Sensitivity of chlorophyll annual cycle to growth rate function over the Yangtze River estuary in a physical-biogeochemical model

Qiong Wu, Nanjing university of information science and technology; Pohang university of science and technology, Nanjing; Pohang, China, Xiaochun Wang, University of California Los Angeles, Los Angeles, CA, United States and Peng Xiu, SCSIO South China Sea Institute of Oceanology, Chinese Acaademy of Sciences, Guangzhou, China
Temperature plays a crucial role in marine biogeochemical processes based on both observational and modeling studies. In present research, the sensitivity of the growth rate of phytoplankton to temperature was systematically studied using a two-level nested physical-biogeochemical coupled model for the Yangtze River estuary of the East China Sea. The physical component of the coupled model is configured from the widely used Regional Ocean Modeling System (ROMS) with the highest horizontal resolution of 3 km. The biogeochemical component of the coupled model is based on the Carbon, Silicon and Nitrogen Ecosystem model (CoSiNE). Five phytoplankton growth rate functions with different relation to temperature were tested with an objective to reproduce the seasonal cycle of sea surface temperature (SST) and chlorophyll-a concentration from the SeaWiFS (Sea-viewing Wide Field-of-view Sensor). Our result indicates that the fifth growth rate function that reaches a maximum at 22°C and levels off with higher temperature can reproduce seasonal cycle of chlorophyll-a very well and may be suitable for application in the physical-biogeochemical coupled model (ROMS-CoSiNE) of the Yangtze River estuary. The seasonal cycle of chlorophyll-a simulated by other four function shows larger biases compared with the observations.