Ocean acidification (OA) affects marine primary productivity and community structure. Therefore, OA may influence the biogeochemical cycles of volatile biogenic dimethyl sulfide (DMS), and its precursor dimethylsulfoniopropionate (DMSP) and photochemical oxidation product dimethyl sulfoxide (DMSO). A 23-day shipboard incubation experiment investigated the short-term response of the production and cycling of biogenic sulfur compounds to OA in the Changjiang River Estuary to understand the effects of OA on biogenic sulfur compounds. Phytoplankton abundance and community composition showed a marked difference at three different pH levels at the late stage of the experiment. Significant reductions in chlorophyll a (Chl-a), DMS, particulate DMSP (DMSPp) and dissolved DMSO (DMSOd) concentrations were identified under high CO2 levels. Moreover, minimal changes were observed in the productions of dissolved DMSP (DMSPd) and particulate DMSO (DMSOp) among the treatments. The ratios of DMS, total DMSP (DMSPt) and total DMSO (DMSOt) to Chl-a were not affected by a change in pH. Furthermore, the concentrations of DMS and DMSOd were closely related to the mean bacterial abundance at the three pH levels. Additional short-term (8 h) incubation experiments on the light and temperature effects showed that the influence of pH on the production of dimethylated sulfur compounds also depended on solar radiation and temperature. Under natural and UVB light, DMS photodegradation rates increased by 1.6 to 4.2 times at low pH levels. Thus, OA may lead to decreasing DMS concentrations in surface seawater. Light and temperature conditions also play important roles in the production and cycling of biogenic sulfur compounds.

In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2019) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2020-10-20.