中文摘要：

根据2004—2009年春季（5月）、夏季（8月）对长江口的监测调查，比较分析了三峡工程蓄水后该海域硅酸盐（DSi）、无机氮（DIN）、无机磷（DIP）浓度变化趋势，营养盐结构变化状况及其影响.结果表明，蓄水后，DSi、DIN的浓度分别呈现出下降、上升的变化趋势，DSi在6年间下降了约63.37%，DIN增加了约3倍多，DIP的浓度则呈微弱波动.蓄水后营养盐结构N：P值呈上升的趋势，而Si：P值和Si：N值则呈下降的趋势，根据化学计量营养盐限制的标准，营养盐结构趋于不平衡，调查水域浮游植物生长限制因子为P，营养盐结构的变化已经导致大型硅藻的减少和浮游植物优势种组成的变化，并可能引起长江口生态系统结构的改变.

英文摘要：

Based on the surveys in the Yangtze River Estuary and its adjacent area after water storage of the Three Gorges Project in the spring （May） and summer （August） of year 2004 to 2009,the contents of dissolved silicate （DSi）,dissolved inorganic nitrogen （DIN）,and dissolved inorganic phosphorus （DIP） were analyzed, and the nutrient structure,limitation after water storage of the Three Gorges Project were compared. The results showed that the concentration of DSi decreased by 63.37%,respectively,while the concentration of DIN increased more then three times, and the concentration of DIP changed little after water storage. The N：P ratio increased whereas Si：P ratio and Si：N ratio declined after water storage. According to the criteria for stoichiometries and probable nutrient limitation,there was a trend for nutrient structure imbalance, and P was the potential limited factor of phytoplankton growth. Such changes in nutrient structure may have led to decrease of large diatoms and a shift of phytoplankton species composition,which may cause the ecosystem changes in the Yangtze River estuary.