Adaptations of Coccolithophore Size to Selective Pressures During the Oligocene to Early Miocene High CO2 World

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Authors

Colleges, School and Institutes

External organisations

  • ETH Zurich

Abstract

Culture experiments with coccolithophore algae—the dominant group of marine calcifying phytoplankton—imply a strong sensitivity in growth rate, degree of cellular calcification, and cell size to changes in the carbon chemistry of their growth environment. These results underpin recent studies that have explored how these physiological parameters have varied on geological time scales, in response to changing surface ocean habitats and the concentrations of carbon in the ocean-atmosphere system. Here, we add to this work with a study of reticulofenestrid coccolith size—the dominant coccolithophore family of the Cenozoic—over the Oligocene to Early Miocene time interval. We examine sediments from contrasting latitudes and regional environmental settings, comparing sites using coherent, updated age models to distinguish globally synchronous trends in cell size from regional trends. Our results confirm several changes in coccolith size—which is strongly correlated to cell size—that are globally reproducible within the ~1 Myr age uncertainty, including a reduction in mean size by >2 μm from 30.2 to 27 and 24.5 to 23 Ma, and then increase in mean size after 20 Ma. The main difference among regions is the presence/absence of coccoliths larger than 8 μm. We evaluate which scenarios of change in carbon dioxide, temperature, and nutrient availability could have exerted selective pressure on cell size for different size classes to produce the observed size trends at each studied site. These million-year scale adaptations of ancient coccolithophores contribute to the understanding of phytoplankton physiology in the transition to the modern “icehouse” world.

Bibliographic note

Funding Information: Sediment samples were provided by the Integrated Ocean Drilling Program (IODP) and Ocean Drilling Program (ODP). This study was supported by the Swiss National Science Foundation (Award 200021_182070 to Heather M. Stoll). Authors acknowledge Madallina Jaggi from Climate Geology Group at ETH Zürich for her support in laboratory analysis and Samuel R. Phelps for essential input on data management. A research stay at Birmingham University for nannofossil work was sustained thanks to a Microplaeontological Society Grant‐in‐Aid awarded to José Guitián. We also thank Jeremy R. Young and two anonymous reviewers for constructive comments that substantially improved this manuscript. Publisher Copyright: ©2020. American Geophysical Union. All Rights Reserved. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

Details

Original languageEnglish
Article numbere2020PA003918
JournalPaleoceanography and Paleoclimatology
Volume35
Issue number12
Publication statusPublished - Dec 2020

Keywords

  • cell size, coccolith, coccolithophore, Miocene, Oligocene, paleoproductivity

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