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| Titel |
Feedbacks and responses of coral calcification on the Bermuda reef system to seasonal changes in biological processes and ocean acidification |
| VerfasserIn |
N. R. Bates, A. Amat, A. J. Andersson |
| 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 ; 7, no. 8 ; Nr. 7, no. 8 (2010-08-24), S.2509-2530 |
| Datensatznummer |
250004936
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| Publikation (Nr.) |
 copernicus.org/bg-7-2509-2010.pdf |
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| Zusammenfassung |
| Despite the potential impact of ocean acidification on ecosystems such
as coral reefs, surprisingly, there is very limited field data on the
relationships between calcification and seawater carbonate chemistry. In
this study, contemporaneous in situ datasets of seawater carbonate chemistry and
calcification rates from the high-latitude coral reef of Bermuda over annual
timescales provide a framework for investigating the present and future
potential impact of rising carbon
dioxide (CO2) levels and ocean acidification on coral reef
ecosystems in their natural environment. A strong correlation was found
between the in situ rates of calcification for the major framework building coral
species Diploria labyrinthiformis and the seasonal variability of [CO32-] and aragonite
saturation state Ωaragonite, rather than other environmental factors such as light and
temperature. These field observations provide sufficient data to hypothesize
that there is a seasonal "Carbonate Chemistry Coral Reef Ecosystem Feedback" (CREF hypothesis) between the primary components
of the reef ecosystem (i.e., scleractinian hard corals and macroalgae) and seawater
carbonate chemistry. In early summer, strong net autotrophy from benthic
components of the reef system enhance [CO32-] and Ωaragonite conditions, and rates of coral calcification due to the
photosynthetic uptake of CO2. In late summer, rates of coral
calcification are suppressed by release of CO2 from reef metabolism
during a period of strong net heterotrophy. It is likely that this seasonal
CREF mechanism is present in other tropical reefs although attenuated
compared to high-latitude reefs such as Bermuda. Due to lower annual mean
surface seawater [CO32-] and Ωaragonite in Bermuda
compared to tropical regions, we anticipate that Bermuda corals will
experience seasonal periods of zero net calcification within the next
decade at [CO32-] and Ωaragonite thresholds of ~184 μmoles kg−1
and 2.65. However, net autotrophy of the reef
during winter and spring (as part of the CREF hypothesis) may delay the onset
of zero NEC or decalcification going forward by enhancing [CO32-]
and Ωaragonite. The Bermuda coral reef is one of the first
responders to the negative impacts of ocean acidification, and we estimate
that calcification rates for D. labyrinthiformis have declined by >50% compared to
pre-industrial times. |
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