Study on the character of distribution of chlorophyll-a off the Changjiang River and its sources of nutrients

We succeeded in implementing baroclinic 3Docean model POM(Princet on ocean model)in Changjiang River mouth and its adjacent area to simulate the tide,tide current,Taiwan Warm Current, and Taiwan Coastal Current. An interdisciplinary comprehensive survey was conducted in November 2004 with modern measurement instruments off the Changjiang River. The analysis of the observation data shows that there existhigh chlorophyll-a(Chl-a)concentration area in the surface plume on the west side of the submerged river val ley(SRV)off the Changjiang mouth. For analyzing the nutrients sources of the high Chl-a concent ration area,two numerical experiments were carried on. In one experiment,the nutrient load via the Changjiang River is considered as the only one input of nutrients. On the other hand,the nutrient load via the Changjiang River and the nutrient input from the open boundaries are coupled together to simulate the nutrients distribution. In the two experiments,the nutrients were considered as conservative mass and were calculated under diffusion and advection processes by tide,tide current,Taiwan Warm Current,and coastal current. In addition,nitrate was representative of nutrients in the simulation. Based on the analysis of the field observation data off the Changjiang River mouth in November 2004 and the calculated results of the 3D numerical model experiments,it indicates that the nutrients of the high Chl-a concent ration area comesfrom two sources. One is the input of nutrients by the upwelling on the west side of the submerged river valley off the Changjiang River mouth,which accounts for 1/2 of the total amount. The other one is the input of fishery in Shengsi and Taiwan Warm Current transport,which accounts for the same amount as the first one.