Study Of The Yangtze River Mouth Nutrients Structural Changes

Nutrients structure of surface of Changjiang Estuary and it抯 adjacent sea area have been researched, nutrients structure horizontal distribution, seasonal and annual change have been reported at the same time. Based on the analysis of marine research data of November, 2000; May, 1999; November, 1998 and August, 1985 to August, 1986, the characters of nutrient Silicon Phosphor and Nitrogen distribution and it influencing factor have been studied. Hydrological factor is one of the most important cause that affects nutrient spatial distribution in the Estuary and it neighbor sea, for example mixing of runoff of Changjiang, Taiwan warm flow, near shore flow of Subei and near shore flow of Huang Sea, all of these current have different physical and chemical character, and mixing of them result in complicated distribution. Growth and reproduction of phytoplankton and other biological activities add complexity on the nutrient distribution. Different behavior of nutrient is also a considerable factor that conduct to different transformation during the process of river water and sea water抯 mixing. Structure of researched sea area and limiting factors have been studied in Stoichiometric and nutrient uptake kinetics by tools of statistics, Sea area that near Changjiang estuary is one of the high nutrient concentration and high production areas, abundant nutrient loads of Changjiang maintain the plankton抯 growth and reproduction rate. But in some special environments, nutrient can also limit the amount of stand corp. High flow period, bloom of phytoplankton deplete local nutrient and nutrient limitation frequency is high; low flow period, the area that affected by dilute water shrinks, nutrient limitation occurs in some parts of researched area. Physical mixing of flows and phytoplankton are both affect the occurring frequency of nutrient limitation, and its period is more shorter than flow period. Result of statistic in Stoichiometric is that: Between potential limiting nutrients in the Changjiang-estuary sea area, Silicon-limitation occurring frequency is the highest, the foIIower is Phosphor, and the third is Nitrogen. This result is not consistent with thecommon opinion which consider the Phosphor is the main limiting factoL Thesedifference may come from the discrepancy in researched area' research period and theestimated method for nutrients limitation.