Nutrient dynamics in the East China Sea: Seasonal changes, budget, and ecological impacts

The continental seas have experienced significant eutrophication due to intensified anthropogenic activities. This study aims to elucidate the processes that govern the budgets of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved silicate (DSi) in the East China Sea (ECS). Key nutrient sources include terrestrial runoff, atmospheric deposition, water column regeneration, and Kuroshio Current (KC) intrusions, jointly influencing the concentrations, distribution, and stoichiometry of nutrients in the ECS. Diffusion at the sediment–water interface contributes over 30% of DIN input, while the KC and the Taiwan Warm Current dominate inputs of DIP (69.1%) and DSi (66.3%), respectively. In contrast, riverine inputs, accounting for 12.3% of DIN and 4.73% of DIP, primarily affect nearshore surface waters and have minimal influence offshore. The distinct sources and cycling processes of DIN, DIP, and DSi lead to imbalanced nutrient stoichiometry in the ECS. This imbalance is further exacerbated by the disparity between nutrient regeneration and primary production. This study highlights the need for effective nutrient management to mitigate negative ecological consequences in the ECS.