Promoting effect of submerged plants on phosphorus source and sink in sediments: Response of phosphorus release and microbial community to Vallisneria natans and Potamogeton malaianus growth

As the significant primary producers, submerged plants occupy key positions in aquatic ecosystem with sediments or overlying water, and play a non-negligible role in the immigration and transformation process of phosphorus (P) cycle. In this study, two submerged plants, Vallisneria natans ( V. natans) and Potamogeton malaianus ( P. malaianus), were planted using two different sediments of source and sink, respectively, and sediment-water-plant (S-W-P) system was constructed. The results showed that the source sediment was more favorable for the growth of submerged plants, and that the number of stems, amount of leaf growth, biomass, and diameter of root were greater than those of the sink sediments in the later periods of growth. The sediment state had a tendency from source to sink in the later period, with the soluble P (SRP) values of 0.11 mg/L and the sediment equilibrium P concentration (EPC0) of 0.09 mg/L in the surface sediment of O-W-V system, the risk of P release was subsequently reduced, P adsorption index (PSI) increased from 0.40 L/g to 0.81 L/g, P adsorption saturation index (DPS) increased from 15.12 % to 25.24 %. In S-W-P system, P release contribution (V1 and V2) of organic P (OP) were positive and it's the main release form of P, which may be related to the production of humic substances at the end of plants growth.