This study reveals that trace atmospheric gases thought to be pollutants are also produced by marine plankton and emitted by the ocean, with potential climate effects.

The air we breathe is much more than oxygen and nitrogen, even more than greenhouse gases like carbon dioxide. It also contains small amounts of many of organic gases, like benzene and toluene. These atmospheric compounds are important because they oxidize into little particles, called aerosols, that seed water condensation into droplets to form the clouds that filter solar radiation. Mathematical models of climate underestimate the amount of clouds, particularly in the Southern Ocean, and thus carry large uncertainties in climate projections. The study published now in the journal Science Advances reports the first measurements of benzene and toluene in the polar oceans and indicates that these compounds have a biological origin. Until now, the occurrence of these compounds in polar marine air was thought to be a sign of the far-reaching spread of human pollution from coal and oil burning and the use of solvents. By incorporating the data into a global model of atmospheric chemistry and climate, we noticed that ocean-borne benzene and toluene were significant contributors to aerosol production, particularly in the extremely clean, non-polluted atmosphere over the Southern Ocean, where these two gases increased the mass of organic aerosols by 8%, and up to 80% in transient events. For future research, the team will further study the impact of marine microscopic life on the atmosphere. In fact, in two weeks the authors of the study published now will travel to Antarctic waters again to confirm the current finding and make further measurements. Wohl, C., Q. Li, C. A. Cuevas, R. P. Fernandez, M. Yang, A. Saiz-Lopez, R. Simó. 2023. Marine biogenic emissions of benzene and toluene and their contribution to secondary organic aerosols over the polar oceans. Science Advances 9: eadd90319, doi: 10.1126/sciadv.add9031.