title: Decrease in coccolithophore calcification and CO2 since the middle Miocene.
abstract: 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 ɛp 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.
authors.affiliation: Geology Department, Oviedo University, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain.|Aix-Marseille University, CNRS, IRD, CEREGE UM34, 13545 Aix en Provence, France.
authors.forename: Clara T
authors.initials: CT
authors.lastname: Bolton
authors.affiliation: Geology Department, Oviedo University, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain.
authors.forename: María T
authors.initials: MT
authors.lastname: Hernández-Sánchez
authors.affiliation: Grupo de Geociencias Oceánicas, Geology Department, University of Salamanca, Salamanca 37008, Spain.
authors.forename: Miguel-Ángel
authors.initials: MÁ
authors.lastname: Fuertes
authors.affiliation: Geology Department, Oviedo University, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain.
authors.forename: Saúl
authors.initials: S
authors.lastname: González-Lemos
authors.affiliation: Geology Department, Oviedo University, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain.
authors.forename: Lorena
authors.initials: L
authors.lastname: Abrevaya
authors.affiliation: Geology Department, Oviedo University, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Mendez-Vicente
authors.affiliation: Grupo de Geociencias Oceánicas, Geology Department, University of Salamanca, Salamanca 37008, Spain.
authors.forename: José-Abel
authors.initials: JA
authors.lastname: Flores
authors.affiliation: CNRS, Sorbonne Universités-Université Pierre et Marie Curie (UPMC) Paris 06, FR2424, Roscoff Culture Collection, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France.
authors.forename: Ian
authors.initials: I
authors.lastname: Probert
authors.affiliation: Department of Geology and Geophysics, Woods Hole Oceanographic Institution, 266 Woods Hole Road, MS# 22, Woods Hole, Massachusetts 02543-1050, USA.
authors.forename: Liviu
authors.initials: L
authors.lastname: Giosan
authors.affiliation: University of New Hampshire, Department of Earth Sciences, 56 College Road, James Hall, Durham, New Hampshire 03824-3589, USA.
authors.forename: Joel
authors.initials: J
authors.lastname: Johnson
authors.affiliation: Geology Department, Oviedo University, Arias de Velasco s/n, 33005 Oviedo, Asturias, Spain.
authors.forename: Heather M
authors.initials: HM
authors.lastname: Stoll
mesh_terms: D002113:Calcification, Physiologic; D002119:Calcium Carbonate / Q000737:chemistry / Q000378:metabolism*; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000737:chemistry*; D058087:Haptophyta / Q000378:metabolism* / Q000648:ultrastructure; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D009792:Oceans and Seas; D012623:Seawater / Q000737:chemistry*
chemical_list: D002245:Carbon Dioxide; D002119:Calcium Carbonate