A Multidomain Lens on the Temporal Dynamics of Surface Microbial Communities in the Southern Ocean (2013-2019)

Abstract

Marine microorganisms are vital to biogeochemical cycles and food web dynamics, with their community structure shaped by environmental factors such as temperature, light, and salinity. While microbial dynamics in the western Antarctic Peninsula are relatively well- studied, the northwestern region remains underexplored, particularly in long-term, multidomain analyses. To fill this gap, we investigated microbial communities encompassing all three domains of life (Bacteria, Archaea, and Eukarya) in the Northwestern Antarctic Peninsula. Using the universal primer set 515Y/926R, we sequenced unfractionated seawater from ten sites over a six-year period (2013-2019). Environmental parameters, temperature and salinity, showed minimal variation across the study. However, microbial diversity and composition, especially among eukaryotic phytoplankton, displayed significant temporal changes among seasons and years. The prokaryotic community, by contrast, was relatively stable, with Gammaproteobacteria-- particularly the Nitrincolaceae family--maintaining high relative abundance throughout all sampling periods, but a few distinct ASVs. In contrast, no eukaryotic group exhibited consistently high relative abundance across sampling periods. The summer of 2016, marked by a strong El Nino event, presented the most distinct microbial community structure, underscoring the sensitivity of these communities to extreme climatic conditions. These results highlight the importance of integrated, long-term studies to better understand the dynamics, interactions, and resilience of microbial ecosystems in the rapidly changing Antarctic environment. IMPORTANCEThis study provides a unique long-term perspective on microbial community dynamics in the Northwestern Antarctic Peninsula, a region still poorly explored through a multidomain lens. By investigating the temporal variability of Bacteria, Archaea, and Eukaryotes over six years, we reveal distinct stability patterns between these groups, with phytoplankton showing the highest variability and prokaryotes remaining relatively stable. The strong response of the microbial community to the 2016 El Nino event highlights its sensitivity to extreme climate conditions, reinforcing the importance of understanding how Antarctic ecosystems will respond to future climate shifts. The consistent presence of Nitrincolaceae, a key bacterial taxon, suggests its ecological relevance in the region, while fluctuations in phytoplankton composition may impact food web dynamics. These findings emphasize the need for continued long-term monitoring to predict how microbial communities will adapt to environmental changes, which is crucial for assessing the future functioning of polar marine ecosystems.