Mesoscale surface distribution of biogeochemical characteristics associated with a frontal system in the Crozet Basin during austral summer 1999.

• Published in: Marine Ecology Progress Series
• Main Authors: Fiala, Michel, Delille, B., Dubreuil, Catherine-Marie, Kopcynska, E., Leblanc, Karine, Morvan, J., Queguiner, Bernard, Cailliau, P., Conan, Pascal, Corvaisier, Rudolph, Denis, Michel, Frankignoulle, M., Oriol, L., Roy, Sylvaine, Blain, Stéphane
• Other Authors: Université Pierre et Marie Curie - Paris 6 (UPMC), Unité d'Océanographie Chimique, Interfacultary Center for Marine Research (MARE), Université de Liège-Université de Liège, 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), Department of Antarctic Biology, Polska Akademia Nauk = Polish Academy of Sciences (PAN), Ecole Nationale Supérieure de Chimie de Rennes (ENSCR), 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)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2003
• Subjects: Bacteria; Biogenic silica; Nutrients; Frontal zones; pCO2; Chlorophyll a; Phytoplankton; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Antarctic; Austral; The Antarctic; Antarc*
• Online Access: https://hal.archives-ouvertes.fr/hal-00700116; https://hal.archives-ouvertes.fr/hal-00700116/document; https://hal.archives-ouvertes.fr/hal-00700116/file/Fiala_2003.pdf; https://doi.org/10.3354/meps249001

International audience A mesoscale study was conducted in January and February 1999 in the Crozet Basin frontal zones (43°50¹ to 45°20¹S; 61°00¹ to 64°30¹E) within the southernmost and easternmost convergence area of the Antarctic Circumpolar Current (ACC) and the Agulhas Return Current (ARC). Distribution of biogeochemical parameters was strongly linked to the merged Subtropical (STF) and Subantarctic (SAF) Fronts which mark the border between the cold and less saline subantarctic waters and the warm and more saline subtropical waters. This survey took place during a post-bloom period. Chlorophyll a concentrations were low throughout the study area ranging from 0.2 µg l-1 in the Polar Frontal Zone (PFZ) to 0.4 µg l-1 in the Subtropical Zone (STZ). Maximum chlorophyll a values (0.8 µg l-1) associated with an increase in biogenic silica concentration (from 0.03 to 0.34 µM) and a diatom peak (1.2 x 105 cells l-1) were encountered in the northeastern part of the STF edge. Despite northwardly decreasing concentrations of nitrates from 14 µM in the PFZ to 6 µM in the STZ, they were not the main factor limiting phytoplankton growth. Low silicic acid (mean = 0.6 µM) could have limited diatom development in the PFZ and the STZ where diatom numbers were low. In STZ waters, where average diatom numbers were highest, various species of Nitzschia and Thalassiothrix were common, but Pseudonitzschia spp. were dominant. Throughout the survey area, pico- and nano-sized cells dominated the phytoplankton assemblage, and their number was the highest in the STZ. Cyanobacteria, only present in subtropical waters >12.5°C, were the major component of the picoplankton size-fraction. While dinoflagellate numbers were low in the Subantarctic Zone (SAZ), their abundance and species numbers increased in the STZ, where Oxytoxum laticeps became dominant and several further large-size species of Prorocentrum, Ceratium and Gymnodinium appeared in addition to those at the STF. The distribution of different biogeochemical parameters ...