Sea spray aerosols created by breaking waves are lofted into the atmosphere and play a key role in weather and climate by helping to seed clouds and scatter solar radiation. But aerosols’ properties depend on the material they carry with them, such as organic matter from phytoplankton blooms. A study using natural seawater pumped into a laboratory wave channel at the University of California, San Diego, helps tease apart some of the key factors affecting sea spray aerosol composition (ACS Cent. Sci. 2015, DOI: 10.1021/acscentsci.5b00148). A team led by UCSD’s Kimberly A. Prather studied aerosols produced during two phytoplankton blooms in the channel. One bloom resulted in aerosols enriched in aliphatic organics. Aerosols from this bloom were also very effective at nucleating ice crystals, which are critical for precipitation. The other bloom coincided with an increase in bacteria that feed on organic compounds. The resulting aerosols contained less aliphatic and more oxidized material, and they were not as good at forming ice. The results suggest that researchers need to track phytoplankton and microbial activity to understand and predict sea spray aerosol properties.