data for Relative resistance of estuarine dimethyl sulfide production to ocean acidification in the Yangtze River Estuary

Dimethyl sulfide (DMS) is a climatically important sulfur gas, yet its response to ocean acidification in estuarine systems remains poorly constrained. Here, we combined three seasonal field surveys with ship-based microcosm experiments in the Yangtze River Estuary and adjacent coastal waters to resolve spatial variability in DMS cycling and assess responses to declining pH. DMS concentrations and cycling rates showed pronounced seasonal variability, remaining broadly comparable in spring and autumn but reaching maxima in summer. During the wet season, mean sea-to-air DMS fluxes estimated using two gas-transfer parameterizations were 11.5–14.3 μmol m-2 d-1, approximately 1.8–2.2 times the global ocean mean. Across all seasons, estuarine waters exhibited lower pH than adjacent coastal waters, yet DMS concentrations showed no corresponding decline. Along the pH gradient, coastal waters exhibited significant positive relationships between pH and chlorophyll a, DMS concentration, DMS accumulation rate, and DMS yield, whereas these relationships were largely absent in the estuary. The microcosm experiments further confirmed this contrast, with pH reductions of 0.2–0.4 units significantly decreasing chlorophyll a, particulate and dissolved dimethylsulfoniopropionate, and DMS in coastal waters by 11.9–31.2%, 10.9–24.6%, 13.0–32.1%, and 13.9–42.4%, respectively, but producing little response in estuarine waters. These results reveal that DMS production in the Yangtze River Estuary is relatively resistant to the 0.2–0.4-unit pH reductions tested across all three seasons, suggesting that natural pH variability and environmental exposure history may modulate acidification responses.