Summer Nutrient Fronts in the Changjiang (Yantze River) Estuary

Silicate, phosphate, nitrate, dissolved oxygen, chlorophyll α and pH were measured during a cruise in August 1988 in the Changjiang Estuary region on board of the Haijian 42 research vessel. Organic matter and carbonate contents in sediments were analysed in laboratory. Well characterized nutrient fronts in the Changjiang Estuary have been observed during this study: on the one hand, the plume water fronts are accompanied by nutrient ones because the nutrient contents in the plume waters are much higher than in the ambient marine water. On the other hand, the removal of nutrients by the consumption of the highest primary production sustained by the plume water fronts enhances the sharpness of the nutrient fronts. The highest primary production just outside the plume water fronts has distinct impacts on sediment and bottom water features beneath: low pH, Eh and dissolved oxygen and high organic matter and carbonate contents, suggesting that the highest primary productivity region as well as the plume water fronts are relatively stable in summer and typical of most large river estuary systems.