为探究钱塘江（杭州段）浮游藻类季节动态及其与环境因子的关系，于2018年1—12月对4个主要监测点位进行了月度采样调查。结果表明:浮游藻类总叶绿素质量浓度月均值为1.74～22.86 μg/L，蓝藻叶绿素质量浓度月均值为0.02～10.82 μg/L，全年浮游藻类组成以蓝藻和硅甲藻为主。环境因子主要选取了水温、水体pH值、浊度、电导率、溶解氧（DO）、高锰酸盐指数（CODMn）、氨氮（NH3-N）、总氮（TN）、总磷（TP）共9项水质参数。浮游藻类叶绿素质量浓度受水体理化因子影响较大，按月均值分析：总叶绿素质量浓度及绿藻叶绿素质量浓度均与水体温度显著正相关，蓝藻叶绿素质量浓度与水体温度极显著正相关；按季节平均值分析，硅甲藻叶绿素质量浓度与总磷质量浓度极显著负相关。由此可见，水温与总磷是影响钱塘江（杭州段）浮游藻类季节动态的主要环境因子。对主要环境因子和重要点位进行分类管理、联动监测和比对监测，尽可能防控环境风险，才能更好地实现浮游藻类环境监测分析的预警功能。
The Qiantang River (Hangzhou Part) is located in the lower reaches of the Yangtze River Economic Belt.It is not only an important source of drinking water,but also related to ecological safety of Hangzhou City and Zhejiang Province.In recent years,due to the rapid social and economic development in the Qiantang River basin,impact of human activities on the water environment has further deepened,and pressure on environmental governance and ecological protection of Qiantang River has significantly increased.Residents in the river basin have further increased their expectations for better water environment,which put forward higher requirements for the water environment management of the Qiantang River (Hangzhou part). To explore the seasonal dynamics of planktonic algae in the Qiantang River (Hangzhou section) and their relationships with environmental factors,and to provide technical support for water environment protection,phytoplankton and environmental factors were monthly monitored in Qiantang River (Hangzhou part) in 2018,including four main sites.Environmental factors mainly include water temperature (T),water pH,turbidity,conductivity,dissolved oxygen (DO),permanganate index (CODMn),ammonia nitrogen mass concentration (NH3-N),total nitrogen mass concentration (TN),and total phosphorus mass concentration (TP). The monthly mass concentration of total chlorophyll of phytoplankton was ranged from 1.74 to 22.86 μg/L,and the monthly chlorophyll mass concentration of cyanobacteria was ranged from 0.02 to 10.82 μg/L.The composition of planktonic algae throughout the year was dominated by cyanobacteria and diatom.The site with highest total chlorophyll mass concentration was Yanlingwu in the four seasons of spring,summer,autumn and winter.The site with the highest mass concentration of cyanobacteria in spring was Jiangjunyan,while the highest mass concentration site in summer,autumn and winter was all Yanlingwu.For all monitoring sites,the highest mass concentration of planktonic algae chlorophyll always occurred in summer.The total chlorophyll mass concentration and the cyanophyll chlorophyll mass concentration showed almost the same seasonal variation trend at Jiangjunyan,indicating that the cyanobacteria had an absolute advantage in composition.It was worth noting that from spring to summer,the chlorophyll mass concentration of cyanobacteria both had increased from the lowest value to the highest value throughout the year at Yanlingwu and Yinzhu.Environmental factors had obvious impacts on the mass concentration of chlorophyll of phytoplankton.There was a significant positive correlation between the annual mass concentration of total chlorophyll of phytoplankton and water temperature.There was a significant positive correlation between the annual mass concentration of cyanobacteria chlorophyll and water temperature.There was a significant negative correlation between the seasonal mass concentration of diatom chlorophyll and total phosphorus. Therefore,the chlorophyll mass concentration of planktonic algae was greatly affected by the physical and chemical factors in Qiantang River (Hangzhou part).Water temperature and total phosphorus were the main environmental factors that affected the seasonal dynamics of planktonic algae.Monitoring and management of different sites all need to focus on different emphasis.It was necessary to implement classified management,linkage monitoring and comparative monitoring of major environmental factors and important points.Preventing and controlling environmental risks as much as possible can help realize the early warning function of monitoring and analysis of plankton algae environment.