Daya Bay, located in the eastern part of Guangdong Province, is one of the significant bays in the South China Sea. The bay is renowned for its excellent water quality, rich biodiversity, and ecological diversity, making it one of the most ecologically valuable coastal areas in China. However, the rapid expansion of industrial, agricultural, and fishing activities in this region is exerting pressure on the marine ecosystem of Daya Bay. Specifically, the thermal discharge from nuclear power plants and the discharge of domestic wastewater have led to increased seawater temperatures and nutrient enrichment, which have significantly impacted the species composition, biomass, and community structure of phytoplankton. Therefore, investigating the response mechanisms of phytoplankton in Daya Bay to environmental changes is of great importance for formulating strategies for marine biological resource management and climate change adaptation.
In this study, we have enhanced the Carbon, Si(OH)4, Nitrogen Ecosystem (CoSiNE) biogeochemical model by expanding the functional groups of phytoplankton to four categories: small phytoplankton, diatoms, coccolithophores, and phaeocystis. First, we evaluate the model performance by directly comparing the model results with the available observations from Daya Bay. The model successfully simulates the dynamics of phytoplankton biomass and associated biogeochemical variables in the Daya Bay region. We further reveal the key environmental factors affecting the growth of phytoplankton in Daya Bay. Additionally, we integrate the impacts of environmental change factors, such as seawater warming and acidification, on different phytoplankton species, quantifying their effects into the phytoplankton growth equations. A series of sensitivity experiments are conducted to explore the potential changes in the phytoplankton community structure under various environmental stress conditions.

climate change, marine ecosystem, phytoplankton community