LAUSR

The abundant marine organosulfur compound, dimethylsulfoniopropionate (DMSP) can be degraded to acrylate and dimethylsulfide (DMS), with some DMS further oxidized to dimethylsulfoxide (DMSO). Despite intensive study of DMSP and DMS in a variety of marine settings, the processes affecting acrylate and DMSO concentrations in marine waters are poorly known, particularly their loss from the dissolved phase through biological uptake. We measured the concentrations of dissolved acrylate (acrylated) and DMSO (DMSOd) in coastal and open-ocean waters of the northern Gulf of Mexico during non-bloom conditions and quantified the rates and kinetics of their biological uptake using 14C labeled substrates. Acrylated concentrations and uptake rates ranged from 0.8–2.1 nmol L−1 and 0.07–1.8 nmol L−1 d−1, respectively. Somewhat higher uptake rates were observed for DMSOd (0.27–3.9 nmol L−1 d−1) owing to higher DMSOd concentrations (5.5–14 nmol L−1). Both compounds were taken up by the microbial community with high affinity uptake systems, with similar Ks and Vmax values to those for other well-studied biological substrates including amino acids and monosaccharides. However, median turnover times were relatively slow, 4.8 d for acrylated and 7.4 d for DMSOd. The slow acrylated turnover points to low supply rates of this compound to the dissolved phase, a finding consistent with previous observations that the microbial DMSP lyase pathway accounts for only a small fraction of dissolved DMSP degradation (and therefore acrylate production) in the Gulf of Mexico.