Yi’an, Lin, Su Jilan, Tang Renyou and Lin Chuanlan

Laboratory of Ocean Dynamic Processes and Satellite Oceanography, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, P.R. China, Tel: (86)-0571-88076924-2497, Fax:(86)-0571-88071539, E-mail: linyian@sio.zj.edu.cn

Nutrient elements flux and biogeochemistry variation of the Changjiang Estuary and its influence on the ecosystem of the East China Sea waters

The Changjiang River is the largest river in China, ranking third among the world’s rivers behind the Amazon and Nile. The river discharges vast sums of water, sediments and biogenic elements into the East China Sea and is regarded as an important material source of the Northwest Pacific marginal sea. According to annals data and the results obtained by the field survey and experiments recently, the biogenic elements flux and biogeochemistry variation of the Changjiang Estuary and its influence on ecosystem environment of the East China Sea was studied in this paper. In the past 30 years, the flux of DIN of the Changjiang trunk stream was in a great extent increased, among others the flux of NO₂^- was increased by 8 times, and the flux of PO₄^3- was increased by more then 2 times; but the flux of SiO₃^3- was a slight decrease. In the estuarine area, species of biogenic elements were transformed by a series physical and biogeochemical action was expatiated. The waters of delta from river mouth to the maximum turbidity zone become a new “source” of PO₄^3-, DIN and NO₃^- that increase the concentration of nutrients in the estuary waters. In one hand, the huge flux of biogenic elements provide plenty nutrients for primary production in the coastal waters; in other hand, superfluous nutrient and exorbitant N/P ratio has conduced eutrophication, hypoxia area formed and extended and frequent red tide in coastal zone, and unfitted N/P ratio become a limit factor of primary productivity.

For example, the concentrations of DIN and NO3- were accretion as a mass of organic matter was degraded and the concentration of PO₄^3- was increase also, while the inorganic P of surface of suspending particle was exchanged by the anion of saltwater.