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| Titel |
Calcification intensity in planktonic Foraminifera reflects ambient conditions irrespective of environmental stress |
| VerfasserIn |
M. F. G. Weinkauf, T. Moller, M. C. Koch, M. Kucera |
| 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 ; 10, no. 10 ; Nr. 10, no. 10 (2013-10-23), S.6639-6655 |
| Datensatznummer |
250085373
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| Publikation (Nr.) |
 copernicus.org/bg-10-6639-2013.pdf |
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| Zusammenfassung |
| Planktonic Foraminifera are important marine calcifiers, and the ongoing change in the oceanic
carbon system makes it essential to understand the influence of environmental factors on the
biomineralization of their shells. The amount of calcite deposited by planktonic Foraminifera
during calcification has been hypothesized to reflect a range of environmental factors. However,
it has never been assessed whether their calcification only passively responds to the conditions
of the ambient seawater or whether it reflects changes in resource allocation due to physiological
stress. To disentangle these two end-member scenarios, an experiment is required where the two
processes are separated. A natural analogue to such an experiment occurred during the deposition
of the Mediterranean sapropels, where large changes in surface water composition and
stratification at the onset of the sapropel deposition were decoupled from local extinctions of
planktonic Foraminifera species. We took advantage of this natural experiment and investigated the
reaction of calcification intensity, expressed as mean area density (MAD), of four
species of planktonic Foraminifera to changing conditions during the onset of Sapropel S5
(126–121 ka) in a sediment core from the Levantine Basin. We observed a significant
relationship between MAD and surface water properties, as reflected by stable isotopes
in the calcite of Foraminifera shells, but we failed to observe any reaction of calcification
intensity on ecological stress during times of decreasing abundance culminating in local
extinction. The reaction of calcification intensity to surface water perturbation at the onset of
the sapropel was observed only in surface-dwelling species, but all species calcified more
strongly prior to the sapropel deposition and less strongly within the sapropel than at similar
conditions during the present-day. These results indicate that the high-salinity environment of
the glacial Mediterranean Sea prior to sapropel deposition induced a~more intense calcification,
whereas the freshwater injection to the surface waters associated with sapropel deposition
inhibited calcification. The results are robust to changes in carbonate preservation and
collectively imply that changes in normalized shell weight in planktonic Foraminifera should
reflect mainly abiotic forcing. |
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