Sea-Air Transfer of <i>Ostreopsis</i> Phycotoxins Is Driven by the Chemical Diversity of the Particulate Fraction in the Surface Microlayer

Blooms of <i>Ostreopsis</i> cf. <i>ovata</i> pose an emerging health threat, causing respiratory disorders in various coastal regions. This dinoflagellate produce potent phycotoxins named ovatoxins that can be transferred from the seawater to the atmosphere. However, the biotic and abiotic conditions affecting their transfer are still unknown. In this study, we investigate the sea-to-air transfer of <i>O.</i> cf <i>ovata</i> phycotoxins using a process study in an aerosol reference tank (MART) and field observations. The process study exhibited a positive correlation between the phycotoxin content in sea spray aerosol (up to 832.59 ng m^-3) and the particulate phycotoxin fraction in the water column and surface microlayer. In contrast, in the natural system, aerosolized phycotoxins were only observed in one out of six air collection (total toxins 0.59 ng m^-3) despite optimal wind conditions. In both the process study and the natural system, ovatoxins represented only a minor fraction of the total toxin content, which was comprised of up to 90% liguriatoxins. In seawater, while no solubilized ovatoxins were detected, the concentration in dissolved liguriatoxin-a reached up to 19.07 μg L^-1. These results underscore the need for future research on the liguriatoxins, and on their toxicity to establish safe exposure thresholds for beachgoers.