长江口海域环境因长期人类活动和自然变化的双重压力而发生改变，可能导致该区域浮游植物群落组成发生较大变化。于2017年8月对长江口浮游植物进行调查，并与历史资料比较，探究该海域浮游植物群落组成及其变化特征。调查共鉴定出浮游植物7门86属205种(含变种、变型和未定种)，总细胞丰度为1.47×105个/L，其中硅藻、甲藻丰度分别占浮游植物细胞总丰度的95.82%、1.19%；柔弱伪菱形藻(Pseudonitzschia delicatissima)、铁氏束毛藻(Trichodesmium thiebautii)、距端假管藻(Pseudosolenia calcaravis)、劳氏角毛藻(Chaetoceros lorenzianus)、翼鼻状藻(Proboscia alata)和巨圆筛藻(Coscinodiscus gigas)等暖水种为主要优势种，平均丰度分别为56.35×103、3.30×103、3.05×103、2.64×103、1.89×103和1.71×103个/L，合计为68.94×103个/L，占浮游植物总丰度的47.00%；各暖水种的丰度高值区均位于长江冲淡水与台湾暖流交汇形成的锋面。相关性分析表明，劳氏角毛藻、距端假管藻丰度与磷酸盐呈显著负相关，巨圆筛藻丰度与溶解无机氮呈显著正相关，距端假管藻丰度与盐度呈明显正相关，劳氏角毛藻和巨圆筛藻丰度与盐度呈明显负相关。对比近30年夏季长江口浮游植物优势种变化，发现暖水种明显增多，且分布范围向北扩展，推测该现象与海水温度升高和暖流水势力增强有关。

The Changjiang (Yangtze River) Estuary has been subject to the double pressure of human activities and natural changes for a long time. As a result, the change of environmental factors may lead to a great alteration of phytoplankton community composition in this area. To explore the composition and variation of phytoplankton community in the Changjiang Estuary and compared with historical data, phytoplankton samples were collected vertically using net trawl method during “LORCE” cruise in August of 2017. Among all the samples collected, 7 phyla, 86 genera, and 205 species were identified, their total abundance was 1.47×105 cells/L. The results showed that diatoms and dinoflagellates accounted for 95.8% and 1.2% of the total phytoplankton abundance, respectively. Warmwater species, including Pseudonitzschia delicatissima (56.35×103 cells/L), Trichodesmium thiebautii (3.30×103 cells/L), Pseudosolenia calcaravis (3.05×103 cells/L), Chaetoceros lorenzianus (2.64×103 cells/L), Proboscia alata (1.89×103 cells/L) and Coscinodiscus gigas (1.71×103 cells/L), were dominant in the phytoplankton community. Their total abundance was 68.94×103 cells/L, which accounted for 47.00% of the total abundance of netcollected phytoplankton. High abundances of these warmwater species were observed near the front formed by the convergence of the Changjiang Diluted Water and Taiwan Warm Current. Spearman’s rank correlation showed that C. lorenzianus and P. calcaravis were negatively correlated with phosphorus, C. gigas were positively correlated with the concentrations of dissolved inorganic nitrogen, and P. calcaravis was positively correlated with salinity, C. lorenzianus and C. gigas were negatively correlated with salinity. Compared with the summer dominant phytoplankton species during the past 30 years, it was found that warmwater species of phytoplankton in the Changjiang Estuary increased significantly and their distribution area expanded northward. It was speculated that this phenomenon was highly associated with sea temperature elevation and the enhancement of warm current.