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| Titel |
Effects of elevated temperature and pCO2 on Arctic and Mediterranean Thecosome pteropods |
| VerfasserIn |
Steeve Comeau, Samir Alliouane, Gaby Gorsky, Ross Jeffree, James Orr, Jean-Pierre Gattuso |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250054337
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| Zusammenfassung |
| Thecosome pteropods (shelled pelagic molluscs) can play a key role in the food web of
various marine ecosystems. They can be an important food source for zooplankton or higher
predators such as fishes, whales and birds, particularly in high latitude regions. Since they
maintain an external calcareous shell made of aragonite, a relatively soluble form of calcium
carbonate (CaCO3), they are suspected to be highly sensitive to changes in seawater
carbonate chemistry. Several physiological parameters such as calcification, respiration,
excretion, gut clearance and larval development were measured on Arctic (Limacina helicina)
and Mediterranean (Creseis acicula, Cavolinia inflexa) pteropods maintained under
laboratory conditions mimicking predicted future ocean conditions. The gut clearance rate is
unaffected by a decrease in pH down to pHT ~7.6. In L. helicina, the respiration rate
is unaffected by pH at 0Ë C (control temperature) but increases significantly at
lower pH at 4Ë C. In contrast, respiration is not affected by pH in C. acicula. These
experiments demonstrate that all three species exhibit a strong reduction in gross
calcification as a function of decreasing aragonite saturation state. Empirical relationships
between gross CaCO3 precipitation and the aragonite saturation state were combined
with model projections of future aragonite saturation stateand with data on the
vertical migration of pteropods in order to estimate the effect of ocean acidification
on in situ calcification. Results suggest that under the IPCC SRES A2 scenario,
Arctic pteropods will not be able to precipitate any CaCO3 by the end of the century.
But even if they would be able to precipitate CaCO3 in slightly undersaturated
conditions, it is unlikely that they could maintain a positive net balance between
gross CaCO3 precipitation and dissolution. This is inferred from measured rates of
dissolution in C. acicula and observations showing that larvae of C. inflexa are unable to
make shells in seawater that is undersaturated with respect to aragonite. Our results
justify the concern about the future of shelled pteropods in the high-latitude oceans. |
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