Biodiv Sci ›› 2023, Vol. 31 ›› Issue (7): 23092.  DOI: 10.17520/biods.2023092

• Original Papers: Plant Diversity • Previous Articles     Next Articles

Deterministic processes dominate the geographic distribution pattern and community assembly of phytoplankton in typical plateau rivers

Shengxian Yang1,2,3, Qing Yang1,2,3, Xiaodong Li1,2,3, Xin Chao1,2,3, Huiqiu Liu1,2,3, Lanruoxue Wei1,2,3, Sang Ba1,2,3,*()   

  1. 1. Provincial Level of Mitika Wetland Ecosystem Observation and Research Station in Tibet Autonomous Region, Naqu, Xizang 852000
    2. Laboratory of Tibetan Plateau Wetland and Watershed Ecosystem, School of Ecology and Environment, Tibet University, Lhasa 850000
    3. Center for Carbon Neutrality in the Earth's Third Pole, Tibet University, Lhasa 850000
  • Received:2023-03-30 Accepted:2023-06-14 Online:2023-07-20 Published:2023-07-31
  • Contact: *E-mail:


Aims: Phytoplankton play a crucial role in biogeochemical cycling of river ecosystems. The ecological environment of the Yarlung Zangbo River, a major representative of high-altitude plateau rivers, is highly complex and more fragile than typical rivers of a lower altitude. Therefore, it features unique geographical characteristics which define the regions biology and ecology. This study aims to elucidate the spatial and temporal distribution patterns and the assembly mechanisms of the phytoplankton community in the middle and upper reaches of the Yarlung Zangbo River and to provide important data reference for the follow-up study of phytoplankton and water environment protection in the Yarlung Zangbo River in Tibetan Plateau.

Methods: In this study, phytoplankton in the middle and upper reaches of the Yarlung Zangbo River were investigated in summer (August 2019), autumn (November 2019) and spring (May 2020). Phytoplankton samples were collected and identified with strict qualitative and quantitative measures, while the physicochemical water features were measured on site. Simpson diversity index, Pielou evenness index and richness index were used to analyze α-diversity. The spatial and temporal differences of the phytoplankton community structure were analyzed by principal coordinate analysis (PCoA) and analysis of similarities (ANOSIM). Neutral models and standardized random rates were used to determine the relative proportions of deterministic and stochastic processes in phytoplankton community assembly. The effects of environmental heterogeneity (environmental distance) and diffusion limitation (geographical distance) on the process of phytoplankton community assembly were investigated through distance-decay patterns. Mantel test (Spearman correlation coefficient) was used to calculate the correlation between phytoplankton abundance and environmental factor distance in each season. Furthermore, network co-occurrence was used to analyze phytoplankton community interactions.

Results: We identified a total of 452 distinct phytoplankton species in the middle and upper reaches of the Yarlung Zangbo River, encompassing 8 phyla, 11 classes, 24 orders, 44 families, and 121 genera. The assembly of phytoplankton communities was found to be influenced by the combined effects of environmental heterogeneity, dispersal limitation, and species interactions. Interestingly, in season (from spring to autumn), we observed a transformation from stochastic to deterministic process, whereas at altitudes (from YJA gradient to YJC gradient), we observed a transition from deterministic to stochastic and then to deterministic. Geographical features along with water quality parameters were identified as pivotal drivers shaping the assembly of phytoplankton communities in the upper reaches of the Yarlung Zangbo River and exhibited pronounced distance-decay patterns, both spatially and temporally.

Conclusion: The middle and upper reaches of the Yarlung Zangbo River were vastly different in both spatial and temporal features, leading to a significant change in phytoplankton ecology between the two regions. Species interactions, environmental heterogeneity and dispersal limitation all play a role in the assembly of phytoplankton communities. Among them, deterministic process (environmental heterogeneity) dominates its assembly process.

Key words: middle and upper reaches of the Yarlung Zangbo River, phytoplankton, community assembly, geographical distribution pattern