Comparison in Nutrient State of Surface Water in the Changjiang River Estuary and the adjacent East China Sea between spring 2002 and 2010 Possible effects caused by the Three Gorges Dam on ecology and environment in the East China Sea in spring

The nutrient state of surface water in the Changjiang River Estuary and the adjacent East China Sea in spring 2002 and 2010 was compared and then possible effects brought by the Three Gorges Dam which was first used in 2003 and finally completed in 2009, on ecology and environment in the East China Sea was preliminary studied. During 2010 cruise, large area of Prorocentrum donghaiense red tide was observed, so although the flux of DIN (dissolved inorganic nitrogen), PO4-P and SiO3-Si from the Changjiang River in 2010 was greater, the average concentration of DIN and PO4-P in the study sea was 15.6% and 40.4% less than that in spring 2002 respectively for phytoplankton uptake, but the concentration of SiO3-Si was 56.1% greater than that in 2002. Increase of DIN, PO4-P and SiO3-Si input from the Changjiang River was mainly caused by increased runoff in May 2010, brought by drain of the Three Gorges Dam, and compared with DIN, more proportion of PO4-P and SiO3-Si was sent into the East China Sea, therefore the Three Gorges Dam operation may impact the growth of phytoplankton, the formation and maintenance of dinoflagellate and diatom bloom in the East China Sea in spring.