Succession and driving factors of Lake Dianchi aquatic ecosystem in the past 60 years

As an essential part of the ecological security barrier in the upper reaches of the Yangtze River and southwest China, Lake Dianchi plays a critical role in safeguarding national and regional environmental security. The succession process and driving factors of phytoplankton, zooplankton, macrophytes, zoobenthos, fish and other essential compositions in Lake Dianchi aquatic ecosystem were systematically analyzed using literature research and classification, combined with the water quality change and eutrophication evolution process of Lake Dianchi in 1950-2020. The results showed that before the 1960s, Lake Dianchi maintained its natural form and belonged to the stage of the macrophyte type lake. Between the 1970s and 1990s, the situation of eutrophication, the physical and chemical properties of the water changed rapidly, and nutrient-tolerant species increased. It indicated that the lake regime shifted from a macrophyte type lake to a macrophyte-algal type lake. From 2000 to 2015, the water environment of Lake Dianchi seriously deteriorated. The water quality was between “Inferior” and “Class V” of Environmental Quality Standards for Surface Water (GB 3838-2002), and the water use function was basically lost, indicating that it belonged to the stage of an algal lake. Since 2016, although the water quality of Lake Dianchi had gradually improved, the eutrophication had remained at a high level. The driving factors of the aquatic ecosystem succession of Lake Dianchi were natural factors, pollutant discharge exceeding Lake Dianchi's environmental capacity, and ecosystem habitat fragmentation. The results could provide important reference values and theoretical support for decision-makers and stakeholders in managing similar shallow lake-water ecosystems.