Anthropogenic CO2–induced seawater acidification driven the biogeochemical processes of dimethylsulfide in Northwestern Pacific marginal seas

Since the Industrial Revolution, oceanic uptake of anthropogenic CO2 emissions has substantially mitigated global warming, yet concurrently induced severe seawater acidification. Seawater acidification exerts significant control over marine biogeochemical cycles, including those involving of dimethylsulfide (DMS), a critical climate-regulating sulfur compound. DMS, the most abundant biogenic volatile sulfur compound in surface oceans, plays critical roles in both the global sulfur cycling and climate regulation through its contribution to aerosol formation. Despite its importance, the mechanistic links between seawater acidification and DMS production/emission dynamics remain poorly constrained.To fill these gaps, we conducted a variety of DMS biogeochemical analyses through the field observations and ship-based incubation experiments. We present direct evidence that seawater acidification can modulate DMS emission by a dual-pathway mechanism. Reduced pH can inhibit high-DMSP producers (dinoflagellate) growth, thereby weakening DMS and DMSP concentrations. Low pH can also suppress DMS biological production and microbial consumption rates and increase DMS photolysis rate, resulting in lower DMS emissions. We estimated that the decreased DMS emission caused by seawater acidification, would account for up to 35% of DMS flux in the marginal seas under the RCP8.5 high-emission scenario. The reduced DMS production and emission due to seawater acidification, would have the potential to amplify anthropogenic global warming. These results clarify the mechanisms governing the biochemical processes of DMS under ocean acidification, advancing our understanding of how sulfur-mediated climate regulation mechanisms may evolve under anthropogenic environmental stressors.