Nutrient conditions in the Yellow Sea and the East China Sea

This paper discusses the distributions of micronutrients in the Yellow Sea (YS) and the East China Sea (ECS), based on the data obtained during field observations. It is pointed out that there are abundant nutrients in the area of the east and northeast of the Changjiang River estuary throughout the year. It is believed that the nutrients come from the extension of the Changjiang River diluted water and the transportation of the Subei coastal water. The maximum extension range of the nutrients of the Changjiang River diluted water was observed during the catastrophic flooding period of the Changjiang River in the summer of 1998. Based on the Redfield ratio (Si :N: P ¼ 16 : 16 : 1) at which three essential nutrients are utilized by marine phytoplankton, the Si/N/P ratios are calculated and studied for the upper water of the YS and the ECS. The results indicate that the Si/N ratios are very high, which suggests that silicate is not the limiting factor for the growth of phytoplankton in the YS and the ECS. Under the influence of terrestrial runoff, especially the Changjiang River runoff which is rich in combined nitrogen and has very high N/P ratios, high N/P ratios occur in the Changjiang estuary and its adjacent areas such as the south and southwest of the YS, the inshore area of the ECS and the area east of the Changjiang estuary in spring and summer. As a result, in contrast to general open marine systems, the systems in these areas resemble estuarine ones rather than typical marine ones. The primary production in a considerable portion of the YS and the ECS may be limited by phosphate rather than nitrogen.