[Effects on phosphorus fraction distribution in sediment by roots of Vallisneria natans].

The present study explored phosphorus fractions in sediments with the growth of Vallisneria natans. Sediment samples in different layers were collected at 20, 50 and 80 d, and vertical change of several phosphorus fractions were measured in the samples. The root distributions and biomass of the V. natans were measured. Our results showed that roots were distributed between 0 and 14 cm in the experimental device. The average number of roots and average root length were 58 and 5.86 cm. After 80 days growth, the percentage of V. natans root biomass were 45.99%, 32.75%, 16.03% and 5.23% in the sediment with depths of 0-3, 4-6, 7-10 and 11-14 cm. Total phosphorus (TP) content, phosphorus extracted by NaOH (NaOH-P), and organic phosphorus (OP) levels remarkably decreased (P < 0.05) in the area with a high concentration of tape grass roots. The content of phosphorus extracted by HCl (HCl-P), and inorganic phosphorus (IP), showed no significant difference (P > 0.05). The results suggest that V. natans root affects the migration and transformation of phosphorus species in the sediment.