The Lhasa River is one of the five tributaries of the Yarlung Zangbo River. It is the main industrial, agricultural and animal husbandry area in Tibet. It plays an important ecological security barrier role in regulating regional climate and maintaining biodiversity. In order to understand the resource utilization ability and relationship of fish in Lhasa River, and provide basic data for the protection and sustainable utilization of fish diversity in Lhasa River, the fishery resources in September 2019 (autumn), June 2020 (summer), November 2020 (winter) and March 2021 (spring) were investigated for the first time. The main fish in the catch were determined by the Index of Relative Importance (IRI). Shannon index and Pianka’s index were used to analyze the niche breadth and overlap values of the main fish caught in Lhasa River Basin from three dimensions of time, space and space–time. The results show that a total of 1399 fish of 3 orders and 4 families were collected. Among them, there is one dominant species, Schizopygopsis younghusbandi, and five common species, Schizothorax waltoni, Schizothorax oconnori, Ptychobarbus dipogon, Triplophysa stenura and Carassius auratus. The spatial–temporal niche breadth ranges from 1.395 to 3.628. They are Schizopygopsis younghusbandi, Carassius auratus, Ptychobarbus dipogon, Schizothorax oconnori, Triplophysa stenura and Schizothorax waltoni in a declining order. The temporal niche breadth is generally small, indicating that the survival activities of the main fish are greatly affected by seasonal changes. The fluctuation range of spatial–temporal overlap value is 0–0.535, and only 20% of the total logarithm is meaningful. The species pairs with temporal niche overlap values exceeding 0.300 reached 80%, while the spatial niche overlap value is generally low. The results show that the spatial and temporal distributions of the main fish in Lhasa River were quite different, and the spatial and temporal niche overlap value of the relationship between species is obviously affected by the change in spatial distribution. This demonstrates that the competition relationship and intensity of the main fish are quite different in different spatial positions.

The dynamic changes in plateau river ecosystems and the driving mechanisms of environmental factors have garnered significant attention. Phytoplankton, a core component of aquatic ecosystems, can directly reflect changes in the aquatic environment. This study focuses on the phytoplankton in the Lhasa River Basin, including the riverbed from the source to the river mouth, five largest tributaries, and two adjacent wetlands. We analyzed the spatial and temporal variation characteristics of phytoplankton and explored the environmental driving mechanisms based on four field surveys conducted between September 2019 and March 2021. Results showed that a total of 127 species of phytoplankton from six algal phyla were identified, including Cyanobacteria. Among these, Bacillariophyta was the dominant group, accounting for 41.7% of the identified species. Spatially, phytoplankton diversity showed a decreasing trend from upstream to downstream while temporally peaking in spring and autumn. Redundancy analysis revealed that upstream phytoplankton were driven by total hardness and altitude, midstream by pH and potassium ions, and downstream by nitrate and ammonium nitrogen. Classification and regression tree analysis showed total hardness, magnesium ions, and nitrite were key factors influencing phytoplankton abundance, diversity, and evenness. This study highlights the ecological dynamics and driving mechanisms of phytoplankton communities in the Lhasa River, demonstrating their high sensitivity to environmental factors. These findings could help to establish phytoplankton as critical indicators of aquatic ecosystem health and provide scientific guidance for the conservation and management of the plateau river ecosystems.

Schizothoracine fishes in saltwater lakes of the Tibetan Plateau are important models for studying the evolution and uplift of the Tibetan Plateau. Examining their adaptation to the high-salt environment is interesting. In this study, we first assembled the RNA-Seq data of each tissue of G. przewalskii, G. selincuoensis, and G. namensis from Qinghai Lake, Selincuo Lake, and Namtso Lake, respectively, obtained by the group previously. After obtaining reliable results, the adaptation of the gills, kidneys, and livers of the three species to the high-salinity environment was assessed by weighted gene co-expression network analysis (WGCNA). Using module eigengenes (ME), 21, 22, and 22 gene modules were identified for G. przewalskii, G. selincuoensis, and G. nemesis, respectively. Functional clustering analysis of genes in the significant association module identified several genes associated with osmolarity-regulated potential KEGG pathways in the gills of three species of Schizothoracine fish. Th17 cell differentiation pathway was up-regulated in the gills of all three species; histocompatibility class 2 II antigen and E alpha (h2-ea) were up-regulated genes in this pathway. Functional clustering analysis of genes in apparently related modules in the kidney unveiled several differential KEGG pathways. The pentose phosphate pathway was up-regulated in the three Schizothoracine fishes, and glucose-6-phosphate dehydrogenase (g6pd) was an up-regulated gene in this pathway. In the livers of the three Schizothorax species, the propanoate metabolism pathway was up-regulated, and succinate-CoA ligase GDP-forming subunit beta (suclg2) was an up-regulated gene in this pathway. The above analyses provide reference data for the adaptation of Schizothorax to high-salt environments and lay the foundation for future studies on the adaptive mechanism of Schizothorax in the plateau. These results partly fill the void in the knowledge gap in the survival adaptations of Schizothoracine fishes to highland saline lakes.

In recent years, heavy metal emissions in Lhasa have been increasing, which has an impact on the local water environment. The negative effects of copper (Cu²⁺) on aquatic ecosystems have attracted much attention, as even low concentrations of Cu²⁺ can exert toxic effects on aquatic organisms. However, the impact of Cu²⁺ on native fish species from the Lhasa River remains poorly understood. In this study, Schizopygopsis younghusbandi (S. younghusbandi) larvae were exposed to Cu²⁺ at concentrations of 0. 5, 5, 50, and 500 μg/L for 7 or 14 days to evaluate its toxic effects on thyroid function and the antioxidant system. The results indicate that whole-body total thyroxine (T4) and triiodothyronine (T3) levels were significantly decreased following Cu²⁺ exposure. This decrease was accompanied by a marked increase in dio1 and dio2 gene expression and decreased expression of thyroid hormone synthesis genes (nis, tg, ttf1 and pax8) after exposure to Cu²⁺. Furthermore, the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR) and the content of lipid peroxidation were increased, while the content of glutathione (GSH) was decreased. In addition, the survival rates and body lengths of S. younghusbandi larvae were significantly reduced following 7- and 14-day Cu²⁺ exposure. The Integrated Assessment of Biomarker Response (IBR) analysis further revealed dose- and time-dependent effects of Cu²⁺ on the larvae. In conclusion, the findings demonstrate that Cu²⁺ exposure induced disruption of thyroid endocrine and antioxidant systems and caused developmental toxicity in S. younghusbandi larvae.

The river ecosystems of the Qinghai–Tibet Plateau, recognized as a vital component of the “Asian Water Tower,” possess unique hydrological conditions and extreme environments that have shaped key indicator groups, most notably zooplankton. The community dynamics and structural characteristics of these zooplankton exhibit regular spatio-temporal distribution patterns across elevational gradients and seasonal successions. However, the intrinsic mechanisms underlying community succession and their correlations with environmental factors remain poorly understood, and the primary environmental drivers influencing community structure require further elucidation. Based on systematic zooplankton surveys and environmental data collection conducted across the Lhasa River basin from 2019 to 2021, this study established a comprehensive species inventory comprising 113 taxa across four major groups, alongside a multi-dimensional environmental dataset. We analyzed the spatio-temporal heterogeneities of zooplankton community structures—including abundance, biomass, and diversity indices—across different seasons and river reaches. The results revealed the composition and seasonal turnover of dominant taxa, with rotifers accounting for 39.82% of the total taxonomic richness. Mean zooplankton abundance and biomass across the basin were 1.18 ind./L and 343.60 × 10⁻⁵ mg/L, respectively, with peak values observed during autumn and within the Chabalang Wetland. The zooplankton community structure in the upstream, midstream, and downstream reaches, as well as associated wetlands, was significantly correlated with specific environmental factors (p < 0.05), including ammoniacal nitrogen (NH₄⁺-N), magnesium (Mg²⁺), total hardness (TH), potassium (K⁺), iron (Fe²⁺), sodium (Na⁺), sulfite (SO₃²⁻), nitrate ion (NO₃⁻), chloride ion (Cl⁻), total phosphorus (TP), and sulfide (S²⁻). Cl⁻, TH, Mg²⁺, SO₃²⁻, and elevation (Ele) were the key environmental drivers significantly influencing zooplankton abundance across seasons (p < 0.05). Furthermore, zooplankton abundance decreased significantly with increasing elevation during the winter. This research deepens our understanding of community assembly mechanisms in plateau river ecosystems and provides a scientific foundation for aquatic biodiversity conservation and ecological management in the Lhasa River basin.