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| Titel |
Coral records of reef-water pH across the central Great Barrier Reef, Australia: assessing the influence of river runoff on inshore reefs |
| VerfasserIn |
J. P. D'Olivo, M. T. McCulloch, S. M. Eggins, J. Trotter |
| 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 ; 12, no. 4 ; Nr. 12, no. 4 (2015-02-25), S.1223-1236 |
| Datensatznummer |
250117832
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| Publikation (Nr.) |
 copernicus.org/bg-12-1223-2015.pdf |
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| Zusammenfassung |
| The boron isotopic (δ11Bcarb) compositions of
long-lived Porites coral are used to reconstruct reef-water pH
across the central Great Barrier Reef (GBR) and assess the impact of river
runoff on inshore reefs. For the period from 1940 to 2009, corals from both
inner- and mid-shelf sites exhibit the same overall decrease in δ11Bcarb of 0.086 ± 0.033‰ per decade,
equivalent to a decline in seawater pH (pHsw) of
~0.017 ± 0.007 pH units per decade. This decline is consistent
with the long-term effects of ocean acidification based on estimates of
CO2 uptake by surface waters due to rising atmospheric levels. We also
find that, compared to the mid-shelf corals, the
δ11Bcarb compositions of inner-shelf corals subject to
river discharge events have higher and more variable values, and hence higher
inferred pHsw values. These higher δ11Bcarb
values of inner-shelf corals are particularly evident during wet years,
despite river waters having lower pH. The main effect of river discharge on
reef-water carbonate chemistry thus appears to be from reduced aragonite
saturation state and higher nutrients driving increased phytoplankton
productivity, resulting in the drawdown of pCO2 and increase in
pHsw. Increased primary production therefore has the potential to
counter the more transient effects of low-pH river water (pHrw)
discharged into near-shore environments. Importantly, however, inshore reefs
also show a consistent pattern of sharply declining coral growth that
coincides with periods of high river discharge. This occurs despite these
reefs having higher pHsw, demonstrating the overriding
importance of local reef-water quality and reduced aragonite saturation state
on coral reef health. |
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