Differential impacts of invasive aquatic plants water lettuce (Pistia stratiotes) and water hyacinth (Eichhornia crassipes) on plankton community dynamics and its ecosystem functionality

Plankton plays a pivotal role in maintaining aquatic ecosystem stability and food web equilibrium. Yet, the mechanistic responses of plankton communities to invasive aquatic plants (e.g., Pistia stratiotes and Eichhornia crassipes) remain poorly understood. This study investigated the temporal effects of these invasive species on plankton biodiversity, native plant (Ludwigia ovalis) growth, and nutrient dynamics in freshwater systems in a 50-day microcosm experiment. Results indicated no significant change in L. ovalis growth (p > 0.05), while pH, EC, TN, and TP significantly decreased (p < 0.05). And plankton dominant species, functional communities (e.g., functional group D and small copepoda and cladocera filter feeders) and their co-occurrence networks were disrupted. Moreover, the Shannon index of phytoplankton was significantly higher at day 10 and lower at day 50 (p < 0.05) than that of P. stratiotes, while the metazoan zooplankton showed the reverse trend. P. stratiotes reduced network complexity including average degree and graph density, while E. crassipes disrupted architectural integrity as modularity, collectively destabilizing plankton interactions. SEM model revealed that E. crassipes indirectly decreased EC via TN reduction (−0.412) while P. stratiotes directly suppressed EC (−0.242), cascading into decreased plankton biomass, density, and diversity. These findings elucidated species-specific invasion mechanisms and their cascading impacts on planktonic ecosystems, which could provide actionable insights for mitigating biodiversity loss in invaded freshwater habitats and enhancing ecological monitoring frameworks to safeguard ecosystem services.