Centennial Lake Environmental Evolution Reflected by Diatoms in Yilong Lake, Yunnan Province, China

The 64 cm sediment diatoms, representing a timescale from 1938 to 2020 A.D., were analyzed to reconstruct the evolutionary history of Yilong Lake in Yunnan Province, China. Some main diatoms with important environmental indicating significance were selected through Principal Component Analysis (PCA). In addition, their ecological affinities indicated that the PCA sample scores 1 and 2, which were the main factors affecting the environmental change of Yilong Lake, corresponded to pH value and eutrophication, respectively. According to the pH value and the eutrophication data obtained from the PCA, the lake had successively gone through six major stages. Though high pH value and eutrophication had been the main characteristics for a long time, the quality of Yilong Lake was gradually improved through planned treatment in the last decades. The drying up of the lake under natural conditions resulted in an increase in pH values and high eutrophication. Meanwhile, the impact of human activities played a more important role in lake evolution: unreasonable human development in lake basins led to abnormal changes in pH values and eutrophication, and planned and targeted treatment could restore the natural state of the lake.