Evaluation of aquatic plant community diversity in an urban eutrophic lake—a combination of traditional survey and metabarcoding methods in Donghu Lake, Wuhan

Aquatic vegetation plays a crucial role in wetland ecosystems but are sensitive to human activities, especially in urban lakes where the loss of aquatic plant diversity is pronounced. Recently, there has been increasing interest in whether the restoration of urban lakes can alleviate ecological degradation, with changes in aquatic plant diversity serving as important ecological indicators. However, methods for evaluating aquatic plant community diversity still require further refinement. Despite the widespread application of environmental DNA (eDNA) in monitoring aquatic biota, its use for assessing aquatic plant community diversity, particularly through metabarcoding methods remains limited. This study assessed aquatic plant diversity and spatial distribution patterns in Donghu Lake and its surrounding wetlands, a typical eutrophic urban lake in China, using both traditional community surveys and eDNA methods. Surveys covered both the littoral zone and open water areas, and considered various eDNA sample types. A total of 69 aquatic plant species were identified by eDNA while 50 were identified by traditional survey methods. This shows that eDNA identified more aquatic plant species than traditional survey methods. Both methods showed similar levels of aquatic plant diversity (alpha diversity) within each habitat type, showing no significant differences in were found between the methods in either the ponds or the lake area. In contrast, both methods consistently identified significant differences in aquatic plant community composition (beta diversity) between the pond and lake areas. Moreover, distinct plant communities were found in different areas of the pond, while no significant variation was observed among regions within the lake. This study provides crucial data for assessing biodiversity in an urban lake, suggesting the potential mitigation of aquatic ecological degradation in Donghu Lake. Our findings also demonstrate the potential of eDNA metabarcoding as a tool for evaluating aquatic plant diversity in habitats within lentic ecosystems. • eDNA detected more aquatic plant species compared to traditional surveys. • Two methods revealed similar diversity patterns in different habitats and sites. • eDNA metabarcoding is a significant tool for aquatic plant diversity estimation. • Urban ponds play a crucial role in maintaining aquatic plant diversity.