Study On The Law Of Biological Toxicity Effect On The Fluorescence Of Algal

Human’s activities and the development of industrial made the pollution ofenvironment increasingly day by day, the effects of biological toxicity on phytoplanktonincluding cyanobacteria has caused widespread concern. So seeking a rapid detectionmethod is very necessary.Chlorophyll fluorescence signal issued by the algae contains a very richphotosynthesis,this photosynthetic signalchange easily when the conditions of theexternal environment change.The fluorescence is an important factor to characteriza thealgal photosynthetic activity.When the toxic inhibit of algal photosynthetic activity, thefluorescence intensity of the algae solution will increase.This method uses fluorescencechanges to determine the effect of the toxicity substances on plantphotosynthetic.Fluorescence measurement techniques does not require to break the celland to harm the organism, so using chlorophyll fluorescence changes to studyphotosynthesis indirectly is a simple, fast, and reliable method.Chlorophyll, carotenoidsand phycocyanin can characterize the photosynthetic activity.In this experiment the author selected Microcystis aeruginosa forexperiment,because cyanobacteria cells is similar to the chloroplast in the structure,socyanobacteria is an excellent material to research the effect of biological toxicity onphotosynthesis. Through cultivating Scenedesmus obliquus,Chlorella pyrenoidosa andMicrocystis aeruginosa,we find that Microcystis aeruginosa is easy to culture and has arelatively short growth cycle and the algae solution is the most uniform in logarithmicgrowth,so Microcystis aeruginosa is suitable for this experiment.Microcystis aeruginosais a kind of autotrophic lower organisms as cyanobacteria, found commonly in surfacewater. In addition to contain chlorophyll, it also contains phycocyanin in fresh water andphycocyanin has a strong fluorescence signal. In this experiment, we need to measure inthe two fluorescence signal,and to find which is more suitable for as a test indicator.When the testing micoalgae growth to logarithmic growth,we can add several kindof biological toxicity solution that configured a certain concentration gradient to thealgae solution to carry on the response experiment.The author do the experiment aboutthe Chlorophyll fluorescence response experiment.We studied on four types of typicalmetals ions(Cd²⁺, Hg²⁺,Cu²⁺, Zn²⁺)response law.Luminescent bacteria test: in experiment, we choose the Qinghai Vibrio Q67to Establish the detection method, and compared with the method of the algal fluorescence.Heavy metal experimental results show that:1) Experiment time:by the experimental we find when heavy metals and algae liquidmixture for25min the fluorescence change is more obvious detrimental to do thisexperiment,so we select25min as the experimental time.2) Select the test target:select the Microcystis aeruginosa’s chlorophyll afluorescence wavelength435/680nm as the best experimental wavelength. In thewavelength of435/680nm, the effect of poison on algae fluorescence is moreextraordinary and sensitive. Its result can be expressed as inhibition rate.3) Then the author do the experiment about the Chlorophyll fluorescence responsewith four types of typical metals.got a conclusion, this four heavy metal toxicity order isHg²⁺> Cu²⁺> Cd²⁺> Zn²⁺. Hg²⁺had a mroe significant and sensitive effection on algaefluorescence.With the stress concentration increaseing, the inhibition of algalphotosynthesis also increased significantly.The fluorescence changes of microalgae likethat can explain the stress level of heavy metals,using the algae characteristics ofchlorophyll fluorescence response to detect heavy metal is feasible.4) The toxicity of HgCl₂can effect Microcystis aeruginosa obviously.there was asignificant positive correlation between the concentration of HgCl₂and inhibition rate ofalgal photosynthetic signal.The regression equation was: y=114.66x+13.008,R=0.9865.The range of luminescent bacteria test’s standard curve linear is0.05-0.08mg/L, and the regression equation was y=2485x-102.06，R²=0.9310。In the experiment of pesticide, the author selectn atrazine to study on the effects ofatrazine on Microcystis aeruginosa fluorescence, and the results are as follows:1) By the experimental the author find when heavy metals and algae liquid mixturefor15min the fluorescence change is more obvious detrimental to do this experiment,sowe select15min as the experimental time.Select the test target:select the Microcystisaeruginosa’schlorophyll a fluorescence wavelength435/680nm as the best experimentalwavelength. In the wavelength of435/680nm, the effect of poison on algae fluorescenceis more extraordinary.Its results can be expressed as inhibition rate and conducive tocompare with the existing literature.2) By studying the laws that the atrazine impact on Microcystis aeruginosafluorescence, the author found that there was a significant positive correlation betweenthe concentration of Atrazine and inhibition rate of algal photosynthetic signal. There wasa significant linear relationship between0.1-0.4mg/L. The regression equation was y= 220.67x+11.550, r=0.9965. This method can determinate the concentration of atrazinequantitatively.