Carbon isotope offsets between benthic foraminifer species of the genus Cibicides ( Cibicidoides ) in the glacial sub-Antarctic Atlantic

• Published in: Paleoceanography
• Main Authors: Gottschalk, Julia, Vázquez Riveiros, Natalia, Waelbroeck, Claire, Skinner, Luke C., Michel, Elisabeth, Duplessy, Jean-Claude, Hodell, David A., Mackensen, Andreas
• Other Authors: Institute of Geological Sciences Bern, University of Bern, 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), Paléocéanographie (PALEOCEAN), 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), University of Cambridge UK (CAM), Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), European Project: 339108,EC:FP7:ERC,ERC-2013-ADG,ACCLIMATE(2014)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Antarctic; Antarc*
• Online Access: https://hal.archives-ouvertes.fr/hal-02915965; https://hal.archives-ouvertes.fr/hal-02915965/document; https://hal.archives-ouvertes.fr/hal-02915965/file/2016PA003029.pdf; https://doi.org/10.1002/2016PA003029

International audience Epibenthic foraminifer δ 13 C measurements are valuable for reconstructing past bottom water dissolved inorganic carbon δ 13 C (δ 13 C DIC), which are used to infer global ocean circulation patterns. Epibenthic δ 13 C, however, may also reflect the influence of 13 C-depleted phytodetritus, microhabitat changes, and/or variations in carbonate ion concentrations. Here we compare the δ 13 C of two benthic foraminifer species, Cibicides kullenbergi and Cibicides wuellerstorfi, and their morphotypes, in three sub-Antarctic Atlantic sediment cores over several glacial-interglacial transitions. These species are commonly assumed to be epibenthic, living above or directly below the sediment-water interface. While this might be consistent with the small δ 13 C offset that we observe between these species during late Pleistocene interglacial periods (Δδ 13 C=−0.19±0.31‰, N=63), it is more difficult to reconcile with the significant δ 13 C offset that is found between these species during glacial periods (Δδ 13 C=−0.76±0.44‰, N=44). We test possible scenarios by analyzing Uvigerina spp. δ 13 C and benthic foraminifer abundances: (1) C. kullenbergi δ 13 C is biased to light values either due to microhabitat shifts or phytodetritus effects and (2) C. wuellerstorfi δ 13 C is biased to heavy values, relative to long-term average conditions, for instance by recording the sporadic occurrence of less depleted deepwater δ 13 C DIC. Neither of these scenarios can be ruled out unequivocally. However, our findings emphasize that supposedly epibenthic foraminifer δ 13 C in the sub-Antarctic Atlantic may reflect several factors rather than being solely a function of bottom water δ 13 C DIC. This could have a direct bearing on the interpretation of extremely light South Atlantic δ 13 C values at the Last Glacial Maximum.