Characteristics of nutrients and eutrophication in the Hangzhou Bay and its adjacent waters

The characteristics of nutrient distributions and eutrophication in the Hangzhou Bay and its adjacent waters were described and analyzed based on the data obtained on four cruises of spring,summer,autumn and winter,from July,2006 to November,2007.The results showed that distributions and variations of nutrient were not only related to input of DIN,phosphorus and silicon directly from rivers around Hangzhou Bay,but also influenced greatly by Changjiang River diluting waters.The distributions of nutrient were mainly controlled by physical mixing of diluting water with seawater and biological and chemical removal was relatively insignificant in this area.Behavior of phosphate was indicative of a buffering effect by sorption and desorption of PO3-4-P on suspended matter in spring and in winter and biological activities in some areas of Zhoushan Islands was considered to be an important factor of influence on nutrient distribution in spring and in summer.The concentrations of DIN,phosphate and silicate in the Hangzhou Bay were quite high and showed rich-nutrients condition around year.DIN overload and extra high N/P ratio in Hangzhou Bay and its adjacent waters may be one of factors of the stress of coastal eutrophication.