Impact of the natural Fe-fertilization on the magnitude, stoichiometry and efficiency of particulate biogenic silica, nitrogen and iron export fluxes

• Published in: Deep Sea Research Part I: Oceanographic Research Papers
• Main Authors: Lemaitre, N., Planquette, Hélène, Dehairs, F., Merwe, P., Bowie, A. R., Trull, T. W., Laurenceau-Cornec, E. C., Davies, D., Bollinger, C., Le Goff, Manon, Grossteffan, E., Planchon, Frédéric
• Other Authors: 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), Analytical, Environmental and Geo- Chemistry, Vrije Universiteit Brussel (VUB), Antarctic Climate and Ecosystems Cooperative Research Centre (ACE-CRC), Institute for Marine and Antarctic Studies Horbat (IMAS), University of Tasmania Hobart, Australia (UTAS), CSIRO Marine and Atmosphere Research Hobart, Commonwealth Scientific and Industrial Research Organisation Canberra (CSIRO), 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), The KEOPS project was supported by the French Agency of National Research (grant: ANR-10-BLAN-0614), the Program LEFE-CYBER of the Institut des Sciences de l’Univers (INSU) and the Institut Paul Emile Victor. Funding for this research was also obtained from Science Policy, Belgium (BELSPO, grant SD/CA/05A), Flanders Research Foundation (FWO, grant G071512N), Vrije Universiteit Brussel (Strategic Research Plan 2), the Antarctic Climate and Ecosystem Cooperative Research Center (ACE-CRC, Hobart, Australia). Finally, this work was funded by ANR grant BITMAP (ANR-12-PDOC-0025-01) to H. Planquette and by the “Laboratoire d’Excellence” LabexMer (ANR-10-LABX-19), ANR-10-BLAN-0614,KEOPS 2,Kerguelen : Comparaison plateau Ocean2(2010), ANR-12-PDOC-0025,BITMAP,Biodisponibilité du fer et des métaux traces dans les particules marines(2012), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: Particulate export fluxes; phytoplankton bloom; ACL; antarctic circumpolar current; biological pump; community structure; drifting sediment trap; elemental stoichiometry; kerguelen plateau; Natural Fe-fertilization; organic-carbon export; southern-ocean; th-234 approach; Thorium-234; upper ocean carbon; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Antarctic; Austral; Kerguelen; Southern Ocean; The Antarctic; Antarc*
• Online Access: https://hal.archives-ouvertes.fr/hal-01483202; https://doi.org/10.1016/j.dsr.2016.09.002

00000 ăWOS:000390514800002 International audience The Kerguelen Plateau is characterized by a naturally Fe-fertilized phytoplanlcton bloom that extends more than 1000 km downstream in the Antarctic Circumpolar Current. During the KEOPS2 study, in austral spring, we measured particulate nitrogen (PN), biogenic silica (BSi) and particulate iron (PFe) export fluxes in order to investigate how the natural fertilization impacts the stoichiometry and the magnitude of export fluxes and therefore the efficiency of the biological carbon pump. At 9 stations, we estimated elemental export fluxes based on element concentration to Th-234 activity ratios for particulate material collected with in-situ pumps and Th-234 export fluxes (Planchon et al., 2015). This study revealed that the natural Fe-fertilization increased export fluxes but to variable degrees. Export fluxes for the bloom impacted area were compared with those of a high-nutrient, low-chlorophyll (HNLC), low-productive reference site located to the south-west of Kerguelen and which had the lowest BSi and PFe export fluxes (2.55 mmol BSi m(-2) d(-1) and 1.92 mu mol PFem(-2) d(-1)) and amongst the lowest PN export flux (0.73 mmol PN m(-2) d(-1)). The impact of the Fe fertilization was the greatest within a meander of the polar front (PF), to the east of Kerguelen, with fluxes reaching 1.26 mmol PN m(-2) d(-1); 20.4 mmol BSi m(-2) d(-1) and 22.4 mu mol PFe m(-2) d(-1). A highly productive site above the Kerguelen Plateau, on the contrary, was less impacted by the fertilization with export fluxes reaching 0.72 mmol PN m(-2) d(-1); 4.50 mmol BSi m(-2) d(-1) and 21.4 mu mol PFe d(-1). Our results suggest that ecosystem features (i.e. type of diatom community) could play an important role in setting the magnitude of export fluxes of these elements. Indeed, for the PF meander, the moderate productivity was sustained by the presence of large and strongly silicified diatom species while at the higher productivity sites, smaller and slightly silicified diatoms dominated. ...