The SeaSCAPE campaign replicated the marine atmosphere in the laboratory to investigate the links between biological activity in the ocean and the properties of primary sea spray aerosols, volatile organic compounds, and secondary marine aerosols.

The oceans cover nearly three-quarters of the Earth's surface and produce vast quantities of sea spray aerosols (SSA). Studies have shown that due to ocean biology SSA particles are comprised of much more than just sea salt and often include proteins, lipids, sugars, viruses, and bacteria. In this study, we show for the first time that a diverse array of microbial enzymes (protease, lipases, and alkaline phosphatase) are transferred from the ocean into the atmosphere and often become even more active with measured activities in SSA particles that are 1−2 orders of magnitude higher than those in bulk seawater. We hypothesize that these enzymatic reactions are enhanced in the interfacial environment of droplets and aerosols that can dynamically modify surface chemical species and properties. Simulations reveal that enzyme-containing SSA particles can rapidly coagulate with other preexisting aerosols, thus transferring the impact of enzyme reactions to a broad range of marine aerosols. These biotic reaction pathways are expected to profoundly change the composition of marine aerosols, particularly at the interface, and thus will impact cloud properties in marine environments. Future studies are needed to determine how photochemistry, changing ocean conditions in a warming climate, and other external factors will influence the activities of these enzymes and their impact on the composition of the marine atmosphere.

Lipopolysaccharides (LPS) in sea spray aerosol (SSA) particles have recently been shown to undergo heterogeneous reactions with HNO3 in the atmosphere. Here, we integrate theory and experiment to further investigate how the most abundant sea salt cations, Na+, Mg2+, and Ca2+, impact HNO3 reactions with LPS-containing SSA particles. Aerosol reaction flow tube studies show that heterogeneous reactions of SSA particles with divalent cation (Mg2+ and Ca2+) and LPS signatures were less reactive with HNO3 than those dominated by monovalent cations (Na+). All-atom molecular dynamics simulations of model LPS aggregates suggest that divalent cations cross-link the oligosaccharide chains to increase molecular aggregation and rigidity, which changes the particle phase and morphology, decreases water diffusion, and consequently decreases the reactive uptake of HNO3. This study provides new insight into how complex chemical interactions between ocean-derived salts and biogenic organic species can impact the heterogeneous reactivity of SSA particles.