Abstract Long‐term observational data in coastal ecosystems indicate a shift from diatom dominance to diatom‐dinoflagellate co‐dominance since the 2000s, coinciding with environmental changes including a shift toward organic‐dominated nutrient regimes and elevated Dissolved inorganic nitrogen (DIN)‐to‐phosphorus (N:P) ratios. In this study, a Nutrient‐bi‐Phytoplankton‐Detritus (NbPD) model integrating physiological and molecular‐scale mechanisms was developed and systematically calibrated using four decade‐spanning mesocosm experiments (2000s–2020s) to unravel phytoplankton succession dynamics in the Bohai Sea (BS). The model innovatively integrates organic nutrient uptake, assimilation, and metabolic processes regulated by Michaelis‐Menten enzyme kinetics. Simulations reveal contrasting nutrient strategies: diatoms exhibit higher inorganic nutrient uptake rates and assimilation efficiency to boost cell reproduction under inorganic nutrient‐replete conditions; however, dinoflagellates demonstrate superior organic nutrient utilization and metabolism to maintain cell growth through molecular mechanisms such as extracellular enzyme activation under organic nutrient‐replete conditions. Competitive outcomes reflect physiological trade‐offs—diatoms dominate in inorganic nutrient‐replete environments via rapid growth and low metabolic losses before 2010s, whereas dinoflagellates prevail under organic nutrient‐enriched, phosphorus‐limited regimes through efficient organic assimilation and metabolic plasticity after 2010s in the Bohai Sea. This study systematically elucidates the cascade response mechanisms linking nutrient regime shifts to phytoplankton succession, offering a process‐based framework for analyzing coastal ecosystem responses to anthropogenic and environmental changes.
Tan et al. (Sun,) studied this question.