Fluxes of Biogenic and Oxygenated VOCs From In Situ Mesocosm Studies of Seawaters From the South‐West Pacific Ocean

Volatile organic compounds (VOCs) are key atmospheric species influencing oxidative capacity and secondary organic aerosol formation. Oceans emit a variety of VOCs via complex biological, chemical, and physical processes. Although dimethyl sulfide (DMS) is a known precursor in marine aerosol formation, marine emissions of organic gases are more diverse. Here, we quantify semi‐controlled sea‐to‐air net fluxes of isoprene (0.50 ± 0.30 ng m −2 s −1 ), monoterpenes (0.93 ± 0.73 ng m −2 s −1 ), and oxygenated organics (methanol: 2.50 ± 1.13 ng m −2 s −1 ) using in situ mesocosm studies of natural seawaters in the south‐west Pacific Ocean. Under wind speeds <3 m s −1 , flux compositions varied between Frontal, Subtropical, and Subantarctic seawaters, with several VOCs exhibiting fluxes comparable to or exceeding DMS (0.75 ± 0.86 ng m −2 s −1 ). Significant associations were observed among biogenic VOC fluxes and phytoplankton groups, notably with nanophytoplankton. The impact of atmospheric ozone changes was tested by introducing additional ozone into one mesocosm, which increased methanol emissions while decreasing monoterpene and acetaldehyde fluxes, making the ocean a sink for the latter. Such studies provide quantitative links between natural phytoplankton assemblages and emissions of climatically relevant marine VOCs, offering the potential to use satellite oceanographic data to improve the representation of these emissions in chemistry‐climate models.