Effects of organic matter and submerged macrophytes on variations of alkaline phosphatase activity and phosphorus fractions in lake sediment.

Organic matter and submerged plants may affect internal phosphate loading in lake sediment. In this study, we investigated the changes of alkaline phosphatase activity (APA) and phosphorus (P) fractions in lake sediment by adding organic matter (0.0%, 0.5% and 1.0% of dry weight) and plant submerged plants under experimental conditions. Results indicated that the APA in sediments significant increased after 50 days incubation than at 7 days. The APA in the treatments by adding organic matter and submerged plants increased by 26.37%-61.78% than that of control after 7 days incubation, and increased by 1.00%-29.51% at 50 days, indicating both organic matter and submerged plants may remarkable affect APA in sediment, especially for the early stage of incubation. In addition, the soluble reactive P (SRP) concentrations of the overlying water increased significantly with increasing sediment organic matter, possibly related to increase of APA in sediment. However, the release of SRP was obvious restrained due to absorption of submerged plant. TP and P fraction in sediment decreased with increasing incubation time, but the decrease of TP content in sediment was mainly from NaOH-P and OP sources, but not from HCl-P and IP. Effects of organic matter and submerged plants on P fractions in sediment mainly occurred in NaOH-P and OP fractions. At the end of experiments, the contents of NaOH-P and OP in the treatments by adding organic matter and submerged plant decreased by 5.46%-20.47% and 7.87%-21.46%, respectively. These results indicated that the relative importance of organic matter and submerged plants during the release and transformation of P in lake sediment.