The Research On The Verenalization In Mi-crocystis Aeruginosa In Dianchi Lake

In recent ten years, Dianchi had suffered from cyanobacteria bloom problems for along time.Since the80’s of the last century algal bloom appeared, up to now this kindof situation has not been fundamentally changed; cyanobacteria bloom will explodeagain the next year and mainly concentrated in the end of spring and the beginning ofsummer. For a long time, there are a lot of researches on the Dianchi of Microcystis ae-ruginosa, mainly concentrated in the growth temperature, light, nutrition salt etc. Forthere was no outbreak about exploring the mechanism of outbreak of Microcystis aeru-ginosa in spring and summer and experimental analysis of environmental factors, asso-ciated Microcystis aeruginosa spring activities and plant vernalization. If the experimentcan confirm the presence of low temperature induced effects of Microcystis aeruginosa,this will not only explain the experimental algae spring activity, but also reveal the ex-istence of vernalization similar to higher plants in the microscopicworld micro algae. Therefore experiment was taken to analysis the relationship betweenthe experimental algae and the vernalization from2009to2013.In this paper, through field sampling, purchasing algae and indoor culture, thegrowth temperature and variable temperature experiments was taken to test the growthtemperature of algae, and analysis the low temperature induction, induction intensityand induction time.The main results and conclusion of the study as follows:The main results：(1) The growth temperature and the temperature point to determine the growth ofMicrocystis aeruginosa: the growth temperature was15.0~31.0℃,the optimum growthtemperature was19℃;less than15℃the experiment algae stopped growing, and lessthan7℃the experiment algae began to die; higher than31℃the experimental algaestopped growing, higher than33℃the experimental algae began to die.(2) Variable temperature experiments：①Without high-temperature treatment: when the algae was cultured followed thesequential temperatures of low growth temperature, optimum growth temperature, highgrowth temperature, optimum growth temperature and low growth temperature, it couldgrow, but the high temperature produced a certain inhibitory effect on the algae.②High-temperature treatment: when the algae was cultured followed the sequen- tial temperatures of growth temperature, dormancy high-temperature andgrowth temperature, only in the first growth temperature range the experimental algaecould grow, this shows that dormancy high-temperature had the effect of stopped algaegrowing.③High-low temperature treatment: when the algae was cultured followed the se-quential temperatures of growth temperature, dormancy high-temperature, inducedlow-temperature and growth temperature， both in the first and the last growth tem-perature range the experiment algae could grow. Compared with thehigh-temperature treatment show that experimental algae need low-temperature treat-ment to break inhibitory effect by dormancy high-temperature to grow.④Lethal high-temperature treatment: when the algae was cultured followed thesequential temperatures of growth temperature, dormancy high-temperature, le-thal high-temperature, induced low-temperature and growth temperature, only in thefirst growth temperature range the experimental algae could grow, this shows that evenafter low-temperature treatment experimental algae could not grow, lethal tempera-ture effect was irreversible.(3) The relationship of the low-temperature treatment approach with the al-gae growth: induced low-temperature strength and growth rate were positively correla-tion in the induced low-temperature range of7.0~10℃, but in the range10.0~14.0℃,induced low-temperature strength and growth rate were positively negative correlated.The most suitable induced low-temperature was10℃. And theaction time of in-duced low-temperature was positively correlated with growth rate.The main conclusion:(1) Microcystis aeruginosa had vernalization which is similar to those higherplants; high temperature may terminate the vernalization. The annual activity rhythm ofMicrocystis aeruginosa was: low-temperature in winter induces growing in spring, andthe sequent dormancy high-temperature leads to the deverenalization in summer, thenthe algae stopped growing, because there is no low temperature induction in au-tumn, algal blooms can occur but not large-scale outbreak.(2) The relationship of the low-temperature treatment approach with the al-gae growth: the action time of induced low-temperature was positively correlated withgrowth rate, positively correlated with temperature intensity (7.0~10.0℃) or anti-cor-related(10.0~14.0℃).(3) Microcystis aeruginosa in Dianchi large-scale outbreaks was related to the number of days of the most suitable induced low-temperature in winter.