To investigate the structure of phytoplankton communities and the ecological niches of dominant species in the middle and upper reaches of the Yarlung Zangbo River, we collected samples at 14 sites in April (spring) and September (autumn) 2023. A total of 198 phytoplankton species were identified belonging to 6 classes, 13 orders, 24 families, and 53 genera. The community structure was dominated by diatoms, green algae, and cyanobacteria. In April, 163 species of phytoplankton from four phyla were identified, with abundance ranging from 2.94 × 10⁵ to 2.32 × 10⁶ cells/m³ and an average of 1.28 × 10⁶ cells/m³. In September, the abundance of phytoplankton ranged from 1.52 × 10⁵ to 1.58 × 10⁶ cells/m³, with an average value of 6.76 × 10⁵ cells/m³. Sixteen species were classified as dominant (Y > 0.02), among which four showed dominance in both sampling periods, with their dominance level and niche width differing with the season. Water temperature increased with decreasing altitude. At 4500 m compared to other elevation ranges (>4500 m; 4000–4500 m; 3500–<4000 m; <3500 m). The effect of elevation on the community structure was greater than that of season. This is the first study to characterize the association of ecological niches of phytoplankton in the upper reaches of the Yarlung Zangbo River with physicochemical environmental parameters. This provides baseline information for the conservation of biodiversity and management of aquatic ecosystems in the rivers of the Tibetan Plateau.

We evaluated growth, mortality, and resource utilization of burbot, Lota lota, in the upper reaches of Heilongjiang River, China. The population has experienced significant decline, and, despite substantial recovery, concerns regarding resource management have arisen. A total of 638 specimens collected from October 2022 to October 2023 were used to calculate the relationship between body length and weight, which ranged from 107 to 529 mm and from 8.91 to 1474.17 g, respectively. FAO FiSAT II software was used to estimate population parameters based on body length frequency distribution of the samples. The calculated progressive body length value and the growth coefficient were 551.25 mm and 0.16, respectively. The natural mortality rate of burbot is 0.31 a⁻¹. Assuming a total mortality rate of 0.41 a⁻¹, the estimated current exploitation rate is 24.39%. Total biomass (94.76 t) and maximum sustainable yield (14.69 t) were estimated based on length-structured virtual population analysis. Burbot, of the upper reaches of Heilongjiang River, is a fast-growing fish that is well-suited to the ecology of the investigated area. The current research yielded suggestions for utilization of resources to ensure the preservation of the species, as well as the development of the local economy.

The community structure and ecological niche of benthic macroinvertebrates in the upper Yarlung Zangbo River were analyzed in April and September 2023. The benthic macroinvertebrate community largely comprises aquatic insects, with Diptera accounting for approximately half. Commonly observed were Chironomus anthracinus, Tadamus sp.1, Piscicola geometra, species of the family Corixidae spp. and the genera Monodiamesa sp., Apatania sp., and Valvata sp. in April, and Orthocladius sp.1, Gammarus sp., Isoperla sp., Nais sp., Baetis sp., Monodiamesa sp., Tanytarsus sp., Ilisia sp., Nebrioporus sp. and species of the family Corixidae spp. in September. The α-diversity analysis showed significant seasonal differences (p < 0.05) in Shannon–Wiener diversity variable and Margalef richness variable. The Pielou evenness variable did not show seasonal effects (p > 0.05). The β-diversity April/September differences can be attributed to species turnover rather than to nestedness, indicating that benthic macroinvertebrate diversity protection strategies are critical to all areas of the river. In April, Chironomus anthracinus exhibited the broadest ecological niche, and, in September, the widest niche was observed in Gammarus sp. The largest observed ecological niche overlap values were between Chironomus anthracinus and Valvata sp. in April and Gammarus sp. and Ilisia sp. in September, indicating interspecific competition. The study clarifies the diversity status of benthic macroinvertebrates in the upper Yarlung Zangbo River and provides data for related research to facilitate formulation of biodiversity conservation policies.