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Can morphological features of coccolithophores serve as a reliable proxy to reconstruct environmental conditions of the past?

Citation

Faucher, G and Riebesell, U and Bach, LT, Can morphological features of coccolithophores serve as a reliable proxy to reconstruct environmental conditions of the past?, Climate of the Past, 16, (3) pp. 1007-1025. ISSN 1814-9324 (2020) [Refereed Article]


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DOI: doi:10.5194/cp-16-1007-2020

Abstract

Morphological changes in coccoliths, tiny calcite platelets covering the outer surface of coccolithophores, can be induced by physiological responses to environmental changes. Coccoliths recovered from sedimentary successions may therefore provide information on paleo-environmental conditions prevailing at the time when the coccolithophores were alive. To calibrate the biomineralization responses of ancient coccolithophore to environmental changes, studies often compared the biological responses of living coccolithophore species with paleo-data from calcareous nannofossils. However, there is uncertainty whether the morphological responses of living coccolithophores are representative of those of the fossilized ancestors. To investigate this, we exposed four living coccolithophore species (Emiliania huxleyi, Gephyrocapsa oceanica, Coccolithus pelagicus subsp. braarudii, and Pleurochrysis carterae) that have been evolutionarily distinct for hundreds of thousands to millions of years, to a range of environmental conditions (i.e., changing light intensity, Mg∕Ca ratio, nutrient availability, temperature, and carbonate chemistry) and evaluated their responses in coccolith morphology (i.e., size, length, width, malformation). The motivation for this study was to test if there is a consistent morphological response of the four species to changes in any of the tested abiotic environmental factors. If this was the case, then this could suggest that coccolith morphology can serve as a paleo-proxy for that specific factor because this response is conserved across species that have been evolutionary distinct over geological timescales. However, we found that the four species responded differently to changing light intensity, Mg∕Ca ratio, nutrient availability, and temperature in terms of coccolith morphology. The lack of a common response reveals the difficulties in using coccolith morphology as a paleo-proxy for these environmental drivers. However, a common response was observed under changing seawater carbonate chemistry (i.e., rising CO2), which consistently induced malformations. This commonality provides some confidence that malformations found in the sedimentary record could be indicative of adverse carbonate chemistry conditions.

Item Details

Item Type:Refereed Article
Keywords:coccolithophores, paleo proxy, morphology
Research Division:Biological Sciences
Research Group:Other Biological Sciences
Research Field:Global Change Biology
Objective Division:Environment
Objective Group:Climate and Climate Change
Objective Field:Climate Change Adaptation Measures
UTAS Author:Bach, LT (Dr Lennart Bach)
ID Code:139725
Year Published:2020
Deposited By:Ecology and Biodiversity
Deposited On:2020-06-30
Last Modified:2020-06-30
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