Objective Effect of submerged planting Vallisneria natans on nitrogen transformation in pond sediment that contained enrofloxacin (ENR) residues was investigated for restoration of aquacultural pollution.

Method A microcosm experiment was carried out in PVC tanks by planting V. natans in sediment soils with or without the presence of ENR or no planting on an ENR-added sediment, along with a blank control. Nitrogen transformation of the soil was monitored by measuring the nitrogen concentration in sediment water, observing the growth of V. natans plants, and determining the abundance of relevant genes presented in the sediment.

Result The planted macrophytes removed 41.4% total nitrogen(TN) and 51.5% NH₄⁺-N in the sediment water and significantly increased amoA, narG, nirK, and nirS by 151.6%, 188.7%, 371.3%, and 210.3%, respectively, in the rhizosphere soil. When the ENR concentration in sediment reached 0.6–0.8 mg·kg⁻¹, the TN and NH₄⁺-N removal rates were significantly reduced to 26.8% and 25.1%, respectively. Meanwhile, the V. natans leaves significantly slowed to increase in length, while the sediment denitrifying genes were not significantly affected.

Conclusion By planting V. natans, the TN and NH₄⁺-N in the sediment water were effectively reduced and the denitrifying microbial population in the soil significantly raised. However, the presence of ENR at the level of 0.6-0.8 mg·kg⁻¹ could significantly inhibit the plant growth mitigating the antipollution effect and the denitrifying bacteria effect.