The role of wave-induced mixing in spring phytoplankton bloom in the South Yellow Sea

Using an ecosystem model, we simulated the spatiotemporal distribution of phytoplankton and studied its spring bloom (SPB) in the South Yellow Sea, aiming to gain a comprehensive understanding of the physical-biological mechanism, in particular the role of wave-induced mixing in the SPB. By incorporating wave mixing into the model, patterns of the SPB are obtained that are consistent with observations. The significant bloom occurs in April, supported by favorable conditions of nutrients, temperature, transparency, solar radiation, and wind speed that favor rapid algal growth in the upper mixed water. The peak of the SPB typically occurs in mid to late April. Subsequently, phytoplankton biomass declines rapidly as nutrients are depleted in the upper water, leading to subsurface maxima. Wave-induced mixing delays the timing of the SPB, creating a more favorable environment that prolongs rapid algal growth and accumulation in the upper mixed water. Consequently, mixing enhances the SPB and increases phytoplankton standing stocks during spring. When modeling SPB in basin-scale seas, it is important not to overlook the role of wave-induced mixing.