Abstract
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 exhibits relative resistance to pH declines of 0.2–0.4 units across all three seasons investigated, suggesting that natural pH variability and environmental exposure history may modulate acidification responses.
Plain Language Summary
Dimethyl sulfide (DMS) is a naturally produced sulfur gas in seawater that can influence clouds and climate after being emitted to the atmosphere and oxidized to form sulfate aerosols. Previous studies have suggested that ocean acidification may reduce marine DMS production, but most evidence has come from open-ocean or relatively stable coastal environments. Here, we combined seasonal field surveys in spring, summer, and autumn with ship-based acidification experiments in the Yangtze River Estuary and adjacent coastal waters to examine how DMS production responds to declining pH. In the adjacent coastal waters, lower pH was associated with reduced phytoplankton biomass and lower DMS concentrations, and experimental acidification further suppressed DMS production. In contrast, DMS and related processes in the estuary showed limited responses to comparable pH reductions. These results demonstrate a marked difference in sensitivity to ocean acidification between the estuarine and adjacent coastal waters of the Yangtze River Estuary. Given the relative resistance of DMS production observed in estuarine waters, the contribution of the Yangtze River Estuary to future ocean-atmosphere sulfur exchange may remain relatively stable under moderate acidification.
Ma Q.-Y., Yang J.-Q., Chen C., He Z., Liu C.-Y. & Yang G.-P., 2026. Relative resistance of estuarine dimethyl sulfide production to ocean acidification in the Yangtze river estuary. Journal of Geophysical Research: Oceans 131: e2026JC024506. doi: 10.1029/2026JC024506. Article (subscription required).
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