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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 14
Biogeosciences, 14, 3603-3613, 2017
https://doi.org/10.5194/bg-14-3603-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 14, 3603-3613, 2017
https://doi.org/10.5194/bg-14-3603-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 31 Jul 2017

Research article | 31 Jul 2017

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

Giulia Faucher1, Linn Hoffmann2, Lennart T. Bach3, Cinzia Bottini1, Elisabetta Erba1, and Ulf Riebesell3 Giulia Faucher et al.
  • 1Earth Sciences Department “Ardito Desio”, Università degli Studi di Milano, Milan, Italy
  • 2Department of Botany, University of Otago, Dunedin, New Zealand
  • 3Biological Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany

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.

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The main goal of this study was to understand if, similarly to the fossil record, high quantities of toxic metals induce coccolith dwarfism in coccolithophore species. We investigated, for the first time, the effects of trace metals on coccolithophore species other than E. huxleyi and on coccolith morphology and size. Our data show a species-specific sensitivity to trace metal concentration, allowing the recognition of the most-, intermediate- and least-tolerant taxa to trace metal enrichments.
The main goal of this study was to understand if, similarly to the fossil record, high...
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