Abstract: Restoring submerged macrophytes is of significant importance for the remediation of water eutrophication. Sediment samples with or without Vallisneria natans were collected at Qinhu Lake, Taizhou in January, May and September of 2019. We analyzed phosphorus content and examined bacterial community structure in sediments by high-throughput sequencing of the 16S rRNA gene. The environmental factors were also investigated. The results showed that the growth of V. natans reduced the concentrations of total phosphorus (TP) and available nitrogen contents in sediments, but increased bioavailable iron, organic matter contents and Fe-P/TP ratio. The dominant bacterial phyla in the sediments included Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteriota and Desulfobacterota, with seasaonal variations of bacterial community structure. With the presence of V. natans, the relative abundance of Proteobacteria and Desulfobacterota increased and the relative abundance of Chloroflexi and Acidobacteria decreased. Results of the redundancy analysis showed that water pH and TP in sediments had the most significant influence on the spatial distribution of bacterial community, followed by dissolved oxygen. Overall, our results indicated that the growth of V. natans affected bacterial community composition in sediments by changing the physical and chemical properties of lake water and sediments, and thus increased phosphorus fixation efficiency in sediments and improved water quality of the lake.

Key words: Vallisneria natans, sediment, phosphorus, bacterial community structure.