Introduction: As an important tributary of the upper Yangtze River without dams, the study of the macroinvertebrate community structure and habitat suitability conditions in the Chishui River holds significant implications for water ecological conservation and restoration.Methods: In order to explore the species composition, community characteristics and their ecological needs of macroinvertebrates in the Chishui River, 26 sampling sites were deployed in the Chishui River in this study in March (dry season), July (wet season), and November (normal season) of 2023 and performed community structure analysis.Results: A total of 153 macroinvertebrate taxa were identified, with 62 taxa recorded in the dry season, 46 in the wet season and 115 in the normal season. The assemblage was predominantly composed of aquatic insects from the EPT group (Ephemeroptera, Plecoptera and Trichoptera). The results of ANOSIM analysis indicate that the species composition of macroinvertebrates varies significantly across different water periods. The Shannon-Wiener diversity index and Margalef index were significantly higher during the normal season compared to the dry and wet seasons. In contrast, the Pielou index and Simpson index remained relatively stable, suggesting a higher level of evenness in community structure across the different water periods. Based on the habitat suitability curves, Corbicula fluminea and Heptagenia prefer environments with high flow velocities and substrate particle sizes (D50) smaller than 300 mm. Hydropsyche sp.1 and Baetis thrive in environments with medium to low water depths, high flow velocities, and D50 ranging from 100 to 300 mm. Caridina favor deeper waters, low flow velocities, and larger substrate particles. The GAM fitting results revealed that the number of macroinvertebrate taxa increased with rising pondus hydrogenii (pH) and electrical conductivity (EC) levels. Species richness initially declined and then rose within certain thresholds of total nitrogen (TN) and total phosphorus (TP) concentrations. The optimal conditions for macroinvertebrate communities in the Chishui River were determined to be a DO concentration of 9.8 mg/L and an NH3-N concentration of 0.12 mg/L.Discussion: Overall, the macroinvertebrate community structure in the Chishui River is significantly influenced by factors such as water quality, flow velocity, and substrate particle size, and it demonstrates strong adaptability to seasonal variations.

In order to promote the development of biodiversity, the present study conducted three sampling surveys at 26 representative sampling sites selected from the Chishui River, a freshwater river in China, in July (rainy season), November (flat water period), and April 2024 (dry season), respectively, focusing on the relationship between benthic algae and the response of water environmental factors. The results revealed that a total of 140 species from 48 genera and 7 phyla of benthic algae were identified, with the highest number of species belonging to the diatom phylum (85 species). The average density of benthic algae was highest during the flat water period, followed by the dry season and the flood season. Microcystis sp. was the dominant species during the flood season, while Gomphonema sp., Achnanthes tumescens, and Oscillatoria sp. were common dominant species during the dry and flat water periods. Achnanthes tumescens was the absolute dominant species in the upstream during the dry and flat water periods; Leptolyngbya sp. was the absolute dominant species in the midstream during the flat water period, and Oscillatoria sp. was the absolute dominant species in the middle reaches during the dry season. The Shannon-Wiener index, Margalef index, and species richness of benthic algae during the dry and flat water periods decreased from upstream to downstream. Non-metric multidimensional scaling analysis revealed significant differences in the community structures of benthic algae in the upper, middle, and downstream areas of the Chishui River during different periods, while cluster analysis indicated high similarity among benthic algae communities in locally adjacent areas. The differences in the benthic algae community structure increased with environmental and geographical distance, with environmental distance playing a greater role than geographical distance. RDA (Redundancy Analysis) identified TN (Total Nitrogen), TP (Total Phosphorus), DO (Dissolved Oxygen), EC (Electrical Conductivity), and NH₃-N (Ammonia Nitrogen) as key water environmental factors influencing the structure of benthic algal communities in the Chishui River.

To investigate the spatiotemporal characteristics of periphytic algae community structure and the Benthic Index of Biotic Integrity (B-IBI) in the Jinsha River, this study conducted two sampling surveys on periphytic algae and physicochemical factors at 15 representative sampling sites in November 2023 (dry season) and May 2024 (normal water period). Results showed that a total of 118 species of periphytic algae belonging to 59 genera and 7 phyla were detected, including 48 species from 5 phyla in the dry season of 2023 and 95 species from 6 phyla in the normal water period of 2024. Spatially, the distribution trends of total species richness and abundance of periphytic algae were basically consistent, both showing a gradually increasing trend from the downstream reservoir section of the Jinsha River to the upstream conservation section of the Yangtze River. Temporally, both the abundance and species richness of periphytic algae in the normal water period were higher than those in the dry season. Overall, the physicochemical indices of the Jinsha River water showed a decreasing trend from the reservoir areas to the river channels, with slightly higher values in the normal water period than in the dry season. Through parameter value distribution range analysis, discriminant ability analysis, and redundancy analysis of candidate parameters, the B-IBI index system for the study area was determined. The baseline values of the periphytic algae integrity index were 6.04 in the dry season of 2023 and 6.62 in the normal water period of 2024. The water ecological health status of the conservation section of the upper reaches of the Yangtze River is generally in a healthy state, and the overall water ecological health status gradually improves with the increase of the distance from the cascade reservoirs in the lower reaches of the Jinsha River.

Phytoplankton communities in the proposed water source area of the Western Route of the South-to-North Water Diversion Project showed multi-level responses across monitoring-period groups and diversion areas. Based on 64 valid samples, total biomass ranged from 0.027 to 5.659 mg L⁻¹ and showed no consistent differences between monitoring-period groups or diversion areas, indicating site- and sampling-period-scale patchiness. Among the dominant biomass-contributing taxa, most were diatom taxa, and the relative contributions of the top ten dominant taxa and Other taxa were reorganized among monitoring-period–area combinations. NMDS, PERMANOVA, and PERMDISP showed that monitoring period was significantly associated with community structure, whereas diversion-area effects were not significant. dbRDA indicated significant environmental–spatial constraints on community composition, with an adjusted explanatory power of 28.2%; T, NH₄⁺–N, TN, NO₃⁻–N, EC, pH, DO, and DTN were significant predictors. VPA showed stronger pure environmental than pure spatial effects, while DDR and EDR revealed significant geographic and environmental distance relationships. Taxonomic Bray–Curtis null models suggested a predominance of stochastic-like taxonomic turnover signatures, with stronger deterministic-like deviations in the upper-line diversion area. GAM identified NH₄⁺–N, DO, and EC as significant biomass predictors. These findings support integrating biomass, community composition, measured physicochemical variables, and taxonomic assembly signatures into sustainability-oriented phytoplankton monitoring for high-elevation riverine water source areas, thereby providing ecological evidence for sustainable water source protection and adaptive management.