Late quaternary variations of elemental ratios (C/Si and N/Si) in diatom-bound organic matter from the Southern Ocean

• Main Authors: Crosta, Xavier, Shemesh, Aldo, Salvignac, Marie-Eve, Gildor, Hezi, Yam, Ruth
• Other Authors: Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Department of Environmental Sciences and Energy Research Rehovot, Weizmann Institute of Science Rehovot, Israël
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2002
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Austral; Indian; Mati; Southern Ocean
• Online Access: https://hal.science/hal-02105704

International audience The carbon cycle in the Southern Ocean is considered as a major factor controlling past atmospheric CO 2 concentration variations. However, accumulation rates of biogenic opal are not linearly related to carbon burial rates. Here, we show that it is possible to measure the carbon and nitrogen content of diatom-bound organic matter (%C diat and %N diat , respectively) and that the signals recorded do not appear to be analytical artifacts. Analyses of two cores from the Atlantic and Indian sectors of the Southern Ocean show that %C diat and %N diat change on glacial-interglacial cycles by 30-40% and 120-175%, respectively. Accordingly, C/N ratios vary between 3 and 7 on glacial-interglacial timescales. If changes recorded in the occluded organic matter are representative of the changes in the diatom bulk organic matter, this provides a new tool to document the carbon cycle in the Southern Ocean and to determine its role on past atmospheric pCO 2 variations. Laboratory experiments on diatom cultures are needed to validate the use of diatom organic bound C and N as a tracer of diatom physiology and of carbon export from surface waters. r 2002 Elsevier Science Ltd. All rights reserved. Re´sume´LeRe´sume´ Re´sume´Le cycle du carbone de l'Oc! ean Austral est certainement un des facteurs majeurs contr # olant les concentrations atmosph! eriques pass! ees en CO 2. Cependant, les taux d'accumulation de l'opale biog" ene ne sont pas lin! eairement li! es aux taux d'accumulation du carbone organique et ne peuvent donc pas # etre directement utilis! es en tant que traceur de la pal! eoproductivit! e. Nous montrons ici qu'il est possible de mesurer les teneurs en carbone et azote dans la mati" ere organique intrins" eque des diatom! ees (%C diat and %N diat respectivement), et que les signaux fossiles ne sont pas le r! esultat d'artefacts analytiques. L'analyse de deux carottes provenant des secteurs Atlantique et Indien de l'Oc! ean Austral indique que les %C diat and %N diat ont respectivement vari! ...