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1999年8月20～30日,对黄海和东海海域进行了一次为期10d的海洋科学考察.在长江河口外发现有一处面积达13700km~2,平均厚度达20m的底层低溶氧区（DO<2mg/L）,其含氧量最低值达到1mg/L.沿-100m的等深线DO值低于3.5mg/L的底部低氧海区向东南方向一直延伸到了东海大陆架.在低溶氧区域,表观耗氧量（AOU）为5.8mg/L,亏损氧总量达1.59×10~6t.在这一海域存在着由于长江径流的注入以及台湾暖流造成的海水上涌形成强的温盐跃层,限制了表层高含量氧向底层扩散,表层浮游植物光合作用产生的大量颗粒态有机碳向底层输送,并在底层进行化学和生物氧化是形成低氧海区底层氧亏损的主要原因.同时,长江径流携带的N,P污染物输入的不断增加更是为氧亏损水域表层浮游植物的生长提供了丰富的营养盐,从而加剧了该水域氧的亏损.
A marine geological survey of 10 days was conducted in the Yellow Sea and the East China Sea from August 20 to August 30, 1999. A low dissolved oxygen zone (DO <13.00 km 2) with an average thickness of 20 m was found outside the Yangtze River estuary (DO < 2mg / L), the lowest oxygen value reached 1mg / L. Along the depth of -100m isobath DO is lower than 3.5mg / L of the bottom of the low-oxygen sea area to the southeast direction has been extended to the East China Sea continental shelf in the low-oxygen region , The apparent oxygen consumption (AOU) was 5.8mg / L, and the total amount of depleted oxygen was 1.59 × 10 ~ 6t. In this area there is a strong warm salt due to the influx of the Yangtze River runoff and the seawater upwelling caused by Taiwan’s warm current The thermocline, which restricts the diffusion of high oxygen content in the surface layer to the bottom layer, the transport of a large amount of particulate organic carbon from surface phytoplankton photosynthesis to the bottom layer, and the chemical and biological oxidation in the bottom layer are the main reasons for the formation of oxygen deficiency in the bottom layer of the hypoxia. The increasing input of N and P pollutants carried by the runoff in the Yangtze River also provided rich nutrients for the growth of phytoplankton in surface waters of oxygen-deficient waters, thus aggravating the oxygen losses in the waters.