The cruise was conducted from June 12 to 22, 2006, on board R/V Dong Fang Hong 2 at the Changjiang Estuary. Water samples were collected at three anchor stations. Femtoplankton and picoplankton were simultaneously determined by flow cytometery. Prochlorococcus was undetectable in all samples. Average abundances of Synechococcus and picoeukaryotes were at the order of 105 - 106 cells/L, but heterotrophic bacteria and viruses at the order of 108 - 109 cells/L. In the turbid Changjiang Estuary, vertical characteristics of femtoplankton and picoplankton were different. Turbidity was a key factor regulating diel variations of picoeukaryotes, heterotrophic bacteria, and viruses. Picoeukaryotes became the most important contributor among the picophytoplankton in turbid estuarine area. As a result, diel variation of picoeukaryotes showed a positive correlation with that of heterotrophic bacteria.%2006年6月12日至22日“东方红2号”考察船夏季航次期间，在长江口3个连续观测站位进行了水样采集，应用流式细胞仪分析了水样中的极微型浮游生物（Femtoplankton）和微微型浮游生物（Picoplankton）。结果显示，原绿球藻（Prochlorococcus）在所有样品中均未检测到；检测到的聚球藻（Synechococcus）和微微型真核浮游植物（Picoeukaryotes）平均丰度达数量级10^5～10^6个／L，异养细菌（Heterotrophic bacteria）和病毒（Viruses）平均丰度达数量级10^8～10^9个／L。在浑浊的长江口水域，极微型和微微型浮游生物的垂向分布特征不同，主要与各站位特有的水动力条件密切相关：浊度是调控微微型真核浮游植物、异养细菌和病毒周日变化的关键因子之一；微微型真核浮游植物成为微微型浮游植物中最重要的组成部分，与异养细菌具有显著的正相关关系。
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