa

The widespread use of aryloxyphenoxypropionic acid herbicides pose a potential danger to the ecological environment.The concentration of herbicides used in the environment is relatively high,and they are easy to transfer to the aquatic environment.Therefore,the ecological behavior and physiological toxicity of the herbicides are worth attention.When a large amount of herbicides enter to the environmental ecosystem,it will inevitably bring great negative effects to the environment and non-target organisms.In recent years,cyanobacterial blooms have occurred frequently all over the world,and the algal toxins released by cyanobacterial blooms pose a serious threat to the safety of aquatic organisms and humans.In this paper,the dominant species of Microcystis aeruginosa was selected as the test object,and fenoxaprop-p-ethyl was used as the representative compound of aryloxyphenoxypropionic acid herbicides to study its physiological to Microcystis aeruginosa.It includes the growth changes under acute and chronic toxicity effects of herbicides;the damage of antioxidant system,the change of microcystins released and the expression of related regulatory genes.The experimental data showed that the growth of Microcystis aeruginosa was inhibited by fenoxaprop-p-ethyl under the acute toxicity of herbicide,and the inhibition increased with the increase of herbicide concentration and culture time.At low concentration(0.5 mg/L),the growth of Microcystis aeruginosa showed a slight stimulating effect,which may promote eutrophication due to the proliferation of cells.At high concentrations(2 and 5 mg/L),the growth of Microcystis aeruginosa was significantly inhibited,which would cause cell division or even death,release microcystins into the water body and polluting the water environment.Under the chronic toxic effect of herbicide,the low concentration of herbicide in the early culture could stimulate the growth of Microcystis aeruginosa cells,and there was no significant difference among different groups.As the culture time increased,the toxicity of fenoxaprop-p-ethyl increased and the growth of Microcystis aeruginosa cells was inhibited.From the results of chlorophyll-a content and protein content of Microcystis aeruginosa,it was found that at high concentrations(2 and 5 mg/L),cells growth were inhibited,photosynthesis was affected,both chlorophyll a content and protein content were decreased.In addition,the expression of photosynthesis-related genes was also inhibited,and the expression of psa B and rbc L genes was significantly different from that of the control group.The results showed that fenoxaprop-p-ethyl stimulated the activities of SOD and CAT and the content of MDA,which indicated that the growth of Microcystis aeruginosa cells was inhibited and the oxidative damage occurred in cells under the influence of herbicide toxicity.In the experiment of the effect on the production and release of microcystins from Microcystis aeruginosa,it was found that the MC-LR content of the intracellular and extracellular showed an upward trend,and on the 6th day of culture,the MC-LR contents were significant increase at high concentrations(2 and 5 mg/L).Under the influence of the toxicity of fenoxaprop-p-ethyl,the expression of the genes mcy A,mcy D,and mcy H were also increased,indicating that the toxicity of herbicide can not only promote the synthesis of microcystins in cells,but also cause the release of microcystin out of cells when the cell structure damaged.In this paper,the ecotoxicity of fenoxaprop-p-ethyl was evaluated through related experiments.The study on the physiological of fenoxaprop-p-ethyl to Microcystis aeruginosa can effectively evaluate the toxic effect of herbicide on non-target organisms in the aquatic environment.It is helpful to understand the ecotoxicity risk of herbicide and reduce the environmental harm caused by herbicide.