We present an observational data set that suggests that the ocean source of carbon monoxide (CO) may influence the atmospheric CO concentration in the marine boundary layer (MBL). Atmospheric CO concentration gradient data obtained during the 1992 Atlantic Stratocumulus Transition Experiment Marine Aerosol and Gas Exchange (ASTEX/MAGE) show significantly (range of 2--47 ppbv, average of 15 ppbv) more CO at altitudes of 0.05 to 0.5 m above sea level as compared to 10 m above sea level. The seawater CO concentrations needed to support the fluxes obtained from an atmospheric gradient calculation are much higher than generally reported in the literature. However, studies of CO production by Jones and Amador (1993) and data from Seiler (1978) suggest the possibility that CO production and the resultant flux to the MBL could be 1--2 orders of magnitude higher than currently estimated using seawater pumped from depths of 4--10 m below the sea-air interface. We infer that the surface ocean production and sea-air exchange of photochemically produced trace gases such as CO may participate in physical, chemical and biological processes on vastly different spatial and temporal scales than those inherent to more stable species such as CO2. ¿ American Geophysical Union 1996