Chemometric perspectives on plankton community responses to natural iron fertilisation over and downstream of the Kerguelen Plateau in the Southern Ocean

• Published in: Biogeosciences
• Main Authors: Trull, Thomas W., Davies, D. M., Dehairs, Frank, Cavagna, Anne-Julie, Lasbleiz, Marine, Laurenceau-Cornec, E. C., d'Ovidio, Francesco, Planchon, Frédéric, Leblanc, K., Queguiner, Bernard, Blain, Stéphane
• Other Authors: Antarctic Climate and Ecosystems Cooperative Research Centre (ACE-CRC), CSIRO Marine and Atmosphere Research Hobart, Commonwealth Scientific and Industrial Research Organisation Canberra (CSIRO), Institute for Marine and Antarctic Studies Hobart (IMAS), University of Tasmania Hobart, Australia (UTAS), Analytical, Environmental and Geo- Chemistry, Vrije Universiteit Brussel (VUB), Aix Marseille Université (AMU), Université de Toulon (UTLN), Processus de couplage à Petite Echelle, Ecosystèmes et Prédateurs Supérieurs (PEPS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), 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 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)-Centre National de la Recherche Scientifique (CNRS), 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), Laboratoire d'Océanographie Microbienne (LOMIC), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Observatoire océanologique de Banyuls (OOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), ANR-10-BLAN-0614,KEOPS 2,Kerguelen : Comparaison plateau Ocean2(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: AUSTRALIAN SECTOR; GROWTH-RATE; BIOGENIC SILICA; PHOTOSYNTHETIC C-13 FRACTIONATION; CARBON-ISOTOPE FRACTIONATION; INORGANIC CARBON; PARTICULATE ORGANIC-CARBON; ELEMENTAL COMPOSITION; MARINE-PHYTOPLANKTON; NITRATE UPTAKE; ACL; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Austral; Kerguelen; Southern Ocean
• Online Access: https://hal.sorbonne-universite.fr/hal-01207916; https://hal.sorbonne-universite.fr/hal-01207916/document; https://hal.sorbonne-universite.fr/hal-01207916/file/bg-12-1029-2015.pdf; https://doi.org/10.5194/bg-12-1029-2015

International audience We examined phytoplankton community responses to natural iron fertilisation at 32 sites over and downstream from the Kerguelen Plateau in the Southern Ocean during the austral spring bloom in October–November 2011. The community structure was estimated from chemical and isotopic measurements (particulate organic carbon – POC; 13 C-POC; particulate nitrogen – PN; 15 N-PN; and biogenic silica – BSi) on size-fractionated samples from surface waters (300, 210, 50, 20, 5, and 1 μm fractions). Higher values of 13 C-POC (vs. co-located 13 C values for dissolved inorganic carbon – DIC) were taken as indicative of faster growth rates and higher values of 15 N-PN (vs. co-located 15 N-NO 3 source values) as indicative of greater nitrate use (rather than ammonium use, i.e. higher f ratios).Community responses varied in relation to both regional circulation and the advance of the bloom. Iron-fertilised waters over the plateau developed dominance by very large diatoms (50–210 μm) with high BSi / POC ratios, high growth rates, and significant ammonium recycling (lower f ratios) as biomass built up. In contrast, downstream polar frontal waters with a similar or higher iron supply were dominated by smaller diatoms (20–50 μm) and exhibited greater ammonium recycling. Stations in a deep-water bathymetrically trapped recirculation south of the polar front with lower iron levels showed the large-cell dominance observed on the plateau but much less biomass. Comparison of these communities to surface water nitrate (and silicate) depletions as a proxy for export shows that the low-biomass recirculation feature had exported similar amounts of nitrogen to the high-biomass blooms over the plateau and north of the polar front. This suggests that early spring trophodynamic and export responses differed between regions with persistent low levels vs. intermittent high levels of iron fertilisation.