Seasonal Depletion of the Dissolved Iron Reservoirs in the Sub‐Antarctic Zone of the Southern Atlantic Ocean

• Published in: Geophysical Research Letters
• Main Authors: Mtshali, Thato, van Horsten, Natasha, Thomalla, S.J., Ryan-Keogh, T. J., Nicholson, Sarah-Anne, Roychoudhury, A. N., Bucciarelli, Eva, Sarthou, Géraldine, Tagliabue, Alessandro, Monteiro, Pedro M.S.
• Other Authors: Council for Scientific and Industrial Research Cape Town (CSIR), Ministery of Science and Technology, Department of Earth Sciences Stellenbosch, Stellenbosch University, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Earth Ocean and Ecological Sciences Liverpool, University of Liverpool, ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: dissolved iron; dissolved inorganic nitrogen; euphotic and aphotic reservoirs; ACL; seasonal dynamics; GEOTRACES; primary productivity; envir; geo; Antarctic; Southern Ocean; Antarc*
• Online Access: https://doi.org/10.1029/2018GL081355; https://hal.archives-ouvertes.fr/hal-02323351/file/Mtshali%20et%20al%202019.pdf; https://hal.archives-ouvertes.fr/hal-02323351

International audience Seasonal progression of dissolved iron (DFe) concentrations in the upper water column was examined during four occupations in the Atlantic sector of the Southern Ocean. DFe inventories from euphotic and aphotic reservoirs decreased progressively from July to February, while dissolved inorganic nitrogen decreased from July to January with no significant change between January and February. Results suggest that between July and January, DFe loss from both euphotic and aphotic reservoirs was predominantly in support of phytoplankton growth (iron‐to‐carbon uptake ratio of 16 ± 3 μmol/mol), highlighting the importance of the “winter DFe reservoir” for biological uptake. During January to February, excess loss of DFe relative to dissolved inorganic nitrogen (iron‐to‐carbon uptake ratio of 44 ± 8 μmol/mol and aphotic DFe loss rate of 0.34 ± 0.06 μmol·m−2·day−1) suggests that scavenging is the dominant removal mechanism of DFe from the aphotic, while continued production is likely supported by recycled nutrients.