Study On Key Factors Affecting Vertical Migration Of Microcystis And Its Mechanism In Lake Dianchi

In order to further study the formation mechanism and major influencing factors of population advantage of Microcystis colonies,this study has explored the influence of major environmental factors(i.e.,light,temperature,nutrient,etc.)on the vertical migration of Microcystis in the Lake Dianchi and evaluated the Microcystis with different size ranges response to the environmental conditions.Moreover,it can also provide basic data and theoretical guidance for the control of N,P nutrient thresholds during the ecological restoration process and the prediction and early warning of surface blooms of Microcystis in Lake Dianchi.(1)The vertical migration patterns of Microcystis with different size class had different characteristics under different environmental conditions: small groups(<50 ?m)can sink more quickly,but the activity was higher than other groups;Large groups(70-150 ?m)can maintain floating in the water surface during the growth period.However,it sunk easily during the decline period.(2)Temperature,light intensity and colony size were all key environmental factors affecting the vertical migration of Microcystis populations.The light intensity had higher impact on the vertical migration of Microcystis in the Lake Dianchi,and the influence of temperature was relatively small.(3)The higher the concentration of nutrient,the less population of Microcystis sink to the bottom of the water.When phosphorus was the limiting factor,the duration of surface scum of Microcystis in water was longer than that of nitrogen as the limiting factor.When the nutrients were sufficient,the Microcystis could uptake the nutrient quickly,a large number of substances,such as carbohydrates and proteins,were synthesized in cells to increase the content of heavy substances in cells.