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| Titel |
From laboratory manipulations to Earth system models: scaling calcification impacts of ocean acidification |
| VerfasserIn |
A. Ridgwell, D. N. Schmidt, C. Turley, C. Brownlee, M. T. Maldonado, P. Tortell, J. R. Young |
| 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 ; 6, no. 11 ; Nr. 6, no. 11 (2009-11-23), S.2611-2623 |
| Datensatznummer |
250004096
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| Publikation (Nr.) |
 copernicus.org/bg-6-2611-2009.pdf |
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| Zusammenfassung |
| The observed variation in the calcification responses of coccolithophores to
changes in carbonate chemistry paints a highly incoherent picture,
particularly for the most commonly cultured "species", Emiliania huxleyi. The disparity
between magnitude and potentially even sign of the calcification change
under simulated end-of-century ocean surface chemical changes (higher
pCO2, lower pH and carbonate saturation), raises challenges to
quantifying future carbon cycle impacts and feedbacks because it introduces
significant uncertainty in parameterizations used for global models. Here we
compile the results of coccolithophore carbonate chemistry manipulation
experiments and review how ocean carbon cycle models have attempted to
bridge the gap from experiments to global impacts. Although we can rule out
methodological differences in how carbonate chemistry is altered as
introducing an experimental bias, the absence of a consistent calcification
response implies that model parameterizations based on small and differing
subsets of experimental observations will lead to varying estimates for the
global carbon cycle impacts of ocean acidification. We highlight two
pertinent observations that might help: (1) the degree of coccolith
calcification varies substantially, both between species and within species
across different genotypes, and (2) the calcification response across
mesocosm and shipboard incubations has so-far been found to be relatively
consistent. By analogy to descriptions of plankton growth rate vs.
temperature, such as the "Eppley curve", which seek to encapsulate the net
community response via progressive assemblage change rather than the
response of any single species, we posit that progressive future ocean
acidification may drive a transition in dominance from more to less heavily
calcified coccolithophores. Assemblage shift may be more important to
integrated community calcification response than species-specific response,
highlighting the importance of whole community manipulation experiments to
models in the absence of a complete physiological understanding of the
underlying calcification process. However, on a century time-scale,
regardless of the parameterization adopted, the atmospheric pCO2 impact
of ocean acidification is minor compared to other global carbon cycle
feedbacks. |
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