Investigation of Li/Ca variations in aragonitic shells of the ocean quahog Arctica islandica , northeast Iceland

• Published in: Geochemistry, Geophysics, Geosystems
• Main Authors: Thébault, Julien, Schöne, Bernd R., Hallmann, Nadine, Barth, Matthias, Nunn, Elizabeth V.
• Other Authors: 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), Department of Applied and Analytical Paleontology, University of Mainz, Johannes Gutenberg - Universität Mainz = Johannes Gutenberg University (JGU), Department of Geochemical Petrology, University of Mainz, Financial support for this study was provided by the German Research Foundation (DFG) to Bernd R. Schöne (SCHO 793/4). Julien Thébault gratefully acknowledges the Alexander von Humboldt Foundation (Bonn, Germany) for the award of a Research Fellowship for Postdoctoral Researchers.
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2009
• Subjects: bivalve; lithium; calcification; shell growth rate; weathering; Iceland; [SDE]Environmental Sciences; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; [SDV.EE.ECO]Life Sciences [q-bio]/Ecology; environment/Ecosystems; Arctica islandica; Ocean quahog
• Online Access: https://hal.science/hal-00449411; https://hal.science/hal-00449411/document; https://hal.science/hal-00449411/file/Thebault_et_al_2009b.pdf; https://doi.org/10.1029/2009GC002789

International audience Interannual and intra-annual variations in lithium-to-calcium ratio were investigated with high temporal resolution in the aragonitic outer shell layer of juvenile Arctica islandica (Mollusca; Bivalvia) collected alive in 2006 off northeast Iceland. Li/Ca shell ranged between 7.00 and 11.12 µmol mol -1 and presented well-marked seasonal cycles with minimum values recorded at the annual growth lines; a general pattern was a progressive increase in Li/Ca shell from March to May, followed by a plateau in June and a decrease down to minimum values in July-August. Li/Ca shell was correlated with d 18 O shell -derived temperature, but the strength of this relationship was weak ( r 2 < 0.25 and p < 0.05). It covaried significantly with microgrowth increment width and with the discharge from one of the closest rivers. Seasonal variations of Li/Ca shell in A. islandica may most likely be explained (1) by calcification rate and/or (2) by significant river inputs of Li-rich silicate particles flowing to the sea as soon as snow melts. In the first case, Li/Ca shell may be a useful proxy for addressing seasonal variations of growth rate in bivalves that lack discernable microgrowth patterns. Abrupt decreases of Li/Ca shell may, in turn, help identify growth retardations due to harsh environmental conditions. Alternatively, if Li/Ca shell variations are linked to particulate Li inputs by rivers, this could be a new proxy for the intensity of mechanical weathering of Icelandic basalts, with interesting perspectives for the reconstruction of frequency and intensity of past jökulhlaups (subglacial outburst floods). Further works, including experimental studies, are needed to test these hypotheses.