From the Surface Ocean to the Seafloor: Linking Modern and Paleo-Genetics at the Sabrina Coast, East Antarctica (IN2017_V01) Armbrecht, Linda López Quirós, Adrián This project was supported through funding from the Australian Government’s Australian Antarctic Science Grant Programs (AAS 4333 and AAS 4419) and the Australian Research Council’s Discovery Projects funding scheme (DP170100557). We thank the team at the Australian Centre for Ancient DNA (ACAD), The Univer- sity of Adelaide, especially Corinne Preuss and Steve Johnson for their techni- cal help during the sedaDNA laboratory work. LA was funded by an Australian Research Council Discovery Early Career Researcher Award (ARC DECRA DE210100929). The modern molecular data analysis was supported by an ARC Grant awarded to IP (FL140100021). KAL is supported by an Australian Research Training Program (RTP) scholarship. We acknowledge the use of imagery from the NASA Worldview application (https://worldview.earthdata. nasa.gov), part of the NASA Earth Observing System Data and Information System (EOSDIS). Open access publish- ing facilitated by University of Tasmania, as part of the Wiley - University of Tasmania agreement via the Council of Australian University Librarians. With ongoing climate change, research into the biological changes occurring in particularly vulnerable ecosystems, such as Antarctica, is critical. The Totten Glacier region, Sabrina Coast, is currently experiencing some of the highest rates of thinning across all East Antarctica. An assessment of the microscopic organisms supporting the ecosystem of the marginal sea-ice zone over the continental rise is important, yet there is a lack of knowledge about the diversity and distribution of these organisms throughout the water column, and their occurrence and/or preservation in the underlying sediments. Here, we provide a taxonomic overview of the modern and ancient marine bacterial and eukaryotic communities of the Totten Glacier region, using a combination of 16S and 18S rRNA amplicon sequencing (modern DNA) and shotgun metagenomics (sedimentary ancient DNA, sedaDNA). Our data show considerable differences between eukaryote and bacterial signals in the water column versus the sediments. Proteobacteria and diatoms dominate the bacterial and eukaryote composition in the upper water column, while diatoms, dinoflagellates, and haptophytes notably decrease in relative abundance with increasing water depth. Little diatom sedaDNA is preserved in the sediments, which are instead dominated by Proteobacteria and Retaria. We compare the diatom microfossil and sedaDNA record and link the weak preservation of diatom sedaDNA to DNA degradation while sinking through the water column to the seafloor. This study provides the first assessment of DNA transfer from ocean waters to sediments and an overview of the microscopic communities occurring in the climatically important Totten Glacier region. 2023-06-01T07:16:05Z 2023-06-01T07:16:05Z 2023-04 journal article Armbrecht, L., Focardi, A., Lawler, K.-A., O’Brien, P., Leventer, A., Noble, T. L., et al. (2023). From the surface ocean to the seafloor: Linking modern and paleo-genetics at the Sabrina Coast, East Antarctica (IN2017_V01). Journal of Geophysical Research: Biogeosciences, 128, e2022JG007252. [https://doi.org/10.1029/2022JG007252] https://hdl.handle.net/10481/82073 10.1029/2022JG007252 eng http://creativecommons.org/licenses/by-nc/4.0/ open access Atribución-NoComercial 4.0 Internacional American Geophysical Union