Spatiotemporal variations of P species and adsorption behavior in water column, interstitial water, and sediments were investigated in the large shallow eutrophic Lake Chaohu. Orthophosphate (Ortho-P) and total phosphorus (TP) concentrations were significantly higher in the western part than in the eastern part of the lake, due to different nutrient inputs from the surrounding rivers. Moreover, particulate phosphorus (PP) concentration was in a similar spatial pattern to Ortho-P and TP concentrations, and also showed significantly positive correlation with the biomass of Microcystis, indicating more uptake and store of phosphorus by Microcystis than by other algae. Increase of pH and intensive utilization of P by phytoplankton were the main factors promoting P (especially Fe-P) release from the sediment to interstitial water during the cyanobacterial blooms in Lake Chaohu. Spatial dynamics in TP concentration, P species and adsorption behavior of the sediment, coupled with the statistical analyses, suggested that the spatial heterogeneity of P contents in the sediment was influenced by various factors, e.g. human activities, soil geochemistry and mineral composition. In spite of similar TP contents in the sediments, increase in proportion of Fe-P concentration in the sediment may result in a high risk of P release.Keywords: eutrophication, water column, sediment, phosphorus, species, sorption and release, Lake Chaohu, cyanobacterial blooms.Dense blooms of phytoplankton, especially cyanobacteria, often occur in the hypereutrophic lakes. Outbreak of cyanobacterial blooms is one of the most important symptoms of eutrophic inland waters. P is considered to be the main factor inducing the nuisance growth of cyanobacteria. Cyanobacterial blooms in eutrophic lakes [1][2][3] are often coincident with the increase of P in the water column [4][5][6] . Song et al. [7] investigated the relationship between algal blooms and phosphorus status of sediment in ponds, and found that compared with the ponds lacking Microcystis aeruginosa the ponds with Microcystis aeruginosa blooms showed relatively high concentrations of Ortho-P in the overlying water or different P species in the interstitial water. However, studies on the influence of phytoplankton on P dynamics are very limited. Wang et al. [8] studied the effects of the variations of environmental conditions on phosphorus release from the sediments in Lake Taihu, and found a significant increase of P release when both algae and sediment were present in the experiment. Anderson [9] suggested that increased P release from the sediment in summer time [10] studied the influence of pH on P release from the sediments sampled from the freshwater tidal portion of the Potomac estuary, and found that the release rate increased markedly when pH of the overlying water was 9.5-10. Xie et al. [11] found the different responses of N and P in the sediment to the cyanobacterial blooms in an enclosure experiment conducted in Lake Donghu in the summer of 2000, and they conducted that ...