Characteristics of phytoplankton community structure and its response to hydro-meteorology in summer of Qiantang River

河流中浮游植物的动态变化能够较好的指示河流水质状况.为探索水文气象过程对筑坝河流浮游植物群落结构的影响，2020年夏季，以钱塘江干流为例，对包括富春江水库在内的11个河段开展了浮游植物群落结构及相关环境因子的调查分析.结果表明：夏季在钱塘江干流共鉴定出浮游植物6门59属95种，优势属为沟链藻（Aulacoseir）、菱形藻（Nitzschia）、平裂藻（Merismopedia）、长孢藻（Dolichospermum）、假鱼腥藻（Pseudoanabaena）和微囊藻（Microcystis），其中梅雨期优势属主要隶属于硅藻门，梅雨后蓝藻门种属则迅速占优，浮游植物总细胞密度快速增加；整个夏季浮游植物的平均细胞密度为（1.57±2.96）×106 cells/L，其中梅雨期细胞密度为（0.37±0.36）×106 cells/L，显著低于梅雨后的细胞密度（4.06±4.38）×106 cells/L.空间上，大坝拦截形成的河流型水库对浮游植物群落结构和藻密度均产生极显著的影响，浮游植物密度在富春江库区段最高，兰江及以上江段其次，新安江库区段及钱塘江河口较低；梅雨后富春江库区水温分层，显著促进了蓝藻和硅藻的增殖.冗余分析表明，气温和降雨是夏季钱塘江干流浮游植物群落结构变化的主要驱动因子，蓝藻门、绿藻门细胞密度与气温呈显著正相关，与降雨呈显著负相关，而硅藻门细胞密度与之相反；梅雨后气温快速增高显著增加库区段水体的蓝藻门细胞密度，蓝藻水华暴发风险迅速增高，水安全管理中应予以重点防范.;The dynamic changes of phytoplankton in rivers can better indicate the water quality rivers. In order to explore effects hydro-meteorological processes on community structure damming rivers, taking main stream Qiantang River as an example, and related environmental factors were investigated analyzed 11 river reaches including Fuchunjiang Reservoir summer 2020. The results showed that:A total 95 species belonging 6 phyla 59 genera identified during River. dominant Aulacoseir, Nitzschia, Merismopedia, Dolichospermum, Pseudoanabaena, Microcystis. During Meiyu period, belonged diatoms, while after rain, cyanobacteria quickly became dominant. average cell density was (1.57±2.96)×106 cells/L, period (0.37±0.36)×106 which significantly lower than that ((4.06±4.38)×106 cells/L). Spatially, reservoir formed by dam interception has extremely significant effect algal density. is highest section, followed Lanjiang its upper reaches, Xin'anjiang section estuary. After temperature stratification promoted proliferation diatoms. Redundancy analysis rainfall driving change summer. Cyanophyta Chlorophyta densities positively correlated with negatively rainfall, Diatomophyta contrary Cyanophyta. rapid increase rapidly area, risk blooms increases rapidly. Therefore, prevention should be emphasized safety management.