The Cretaceous ocean witnessed intervals of profound perturbations such as volcanic input of large amounts of CO2, anoxia, eutrophication and introduction of biologically relevant metals. Some of these extreme events were characterized by size reduction and/or morphological changes of a few calcareous nannofossil species. The correspondence between intervals of high trace metal concentrations and coccolith dwarfism suggests a negative effect of these elements on nannoplankton biocalcification processes in past oceans. In order to test this hypothesis, we explored the potential effect of a mixture of trace metals on growth and morphology of four living coccolithophore species, namely <i>Emiliania huxleyi, Gephyrocapsa oceanica, Pleurochrysis carterae</i> and <i>Coccolithus pelagicus</i>. The phylogenetic history of coccolithophores shows that the selected living species are linked to Mesozoic species showing dwarfism under excess metal concentrations. The trace metals tested were chosen to simulate the environmental stress identified in the geological record and upon known trace metal interactions with living coccolithophore algae.<br><br>Our laboratory experiments demonstrated that elevated trace metal concentrations, similarly to the fossil record, affect coccolithophore algae size and/or weight. Smaller coccoliths were detected in <i>E. huxleyi</i> and <i>C. pelagicus,</i> while coccoliths of <i>G. oceanica</i> showed a decrease in size only at the highest trace metal concentrations. <i>P. carterae</i> coccolith size was unresponsive to changing trace metal concentrations. These differences among species allow discriminating the most-(<i>P. carterae</i>), intermediate-(<i>E. huxleyi</i> and <i>G. oceanica</i>) and least-tolerant (<i>C. pelagicus</i>) taxa. The fossil record and the experimental results converge on a selective response of coccolithophores to metal availability.<br><br>These species-specific differences must be considered before morphological features of coccoliths are used to reconstruct paleo-chemical conditions.

Impact of trace metal concentrations on coccolithophore growth and morphology : Laboratory simulations of Cretaceous stress / G. Faucher, L. Hoffmann, T.L. Bach, C. Bottini, E. Erba, U. Riebesell. - In: BIOGEOSCIENCES. - ISSN 1726-4170. - 14:14(2017 Jul 31), pp. 3603-3613. [10.5194/bg-14-3603-2017]

Impact of trace metal concentrations on coccolithophore growth and morphology : Laboratory simulations of Cretaceous stress

G. Faucher
;
C. Bottini;E. Erba;
2017

Abstract

The Cretaceous ocean witnessed intervals of profound perturbations such as volcanic input of large amounts of CO2, anoxia, eutrophication and introduction of biologically relevant metals. Some of these extreme events were characterized by size reduction and/or morphological changes of a few calcareous nannofossil species. The correspondence between intervals of high trace metal concentrations and coccolith dwarfism suggests a negative effect of these elements on nannoplankton biocalcification processes in past oceans. In order to test this hypothesis, we explored the potential effect of a mixture of trace metals on growth and morphology of four living coccolithophore species, namely Emiliania huxleyi, Gephyrocapsa oceanica, Pleurochrysis carterae and Coccolithus pelagicus. The phylogenetic history of coccolithophores shows that the selected living species are linked to Mesozoic species showing dwarfism under excess metal concentrations. The trace metals tested were chosen to simulate the environmental stress identified in the geological record and upon known trace metal interactions with living coccolithophore algae.

Our laboratory experiments demonstrated that elevated trace metal concentrations, similarly to the fossil record, affect coccolithophore algae size and/or weight. Smaller coccoliths were detected in E. huxleyi and C. pelagicus, while coccoliths of G. oceanica showed a decrease in size only at the highest trace metal concentrations. P. carterae coccolith size was unresponsive to changing trace metal concentrations. These differences among species allow discriminating the most-(P. carterae), intermediate-(E. huxleyi and G. oceanica) and least-tolerant (C. pelagicus) taxa. The fossil record and the experimental results converge on a selective response of coccolithophores to metal availability.

These species-specific differences must be considered before morphological features of coccoliths are used to reconstruct paleo-chemical conditions.
Trace Metals, Coccolithophore, OAEs, morphometry
Settore GEO/01 - Paleontologia e Paleoecologia
   Eccesso di CO2 nel passato geologico: risposte del biota a cambiamenti globali di caldo estremo e acidificazione degli oceani
   MINISTERO DELL'ISTRUZIONE E DEL MERITO
   2010X3PP8J_001
31-lug-2017
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/521689
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