The Comparision Of Microcystis Aeruginosa And Scenedesmus Obliquus Under Different Environmental Condition

Lake eutrophication is one of the important environmental problems needed to be settled by China, even the whole world. Cyanobacteria is the predominance alga in large shallow Chinese lake, which is called cyanobacteria bloom.Cyanobacteria is one of the species in lake ecosystem, it must has competitive relation with other species, especially with other algae, which can bring important effect to cyanobacteria bloom. Why microcystis aeruginosa has superiority in mixed culture?Microcystis aeruginosa and Scenedesmus obliquus are two kinds of common algae in lakes of China. A simulative experimental appliance was designed to investigate the effect of temperature, nutrition, light and disturbance to the algae in pure culture and mixed culture (10:1, 1:1, 1:10).In pure culture, the quantity and growth rate of microcystis aeruginosa and Scenedesmus obliquus have positive correlation with the temperature;at the light of 30001x, Microcystis aeruginosa get the maximal growth rate, to Scenedesmus obliquus, the value should be higher;the increase rate of the two kinds of algae has the same trend with the concentration of nutrition, which can explain the relationship of pollution load and microcystis bloom;weak disturbance has beneficial to algaes growth, while large disturbance can weaken the annoying bloom.Microcystis aeruginosa and Scenedesmus obliquus's growth in mixed culture was researched and the results is following.Microcystis aeruginosa get superiority in all of the designed temperature of 7℃, 18 ℃ and 25 ℃, the difference of the two kinds of algae was appearing, besides, the difference became larger along with the decreasing share of microcystis aeruginosa in mixed culture. On the other hand, the restraining parameter of microcystis aeruginosa to scenedesmus obliquus is always bigger than the parameter of scenedesmus obliquus to microcystis aeruginosa.Within the range of light intensity, microcystis aeruginosa's growth rate isalways larger that of scenedesmus obliquus in 1:1 and 1:10 mixed culture, when in 10:1 mixed culture, the circs is abhorrent. The light-half-saturated constant of microcystis aeruginosa is becoming bigger when the share of microcystis aeruginosa is higher, to scenedesmus obliquus, the circs is contrary. The light-half-saturated constant of microcystis aeruginosa is always smaller than that of scenedesmus obliquus.Along with the accretion of phosphorus, the growth rate of the two kinds of algae is getting higer. In 1:10 mixed culture, microcystis aeruginosa got the maximum growth rate, scenedesmus obliquus got it in 10:1 mixed culture. In 10:1 mixed culture, the phosphorus-half-saturated constant of microcystis aeruginosa is the biggest (24.07|ig/l), besides, the phosphorus-half-saturated constant of microcystis aeruginosa is always smaller than that of scenedesmus obliquus.When disturbance appears, microcystis aeruginosa's growth is speedy than that of scenedesmus obliquus at all times. At the instance of 60r/min and 90r/min, the differences are maximal obvious, which are 60% and 68% separately. Disturbance increases the difference between the two kinds of algae in mixed culture, which makes microcystis aeruginosa hold superiority.