Recognition on the forming-vanishing process and underlying mechanisms of the hypoxia off the Yangtze River estuary

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• 作者：QinSheng Wei ; BaoDong Wang ; JianFang Chen ; ChangShui Xia…
• 关键词：Yangtze River estuary ; hypoxic zone ; stratification ; flow field environment ; organic decomposition
• 刊名：Science China Earth Sciences
• 出版年：2015
• 出版时间：April 2015
• 年：2015
• 卷：58
• 期：4
• 页码：628-648
• 全文大小：4,076 KB
• 参考文献：1. Beardsley, R C, Limeburner, R, Yu, H (1985) Discharge of the Changjiang (Yangtze River) into the East China Sea. Cont Shelf Res 4: pp. 57-76 CrossRef
  2. Cai, W J, Hu, X P, Huang, W J (2011) Acidification of subsurface coastal waters enhanced by eutrophication. Nat Geosci 4: pp. 766-770 CrossRef
  3. Chen, C C, Gong, G C, Shiah, F K (2007) Hypoxia in the East China Sea: One of the largest coastal low-oxygen areas in the world. Mar Environ Res 64: pp. 399-408 CrossRef
  4. Chen, C T A (1996) The Kuroshio intermediate water is the major source of nutrients on the East China Sea continental shelf. Oceanol Acta 19: pp. 523-527
  5. Chen, D, Zhang, L X, Liu, H Q (2008) Distribution characteristics and correlating factors analysis of dissolved oxygen in spring and summer in the Yangtze Estuary (in Chinese). Mar Environ Sci 27: pp. 49-53
  6. Chen, S L, Gu, G C, Hu, F X (2011) The barrier effect of plume front on the submerged delta development of Yangtze River Estuary (in Chinese). Mar Sci 25: pp. 55-57
  7. Dai, M H, Guo, X H, Zhai, W D (2006) Oxygen depletion in the upper reach of the Pearl River estuary during a winter drought. Mar Chem 102: pp. 159-169 CrossRef
  8. Diaz, R J (2001) Overview of hypoxia around the world. J Environ Qual 30: pp. 275-281 CrossRef
  Atlas of the Oceans for the Bohai Sea, Yellow Sea, and East China Sea: Hydrology (in Chinese). China Ocean Press, Beijing
  9. Grasshoff, K, Kremling, K, Ehrhardt, M (1999) Methods of Seawater Analysis. Wiley-VCH, Weinheim CrossRef
  10. Hao, Q (2010) The distribution of Chlorophyll a and primary production and the environmental control mechanism in the China Sea: Ship-measured and satellite study (in Chinese). Ocean University of China, Qingdao
  11. Hu, D X (1984) Upwelling and sedimentation dynamics I: The role of upwelling in sedimentation in the Huanghai Sea and East China Sea—A description of general features. Chin J Oceanogr Limnol 2: pp. 12-19 CrossRef
  12. Li, D J, Zhang, J, Huang, D J (2002) Oxygen depletion off the Changjiang (Yangtze River) Estuary. Sci China Ser D-Earth Sci 45: pp. 1137-1146 CrossRef
  13. Li, H L, Chen, J F, Lu, Y (2011) Seasonal variation of DO and formation mechanism of bottom water hypoxia of Changjiang River estuary (in Chinese). J Mar Sci 29: pp. 78-87
  14. Li, X A, Yu, Z M, Song, X X (2011) The seasonal characteristics of dissolved oxygen distribution and hypoxia in the Changjiang Estuary. J Coast Res 27: pp. 52-62 CrossRef
  15. Liu, H X, Li, D J, Gao, L (2012) Study on main influencing factors of formation and deterioration of summer hypoxia off the Yangtze River estuary (in Chinese). Adv Mar Sci 30: pp. 186-197
  16. Lü, X G, Qiao, F L, Xia, C S (2007) Tidally induced upwelling off Yangtze River estuary and in Zhejiang coastal waters in summer. Sci China Ser D-Earth Sci 50: pp. 462-473 CrossRef
  17. Lü, X G (2010) A numerical study on the mechanisms of the upwelling in Yellow Sea and East China Sea (in Chinese). Institute of Oceanology, Chinese Academy of Sciences, Qingdao
  18. Lu, Y, Li, H L, Chen, J F (2011) Seasonal variations of the surface dissolved oxygen saturation in Changjiang River Estuary and its adjacent waters (in Chinese). J Mar Sci 29: pp. 71-77
  19. Ning, X R, Shi, J X, Cai, Y M (2004) Biological productivity front in the Changjiang Estuary and the Hangzhou Bay and its ecological effects (in Chinese). Acta Oceanol Sin 26: pp. 96-106
  20. Pan, Y P, Sha, W Y (2004) Numerical study on winter coastal upwelling off Fujian and Zhejiang coast (in Chinese). Oceanol Limnol Sin 35: pp. 193-201
  21. Rabouille, C, Conley, D J, Dai, M H (2008) Comparison of hypoxia among four river-dominated ocean margins: The Changjiang (Yangtze), Mississippi, Pearl, an
• 刊物主题：Earth Sciences, general;
• 出版者：Springer Berlin Heidelberg
• ISSN：1869-1897

文摘

On the basis of compiled multidisciplinary historical data in 2006-007 and incorporation of relevant simulation results and remote sensing data, we performed an in-depth study of the generation and dissipation process of the hypoxic zone and its distribution morphology and structure off the Yangtze River estuary. Based on the hydrological circulation dynamics, reproduction of phytoplankton (leading to the decomposition of organic matter), and other factors, we comprehensively and systematically investigated the generation and dissipation of the hypoxic zone and underlying mechanisms for the seasonal variation in its position, explored the multi-factorial synergistic reactions during the generation and dissipation process of the hypoxic zone, and revealed the controlled mechanism for the morphology and structure of the hypoxic zone’s distribution. Our studies indicate that in the winter and spring seasons, the hydrological environment off the Yangtze River estuary provides a water body with relatively low contents of dissolved oxygen (DO), which is the background for the formation of a hypoxic zone. After entering into the summer season, the hypoxic zone gradually develops towards the north and becomes mature. Because of the impact of the terrain, local decomposition of organic matter, and upwelling of the Kuroshio subsurface water in July–August, the hypoxic zone off the Yangtze River estuary exhibits the characteristics of discontinuous distribution in space and has a south and north “dual-core-structure in the inner continental shelf. In addition, there is a hypoxic core in the eastern outer continental shelf. The degrees of hypoxia vary for different areas; they are strongest overall in the north, next strongest in the south; they are weakest on the outer continental shelf. In summer, the hypoxic zone in the north is related to the northward differentiation of the southern hypoxic zone and results from local development and intensification. In August, the hypoxic zone in the north reaches its peak, and after September, it rapidly retreats southward and disappears because of weakening stratification. In the fall, there is hypoxic zone along the coast of Zhejiang in the south, and there is also a low-DO area to the southwest of Jeju Island, with both zones disappearing rapidly. In addition, the change of dynamic environment also causes the low-DO area of the outer continental shelf to move outward in the fall. The variation in the intensity of the stratification and its cumulative effects as a barrier of vertical DO transportation over long periods of time have a significant impact on the degree of hypoxia in the hypoxic zone. In addition, the seasonal variations in the size of the stratified region, intensity of each current system/water mass, upwelling, front, and high-value area of phytoplankton biomass jointly restrict the extension of the hypoxic zone in the inner continental shelf and latitudinal (south-north direction) movement of its location off the Yangtze River estuary. The combined effect of dynamic factors, such as that of the Kuroshio subsurface water, causes a low-DO core in the outer continental shelf. The bottom cold water to the north of the East China Sea is the dynamic basis for the formation of the low-DO area to the southwest of Jeju Island during the fall season. The special seabed topography and mud area distribution off the Yangtze River estuary have a certain degree of influence on the development of the hypoxic zone. The generation and dissipation of the hypoxic zone and its distribution morphology off the Yangtze River estuary, and seasonal variation of its structure and position are a result of the synergistic effects of various factors.