Small Hydropower Plants With Ecological Flow Influence Nestedness of Riverine Algae: Insights From treeNODF Analysis in Oujiang River Basin.

Understanding the nested distribution patterns is ecologically crucial for revealing river ecosystem heterogeneity and biodiversity maintenance. However, there is a notable research gap in understanding the nested patterns of river algae under the influence of small hydropower plants (SHPs), particularly in the context of ecological flow regulation. This study focused on the Oujiang river basin, where SHPs are widely distributed, exploring the effects of SHPs on the nestedness (NODF) of river algae under ecological flow and intensive development conditions. By calculating NODF, functional nestedness (traitNODF), phylogenetic nestedness (phyloNODF), and environmental nestedness (envNODF) for different river sections, the results indicated: (1) the entire basin and its different river sections exhibited significant nestedness; (2) the reservoir and dewatering sections were more strongly affected by SHPs, with traitNODF and phyloNODF remaining unchanged despite some environmental factors; (3) species with weaker attachment abilities and larger cell sizes tended to inhabit more unique habitats, particularly in reservoirs. These findings demonstrate that SHPs reshape algal communities primarily through environmental filtering, with reservoirs experiencing the strongest habitat modification. The study highlights the need for segment-specific management strategies in SHPs development to balance water use and ecosystem conservation. Future work should further explore nestedness-ecosystem stability relationships under human disturbances.