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| Titel |
Phytoplankton calcification as an effective mechanism to alleviate cellular calcium poisoning |
| VerfasserIn |
M. N. Müller, J. Barcelos e Ramos, K. G. Schulz, U. Riebesell, J. Kaźmierczak, F. Gallo, L. Mackinder, Y. Li, P. N. Nesterenko, T. W. Trull, G. M. Hallegraeff |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 21 ; Nr. 12, no. 21 (2015-11-13), S.6493-6501 |
| Datensatznummer |
250118164
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| Publikation (Nr.) |
 copernicus.org/bg-12-6493-2015.pdf |
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| Zusammenfassung |
| Marine phytoplankton have developed the remarkable ability to tightly
regulate the concentration of free calcium ions in the intracellular cytosol
at a level of ~ 0.1 μmol L−1 in the presence of
seawater Ca2+ concentrations of 10 mmol L−1. The low cytosolic
calcium ion concentration is of utmost importance for proper cell signalling
function. While the regulatory mechanisms responsible for the tight control
of intracellular Ca2+ concentration are not completely understood,
phytoplankton taxonomic groups appear to have evolved different strategies,
which may affect their ability to cope with changes in seawater Ca2+
concentrations in their environment on geological timescales. For example,
the Cretaceous (145 to 66 Ma), an era known for the high abundance of
coccolithophores and the production of enormous calcium carbonate deposits,
exhibited seawater calcium concentrations up to 4 times present-day
levels. We show that calcifying coccolithophore species (Emiliania huxleyi, Gephyrocapsa oceanica and Coccolithus braarudii) are able
to maintain their relative fitness (in terms of growth rate and
photosynthesis) at simulated Cretaceous seawater calcium concentrations, whereas these rates are severely reduced under these
conditions in some non-calcareous phytoplankton species (Chaetoceros sp., Ceratoneis closterium and
Heterosigma akashiwo). Most notably, this also applies to a non-calcifying strain of E. huxleyi which
displays a calcium sensitivity similar to the non-calcareous species. We
hypothesize that the process of calcification in coccolithophores provides
an efficient mechanism to alleviate cellular calcium poisoning and thereby
offered a potential key evolutionary advantage, responsible for the
proliferation of coccolithophores during times of high seawater calcium
concentrations. The exact function of calcification and the reason behind
the highly ornate physical structures of coccoliths remain elusive. |
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