The Responses of Aquatic Plants to Water-Level Fluctuation: A Review.

Water-level fluctuation (WLF) is a key factor disturbing aquatic ecosystems, particularly aquatic plants (macrophytes in this review). These organisms are exceptionally sensitive to WLF as it profoundly governs their spatial distribution, productivity, species richness, community composition and successional trajectories. In this review, we synthesized recent advances regarding the impacts of WLF on the growth environment, survival strategies, and the integrated morphological, physiological, and reproductive responses of aquatic macrophytes. While existing research has predominantly focused on flooding-related WLF responses and freshwater macrophytes, the ecological consequences of drawdown and the responses of marine macrophytes remain comparatively underexplored. Despite the adverse alterations in sediment dynamics, light availability, hydrostatic pressure, pollutant concentrations, wind and wave exposure, dissolved oxygen levels and nutrient concentration conditions under WLF, aquatic macrophytes can demonstrate remarkable adaptive plasticity. This resilience was mediated through rapid adjustments in survival strategies, coupled with morphological traits, physiological processes and reproductive modifications. While their adaptive capacities were limited, and varied depending on life-forms, species or the WLF amplitudes, fluctuations in water level often precipitated rapid shifts in dominant species or even community succession over short timeframes. Consequently, while moderate WLF might confer ecological benefits, prolonged or extreme WLF posed substantial threats to aquatic vegetation. Synthesizing these findings, we developed a conceptual model diagram integrating the multifaceted responses of aquatic macrophytes to flooding-induced WLF. Future research should prioritize investigating the ecological consequences of drawdown-induced WLF and the responses of marine macrophytes-areas that remain comparatively underexplored. Furthermore, implementing refined water-level-management regimes could help optimize the good functions and services delivered by aquatic ecosystems.