Study On Alternative Stable State Transition Trends And Its Influencing Factors In Lake And Reservoir Ecosystem

Nowadays,the outbreak of cyanobacteria bloom is becoming more and more serious both at home and abroad,and the eutrophication of closed water bodies has increasingly become the focus of global attention.In order to control water pollution and eutrophication,we must firstly understand the causes of algal bloom and water quality deterioration.Therefore,it's particularly important to explore the influencing factors and influence modes of algal blooms in lakes and reservoirs.In this study,we collected the morphological parameters,hydrological factors,physical parameters,climate factors and water quality data of a large number of lakes and reservoirs in the world,and analyzed the distribution rules of the above variables,as well as evaluated the health status of the lakes and reservoirs.We used statistical methods to explore the correlations between the above factors and water quality indicators.Generalized additive model was used to explore the influence of lake secchi depth and water depth on chlorophyll a concentration in water bodies of several representative countries.The results showed that there was a significant negative correlation between secchi depth and chlorophyll a in most lakes,while there were different forms of correlation between water depth and chlorophyll a.Analyzing the correlations between watershed area: lake area(WA:LA)and hydraulic residence time(HRT)in global lakes and reservoirs,negative correlations were found.Analyzing the distribution law of total phosphorus(TP)concentration in different countries/regions,and comparing it with HRT,we found negative correlations in most areas,and positively correlations in some areas.Taking Tianjin Yuqiao Reservoir as an example,the effects of climate change on chlorophyll a and suspended solids(SS)in different seasons were studied.Significant correlations between average wind velocity,maximum wind velocity,rainfall,solar radiation,net radiation,temperature and chlorophyll a concentration were found.And there were significant correlations between maximum wind velocity,rainfall,solar radiation and SS.To explore the influence of various factors on water quality is helpful to better understand the causes of cyanobacteria bloom and lake eutrophication,and can help us to explore the mechanism of lake alternative transformation,meanwhile may provide theoretical reference for lake and reservoir management.