Chasing iron bioavailability in the Southern Ocean: Insights from Phaeocystis antarctica and iron speciation

• Published in: Science Advances
• Main Authors: Fourquez, Marion, Janssen, David, J, Conway, Tim, M, Cabanes, Damien, Ellwood, Michael, J, Sieber, Matthias, Trimborn, Scarlett, Hassler, Christel
• Other Authors: Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Université de Genève = University of Geneva (UNIGE), Swiss Federal Insitute of Aquatic Science and Technology Dübendorf (EAWAG), University of South Florida Tampa (USF), Australian National University (ANU), Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine (AWI), Helmholtz-Gemeinschaft = Helmholtz Association, This study was supported by Project 16 of the Antarctic Circumnavigation Expedition (ACE). ACE was a scientific expedition that carried out under theauspices of the Swiss Polar Institute (SPI), supported by funding from the ACE Foundation and Ferring Pharmaceuticals. M.F. and C.H. were supported by the Swiss National Science Foundation (PP00P2_138955 and PP00P2_166197), European Project: 894264,BULLE, European Project: 101044637 ,HOPE
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [SDV.MP]Life Sciences [q-bio]/Microbiology and Parasitology; Southern Ocean; Antarc*; Antarctica
• Online Access: https://hal.science/hal-04148414; https://hal.science/hal-04148414/document; https://hal.science/hal-04148414/file/Fourquezetal_2023.pdf; https://doi.org/10.1126/sciadv.adf9696

International audience Dissolved iron (dFe) availability limits the uptake of atmospheric CO 2 by the Southern Ocean (SO) biological pump. Hence, any change in bioavailable dFe in this region can directly influence climate. On the basis of Fe uptake experiments with Phaeocystis antarctica , we show that the range of dFe bioavailability in natural samples is wider (<1 to ~200% compared to free inorganic Fe′) than previously thought, with higher bioavailability found near glacial sources. The degree of bioavailability varied regardless of in situ dFe concentration and depth, challenging the consensus that sole dFe concentrations can be used to predict Fe uptake in modeling studies. Further, our data suggest a disproportionately major role of biologically mediated ligands and encourage revisiting the role of humic substances in influencing marine Fe biogeochemical cycling in the SO. Last, we describe a linkage between in situ dFe bioavailability and isotopic signatures that, we anticipate, will stimulate future research.