The Impact of Extreme Droughts on Aquatic Macrophyte Communities in the Sub-lakes of Poyang Lake

Aquatic macrophytes play a crucial role in aquatic ecosystems, serving as both food sources and habitats for various organisms, including macrobenthos, fish, and waterbirds. In recent years, Poyang Lake has experienced significant fluctuations in water levels, with frequent extreme hydrological events adversely affecting the growth of aquatic macrophytes. However, limited research has been conducted on the impact of extreme drought on aquatic macrophytes in Poyang Lake. This study investigated the aquatic macrophyte communities in the typical sub-lakes (Dahu Lake, Shahu Lake, and Changhuchi Lake) of Poyang Lake in July 2022 and July 2023. The results indicate that the average water depths of the sub-lake areas in Poyang Lake were (160.27±50.70) and (58.00±21.46) cm in 2022 and 2023, respectively, with corresponding transparency values of (49.10±14.41) and (47.25±10.91) cm. Notably, the dominance of floating-leaved plants, particularly Trapa spp., was observed in both years, while submerged species such as Vallisneria spinulosa and Hydrilla verticillata exhibited increased dominance and biomass in 2023. The drought in the lake area resulted in a reduction in water level and alterations in water transparency, which affected the species richness of plant communities and promoted plant diversity. Variations in water level and transparency within the sub-lakes across different years exerted significant influence on aquatic macrophyte diversity. Substantial disparities in species composition of aquatic macrophytes communities within the sub-lakes of Poyang Lake between the two years were observed, marked by an augmented proportion of emergent plants and wetland plants after the drought in 2023. This study investigates the impact of extreme drought on aquatic macrophytes in the sub-lakes through a comparative analysis of two years of monitoring data. The findings of this research can provide a scientific basis for the restoration of aquatic macrophytes in Poyang Lake and the management of food resources for overwintering waterbirds.