Spatial-temporal Succession And In-situ Control Of Algae In Jinpen Reservoir

In order to explore the spatial-temporal succession of algae in water body of the Jinpen reservoir and the effect and mechanism of the in-situ control of algae by water-lifting aerators,a vertical monitoring profile was set up at the deepest point of the Jinpen Reservoir.From June 2018 to August 2019,algae and its growth environment factors of water body at the monitoring profile were monitored in situ.The seasonal and diurnal changes of the vertical distribution of the algae in water body were studied,and the seasonal changes of the algae growth environment factors in water body and their influencing factors was revealed.The relationship between the spatial-temporal succession of algae in water body and the changes of its growth environment factors was analyzed,and then the main environmental factors affecting the spatial-temporal succession of algae and the effect and mechanism of in-situ control of algae by water-lifting aerators were clarified.The main results and conclusions of this article are as follows:?1?The seasonal changes of algae growth environmental factors in water body of Jinpen Reservoir were significant.The change of water temperature was mainly caused by the change of air temperature.The vertical distribution of water temperature tended to be uniform in autumn and winter?September 2018 to February 2019?,the vertical distribution of water temperature showed the characteristic of"high in surface water body,and low in middle and bottom water body"in spring and summer?March 2019 to August 2019?.The underwater light intensity and the underwater decay coefficient of light?K?of water body and the concentration of nitrogen and phosphorus nutrients of surface water all showed the seasonal variation characteristic of"low in autumn and winter,and high in spring and summer".The change of underwater light intensity with water depth conformed to Lambert-Beer's law.The seasonal variation of the underwater decay coefficient of light?K?in water body was mainly affected by the concentration of chlorophyll-a.The dissolved inorganic nitrogen?DIN?could provide sufficient nitrogen nutrients for algae growth;The concentration of total total phosphorus?DTP?was low,so phosphorus nutrients are a limiting factor for algae growth.The vertical hydrodynamic condition of water body showed the characteristic of"strong in autumn and winter,and weak in spring and summer".?2?The spatial-temporal succession of algae in water body of Jinpen Reservoir were significant throughout the year.The annual maximum values of the chlorophyll-a concentration and algae density in water body were 18.54?g·L^-11 and 14.71×10⁶ cells·L^-1,respectively.A total of 76 species of 51 genera of 6 families of algae of water body were identified,the dominant species and genera of algae showed the seasonal succession characteristic of"Cyclotella sp.and Melosira sp.were the dominant species and genera of algae in autumn and winter,Kephyrion sp.were the dominant species and genera of algae in spring?April 2019?,Chlorella vulgaris and Microcystis aeruginosa were the dominant species and genera of algae in summer";In autumn and winter,the vertical distribution of the main species and genera of algae in water body were uniform,which was mainly affected by the vertical hydrodynamic condition;In spring and summer,the vertical distribution of the main species and genera of algae in water body presented the characteristic of"high in surface water body,and low in middle and bottom water body",which was mainly affected by the physiological characteristic of algae suspended sedimentation and cell proliferation.The spatial-temporal succession of algae in water body of Jinpen Reservoir was mainly caused by the combined effects of water temperature,underwater light intensity,vertical hydrodynamic condition,nitrogen and phosphorus nutrients of the algae growth environmental factors,as well as the physiological characteristic of algae suspended sedimentation and cell proliferation.Vertical hydrodynamic condition was the key factor affecting the vertical distribution of algae in water body.?3?The vertical distribution of algae in water body of Jinpen Reservoir changed significantly throughout the day and night.The vertical distribution of algae in water body at night gradually became uniform;The vertical distribution of algae in water body during the day had significant differences,showing the characteristic of"high in surface water body,and low in middle and bottom water body".The diurnal variation of the vertical distribution of algae in water body was mainly affected by the physiological characteristic of algae suspended sedimentation and cell proliferation,as well as the underwater light intensity and vertical hydrodynamic condition of the algae growth environmental factors,and increased vertical hydrodynamic condition of water body could inhibit the upward suspension of algae.?4?The mixing effect of water-lifting aerators significantly affected the spatial-temporal succession of algae community in water body of Jinpen Reservoir.After water-lifting aerators run,the algae density of surface water body continued to decrease,and the vertical distribution of algae density in water body tended to be uniform;The dominant species and genera of algae community in water body gradually succeed from Chlorella vulgaris to Cyclotella sp.The mixing effect of water-lifting aerators mainly affected the spatial-temporal succession of algae community by rapidly enhancing the vertical hydrodynamic condition of water body,and could significantly inhibit the growth of algae.