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| Titel |
Response of benthic foraminifera to ocean acidification in their natural sediment environment: a long-term culturing experiment |
| VerfasserIn |
K. Haynert, J. Schönfeld, R. Schiebel, B. Wilson, J. Thomsen |
| 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 ; 11, no. 6 ; Nr. 11, no. 6 (2014-03-25), S.1581-1597 |
| Datensatznummer |
250117306
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| Publikation (Nr.) |
 copernicus.org/bg-11-1581-2014.pdf |
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| Zusammenfassung |
| Calcifying foraminifera are expected to be endangered by ocean acidification;
however, the response of a complete community kept in natural sediment and
over multiple generations under controlled laboratory conditions has not been
constrained to date. During 6 months of incubation, foraminiferal assemblages
were kept and treated in natural sediment with pCO2-enriched seawater
of 430, 907, 1865 and 3247 μatm pCO2. The fauna was
dominated by Ammonia aomoriensis and Elphidium species,
whereas agglutinated species were rare. After 6 months of incubation, pore
water alkalinity was much higher in comparison to the overlying seawater.
Consequently, the saturation state of Ωcalc was much higher
in the sediment than in the water column in nearly all pCO2 treatments
and remained close to saturation. As a result, the life cycle (population
density, growth and reproduction) of living assemblages varied markedly
during the experimental period, but was largely unaffected by the pCO2
treatments applied. According to the size–frequency distribution, we
conclude that foraminifera start reproduction at a diameter of
250 μm. Mortality of living Ammonia aomoriensis was
unaffected, whereas size of large and dead tests decreased with elevated
pCO2 from 285 μm (pCO2 from 430 to
1865 μatm) to 258 μm (pCO2 3247 μatm).
The total organic content of living Ammonia aomoriensis has been
determined to be 4.3% of CaCO3 weight. Living individuals had a
calcium carbonate production rate of 0.47 g m−2 a−1, whereas
dead empty tests accumulated a rate of 0.27 g m−2 a−1. Although
Ωcalc was close to 1, approximately 30% of the empty
tests of Ammonia aomoriensis showed dissolution features at high
pCO2 of 3247 μatm during the last 2 months of incubation. In
contrast, tests of the subdominant species, Elphidium incertum,
stayed intact. Our results emphasize that the sensitivity to ocean
acidification of the endobenthic foraminifera Ammonia aomoriensis in
their natural sediment habitat is much lower compared to the experimental
response of specimens isolated from the sediment. |
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