| In recent years,the eutrophication status of various lakes and reservoirs in the country is still very serious,and the algae outbreaks frequently.The internal waves can be applied to destroy the thermal stratification,and to obviously improve the water quality.However,the mechanism of controlling algae by internal waves in water environments is not clear,and the mechanism research has important significance for practical application.In this study,a photoreactor that can simulate the change of light intensity was designed and controlled by a single-chip microcomputer.The photoreactor can make the light intensity vary as required to simulate the light environments under internal waves.Taking Microcystis aeruginosa in Cyanobacteria and Scenedesmus obliquus in green algae as study objects,which are dominant algae in most domestic source water reservoirs,the characteristics of growth status and photosynthesis under constant light intensity and periodic fluctuation light intensity conditions was analyzed with microscopic and macroscopic methods.The main conclusions are as follows:(1)Under periodic and frequent light intensity fluctuation conditions,the growth of Microcystis aeruginosa and Scenedesmus obliquus will be disturbed to a certain extent,among which the interference to Scenedesmus obliquus is particularly serious.The reduction of the biomass of Scenedesmus obliquus was greater than that of Microcystis aeruginosa.(2)Under the same amount of total radiation,the periodical fluctuations of the light intensity significantly affect the chlal and carotenoid contents of the two algae,especially for Scenedesmus obliquus,in which the inhibition of the formation ofclerodin should be the main reason for the inhibition of photosynthesis of the two algae;(3)Under the same total light irradiation,when the light intensity fluctuates periodically,the color of Scenedesmus obliquus appears yellow,the light-capturing performance decreases,the Fv/Fm,YII,and ETR decrease,and the photosynthesis activity and electron transport are blocked.The color of Microcystis aeruginosa was a little yellow and the light-harvesting performance was also reduced,but the Fv/Fm,YII,and ETR generally showed a tendency of decreasing first and then increasing slightly.(4)When the light intensity fluctuates periodically,the NPQ of both algae increases greatly in the later period,and the utilization rate of light energy is reduced,and the algae was in its own protection mechanism,which leads to increase of NPQ due to inhibition of photosynthesis;(5)Both strong light and weak light will inhibit the growth of two algae biomass,chla and carotenoid content,and the periodic fluctuation of light intensity has little effect on the chla of Microcystis aeruginosa.The inhibition of chla content in Scenedesmus obliquus was strong,and the carotenoid content and growth rate of two species of algae were greatly inhibited.(6)Both strong light and weak light suppression made Fv/Fm ?YII and ETR.Microcystis aeruginosa had less influence on Fv/Fm in the periodic fluctuation illumination,but the influence of Scenedesmus obliquus was stronger.The YII of Microcystis aeruginosa was 6100 lx >12000lx>3000lx after 6 day,and YII of Scenedesmus obliquus was 6100lx> 12000lx> undulation intensity> 3000 lx after 9day.The ETR of two algae was approximately the same as that of YII.In the dark experiment,the two algae's Fv/Fm,YII,ETR,NPQ had an adaptive growth,and then decreased to 0;(7)Non-photochemical quenching NPQ of two species of algae gradually decreased with time under the light intensity of 3000 lx,kept a low loss,the NPQ values of 6100 lx and 12000 lx were relatively higher,and the energy consumption of algae was the highest under periodical fluctuating light condition. |
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