[Impacts of Microorganisms on Degradation and Release Characteristics of Organic Phosphorus in Lake Sediments During Freezing Season].

Organic phosphorus (OP) has been considered as an important pool for bioavailable phosphorus. In this work, impacts of microorganisms on the degradation and release of OP in sediments from Lake Wuliangsuhai during freezing season were investigated using chemical sequential extraction methods. The results showed that the concentrations of dissolved total phosphorus (DTP) dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) in overlying water of the sterilization (T(N)) treatments were higher than those of the substrate addition (T(M)) treatments, indicating that the assimilation of anaerobic microorganisms and the disassimilation reduction of iron driven by microorganisms were the main mechanisms govening OP behavior and process across the water-sediments interface. The concentrations of labile OP (LOP) and total labile phosphorus (TLP) decreased during the releasing period. During the first 60 days, the concentrations of moderately labile OP (MLOP) of T(M) treatments decreased, while those of the nonlabile OP (NLOP) increased. During 60-180 days, the MLOP concentrations of T(M) treatments were found increasing, while those of NLOP decreased. During the beginning period (0-60 d), the concentrations of MLOP of T(M) treatments were higher than those of T(N) treatments, while the NLOP concentrations were lower than those of T(N) treatments; and these trends were reversed during 60-180 days. These trends revealed the possibility of transformation between MLOP and NLOP during the releasing process. Furthermore, the percentage of OP was found decreasing, while inorganic phosphorus (IP) of T(M) treatments increased, which indicated the transfromation trend from OP to IP (about 6.1% of OP was transformed to IP) in sediments. On the basis of this work, it can be conclueded that microorganisms can improve the transformation from OP to IP elevating the bioavailability and contribution of OP in the eutrophication process of Iakes.