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Ocean acidification affects coral growth by reducing skeletal density

Ocean acidification affects coral growth by reducing skeletal density
Ocean acidification affects coral growth by reducing skeletal density
Ocean acidification (OA) is considered an important threat to coral reef ecosystems, because it reduces the availability of carbonate ions that reef-building corals need to produce their skeletons. However, while theory predicts that coral calcification rates decline as carbonate ion concentrations decrease, this prediction is not consistently borne out in laboratory manipulation experiments or in studies of corals inhabiting naturally low-pH reefs today. The skeletal growth of corals consists of two distinct processes: extension (upward growth) and densification (lateral thickening). Here, we show that skeletal density is directly sensitive to changes in seawater carbonate ion concentration and thus, to OA, whereas extension is not. We present a numerical model of Porites skeletal growth that links skeletal density with the external seawater environment via its influence on the chemistry of coral calcifying fluid. We validate the model using existing coral skeletal datasets from six Porites species collected across five reef sites and use this framework to project the impact of 21st century OA on Porites skeletal density across the global tropics. Our model predicts that OA alone will drive up to 20.3 ± 5.4% decline in the skeletal density of reef-building Porites corals.
0027-8424
Cohen, Anne L.
b20be412-6349-4bc6-85c1-e5d5a3aafdcf
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022
Cohen, Anne L.
b20be412-6349-4bc6-85c1-e5d5a3aafdcf
Foster, Gavin L.
fbaa7255-7267-4443-a55e-e2a791213022

Cohen, Anne L. and Foster, Gavin L. (2018) Ocean acidification affects coral growth by reducing skeletal density Proceedings of the National Academy of Sciences (doi:10.1073/pnas.1712806115).

Record type: Article

Abstract

Ocean acidification (OA) is considered an important threat to coral reef ecosystems, because it reduces the availability of carbonate ions that reef-building corals need to produce their skeletons. However, while theory predicts that coral calcification rates decline as carbonate ion concentrations decrease, this prediction is not consistently borne out in laboratory manipulation experiments or in studies of corals inhabiting naturally low-pH reefs today. The skeletal growth of corals consists of two distinct processes: extension (upward growth) and densification (lateral thickening). Here, we show that skeletal density is directly sensitive to changes in seawater carbonate ion concentration and thus, to OA, whereas extension is not. We present a numerical model of Porites skeletal growth that links skeletal density with the external seawater environment via its influence on the chemistry of coral calcifying fluid. We validate the model using existing coral skeletal datasets from six Porites species collected across five reef sites and use this framework to project the impact of 21st century OA on Porites skeletal density across the global tropics. Our model predicts that OA alone will drive up to 20.3 ± 5.4% decline in the skeletal density of reef-building Porites corals.

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More information

Accepted/In Press date: 11 December 2017
e-pub ahead of print date: 29 January 2018

Identifiers

Local EPrints ID: 417521
URI: https://eprints.soton.ac.uk/id/eprint/417521
ISSN: 0027-8424
PURE UUID: 90eac2bf-7022-436e-a5d9-58aa107d79bc

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Date deposited: 02 Feb 2018 17:30
Last modified: 02 Feb 2018 17:30

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