Numerical investigation on the ecological influence of Changjiang Diluted Water to the Yellow Sea

Abstract

Considerable attention has been recently paid to the eutrophication in relation to changes in the ecosystem of the East China Sea. The inflowing nutrients from the Changjiang River are characterized by high concentration and lofty N/P ratio. The eutrophication occurs frequently in the vicinity of the Changjiang River mouth. The distribution of the Changjiang Diluted Water(CDW), characterized as water with relatively low salinity (< 30~32) in general, have seasonal variation with change in flow patterns(southward along the coastline of China in winter while the northeastward heading for Cheju Island in summer). In this study, the effect of the CDW on the lower trophic ecosystem of the central Yellow Sea has been investigated based on the POLCOMS-ERSEM coupled physico-biogeochemical ecosystem model.The physical and biogeochemical borderlines of the CDW are defined by the distribution of the salinity and nitrate concentration at the surface. The extension region of both CDW borderlines has maximum in August and the borderlines don’t reach to the center of the Yellow Sea and usually propagate toward the Korea Strait. The variation of the lower trophic ecosystem of the Changjiang Estuary located inside the CDW and the center of YS has been compared. The nutrients have mostly high concentration in winter due to vertical mixing derived by strong wind while the nitrate in the Changjiang Estuary shows high concentration in. The eutrophication occurs frequently in the vicinity of the Changjiang River mouth. The distribution of the Changjiang Diluted Water(CDW), characterized as water with relatively low salinity (< 30~32) in general, have seasonal variation with change in flow patterns(southward along the coastline of China in winter while the northeastward heading for Cheju Island in summer). In this study, the effect of the CDW on the lower trophic ecosystem of the central Yellow Sea has been investigated based on the POLCOMS-ERSEM coupled physico-biogeochemical ecosystem model.The physical and biogeochemical borderlines of the CDW are defined by the distribution of the salinity and nitrate concentration at the surface. The extension region of both CDW borderlines has maximum in August and the borderlines don’t reach to the center of the Yellow Sea and usually propagate toward the Korea Strait. The variation of the lower trophic ecosystem of the Changjiang Estuary located inside the CDW and the center of YS has been compared. The nutrients have mostly high concentration in winter due to vertical mixing derived by strong wind while the nitrate in the Changjiang Estuary shows high concentration in