ABSTRACT
The overwinter period is the pre-stage of the algal bloom, and the endogenous phosphorus (P) in sediments is one of the main P sources of algal blooms during this period. Based on the investigation of the water quality and sediment pollutants during the overwinter period of cyanobacteria (recruitment period and dormancy period), this study analyzed the P release characteristics of sediments in the horizontal and vertical directions and clarified the P release risk of sediments and the change in microbial community structures. The results showed that the lake bay was moderately eutrophic in the two periods of the study area, and the water quality and sediment nitrogen and P pollution were more serious, and the chlorophyll a content (Chl-a) was still at a high level in the overwinter period. The pseudo-second order model and the modified Langmuir model could respectively describe the P kinetics and sorption isotherm behavior in the sediment. The theoretical maximum P sorption capacities (Qmax) of sediments were bottom layer>middle layer>surface layer, and the highest value was 1.648 mg·g-1 with the highest P sorption rate constant of the pseudo second-order kinetic model of 6.292 g·(mg·min)-1. Additionally, the P adsorption parameters (Qmax, NAP, and EPC0) were mainly affected by the physical and chemical properties of the sediment itself and the nutritional level of the lake bay. The surface sediments from the dormancy period mainly played the role of P sinks, and the part of sediments from the recruitment period played the role of P sources, in which existed the risk of endogenous P release. The analysis of the microbial community structure in sediments indicated that the microbial diversity in the sediments during the dormancy period was higher than that during the recruitment period, and some microbial categories with phosphate-solubilizing function of relative abundance was high.
