Abstract
Planktonic eukaryotes are widespread in aquatic ecosystems, and the study of their community composition and driving factors is of great significance to protecting and maintaining the balance of these ecosystems. This study evaluates five typical ecological sites in the Danjiangkou Reservoir—the water source for the project. This was done to comprehensively understand the composition of Danjiangkou Reservoir planktonic eukaryotes, and ensure the ecological balance of the water source for the South-to-North Water Diversion Project. The diversity of the planktonic eukaryotes in surface water and the factors driving changes in their abundance are analyzed with an 18S ribosomal DNA sequencing approach. Monitoring shows that the Danjiangkou Reservoir has good water quality. The Danjiangkou Reservoir planktonic eukaryote community is mainly composed of 11 phyla, of which Cryptomonadales is dominant, accounting for an average percentage of 65.19% of the community (47.2–84.90%). LEFSe analysis shows significant differences among samples in the abundances of 13 phyla, 20 classes, 23 orders, 26 families, and 27 genera, and there are also significant differences in the diversity of planktonic eukaryotes at different temporal and spatial scales. Redundancy analysis (RDA) show that water temperature, DO, SD, TN, and Chla are significant factors that affect the composition of the planktonic eukaryote community. Spearman rank correlation analysis combined with taxonomic difference analysis shows that Kathablepharidae and Choanoflagellida are not sensitive to environmental or physicochemical factors and that the interannual variations in their abundance are not significant. Network analysis shows that Protalveolata, Basidiomycota, P1-31, Bicosoecida, and Ochrophyta represent important nodes in the single-factor network, while Chytridiomycota, P1-31, Cryptomycota, Ochrophyta, Ichthyosporea, Bicosoecida, Protalveolata, and physicochemical factors (ORP, TN, WT, DO, SD, NH3-N, and NO3-N) represent important nodes in the two-factor network.
Highlights
Planktonic eukaryotes are important taxa in aquatic communities and perform critical ecological functions [1,2,3,4]
The Redundancy analysis (RDA) showed that water temperature (WT), dissolved oxygen (DO), Secchi depth (SD), total nitrogeneukaryotic (TN), and chlorophyll a (Chla) were the significant factors affecting the community distribution of planktonic eukaryotes in the Danjiangkou Reservoir
Research shows that the water quality of the Danjiangkou Reservoir is generally good, in accordance with the class II drinking water standard, while the TN content is still high
Summary
Planktonic eukaryotes are important taxa in aquatic communities and perform critical ecological functions [1,2,3,4]. They play a vital role in lake ecosystems as major participants in material and energy cycles [4,5]. Its application in water quality monitoring has attracted the attention of an increasing number of researchers [21], who currently use this method to study the composition, distribution characteristics, and factors influencing the microplankton eukaryotic community [19,22]. The structural characteristics and driving factors of the planktonic eukaryotic community in the Danjiangkou Reservoir have rarely been studied
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