Flynn, Raquel F.Haraguchi, LumiMcquaid, JeffBurger, Jessica M.Lunga, Percy MutsekaStirnimann, LucaSamanta, SaumikRoychoudhury, Alakendra N.Fawcett, Sarah E.2024-01-302024-01-302023-12Flynn, R.F., Haraguchi, L., McQuaid, J. et al. 2023, 'Nanoplankton : the dominant vector for carbon export across the Atlantic Southern Ocean in spring', Science Advances, vol. 9, no. 48, art. eadi3059, pp. 1-17, doi : 10.1126/sciadv.adi3059.2375-2548 (online)10.1126/sciadv.adi3059http://hdl.handle.net/2263/94156DATA AND MATERIAL AVAILABILITY : The data used in this manuscript are available in the Zenodo data repository: 10.5281/zenodo.7820428. All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials.SUPPLEMENTARY MATERIAL : Supplementary Text; Figs. S1 to S4; Tables S1 and S2.Across the Southern Ocean, large (≥20 μm) diatoms are generally assumed to be the primary vector for carbon export, although this assumption derives mainly from summertime observations. Here, we investigated carbon production and export potential during the Atlantic Southern Ocean’s spring bloom from size-fractionated measurements of net primary production (NPP), nitrogen (nitrate, ammonium, urea) and iron (labile inorganic iron, organically complexed iron) uptake, and a high-resolution characterization of phytoplankton community composition. The nanoplankton-sized (2.7 to 20 μm) diatom, Chaetoceros spp., dominated the biomass, NPP, and nitrate uptake across the basin (40°S to 56°S), which we attribute to their low iron requirement, rapid response to increased light, and ability to escape grazing when aggregated into chains. We estimate that the spring Chaetoceros bloom accounted for >25% of annual export production across the Atlantic Southern Ocean, a finding consistent with recent observations from other regions highlighting the central role of the phytoplankton “middle class” in carbon export.en© 2023 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).NanoplanktonSouthern OceanCarbon exportAtlantic Southern OceanNet primary production (NPP)SDG-14: Life below waterArticle