UC San Diego

Atmospheric aerosols shape Earth’s climate impact human health. Sea spray aerosol is the most abundant atmospheric aerosol by mass. Its composition influences its atmospheric roles and is initially determined by the composition of seawater. Seawater is full of microbial life and can also be heavily impacted by pollution. This dissertation investigates the transfer of bacteria, enzyme activity, and contaminants from seawater to sea spray aerosol. Heterotrophic bacteria significantly shape ocean carbon cycling and the composition of marine organic material by expressing extracellular enzymes. These enzymes transfer to the atmosphere in sea spray aerosol where they can continue to catalyze their chemical reactions. Comparisons of enzyme activities in isolated seawater and sea spray aerosol demonstrate that the enzyme activity of sea spray aerosol is distinct from that of its source waters. Aminopeptidase, lipase, and alkaline phosphatase show similar activity levels in sea spray aerosol despite aminopeptidase being dominant in seawater. This demonstrates that the enzyme activity of sea spray aerosol is tuned to prioritize different reactions in the atmosphere than in seawater. Along with the enzymes they produce, bacteria also transfer to the atmosphere in sea spray aerosol. Our understanding of the airborne microbiome stands to benefit from advances in techniques. Coupling high efficiency aerosol sampling with a high throughput, low biomass 16S gene amplicon sequencing protocol produced a novel workflow for the sampling and sequencing of bacteria in sea spray aerosol. This methodology achieved sequencing success at 4.1 million sea spray aerosol particles and 1046 airborne bacteria. The results demonstrate that different water masses with different bacteria communities produce different sea spray aerosol bacteria communities. Along the many populated coastlines worldwide, pollution significantly impacts seawater composition and has the potential to reach people on land by transferring in sea spray aerosol. To investigate this potential, three dye releases were conducted in coastal waters to mimic coastal water pollution at full scale in the environment. Coordinated aerosol sampling detected the dye in the coastal aerosol up to 668 m inland and 720 m downwind. These findings demonstrate that coastal water pollution transfers to the atmosphere in sea spray aerosol and reaches many people on land through this airborne exposure pathway. Non-targeted high resolution tandem mass spectrometry and 16S gene amplicon sequencing were applied to investigate chemical and bacterial signs of coastal water pollution in coastal aerosol. Chemicals and bacteria identified in a major pollution source were also found in coastal aerosol in onshore winds. The bacteria included members independently linked to sewage pollution and accounted for up to 76% of the bacteria identified in the air. Although more abundant in terrestrial aerosols, the chemicals identified in marine aerosols also indicated pollution in sea spray aerosol.