Seasonal dynamics and coexistence mechanisms of plankton communities in a Karst Plateau reservoir: Integrating network analysis and environmental drivers

Understanding seasonal plankton dynamics in karst aquatic ecosystems is crucial for water resource management. Monthly ecological survey was conducted from July 2023 to June 2024 in Yelang Reservoir, a typical karst reservoir in Southwest China. To elucidate plankton community coexistence mechanisms. Our integrated approach combined community structure analysis, environmental monitoring, and ecological network modeling. Key findings revealed that:(1) Phytoplankton diversity peaked in spring, with Pseudanabaena limnetica (Cyanobacteria) maintaining year-round dominance. Zooplankton diversity reached its maximum in summer, dominated by the Keratella cochlearis . (2) Mantel tests indicated phytoplankton diversity was significantly correlated with water temperature (T), whereas zooplankton diversity correlated with total nitrogen, nitrate nitrogen, and T. (3) Co-occurrence networks demonstrated predominantly positive interactions (86.21% ~ 100%) between phytoplankton and zooplankton, suggesting symbiotic coexistence. (4) Partial Least Squares Path Modeling (PLS-PM) identified T as the primary driver of phytoplankton succession, while zooplankton assembly was governed by nutrient-temperature coupling effects. These results unveil asymmetric physicochemical regulation mechanisms in karst plankton dynamics, providing a conceptual framework for managing vulnerable aquatic ecosystems under global change scenarios. • Phytoplankton diversity was the highest in spring, and P seudoanabaena limnetica of Cyanobacteria was dominant throughout the year; The diversity of zooplankton is the highest in summer, dominated by Keratella cochlearis of rotifers, which reveals the law of trophic asynchronous succession. • Mantel test confirmed that phytoplankton was controlled by single factor of water temperature (T), while zooplankton responded to total nitrogen (TN), nitrate nitrogen (NO₃-N)and WT at the same time, reflecting the difference of hierarchical regulation. • The plankton interaction network showed 86% ~ 100% positive correlation, which broke through the traditional predator-prey framework, and confirmed that mutualism in Karst drinking reservoir water was the core mechanism of community coexistence. • Combined with PLS-PM and network analysis, it is revealed that phytoplankton succession is directly driven by T, while zooplankton is controlled by nutrient temperature coupling effect, and the cascade response path of complex system is clarified. • It is found that the dominant ecological elasticity of cyanobacteria and the sensitivity of zooplankton to nitrogen provide a theoretical target for reservoir management under the combined stress of climate warming and eutrophication.