Exploring precipitation over the northern Antarctic Peninsula - a microbiological perspective

Keywords: precipitation, aerosols, microorganisms, Antarctica, cloudsClouds and precipitation play an intrinsic role in the global climate, upholding the Earth's surface energy equilibrium and water cycle. Despite their significance, clouds and aerosols over Antarctica and the Southern Ocean remain poorly understood, primarily due to the extreme environment for observations and insufficient data. The Antarctic Peninsula (AP) has been exhibiting a significant warming trend over the last 60 years (Jones et al, 2019). Coupled with the rising temperatures, an increase in precipitation and surface melt is being observed across the AP, with major surface melts and precipitation events, both snowfall and rainfall, being associated with atmospheric rivers (ARs) (Gorodetskaya et al., 2023; Wille et al., 2021). ARs are long corridors of intense moisture and heat transport from subtropical and mid-latitude regions poleward, typically also carrying liquid-containing clouds to the AP. Moreover, ARs can impact the long-range transport of aerosols, as well as contribute to gas and aerosol exchange between the atmosphere and the ocean. Aerosols, which serve as cloud condensation and ice nuclei, determine cloud microphysical properties and influence cloud radiative forcing and precipitation formation. Given that a substantial percentage of aerosols are of biological origin, it is crucial to effectively identify and describe them.In this project, we aim to characterize bioaerosols, specifically microorganisms, present in the precipitation and surface snow in the AP. Rainfall and snowfall samples were collected during PROPOLAR campaigns on King George Island, northern AP, in the vicinity of Escudero and King Sejong stations. The precipitation samples were preserved and analysed using culturable and non-culturable methodologies. Bacterial strains were obtained and identified through 16S rRNA gene sequencing, which provided information about the diversity and phylogenetic relationships of the identified microorganisms. The identified organisms were categorized into six distinct genera, including those recognized for their ice nucleation capabilities, such as the Pseudomonas genus (Attard et al, 2012). The main phylum identified was Proteobacteria. We identified four strains among those analyzed as potentially novel species affiliated with the Spirosoma and Paenibacillus genera. These findings highlight the untapped potential of these regions in harbouring unique microbial biodiversity. Obtaining a comprehensive study of the microbial community in precipitation in Antarctica will pave the path to understanding the role these microorganisms have in cloud condensation processes and ice nucleation. More international efforts and campaigns are needed to gain information about aerosols, clouds and precipitation over the Southern Ocean. Acknowledgements: PROPOLAR (Portuguese Polar Program) projects APMAR/TULIP/ APMAR2 and FCT project MAPS (2022.09201.PTDC)References: Attard et al. 2012. Effects of atmospheric conditions on ice nucleation activity of Pseudomonas.  Atmos. Chem. Phys. https://doi.org/10.5194/acp-12-10667-2012Gorodetskaya et al. (2023): Record-high Antarctic Peninsula temperatures and surface melt in February 2022: a compound event with an intense atmospheric river. npj Clim.Atmos.Sci. https://doi.org/10.1038/s41612-023-00529-6Jones et al. (2019). Sixty years of widespread warming in the Southern middle and high latitudes(1957–2016). J.Clim.https://doi.org/10.1175/JCLI-D-18-0565.1 Wille et al. (2021).  Antarctic atmospheric river climatology and precipitation impacts. J.Geophys.Res.https://doi.org/10.1029/2020JD033788