Particulate biogenic silica and carbon production rates and particulate matter distribution in the Indian sector of the Subantarctic Ocean

• Published in: Deep Sea Research Part II: Topical Studies in Oceanography
• Main Authors: LEBLANC, Karine, QUEGUINER, Bernard, Fiala, Michel, Blain, Stéphane, Morvan, J., Corvaisier, Rudolph
• 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), Université Pierre et Marie Curie - Paris 6 (UPMC), Université de Brest (UBO), 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 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 2002
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Indian; Southern Ocean
• Online Access: https://hal.archives-ouvertes.fr/hal-02500690; https://doi.org/10.1016/S0967-0645(02)00078-4

International audience The silicon and carbon cycles in the Subantarctic region have been investigated in the summer 1999 during the Antares 4 cruise in the Indian sector of the Southern Ocean. Both biogenic silica (BSi) biomass and production values were low and indicative of the end of the productive period. Biogeochemical parameters revealed that the siliceous components of the phytoplankton were scarce. The study area was characterized by nanoplanktonic communities. Depth-integrated values of BSi showed a north-south positive gradient: average values were 45.65 mmol m−2 in the Polar Frontal Zone (PFZ) and 19.82 mmol m−2 in the Subtropical Zone (STZ). Diatom frustules appeared slightly deteriorated, and BSi distribution suggested particulate matter sedimentation especially at the southern boundary of the study area, where the highest concentrations were found (750 nmol l−1). BSi tended to accumulate along the Subtropical Front, with values reaching up to 420 nmol l−1. Depth-integrated BSi production rates showed an inverse pattern compared to BSi: the maximum and the minimum values were found, respectively, in the STZ (0.72 mmol Si m−2d−1) and in the PFZ (0.25 mmol Si m−2 d−1). The Subantarctic region, located between the PFZ and the STZ, showed intermediate values for both BSi standing stock (31.58 mmol m−2) and production rates (0.50 mmol Si m−2 d−1). A production regime based on orthosilicic acid regeneration is hypothesized in the STZ where surface temperatures appear high enough to sustain higher BSi dissolution rates. During summer, BSi production in the frontal zone of the Indian sector is comparable to the lowest production rates of oligotrophic waters.