Environmental factors controlling the spatial distribution of subfossil Chironomidae in surface sediments of Lake Dongping, a warm temperate lake in North China

Lake Dongping is a typical warm temperate floodplain lake located in the lower reaches of the Yellow River, North China. As part of the waterway for the South-to-North Water Diversion Project of China, the water quality and trophic status of Lake Dongping are crucial for the successful operation of this project. In order to better understand the controlling factors of water quality and trophic status of Lake Dongping and to provide data for studying ecological baseline of lake restoration, the distribution and the controlling factors of subfossil chironomids were studied here. Our results show that a total of 41 taxa of subfossil chironomids are present in Lake Dongping. The dominant taxa consist of Stempellinella–Zavrelia (30.88%), Propsilocerus akamusi-type (26.79%), Paratanytarsus (13.15%), Cricotopus sylvestris-type (9.12%), and Hydrobaenus conformis-type (6.67%). Among them, the nutrient-tolerant taxa of Stempellinella–Zavrelia and eutrophic taxa of Propsilocerus akamusi-type are widely present in the lake, indicating that Lake Dongping is in a transition from mesotrophication to eutrophication. Redundancy analysis reveals that total phosphorus, water depth, and sulfate (SO₄ ²⁻) concentrations are dominant factors controlling the spatial distribution of subfossil chironomids, which explain 12, 9, and 8.5% of the variance, respectively. Therefore, in order to secure the water quality for the South-to-North Water Diversion Project, it is crucial to regulate the input of nutrient and sulfate to Lake Dongping.