Contribution of the Yangtze River to Ecosystem of the East China Sea

The Yangtze River of the China main land has recorded the decrease of sediment load in these 10 years because of construction of dams in the upstream region. The Three Gorgeous Dam, partly started its operation since July of 2003, has a significant contribution to reduce the sediment load with sedimentation. According to the Yangtze River hydrological report, the amount of discharge and the sediment concentration exhibit a clear migration in season and temporal changes. The seasonal and annual variations of discharge and sediment concentration are expected to have a strong contribution to the ecosystem in the East China Sea. In this study, a primary productivity in the East China Sea, especially over the offshore region of the Yangtze River mouth, is estimated with satellite monitoring of chlorophyll-a concentration, sea surface temperature, photo-synthetically available radiation, which are observed by MODIS on the polar orbiting satellite AQUA. The depth resolved primary productivity model was implemented to estimate the primary productivity where sufficient amount of nutrients are supplied and the variation of environments by the river compounds. In-situ measurements are also conducted at the entrance of the Kuroshio into the East China Sea, at one exit of the Kuroshio into the Pacific and at another exit of the Kuroshio into the Japan Sea to monitor effects of the Yangtze River. The in-situ measurements were conducted to evaluate the extensions of diluted water into the Kuroshio in the spring, when the discharge exhibits lower value, and in the summer, when the discharge exhibits the maximum value through the year. This paper discusses the contribution of the Yangtze River to the ecosystem of the East China Sea through the primary productivity and the effects of the diluted water into the Kuroshio.