A biogeochemical study of the island mass effect in the context of the iron hypothesis: Kerguelen Islands, Southern Ocean

• Published in: Deep Sea Research Part I: Oceanographic Research Papers
• Main Authors: Blain, Stéphane, Tréguer, Paul, Belviso, Sauveur, Bucciarelli, Eva, Denis, Michel, Desabre, Stéphanie, Fiala, Michel, Martin-Jézéquel, Véronique, Le Fèvre, Jacques, Mayzaud, Patrick, Marty, Jean-Claude, Razouls, Suzanne
• Other Authors: Laboratoire d'océanographie et de biogéochimie (LOB), Université de la Méditerranée - Aix-Marseille 2-Institut national des sciences de l'Univers (INSU - CNRS)-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 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), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), ICOS-RAMCES (ICOS-RAMCES), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Laboratoire de MicrobiologiE de Géochimie et d'Ecologie Marines (LMGEM), Centre National de la Recherche Scientifique (CNRS)-Université de la Méditerranée - Aix-Marseille 2, Laboratoire d'océanographie biologique de Banyuls (LOBB), Observatoire océanologique de Banyuls (OOB), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'océanographie de Villefranche (LOV), Observatoire océanologique de Villefranche-sur-mer (OOVM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2001
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Antarctic; Austral; Kerguelen; Kerguelen Islands; Southern Ocean; The Antarctic; Antarc*
• Online Access: https://hal.archives-ouvertes.fr/hal-00481371; https://doi.org/10.1016/S0967-0637(00)00047-9

International audience In the context of the iron hypothesis, the biogeochemical characteristics of the water masses located in the N-E wake of the Kerguelen archipelago were studied in austral spring 1995 during the ANTARES 3/France JGOFS cruise. In agreement with satellite observations (CZCS and SeaWifs data), this cruise showed the surface waters in the wake of the Kerguelen archipelago to be rich in both chlorophyll a and dissolved iron, compared to other observations in the HNLC oceanic waters of the Southern Ocean. This gives support to the hypothesis that natural fertilization due to iron inputs occurs in the waters surrounding the Antarctic Islands. However, the mesoscale structure of the water masses in the study area was complex, and three contrasted zones were identified within the region of lesser or greater iron enrichment. The coastal zone was characterized by very high concentrations of dissolved iron (>10 nM) and lithogenic material, but the phytoplankton biomass, dominated by small species, was low. An intrusion of cold Antarctic surface water, rich in silicic acid, was eparated from the coastal zone by a shelf-break front. This water tongue contained chlorophyll a concentrations as low (<0.3 µg l-1) as in the iron-poor open ocean. A third water body, offshore, was characterized by the highest concentrations of phytoplankton (cell abundance and chlorophyll a) and biogenic silica, the community being dominated by large diatoms and dinoflagellates. The distribution of conservative tracers and lithogenic elements, as well as the phytoplankton taxonomic composition, indicate that this offshore water was not derived from a coastal origin. It more likely resulted from the mixing of the Antarctic water tongue flowing northward along the island continental slope with subantarctic surface water flowing eastward north of the Kerguelen Islands. As regards the interactions between dissolved iron and phytoplankton biomass and growth in surface waters, two typical situations were encountered. Although ...