Ecological Characteristics of Eukaryotic Communities in Water Diversion Rivers of the Eastern Route of China’s South-to-North Water Diversion Project During Flood and Non-Flood Seasons

The composition, ecological network characteristics, and community assembly mechanisms of eukaryotic communities in the sediments of typical water diversion rivers (WDRs) of the Eastern Route of the South-to-North Water Diversion Project were analyzed using 18S rRNA gene sequencing during the flood and non-flood seasons. Against the backdrop of global climate change and intensified anthropogenic disturbances, shifts in hydrological regimes induced by inter-basin water transfer projects have become key factors altering the structure and function of aquatic microbial ecosystems. Clarifying the spatiotemporal dynamics and assembly mechanisms of sedimentary eukaryotic communities in water diversion rivers under different hydrological conditions is crucial for understanding the ecological response of river ecosystems to water diversion and safeguarding the ecological security of diverted water resources. The eukaryotic communities were primarily composed of Bacillariophyta, Ciliophora, Arthropoda, and Chlorophyta. The composition and distribution patterns of eukaryotic communities exhibited distinct temporal and spatial shifts under varying hydrological regimes. Stochastic dispersal was identified as the primary driver of community assembly. During the flood season, eukaryotic communities showed increased complexity, more competitive interactions, and enhanced modularity, with species turnover being the dominant structuring process. During the non-flood season, eukaryotic communities exhibited higher spatial heterogeneity.