Environmental control of dimethylsulfoxide (DMSO) cycling under ocean acidification

Environmental context Ocean acidification affects marine algae and bacteria, which can produce climate active trace gases such as methane or dimethylsulfide from marine dimethylsulfoxide. We conducted field experiments simulating future ocean acidification, and showed that dimethylsulfoxide concentrations decreased with increasing acidification. Less dimethylsulfoxide in the future can affect climate by influencing the concentration of methane and dimethylsulfide. Abstract Ongoing ocean acidification (OA), caused by continuous anthropogenic CO2 emissions, seems to decrease the concentrations of dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) in the surface oceans. This might have consequences for future climate due to changes in formation and growth of atmospheric sulfate aerosols formed from DMS. However, the effect of OA on dimethylsulfoxide (DMSO), another intermediate of the DMS pathway and a potential precursor of oceanic methane, is unknown. Therefore, we investigated the effect of OA on the DMSO concentrations in a mesocosm study conducted in a Norwegian fjord in spring 2011. Dissolved and particulate DMSO concentrations (DMSOd/p) decreased with pH during the course of the experiment. Temperature correlated inversely with DMSOd concentrations during the first week of the experiment, reflecting the influence of temperature dependent biological activities on DMSOd pathways. Furthermore, DMSOd increased with the cell abundance of heterotrophic bacteria, cryptophytes, and the cyanobacterium Synechococcus sp. Nitrate availability influenced the distribution of cryptophytes and Synechococcus sp. in the same way as DMSOd, indicating again a possible link between these phytoplankton taxa and DMSOd. We conclude that ongoing OA may lead to decreasing DMSO concentrations in the surface ocean that, in turn, might affect the oceanic distributions of DMS and methane.