Diurnal Emissions of Sea Spray Aerosols in Algal Blooms

Understanding the factors that influence the production of sea spray aerosols (SSA) is crucial for better understanding their impact on our climate. However, the role of oceanic microbial activity in contributing to SSA production is still underexplored. Here, we investigated the dynamics of SSA number concentration (<i>N</i>_SSA) during induced algal blooms within three airtight mesocosm enclosures. Monitoring algal abundance throughout a 24-day experiment revealed two main blooms: a mixed algal bloom followed by an extensive bloom of the coccolithophore <i>Gephyrocapsa huxleyi</i> and its subsequent demise. We observed two main patterns in <i>N</i>_SSA: (1) a diurnal variation with higher daytime emissions; and (2) a progressive decrease in <i>N</i>_SSA throughout the bloom succession, with peak <i>N</i>_SSA during the first mixed algal bloom and a decline during the <i>G. huxleyi</i> bloom and its demise. We hypothesize that photosynthetic processes could contribute to the observed diurnal changes, potentially through effects of enhanced bubble formation and subsequent SSA production. The suppression of <i>N</i>_SSA during the <i>G. huxleyi</i> bloom and its demise correlates with the accumulation of particulate organic carbon and transparent exopolymer particles, which can act as surfactants and potentially suppress SSA production by altering surface tension dynamics. Our findings underscore the complex interplay between algal bloom dynamics and SSA production, with implications for understanding aerosol dynamics in marine environments, particularly under changing climate conditions.