Effects Of Temperature And Light Intensity On Physiological And Ecological Characteristics Of Four Alga

Water bloom is an important research topic in water environment field.It is of great significance to study the physiological and ecological characteristics of algae in order to understand the mechanism of algal blooms and to establish the early warning and prevention system.The Stephanodiscus hantzschii,Microcystis aeruginosa,Cyclotella sp.and Scenedesmus obliquus four common algae as the research objects,the effects of temperature and light intensity on the chlorophyll fluorescence parameters of different alga,photosynthetic rate,growth and metabolism were compared.The effects of different concentrations of H₂O₂ solution,CuSO₄ solution and different gradients of ultrasound on Stephanodiscus hantzschii,Microcystis aeruginosa and Scenedesmus obliquus were further analysised.The main conclusions are as follows:1.The effects of temperature on the chlorophyll fluorescence characteristics and growth status of four species of algae were analyzed,and the suitable temperature range for the growth of the four kinds of algal blooms was revealed.Stephanodiscus hantzschii has a strong adaptability to low temperature,the growth condition is obviously better than 22? and 30? at 3¹5?,and the high temperature of 30? can cause heat stress.Under the condition of low temperature of 3¹0?,Microcystis aeruginosa almost keep stablility and the growth condition was better under the conditions of 15³0?,especially at 30?.Cyclotella sp.growth retardation in low temperature of 3¹0?,the growth rate under30?was faster than that under 3? and 10?,but slower than 15?and 22?,shows the suitable temperature range for Cyclotella sp.is 15²2?.Scenedesmus obliquus has good adaptability to high temperature,and it has a wider range of adaptation to temperature,and low temperature conditions do not inhibit its growth.with the increase of temperature,the proliferation rate was accelerated.2.The photosynthetic activities of the four alga were analyzed with the change of light intensity.Microcystis aeruginosa,Cyclotella sp.and Scenedesmus obliquus light saturation point decreased with the decrease of the temperature.The photosynthetic activity was positively correlated with light intensity at 15³0?,Microcystisaeruginosa and Cyclotella sp.Due to low temperature inhibition of 3?.Electron transport Rate?ETR?of photosynthetic system?PSII?is almost zero,photosynthetic activity at 3?,Scenedesmus obliquus has a slight upward trend with increasing light intensity,indicating the three species have strong light use efficiency and light protection ability under high temperature,the adaptability of Scenedesmus obliquus to temperature more widely.ETR of Stephanodiscus hantzschii under 30 degrees was zero due to heat stress,At 15?,Stephanodiscus hantzschii has the highest photosynthetic activity under different light intensity,without causing inhibition in the test set of intensity range,showed strong light use efficiency and light protection ability under low temperature.3.The effects of different concentrations of H₂O₂ solution,CuSO₄ solution and different gradient ultrasound on the inhibition of Stephanodiscus hantzschii,Microcystis aeruginosa,and Scenedesmus obliquus were studied.The results showed that the higher the concentration of H₂O₂ was,the more obvious the inhibitory effect on algae cells was.The concentrations of H₂O₂ in Scenedesmus obliquus Microcystis aeruginosa and Stephanodiscus hantzschii were significantly inhibited by 50mg/L,10mg/L and 30mg/L,respectively.After four days,H₂O₂ decomposed and the inhibition effect of algae were weakened.In practical application,the H₂O₂ should be put in to maintain the effect.The higher the concentration of CuSO₄ was,the more obvious the inhibitory effect on algae cells was.The concentrations of CuSO₄ in Scenedesmus obliquus Microcystis aeruginosa and Stephanodiscus hantzschii were significantly inhibited by 2.0mg/L,0.5mg/L and 2.5mg/L,respectively.Results showed that the tolerance of Microcystis aeruginosa to Cu2+ was weak,and the tolerance of Scenedesmus obliquus and Stephanodiscus hantzschii to Cu2+ was stronger.The ultrasonic experiment results show that the effect of ultrasonic may increase the speed of PSII and enhance chlorophyll fluorescence activity,but due to cell fracture,unable to synthetic chlorophyll and proliferation,and can play the inhibitory effect.At the same time,it is proved that the use of chlorophyll fluorescence parameters to evaluate the effect of algae inhibition is still open to discussion.