Ontogenetic effects on stable carbon and oxygen isotopes in tests of live (Rose Bengal stained) benthic foraminifera from the Pakistan continental margin |
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| Institution: | 1. Laboratory of Recent and Fossil Bio-Indicators (BIAF), Angers University, 2 Bd Lavoisier, 49045 Angers Cedex 01, France;2. Laboratory of Marine Bio-Indicators (LEBIM), Ile d''Yeu, Ker Chalon, France;3. Alfred Wegener Institute for Polar and Marine Research, Am Alten Hafen 26, 27568 Bremerhaven, Germany;4. National Oceanography Centre, Southampton, European Way, Southampton SO14 3ZH, United Kingdom;5. LEESA, Ecology and Conservation Biology group, Angers University, 2 Bd Lavoisier, 49045 Angers Cedex 01, France;1. Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany;2. Instituto Mediterráneo de Estudios Avanzados, IMEDEA (CSIC-UIB), C/Miquel Marqués 21, 07190 Esporles, Illes Balears, Spain;3. National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, P.O. Box 4321, Coffs Harbour, NSW 2450, Australia;4. Fisheries NSW, NSW Department of Primary Industries, P.O. Box 4321, Coffs Harbour, New South Wales 2450, Australia;1. CRCNA-Inserm-U892, 8, quai Moncousu, 44007 Nantes cedex 1, France;2. Unité mixte de recherche, université-Inserm U-1039 radiopharmaceutiques biocliniques, université Grenoble 1, domaine de la Merci, 38706 La Tronche cedex, France;3. Radiopharmacie, CHU A.-Michallon, CS 10217, 38043 Grenoble cedex 9, France;4. Institut de cancérologie de l’Ouest, site René-Gauducheau, boulevard Jacques-Monod, 44805 Saint-Herblain cedex, France;5. LUNAM université, université d’Angers, Inserm UMR_S 1066, 4, rue Larrey, 49933 Angers cedex 9, France;6. Service de médecine nucléaire, CHU d’Angers, 4, rue Larrey, 49933 Angers cedex 9, France;7. Aix-Marseille université, UMR_S_1076, CERIMED, 13385 Marseille, France;8. AP–HM, Radiopharmacie, 13385 Marseille, France;1. The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand;2. Department of Chemical Engineering, University of Michigan, MI, USA |
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| Abstract: | We determined the stable oxygen and carbon isotopic composition of live (Rose Bengal stained) tests belonging to different size classes of two benthic foraminiferal species from the Pakistan continental margin. Samples were taken at two sites, with water depths of about 135 and 275 m, corresponding to the upper boundary and upper part of the core region of the oxygen minimum zone (OMZ). For Uvigerina ex gr. Uvigerina semiornata and Bolivina aff. Bolivina dilatata, δ13C and δ18O values increased significantly with increasing test size. In the case of Uvigerina ex gr. U. semiornata, δ13C increased linearly by about 0.105‰ for each 100-μm increment in test size, whereas δ18O increased by 0.02 to 0.06‰ per 100 μm increment. For Bolivina aff. B. dilatata the relationship between test size and stable isotopic composition is better described by logarithmic equations. A strong positive linear correlation is observed between δ18O and δ13C values of both taxa, with a constant ratio of δ18O and δ13C values close to 2:1. This suggests that the strong ontogenetic effect is mainly caused by kinetic isotope fractionation during CO2 uptake. Our data underline the necessity to base longer δ18O and δ13C isotope records derived from benthic foraminifera on size windows of 100 μm or less. This is already common practice in down-core isotopic studies of planktonic foraminifera. |
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