Contribution of Large Marine Aerosols in Phytoplankton Dispersal.

Sea-spray aerosol (SSA) plays a crucial role in climate processes by influencing radiative forcing, cloud formation, and precipitation. While SSA particles with diameters between 0.1 and 10 μm are commonly studied, larger aerosols (>20 μm) have been observed over terrestrial and oceanic regions but are generally overlooked. Large bioaerosols can be formed by pollen, fungal spores, and cell debris. However, the abundance, dynamics, and composition of large marine aerosols remain poorly understood. This study observed wave and atmospheric conditions driving aerosol production, the resulting SSA abundance, and sizes (up to 90 μm), and collected collocated SSA samples for microscopy analysis during a two-month time period. SSA above 20 μm were frequently observed, containing a diverse range of intact phytoplankton cells, including small flagellates (2 μm), to diatoms, and colonial cells (above 40 μm). The abundance of small flagellates suggests that sea-to-air transfer may be an important, yet overlooked, dispersal mechanism for these groups. To the best of our knowledge, this is the first evidence of direct airborne observation (rather than deposition) of large intact phytoplankton cells. These findings highlight the ubiquity of large marine aerosols and their capacity to carry intact phytoplankton cells.