Effect of environmental factors on phosphorus transformation during the growth of submerged macrophytes

Three submerged macrophytes, Hydrilla verticillata , Vallisneria natans, and Potamogeton crispus , were planted in winter and spring to investigate the environmental mechanism of phosphorus transformation during submerged macrophyte growth periods. The experimental buckets each contained 4,832.80 g of dry sediment (depth: 10 cm) and 100 L water. The phosphorus (P) fractions in the water and sediment were investigated along with the environmental factors, including pH, dissolved oxygen (DO), and redox potential (ORP). The concentrations of the different forms of P in the water and sediment were lower in the submerged macrophyte groups. Submerged macrophyte uptake was the primary reason for the decrease in P in the water and sediment. At the end of the experiment, the total amounts of phosphorus accumulated by H. verticillata, V. natans , and P. crispus were 156.05 g, 282.24 g, and 115.84 g, respectively, and the three submerged macrophytes enriched P by 4.18%, 7.56%, and 3.10%. The levels of the environmental factors pH, DO, and ORP were higher in the submerged macrophyte groups than the control groups. The environmental factors had different effects on the different forms of P during growth of the submerged macrophytes. H. verticillata primarily acted on the soluble reactive phosphorus (SRP) through environmental factors, while P. crispus acted on the dissolved total phosphorous, SRP, dissolved organic phosphorus, and particulate phosphorous through these factors. V. natans had a weak impact on P content in the water through the environmental factors. Hence, the transformation of P between the sediment and water was affected by environmental factors. Overall, the results of this study reveal the effects of environmental factors under submerged macrophyte growth on water purification as well as the migration and transformation of P in the sediment and on the surface and provide a theoretical basis for the ecological restoration of eutrophicated shallow lakes.