Small hydropower plants affect aquatic community diversity: A longitudinal study under ecological flow.

Small hydropower plants (SHPs) play a crucial role in clean energy production, yet they also disrupted river ecosystems. To achieve a balance between energy production, biodiversity conservation, and ecosystem integrity, it is essential to study how aquatic organisms respond to SHP operations. Prior researches had shown that SHP operations have the most significant impact in dewatering sections, but studies often overlook the influence of ecological flows. Therefore, our study focused on the Oujiang river basin, where SHPs are prevalent, to investigate the effects of SHP operations on riverine algae under ecological flow and conditions of intensive exploitation. We compared species composition, traits composition, and diversity indices across different river sections and used multiple linear regression models to identify the main drivers influencing algal communities. The results showed: 1) SHP operations significantly altered hydrological and physicochemical conditions in reservoir sections, leading to distinct differences in algal community composition and traits; 2) physicochemical factors had the greatest influence on diversity indices, driving the observed patterns; and 3) SHP operations indirectly affected algal communities through interspecific interactions, particularly with macroinvertebrates like Scrapers. These findings emphasize the need for stronger governance and enforcement to ensure adequate ecological flow releases by SHPs, especially under growing environmental and climate challenges.