Increasing Freshwater Salinity Impacts Aerosolized Bacteria

Increases in the salt concentration of freshwater result in detrimental impacts on water quality and ecosystems biodiversity. At the microbial ecology level, increasing salinity induces shifts in the freshwater bacterial composition. Moreover, salinity affects the wave breaking and bubble bursting mechanisms via which water-to-air dispersal of bacteria occurs. While the effect of increasing freshwater salinity on the waterborne bacterial community has been studied before, its effect on bacteria aerosolization by breaking waves is not well understood. Cumulative salt additions in the freshwater-euhaline continuum (0-35 g/kg) are administered to a freshwater sample aerosolized inside a breaking wave analogue tank. Waterborne as well as the corresponding aerosolized bacteria are sampled at each salinity treatment, and later analyzed for diversity and abundance. We show that the aerosolized bacterial community is significantly different from the waterborne community driven by family-specific aerosolization enhancement or diminishment. Going from freshwater to euhaline conditions, bacteria aerosolization abundance exhibits a non-monotonic response with a maximum peak at lower oligohaline conditions (0.5-1 g/kg) followed by an increase at polyhaline and euhaline conditions. Our results show that increases in freshwater salinity are likely to influence the abundance and diversity of aerosolized bacteria.