夏季，长江口底层极易发生大面积低氧甚至缺氧。比较2016和2017年夏季长江口缺氧区(DO＜2 mg/L)、低氧区(2 mg/L＜DO＜3 mg/L)和正常海区(DO＞3 mg/L)浮游动物群落(＞160 μm)特征发现：2016年群落丰度和生物量均表现为缺氧区明显高于低氧区和正常海区；中小型桡足类、胶质浮游动物丰度表现为缺氧区和低氧区均高于正常海区；胶质浮游动物的组成，在低氧程度较严重的2016年夏季，以滤食性的海樽纲和有尾纲为主，在2017年夏季，以肉食性毛颚动物为主。

 In summer, large areas of low dissolved oxygen or hypoxia are prone to occur in the bottom waters of Changjiang (Yangtze River) Estuary. The zooplankton community (＞160 μm) in hypoxic area (DO＜2 mg/L), low dissolved oxygen area (2 mg/L＜DO＜3 mg/L) and normal area (DO＞3 mg/L) of the Changjiang Estuary in summer of 2016 and 2017 were compared. The results showed that the abundance and biomass of zooplankton in hypoxic area were significantly higher than those in the low dissolved oxygen area and normal area in 2016. The abundance of small mediumsized copepods and gelatinous zooplankton in hypoxic area and the low dissolved oxygen area were all higher than those in the normal area. It was dominated by filterfeeding of the class Thaliacea and Appendiculata in the summer of 2016 when the degree of hypxia was more serious, but in the summer of 2017, it was dominated by carnivorous Chaetognaths of the class Sagitta.