Linking Sea Spray, Bioaerosols and Ice-Nucleation Proteins in Arctic Marine Environments

Clouds have one of the most profound effects on Earth’s climate, yet they are still responsible for some of the biggest uncertainties in climate models. Cloud formation, radiative properties, thickness and lifetime are tightly interlinked with the presence of atmospheric particles (aerosols) and the formation of ice. Biological aerosols (bioaerosols) such as ice-nucleation proteins (INpro) produced by microorganisms are most efficient catalysts in the formation of ice and can trigger heterogenous freezing between -1°C and -15°C. Several studies have demonstrated that Arctic environments are a source of airborne INpro. Sea spray is one of the major sources of aerosols, which aside of the sea salt contain large amounts of organic material. These are ejected into the atmosphere through the process of wave breaking and bubble bursting of small bubbles, which eject drops from the sea surface microlayer (SML) to the atmosphere. Here, we present results derived from droplet freezing assays and amplicon sequencing combined with quantitative PCR, targeting the 16S rRNA gene from sea and aerosol samples collected along a transect from sub- to high Arctic Greenland (Baffin Bay). We demonstrate a positive correlation between INpro concentration and higher latitudes in sea bulk water (SBW) and SML. Additionally, we try to link specific taxonomic groups from the microbial communities to INpro production. Last, we aim to investigate if partitioning of specific taxonomic groups can be observed from SBW to SML and from SML to the atmosphere. Finally, we performed laboratorial sea-spray experiments simulating turbulent sea conditions. This study has the potential to help closing the current knowledge gap in understanding the partitioning of microorganisms from the sea to the atmosphere and unravel which microbes are the major contributors to atmospheric INpro and hence cloud formation.