Aerosolisation of microalgae: unveiling dimethyl-sulfide emissions during bubbling

Microalgae emit volatile organic compounds (VOCs) that can profoundly impact climate by leading to new particle formation and influencing clouds. Among these VOCs, dimethyl-sulphide (DMS) is of particular interest due to its key role in atmospheric processes. Despite its importance, many detailed processes linking microalgae and sea-atmosphere interactions remain poorly understood. We investigated the response of a freshwater and saltwater microalgal species of haptophytes known to produce DMS, to air entrainment and bubble-bursting mechanisms relevant for wave-breaking over the ocean. We show that bubbling resulted in the successful aerosolisation of microalgae and concurrent emission of DMS. In contrast, only background levels of DMS were detected when bubbling ceased, suggesting a critical role of bubbles in the sea-air exchange of DMS under the studied conditions. DMS mixing ratios were not correlated with the emitted particle concentrations and decreased over time, while particle concentrations remained stable. Bubbling also significantly reduced the viability of aquatic microalgae. Approximately half of the aerosolised microalgae were viable upon emission, but were not able to grow during subsequent cultivation recovery. Thus, the potential for microalgae to disperse to new environments via aerosolization is low, while their climate impact through the release of DMS remains substantial.