Spatial Distribution and Biogeochemical Cycling of Dimethylated Sulfur Compounds and Methane in the East China Sea During Spring

Abstract The spatial distributions of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), dimethylsulfoxide (DMSO), and methane (CH4) were studied in the East China Sea during May 2017, and the possible controlling factors and biogeochemical cycling processes are discussed. The mean surface concentrations of DMS and CH4 were 10.66 and 9.93 nmol/L in the coastal area and 7.60 and 6.88 nmol/L in the open ocean, respectively. Horizontal and vertical profiles of the dimethylated sulfur compounds and CH4 were largely affected by different water masses, with enhancement observed in the coastal area. Significant correlations were found between CH4 and particulate DMSP (r = 0.609, p < 0.01, n = 42), and between CH4 and dissolved DMSO (r = 0.654, p < 0.01, n = 42). A dissolved DMSP (DMSPd) spike experiment revealed that the bacterial communities had potential to utilize DMSPd, meanwhile producing CH4 under oligotrophic conditions. The average mixing ratio of atmospheric DMS was 109 ± 49 pptv. Variations of marine DMS and wind speed explained 23 and 40% of the variation in the mixing ratios of atmospheric DMS, respectively. The sea‐to‐air fluxes of DMS and CH4 were estimated to be 18.64 ± 14.92 and 13.85 ± 15.03 μmol m−2 d−1, respectively.