Long-term succession of diatom community under hydro-climatic fluctuations in Taiping Reservoir, Yunnan Province, China.

Under the background of regional climate warming, frequent fluctuation of water level caused by drought events and pollutant influx due to catchment development can directly threaten the ecological safety of reservoirs. Through the analysis of physical (particle size, loss on ignition), chemical (carbon, nitrogen), biological (diatom community) and other substitute indicators of sediment, combined with monitoring data and investigation data, we reconstructed the environmental changes in Taiping Reservoir in Yunnan Province from 1937 to 2018, and analyzed the succession characteristics of diatom community and its environmental impact factors. The grain size records indicated that the hydrodynamic condition of Taiping Reservoir was increased during the impounding period (1956-1984) and was steadily reduced thereafter, corresponding well with the documented history of reservoir construction and hydrologic regulation. Changes of total nitrogen, total carbon and organic matter contents indicated the decline of water nutrient level during the construction of the reservoir and the rising process of primary productivity and endogenous organic matter after the completion of the reservoir. The dominant taxa of diatom community shifted from planktonic species to benthic species and then to planktonic ones. The main factors driving the succession of diatom community in Taiping Reservoir were climate change, hydrodynamic condition, and nutrient level. Under the background of long-term climate warming, strict controlling exogenous nutrition input, and reasonable hydrological regulation would be the important premise to maintain ecological health and environmental safety of reservoir water.