Marine bacterial enrichment in the sea surface microlayer, and surface taxa aerosolization potential in the Western Mediterranean Sea

The sea surface microlayer (SSML) is critical to air-sea exchanges of gases and primary aerosols. However, despite the extent of this boundary layer, little is known about its specific bacterial community (bacterioneuston) and how it may affect ocean-atmosphere exchanges. Here, we studied the bacterial community composition in the surface waters of three different basins of the Western Mediterranean Sea and assessed the selective air-sea transfer of marine bacteria through experimental nascent sea spray aerosol production in a 10 L tank with plunging jets. In situ, the bacterioneuston harbored basin-specific enriched taxa and followed a similar spatial pattern as the underlying bacterioplankton community. Aerosolization potential showed that sea spray taxa might be recruited from both the underlying water and the SSML, and that taxa enriched in the bacterioneuston were not always aerosolized. Our results suggest that the Mediterranean nutrient gradient, as well as pulse events such as dust deposition, affect the distribution of the bacterial community at the ocean-atmosphere interface, which may impact biogeochemical processes, climate regulation and bacterial dispersal through aerosolization. ### Competing Interest Statement The authors have declared no competing interest.