Comparative study on the assembly mechanisms and co-occurrence patterns of picoeukaryotic and nanoeukaryotic communities in lakes of arid and semi-arid regions (PRJCA037946)

In recent years, the large-scale shrinkage of lakes in arid and semi-arid regions has been significantly influenced by anthropogenic activities and climate change. This process is expected to induce profound shifts in the structure of eukaryotic microbial communities. However, research on the diversity patterns, driving mechanisms, and ecological functions of eukaryotic microbial communities of different size fractions in these lakes remains limited. In particular, there is a lack of understanding regarding the differences in assembly mechanisms and ecological network characteristics between picoeukaryotic and nanoeukaryotic communities. In this study, we collected 34 water samples from five plateau lakes in Xinjiang, which included freshwater lakes (BST, sBST), brackish lakes (SLM, WLG), and a saline lake (CWP). Each sample contained both picoeukaryotes and nanoeukaryotes. Using high-throughput sequencing targeting the V4 region of the 18S rRNA gene, we systematically analyzed the community composition, assembly processes, and co-occurrence network patterns of different eukaryotic microbial size fractions within these lake ecosystems. Our results revealed that the a-diversity of nanoeukaryotic community decreased with increasing salinity, whereas the a-diversity of picoeukaryotes initially declined and then showed a slight increase. At the ß-diversity level, significant structural differences were observed between the two groups across the five lakes. Redundancy analysis (RDA) indicated that both communities were primarily influenced by similar environmental factors, with total dissolved solids (TDS) identified as the key environmental variable driving community variation. Community assembly analysis suggested that stochastic processes predominantly governed the structuring of both picoeukaryotic and nanoeukaryotic communities. Furthermore, co-occurrence network analysis demonstrated that picoeukaryotic community exhibited higher network complexity and modularity, whereas nanoeukaryotic community showed predominantly positive co-occurrence relationships, suggesting a potentially greater ecological stability. This study enhances the understanding of the ecological characteristics of eukaryotic microbial communities of different size fractions in lakes within arid and semi-arid regions.