Abstract: High-throughput 16S rRNA gene sequencing was used in this study to dissect the bacterial community structure and nitrogen cycling functions in Vallisneria natans and bionic aquatic plant when subjected to three nitrogen forms in water: 2 mg/L NH⁺₄-N, a combination of 1 mg/L NH⁺₄-N and 1 mg/L NO^－₃-N, and 2 mg/L NO^－₃-N. The results indicated that V. natans supported the greatest biofilm biomass under NH⁺₄-N exposure. Sole NO^－₃-N treatment resulted in the highest α diversity within the bacterial community attached to submerged plants, while the co-occurrence of NH⁺₄-N and NO^－₃-N notably influenced on the community’s β diversity. Pseudomonas, Aeromonas, and Acinetobacter were identified as the dominant bacterial genera, exhibiting distinct responses to the different nitrogen conditions. Furthermore, the modularity of bacterial co-occurrence networks was most pronounced under NH⁺₄-N treatment alone, whereas increased interspecies competition was observed with the combined nitrogen forms. PICRUSt2 function prediction indicated a reduction in the relative abundance of nitrification genes in the V. natans biofilm under NO^－₃-N treatment. These findings shed light on the impact of various nitrogen forms on the structures and functions of bacterial community on submerged plants, which is instrumental for the advancement of water purification techniques utilizing submerged vegetation across varying water quality scenarios.

Key words: submerged aquatic plants, attached bacteria, diversity, community composition, nitrogen cycle functional genes