| In recent years, influence by the activity of human beings, eutrophication of the marine environment became more serious and enlarge in level and the scale as well, in the East China Sea. Thus serious problems in marine environment and ecosystem were induced, such as the worsen of sea water, unbalance of marine ecosystem and the high frequency of Red Tide, especially in Changjiang estuary and the adjacent area which become the high frequency area of Red Tide.Aimed at the hot point of the marine environmental ecosystem, the distribution and variation of nutrients and petroleum hydrocarbon, controlling mechanism and the influence to marine ecosystem were conducted in this thesis, according to the 2 cruise of field survey in the Changjiang estuary and adjacent area, in suit mesocosm experiment and the dynamic model of ecosystem as well. The research would give some necessary scientific foundation to the research work for mechanism of the Red Tide in East China Sea. The main research work and conclusions listed as follows:1. In the field survey, primary discussion was conducted for the distribution and variation of chemical factors in the Changjiang estuary and adjacent area. Various kinds of nutrients were analyzedfor the first time in the survey area, the nutrient structure and control mechanism were discussed as well. It indicates the variation of nutrients in the survey area is mainly controlled by the Changjiang Dilute Water, Taiwain Warm Current and the activity of plankton as well. The nutrients control mechanism show a clear seasonal variation, in which the Changjiang Dilute Water has higher influence to the nutrients concentration of survey area in autumn, and the Taiwain Warm Current's influence to the survey area is higher in spring than autumn.1.1. Nutrients concentration has an obvious increase than those in 1980s, and clear seasonal variation of nutrients distribution and structure was observed in this area. The concentration of silicate, phosphate, DOP, PP and TP in autumn 1997 were higher than those in spring 1998, the average concentration were 11.6?.7, 0.44?.09, 0.26?.18, 0.82?.99 and 1.52眑.l5μmol/dm3 for autumn, and 9.61?.84, 0.3410.13, 0.13?.11, 0.2110.14 1 0.6810.24μmol/dm3 in spring, respectively. However, except nitrate, the nitrogen concentration including nitrite, ammonia, DON, PN and TN in spring 1998 were higher than those in autumn 1997, with the average concentration of 4.9714.65, 0.67?.20, 0.7210.30, 9.2516.88, 7.3014.42 and 22.9眑0.2μmol/dm3 in autumn, and 4.5812.39, 0.70+0.14, 2.2611.05, 9.8814.92, 7.8816.21 and 25.318.94 μmol/dm3 in spring, respectively. The N/P ratio in autumn 1997 was 13.217.54 in average which a little lower than Redfield ratio, nevertheless in spring 1998 the value was as high as 25.6113.0, much higher than Redfield ratio. There shows a clear seasonal variation of phosphorus structure in two seasons, but the nitrogen structure almost unchanged. The main phosphorus in autumn 1997 was PP, with the percentage about 54%, phosphateand DOP was about 29% and 17% respectively. While phosphate was the dominate fraction with about 51% of phosphorus in spring 1998, the PP and DOP was 30% and 19% respectively. Both DON and PN were the main fraction of nitrogen in autumn 1997 and spring 1998 as well, but nitrate ratio higher in autumn 1997 and ammonia ratio higher in spring 1998. The PN and DON were 32% and 40% in autumn, 31% and 39% in spring 1998, respectively. PN and PP in autumn shows strong vertical gradation in autumn other than spring, and other nutrient species shows relatively uniformity in vertical scale.1.2. The variation of nutrients in the survey area is mainly controlled by the combination of Changjiang Dilute Water, Taiwain Warm Current and the activity of plankton as well, and the control mechanism of nutrients also shows a seasonal variation in the survey area. Due to the influence of the Changjiang Diluter Water, the concentration of phosphate, nitrate and sili...
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