Impacts of hydrodynamic disturbance on sediment resuspension, phosphorus and phosphatase release, and cyanobacterial growth in Lake Tai

摘要

The objective of this study was to link hydrodynamic disturbance with sediment resuspension, phosphorus release, and algal growth in Lake Tai, a typical shallow lake located in the south of the Yangtze River Delta in China. With this regard, a sediment-water-algae laboratory experiment was conducted and extrapolated to the real situation in terms of field observations. The results show that the algal growth rate synchronically increased with dissolved total phosphorus (DTP) release rate. The DTP decreased with increase of bottom flow velocity, indicating that the phosphorus release rate was lower than its transfer rate into algal biomass. While all levels of hydrodynamic disturbances could increase sediment resuspension and phosphorus release, a low to moderate disturbance was beneficial, but a strong disturbance was harmful for algal growth. Also, a low to moderate disturbance caused the dissolved alkaline phosphatase activity (DAPA) to increase with time, which provided the enzyme for hydrolyzing a variety of organic phosphorus compounds from bed sediment into algae-needed nutritional DTP. The experiment proved to be an efficient means to understanding eutrophication mechanisms of large shallow lakes such as Lake Tai.