Seasonal Variation of Phytoplankton community structure in Hengshan Reservoir
横山水库浮游植物群落结构季节性变化特征

As a large reservoir in Taihu basin, Hengshan reservoir plays an important part in flood control and drinking water safety of Yixing city. Seasonal variation of phytoplankton assemblages were investigated between 2010 and 2010. 90 taxa were identified and most of them belong to blue-green algae and diatom. Cylindrospermopsis sp. was first time found in Taihu basin, which could induced algal bloom in summer with the density reach to 1.01×108 cell/L. Recently, more and more pollutants flowed into Hengshan reservoir, which lay the foundation for Cylindrospermopsis bloom. Cylindrospermopsis is an invasive cyanobacterium and could produce several toxins, endangering ecological system equilibrium and public healthy. It was suggested that regulated the nutrients concentrations and water level or hydraulic retention time in Hengshan reservoir was a good way to control Cylindrospermopsis bloom expansion. Meanwhile, we should increase monitoring frequency and strengthen management in order to prevent it invading other large reservoirs of Taihu basin.