A numerical study on hypoxia and primary production in the Pearl River Estuary in summer using the modified RCA water quality model
基于改进的RCA水质模型对珠江口夏季缺氧及初级生产力的数值模拟研究

The RCA water quality model was incorporated with the sediment module and the light shading effect due to the high turbidity in the Pearl River Estuary (PRE). The modified RCA water quality model was then applied to the PRE. Results show that the modified RCA model can reproduce the distribution of nutrients, phytoplankton and dissolved oxygen (DO) in the PRE successfully, which means the modified model can capture the main processes of water quality in the PRE. In the wet season, huge amount of fresh water enters the PRE and results in a river plume. Particulate organic matter (POM) deposits intensely in specific areas of western and central shoal of the Lingdingyang Estuary and outside Modaomen as a result of the plumes. Furthermore, high deposition rate of POM in specific areas leads to high sediment oxygen demand (SOD), which coincides with the areas with strong stratification. High SOD and strong stratification lead to hypoxia. On the shelf areas, primary production increases as the suspended sediment concentration decreases, but the increasing primary production does not result in hypoxia as the marine particulate organic carbon (POC) spreads all over the shelf and the stratification is weak.