Decrease in coccolithophore calcification and CO2 since the middle Miocene

• Published in: Nature Communications
• Main Authors: Bolton, Clara T., Hernández-Sánchez, María T., Fuertes, Miguel-Ángel, González-Lemos, Saúl, Abrevaya, Lorena, Mendez-Vicente, Ana, Flores, José-Abel, Probert, Ian, Giosan, Liviu, Johnson, Joel, Stoll, Heather M.
• Other Authors: Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Geology Department, Oviedo University, Grupo de Geociencias Oceánicas, University of Salamanca, Station biologique de Roscoff Roscoff (SBR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Department of Geology and Geophysics, Woods Hole Oceanographic Institution (WHOI), Department of Earth Sciences UNH Durham, University of New Hampshire (UNH)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: Earth sciences; Biogeochemistry; Climate science; Ecology; [SDV.EE]Life Sciences [q-bio]/Ecology; environment; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; Ocean acidification
• Online Access: https://hal.sorbonne-universite.fr/hal-01277350; https://hal.sorbonne-universite.fr/hal-01277350/document; https://hal.sorbonne-universite.fr/hal-01277350/file/gbc20392.pdf; https://doi.org/10.1038/ncomms10284

International audience Marine algae are instrumental in carbon cycling and atmospheric carbon dioxide (CO2) regulation. One group, coccolithophores, uses carbon to photosynthesize and to calcify, covering their cells with chalk platelets (coccoliths). How ocean acidification influences coccolithophore calcification is strongly debated, and the effects of carbonate chemistry changes in the geological past are poorly understood. This paper relates degree of coccolith calcification to cellular calcification, and presents the first records of size-normalized coccolith thickness spanning the last 14 Myr from tropical oceans. Degree of calcification was highest in the low-pH, high-CO2 Miocene ocean, but decreased significantly between 6 and 4 Myr ago. Based on this and concurrent trends in a new alkenone εp record, we propose that decreasing CO2 partly drove the observed trend via reduced cellular bicarbonate allocation to calcification. This trend reversed in the late Pleistocene despite low CO2, suggesting an additional regulator of calcification such as alkalinity.