To understand the characteristics of dissolved oxygen and its annual and seasonal changes, seven surveys were carried out from August 2008 to September 2010 in the Yangtze Estuary covering the area from 30?0'-32?0'N to 122?15'-124?0'E. The results showed that, there co-existed two hypoxic zones in the survey area in summer. Hypoxia occurred mainly between 20m to 50 m water layers in summer. Dissolved inorganic nitrogen, active phosphate and Chlorophyll a had discrepancy between hypoxic zone and other areas, yet hypoxia affected planktons slightly. The hypoxia area was high distribution center of biomass. Polychaetes were the most species of benthic community, which had high tolerance to hypoxemia.%通过对2008年8月至2010年9月在长江口30°20′N-32°30′N,122°15′E-124°20′E范围海域开展的7次综合海洋调查资料进行分析,以期了解长江口海域低氧现象的年际、季节变化及其对海洋环境和生物的影响.研究结果发现,该海域夏季存在长江口和浙江南部两处低氧区域,低氧现象主要发生在20～50 m水层；低氧海域与非低氧海域的无机氮(DIN)、活性磷酸盐、叶绿素a含量存在一定差异；长江口海域浮游动物、浮游植物的分布状况与低氧区的存在与否未能发现相关关系.低氧区是底栖生物生物量的高值区,多毛类是其中最多的底栖生物种类,对低氧环境的耐受程度较高.
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