Seasonal Dynamics of Marine Dimethylsulfide in the Yangtze River Estuary: Production, Loss, and Environmental Drivers

Dimethyl sulfide (DMS) plays a critical role in climate regulation and the global sulfur cycle. Estuarine-shelf systems contribute substantially to global DMS emissions, yet the seasonal dynamics and cycling processes of DMS in these regions remain poorly understood. This study conducted seasonal field investigations (summer and winter) in the Yangtze River Estuary and Adjacent Sea to elucidate the sources, sinks, and environmental controls of DMS. Our findings reveal that elevated temperature and irradiance promote the biological production of DMS, resulting in a summer net accumulation rate approximately five times higher than that in winter. Seasonal variations in environmental drivers (e.g., temperature, light) did not significantly alter the hierarchy of DMS sinks, with microbial consumption dominating removal processes in both seasons, followed by sea-air exchange and photodegradation. Approximately 80% of DMS was recycled within the mixed layer, while ~20% was emitted to the atmosphere. The sea-air fluxes of DMS substantially exceed climatological mean fluxes, suggesting the survey region is a potential hotspot for global oceanic DMS emissions. By delineating seasonal source-sink dynamics, this study provides comprehensive insights into DMS cycling in estuarine-shelf systems, contributing to refined bottom-up models for reducing uncertainties in global DMS atmospheric budgets.