Underwater light source changes microecosystem constructed by Vallisneria spinulosa Yan for water restoration: Efficiency of water purification, characteristics of growth, and rhizosphere.

[Display omitted] • Underwater light source obviously affected the microecosystem of V. spinulosa Yan. • Removal loads of TN and TP were enhanced by 61.5 and 8.5 mg m−2 d-1, respectively. • Growth of leaf and root of V. spinulosa Yan were obviously improved. • Abundance of Methylocystis , Dechloromonas was reduced but Clostridium was increased. • Metabolism of carbohydrate, lipid, and energy of V. spinulosa Yan were promoted. Submerged macrophytes are effective in ecological restoration of water bodies polluted by nitrogen and phosphorus, and its restoration capacity depends on underwater illumination condition. This study explored the influencing mechanism of illumination on Vallisneria spinulosa Yan (V. spinulosa Yan) for water restoration. Addition of underwater light source increased the total nitrogen, ammonia nitrogen, total phosphorus, and phosphate removal loads of the V. spinulosa Yan growth system by 61.5, 39.2, 8.5, and 5.0 mg m−2 d-1, respectively. Meanwhile, the growth of V. spinulosa Yan was obviously promoted, even with high water turbidity. Although the biological nitrogen removal processes were inhibited by adding underwater light source, the growth of V. spinulosa Yan can be significantly improved, thus enhancing the efficiency of water purification via the absorption of nitrogen and phosphorus by V. spinulosa Yan. This study provides a theoretical foundation and technical support for application of submerged macrophytes in ecological water restoration. [ABSTRACT FROM AUTHOR]