Physiological And Metabolic Response Of Freshwater Diatom Nitzschia Palea To Two Organophosphorus Pesticides

Organophosphorus pesticides,one of the most extensively used organic chemicals to control several insect pests,making them threat the aquatic creatures.Diatoms were the most generally used bio-indicators in freshwaters and fluvial ecosystems.Besides,diatom species are well known that some of them can be found in almost all kind of waters and some have high sensitivity to water chemistry parameters.Nitzschia palea,one member of the genus Nitzschia,has the characteristic of wide distribution,short generation time,well known an important species for diatom biomonitoring.Organophosphorus pesticides are extensive application,which lead to serious pollution of water environment and endangers the health of aquatic organisms and human beings.In order to explore the toxic effect of organophosphorus pesticides on aquatic plants and understand the indicator effect of aquatic plants on organophosphorus pesticide residues in water.Here,we analyzed the response mechanism of Nitzschia palea to insecticides(acephate and trichlorfon)exposure,through physiological,biochemical,morphological changes and metabolism.Results are as following:The growth of N.palea was inhibited by trichlorfon,with the cell density was significantly decreased at 7 days of exposure.Although the diatom growth was hardly inhibited after acephate treatment.Based the observation of SEM,the diatom valve significantly abnormal morphology be found at 50 mg/L acephate treatment after 7 days.Meanwhile,low-level trichlorfon had positive effect on the chlorophyll a content of N.palea.For further analysis revealed that the content of malondialdehyde(MDA)and extracellular polysaccharides(EPS)increased on exposure to both insecticides.In addition,trichlorfon induced the activities of superoxide dismutase(SOD)and catalase(CAT)and acephate trichlorfon induced the activities of peroxidase(POD)in the diatom,which play a defensive role against various environmental stresses.There were significant differences in metabolic markers after organophosphorus pesticide treatment.The metabolic pathway analysis of differential metabolites showed that organophosphorus pesticide affected the metabolic pathways of amino acid(lysine)synthesis and fatty acid(arachidonic acid)metabolism in diatom.This study showed the result that the growth trend,biochemical changes,metabolizing process,and morphological characteristics of N.palea changed to both insecticides.Organophosphorus pollution is more comprehensively and accurately assessed by a combination of cytology,biochemistry and metabonomic analysis.