Study On Algal Inhibition Efficiency And Mechanism Of Phenolic Group Active Substance Based On Allelopathy In Algae-algae

The outbreak of harmful cyanobacteria blooms caused by eutrophication has caused serious environmental problems and huge economic losses.Allelochemicals,which are derived from secondary metabolites of natural plants,have the characteristics of selectivity,easy degradation and environmental safety.Therefore,the use of allelochemicals to inhibit algae growth is considered to be an effective strategy for controlling cyanobacteria bloom.In recent years,algal allelochemicals with algal inhibitory effect have been found gradually,which provides more possibilities for the application of allelochemicals in the control of cyanobacteria bloomThe aim of the dissertation is to study the allelopathy between different algae species and identify the allelochemicals;to explore the efficacy and influencing factors of effective allelochemicals;to clarify the mechanism of allelochemicals;to explore the efficacy and safety of effective allelochemicals in natural raw water.The results of this paper have found a kind of efficient,new and green algae removal material,which provides theoretical basis and technical support for the treatment and emergency control of algae-laden water environment and the emergency treatment of algae containing water in water plant.The specific research contents and conclusions are as follows(1)The competitive pathways between three kinds of green algae(Scenedesmus quadricauda,Scenedesmus obliquus,Chlorella vulgaris)and three kinds of cyanobacteria(Microcystis flos-aquae,Anabaena flos-aquae,Aphanizomenon flos-aquae)were studied.It was found that S.quadricauda had strong allelopathic inhibition on M.flos-aquae.The components of its culture medium filtrate were identified and 4-tert-butylpyrocatechol(TBC)has been identified as an allelochemicals with strong algal inhibitory activity to inhibit the growth of M.flos-aquae(2)The effects of TBC on the proliferation of four common freshwater cyanobacteria(M.flos-aquae,Microcystis aeruginosa 905,Microcystis aeruginosa 469 and A.flos-aquae)in different initial TBC dose,water temperature,pH and initial biomass of cyanobacteria were investigated.The results showed that the order of inhibitory effect of TBC on four kinds of cyanobacteria was M.aeruginosa 905>M aeruginosa 469>M flos-aquae>A.flos-aquae.When the water pH was 5.5-9.5,the algae inhibition efficiency of TBC was better;when the water pH was 10.5 or water temperature was low(15℃),the algae inhibition efficiency of TBC was not good.The initial algal biomass directly determines whether the amount of TBC exceeds the tolerance threshold of algal cells.When the initial algal biomass is higher and the amount of TBC is lower than the tolerance threshold of algal cells,the inhibition efficiency of TBC is affected.(3)The inhibition mechanism of TBC on the two kinds of Microcystis was studied and the results showed that TBC promoted the production of superoxide anion radical(O2·-)and increased the content of malondialdehyde(MDA),the activity of superoxide dismutase(SOD)and reduced ascorbic acid(ASA)in Microcystis.It was suggested that TBC can damage the structure and function of cell membrane and lead to the death of algal cells by causing lipid peroxidation of cell membrane.At the same time,TBC can enhance the antioxidant capacity of algal cells,so as to eliminate excessive free radicals in time and to"deal with" the cell damage caused by TBC.When Microcystis cells came into contact with TBC,they also released polysaccharides and proteins to protect the cells from TBC.(4)The algal inhibition effects of TBC and three allelochemicals(catechol,berberine chloride hydrate and gentisic acid)were compared by calculating the 50%inhibiting concentration.The results showed that the order of inhibition ability of four allelochemicals to M.flos-aquae was as follows:TBC(96h·EC50=0.035 mg/L)>catechol(96h·EC50=1.202 mg/L)>gentisic acid(96h·EC50=2.414mg/L)>berberine chloride hydrate(96h’EC50=3.618 mg/L).The order of inhibition ability of four allelochemicals to M.aeruginosa was as follows:TBC(96h·EC50=0.099 mg/L)>catechol(96h·EC50=1.607 mg/L)>berberine chloride hydrate(96h·EC50=4.691 mg/L)>gentisic acid(96h·EC50=4.557 mg/L).These four allelochemicals had better inhibitory effects on M.aeruginosa than M.flos-aquae.(5)The application efficiency and safety of TBC in natural raw water were studied.The results showed that the inhibition effect of TBC in natural water was selective,and had strong inhibition effect on cyanobacteria,but had no inhibition effect or slight promotion effect on green algae.TBC can cause changes in the quality of natural raw water.The specific performance is as follows:the turbidity of water containing cyanobacteria was significantly reduced,the concentration of humus increased with the increase of TBC concentration,and the concentration of polysaccharides gradually decreased after a brief increase after the addition of TBC.Cyanobacteria in natural raw water can effectively alleviate the toxicity of TBC to zebrafish and Daphnia magna,and the greater the proportion of cyanobacteria,the stronger the mitigation.In the water samples with cyanobacteria as the main genus,the safe concentrations of TBC to zebrafish and Daphnia magna were 0.626 mg/L and 0.979 mg/L,respectively.The degradation rate of TBC was fast and the half-life was short when TBC was put into acidic natural water with low initial concentration(1.0 mg/L).