The Temporal and Spatial Variation of the Nutrientsin the Yangtze River Estuary

This paper mainly focuses on the temporal and spatial variation of nutrients in the Yangtze River Estuary. Observations show that the high level of nitrate concentration appears in the coast waters and gradually decreases toward the continental shelf both in summer and in winter; while the ammonium and phosphate concentrations show the relatively high level in the bottom layer of the water column in summer, since ammonium and phosphate can be regenerated on the sediments and reenter the bottom layer of the water column to make up their contents. In winter, the nutrients are well-distributed in the vertical due to the strong mixing mechanism. The further examination of the nutrient limitation, according to the Redfield theory, shows that the phosphorus limitation dominates in the river mouth and then shift to the nitrogen limitation toward the continental shelf gradually. The variation of the nutrient limitation may be dependent on the relative strength between the Changjiang Diluted Water and the Intrusion Branch of the Kuroshio Current.