Precipitation determines the dynamic and network stability of phytoplankton communities in the three gorges reservoir

• Influence of precipitation on phytoplankton communities in the Three Gorges Reservoir were demonstrated. • Significant correlations between climate variables (temperature and precipitation) and algal diversity indices was verified. • Dominant species played a crucial role to ensure the stability of phytoplankton community. • Rare species significantly decreased during the rainy season. Phytoplankton plays a vital role as primary producer in reservoir ecosystem. However, few information could be obtained on precipitation affecting the spatiotemporal dynamics of phytoplankton communities. To fulfill this gap, we conducted a 12-month continuous field survey at 48 sampling sites in the Three Gorges Reservoir. Random forest modeling (RF), structural equation model (SEM), and co-occurrence networks analysis were employed to screen the roles of precipitation in shaping of phytoplankton communities. A total of 74 phytoplankton species into 8 phyla and 63 genera were identified. Bacillariophyta predominated during the dry season, whereas Cyanobacteria and Chlorophyta emerged as the dominant phyla during the rainy season. Phytoplankton species composition and biomass displayed significant difference between the dry and rainy seasons (p < 0.05); cell density peaked in the rainy season, significant spatial heterogeneity in phytoplankton community were also observed (p < 0.05). Noteworthy correlations were discerned between climatic variables (temperature and precipitation) and phytoplankton diversity indices. Significantly higher complexity and stability in the network structure was observed in the dry season (p < 0.05). In the rainy season, rare species declined significantly (p < 0.05), while dominant species played a critical role in responding to climatic changes and maintaining the community stability. Precipitation altered nutrient level and transparency, consequently influencing the dynamic and network of phytoplankton communities. It was confirmed the pivotal role of precipitation as environmental filter in shaping of phytoplankton community. This study advanced our understanding of the driving mechanism of precipitation in the dynamic and network stability of phytoplankton communities in reservoir.