Marine volatile organic compound exchange reorganizes compositionally on event‑to‑season timescales

Marine ecosystems influence atmospheric chemistry and climate by exchanging volatile organic compounds (VOCs) with the atmosphere, yet the chemical diversity and the environmental controls of the exchanged compounds remain poorly constrained at ecosystem timescales. This gap persists because most marine observations are targeted, short-term, and narrow-suite measurements that seldom deliver chemically broad, continuous fluxes. Here we show that marine VOC exchange is chemically diverse and changes in magnitude and composition on event‑to‑season timescales. Using continuous flux measurements of 48 compounds in the Baltic Sea, we observe a pronounced reorganization of net exchange: early organosulfur emissions diminish as cyanobacterial biomass declines (indicating water-side source limitation), while oxygenated and nitrogen-containing VOCs exhibit mixed behaviors ranging from deposition to episodic emissions (often driven by kinetic factors). Together, these results demonstrate that chemically diverse marine VOC exchange is closely coupled to wind-induced mixing, water‑column structure, and phytoplankton community succession, highlighting the need to resolve these dynamic ecosystem states to predict future atmospheric composition.