Nutrient characteristics driven by multiple factors in large estuaries during summer: A case study of the Yangtze...

Nutrients directly control the level of primary productivity and are crucial for the stability of marine ecosystems. Focusing on the survey results in August 2020 of the Yangtze River Estuary, this study elucidated the distribution characteristics and controlling factors of three nutrients: NO₃-N, PO₄-P, SiO₃-Si. The results showed that the concentrations of NO₃-N, PO₄-P, SiO₃-Si in the study area were generally higher near the shore than far shore, with average concentrations of 11.40, 0.70, and 23.73 μmol/L, respectively. The ocean currents drove the distribution of nutrients, and the transport of CDW and YSCC increased the nutrient levels. The resuspension of sediment caused by factors such as terrain and weather may lead to an abnormal increase in nutrients in the bottom waters. The main controlling factors of the three nutrients were different. NO₃-N was significantly affected by human activities, PO₄-P and SiO₃-Si were mainly affected by natural factors.