Phytoplankton blooming mechanisms over the East China Sea during post-El Nino summers

During post-El Niño summers, the East China Sea (ECS) has experienced anomalous phytoplankton blooming, but the understanding of associated generating mechanisms remains limited. Here, we analyzed observational (25 years) and long-term simulation data (1,000 years) to investigate the underlying mechanisms for the anomalous phytoplankton blooming in ECS. Results highlight three mechanisms associated with enhanced phytoplankton blooming in ECS during post-El Niño summers: inland runoff, nutrient inputs from the Taiwan Strait (TS), and oceanic sub-surface upwelling-driven blooming mechanisms. Firstly, increased river discharge from the Yangtze River (YR) induces phytoplankton blooms. Secondly, enhanced nutrient inputs through TS promote phytoplankton growth. Additionally, wind-driven Ekman upwelling in ECS provides nutrients for phytoplankton growth from the sub-surface to the surface water layer. These three mechanisms are all linked to the Western North Pacific Anti-Cyclone (WNPAC), suggesting the WNPAC can be a key precursor to predict ECS blooming. Climate model simulations support these complex mechanisms, and thus our results suggest that all mechanisms can contribute to the phytoplankton bloom concurrently.