The oceans hold a massive quantity of organic carbon, nearly all of which is dissolved and more than 95% is refractory, cycling through the oceans several times before complete removal. The vast reservoir of refractory dissolved organic carbon (RDOC) is a critical component of the global carbon cycle that is relevant to our understanding of fundamental marine biogeochemical processes and the role of the oceans in climate change with respect to long‐term storage and sequestration of atmospheric carbon dioxide. Here we show that RDOC includes surface‐active organic matter that can be incorporated into primary marine aerosol produced by bursting bubbles at the sea surface. We propose that this process will deliver RDOC from the sea surface to the atmosphere wherein its photochemical oxidation corresponds to a potentially important and hitherto unknown removal mechanism for marine RDOC.

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 (acrylate d ) and DMSO (DMSO d ) 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 14 C labeled substrates. Acrylate d concentrations and uptake rates ranged from 0.8-2.1 nmol L 21 and 0.07-1.8 nmol L 21 d 21 , respectively. Somewhat higher uptake rates were observed for DMSO d (0.27-3.9 nmol L 21 d 21 ) owing to higher DMSO d concentrations (5.5-14 nmol L 21 ). Both compounds were taken up by the microbial community with high affinity uptake systems, with similar K s and V max 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 acrylate d and 7.4 d for DMSO d . The slow acrylate d 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.