Tropical cyclones represent strong episodic disturbances in the western North Pacific, yet their short-term impacts on pelagic ecosystem metabolism and carbon dynamics remain insufficiently constrained due to limited field observations. We examined the effects of Typhoon Maria (July 2018) on the pelagic ecosystem of the southern East China Sea shelf using shipboard observations conducted 2–4 days before and 3–6 days after typhoon passage. Typhoon-induced physical forcing enhanced vertical mixing and intensified upwelling, resulting in a deepened mixed layer, modest surface cooling, and increased nutrient availability—particularly nitrate—in the upper water column. These changes stimulated pronounced biological responses, including elevated chlorophyll a, primary production, bacterial production, and plankton community respiration. The phytoplankton assemblage shifted toward a higher contribution of larger cells (>2 μm), accompanied by an increased relative abundance of picoeukaryotes within the picophytoplankton community. Plankton community respiration showed strong positive relationships with both primary production and bacterial production, indicating tight coupling between autotrophic and heterotrophic processes following the disturbance. Despite enhanced biological activity, mean surface fugacity of CO₂ (fCO₂) exhibited little net change after the typhoon. Although vigorous phytoplankton growth likely promoted biological CO₂ uptake, this drawdown was largely offset by increased plankton community respiration and the upward transport of CO₂-rich subsurface waters driven by mixing and upwelling. As a result, the shelf ecosystem remained close to carbon balance or experienced only a slight reduction in surface fCO₂. These findings demonstrate that typhoons can rapidly restructure pelagic ecosystem metabolism and carbon cycling on continental shelves. Resolving such short-term, event-scale disturbances is essential for understanding carbon dynamics and ecosystem responses in Pacific marginal seas under a changing climate.

Dissolved inorganic nutrients,Fugacity of CO2 (fCO2),Heterotrophic bacteria,Organic carbon consumption