History change and influence factor of nutrient in Lingdinyang sea area of Zhujiang River Eestuary

Based on the data obtained by field survey and experiments of the Zhujiang River Estuary in 2006, the distribution and concentration of nutrients in water mass of the Lingdingyang sea area are studied.It is discovered that there is a large content of nitrite and phosphate nearby Shenzhen sea area, and contents of nitrate and silicate constantly reduced off the Zhujiang River Estuary in wet season.The contents of five nutrients constantly reduced off the Zhujiang River Estuary in dry season.Based on the historical data obtained in 1990, 1998 and 2000, the variation of nutrients in water mass of the Lingdingyang sea area is studied, and the influence factors are also discussed.The results show that the contents of nitrate, nitrite, and phosphate in water mass increased remarkably, but DIN/DIP reduced constantly.The contents of nitrate and silicate in wet season are higher than dry season, but nitrite and phosphate is opposite.The runoff is an important source for nitrate and silicate, but it plays dilution function to nitrite and phosphate.In addition, the agriculture fertilizer, the sea area acreage reduction caused by filling the sea, the unreasonable utilization of bait in net cage culture are also the main reasons which bring about the increase of DIN and DIP concentration in water mass of Lingdingyang sea area.