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| Titel |
Impact of trace metal concentrations on coccolithophore growth and
morphology: species-specific responses in past and present ocean |
| VerfasserIn |
Giulia Faucher, Linn Hoffmann, Lennart Thomas Bach, Cinzia Bottini, Elisabetta Erba, Ulf Riebesell |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150999
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| Publikation (Nr.) |
 EGU/EGU2017-15537.pdf |
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| Zusammenfassung |
| The Cretaceous witnessed intervals of profound perturbation named “Oceanic Anoxic Events
(OAEs)” characterized by volcanic injection of large amounts of CO2, ocean anoxia,
eutrophication, and introduction of biologically relevant metals. Some of these extreme
events were characterized by size reduction and/or morphological changes of a number of
nannofossil species. To detect the cause/s of such changes in the fossil record is challenging.
Evidence of a correspondence between intervals of high trace metals concentrations and
nannofossil dwarfism may be suggestive for a negative effect of these elements on
nannoplankton biocalcification process.
In order to verify the hypothesis that anomalously high quantities of essential and/or toxic
metals were the cause of coccolith dwarfism, we explored the toxicities of a mixture of
trace metals on four living coccolithophores species, namely Emiliania huxleyi,
Gephyrocapsa oceanica, Pleurochrysis carterae and Coccolithus pelagicus. The
trace metals tested were chosen based upon concentration peaks identified in the
geological record and upon known trace metal interaction with living coccolithophores
algae.
Our results demonstrate a species-specific response to trace metal enrichment in living
coccolithophores: E. huxleyi, G. oceanica and C. pelagicus showed a decrease in their growth
rate with progressively and exponentially increased trace metal concentrations, while P.
carterae is unresponsive to trace metal content. Furthermore, E. huxleyi, G. oceanica and C.
pelagicus evidenced a decrease in the cell diameter. Smaller coccoliths were detected in E.
huxleyi and C. pelagicus, while coccolith of G. oceanica showed a decrease in size only at the
highest trace metal concentrations tested. P. carterae size was unresponsive for changing
trace metal concentration.
Our results on living coccolithophore algae, demonstrate that elevated trace metal
concentrations not only affect growth but also coccolith size and/or weight and that there are
large differences between different species. These species-specific differences must
be considered before morphological features of coccoliths are used to reconstruct
paleo-chemical conditions.
Following the laboratory experiment results, elevated trace metal conditions in the past
oceans could have caused at least part of the observed morphological changes detected during
some Mesozoic OAEs. |
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