@article {bottini_high_2020, title = {High resolution spatial analyses of trace elements in coccoliths reveal new insights into element incorporation in coccolithophore calcite}, journal = {Scientific Reports}, volume = {10}, number = {1}, year = {2020}, note = {Number: 1 Publisher: Nature Publishing Group}, pages = {9825}, abstract = {Coccolithophores are phytoplanktonic algae which produce an exoskeleton made of single platelets of calcite named coccoliths. They are widespread in all oceans and directly impact the short- and long-term C cycle. The study of coccolith size, morphology and elemental composition reveals important information regarding the ability of the cell to calcify and on the factors that influence this process. In this regard, very little is known about coccolith composition and its changes under altered environmental conditions. Here, we present high resolution (50 {\texttimes} 50 nm) elemental spatial distribution in pristine coccoliths of Coccolithus pelagicus and Gephyrocapsa oceanica reconstructed via X-ray fluorescence analyses at synchrotron. The studied specimens are from control culture and metal-enriched (V, Ni, Zn and Pb) experiments. The analysed specimens produced under stress conditions, display an irregular shape and are thinner, especially in the external rim, with ca. 1/3 lower Ca concentrations compared to specimens from the control. The same specimens also have higher Sr/Ca ratio with highest values in the coccolith external rim, suggesting that difficulty in calcification is additionally reflected in increased Sr/Ca ratios. Selenium is found in the coccolith as possible substitute of carbonate in the calcite. V and Pb apparently did not interact with the coccoliths while Zn and Ni were deposited on the coccolith surface.}, keywords = {Environmental chemistry, Environmental impact, Marine chemistry, Pollution remediation, RCC1198, RCC1303}, issn = {2045-2322}, doi = {10.1038/s41598-020-66503-x}, url = {http://www.nature.com/articles/s41598-020-66503-x}, author = {Bottini, Cinzia and Dapiaggi, Monica and Erba, Elisabetta and Faucher, Giulia and Rotiroti, Nicola} } @article {faucher_impact_2017, title = {Impact of trace metal concentrations on coccolithophore growth and morphology: laboratory simulations of Cretaceous stress}, journal = {Biogeosciences}, volume = {14}, number = {14}, year = {2017}, note = {Publisher: Copernicus GmbH}, month = {jul}, pages = {3603{\textendash}3613}, abstract = {

Abstract. The Cretaceous ocean witnessed intervals of profound perturbations such as volcanic input of large amounts of CO$_\textrm2$, 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 \textitEmiliania huxleyi, Gephyrocapsa oceanica, Pleurochrysis carterae and \textitCoccolithus 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 \textitE. huxleyi and \textitC. pelagicus, while coccoliths of \textitG. oceanica showed a decrease in size only at the highest trace metal concentrations. \textitP. carterae coccolith size was unresponsive to changing trace metal concentrations. These differences among species allow discriminating the most- (\textitP. carterae), intermediate- (\textitE. huxleyi and \textitG. oceanica) and least-tolerant (\textitC. 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.

}, keywords = {RCC1198, RCC1216, RCC1303}, issn = {1726-4170}, doi = {10.5194/bg-14-3603-2017}, url = {https://bg.copernicus.org/articles/14/3603/2017/}, author = {Faucher, Giulia and Hoffmann, Linn and Bach, Lennart T. and Bottini, Cinzia and Erba, Elisabetta and Riebesell, Ulf} }