Short-term coral bleaching is not recorded by skeletal boron isotopes.
Coral skeletal boron isotopes have been established as a proxy for seawater pH, yet it remains unclear if and how this proxy is affected by seawater temperature. Specifically, it has never been directly tested whether coral bleaching caused by high water temperatures influences coral boron isotopes....
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Public Library of Science (PLoS)
2014-01-01
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| Series: | PLoS ONE |
| Online Access: | http://europepmc.org/articles/PMC4232377?pdf=render |
| _version_ | 1818286563658825728 |
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| author | Verena Schoepf Malcolm T McCulloch Mark E Warner Stephen J Levas Yohei Matsui Matthew D Aschaffenburg Andréa G Grottoli |
| author_facet | Verena Schoepf Malcolm T McCulloch Mark E Warner Stephen J Levas Yohei Matsui Matthew D Aschaffenburg Andréa G Grottoli |
| author_sort | Verena Schoepf |
| collection | DOAJ |
| description | Coral skeletal boron isotopes have been established as a proxy for seawater pH, yet it remains unclear if and how this proxy is affected by seawater temperature. Specifically, it has never been directly tested whether coral bleaching caused by high water temperatures influences coral boron isotopes. Here we report the results from a controlled bleaching experiment conducted on the Caribbean corals Porites divaricata, Porites astreoides, and Orbicella faveolata. Stable boron (δ11B), carbon (δ13C), oxygen (δ18O) isotopes, Sr/Ca, Mg/Ca, U/Ca, and Ba/Ca ratios, as well as chlorophyll a concentrations and calcification rates were measured on coral skeletal material corresponding to the period during and immediately after the elevated temperature treatment and again after 6 weeks of recovery on the reef. We show that under these conditions, coral bleaching did not affect the boron isotopic signature in any coral species tested, despite significant changes in coral physiology. This contradicts published findings from coral cores, where significant decreases in boron isotopes were interpreted as corresponding to times of known mass bleaching events. In contrast, δ13C and δ18O exhibited major enrichment corresponding to decreases in calcification rates associated with bleaching. Sr/Ca of bleached corals did not consistently record the 1.2°C difference in seawater temperature during the bleaching treatment, or alternatively show a consistent increase due to impaired photosynthesis and calcification. Mg/Ca, U/Ca, and Ba/Ca were affected by coral bleaching in some of the coral species, but the observed patterns could not be satisfactorily explained by temperature dependence or changes in coral physiology. This demonstrates that coral boron isotopes do not record short-term bleaching events, and therefore cannot be used as a proxy for past bleaching events. The robustness of coral boron isotopes to changes in coral physiology, however, suggests that reconstruction of seawater pH using boron isotopes should be uncompromised by short-term bleaching events. |
| first_indexed | 2024-12-13T01:26:35Z |
| format | Article |
| id | doaj.art-b1f254edd16c4318bad776395b3a5519 |
| institution | Directory Open Access Journal |
| issn | 1932-6203 |
| language | English |
| last_indexed | 2024-12-13T01:26:35Z |
| publishDate | 2014-01-01 |
| publisher | Public Library of Science (PLoS) |
| record_format | Article |
| series | PLoS ONE |
| spelling | doaj.art-b1f254edd16c4318bad776395b3a55192022-12-22T00:04:07ZengPublic Library of Science (PLoS)PLoS ONE1932-62032014-01-01911e11201110.1371/journal.pone.0112011Short-term coral bleaching is not recorded by skeletal boron isotopes.Verena SchoepfMalcolm T McCullochMark E WarnerStephen J LevasYohei MatsuiMatthew D AschaffenburgAndréa G GrottoliCoral skeletal boron isotopes have been established as a proxy for seawater pH, yet it remains unclear if and how this proxy is affected by seawater temperature. Specifically, it has never been directly tested whether coral bleaching caused by high water temperatures influences coral boron isotopes. Here we report the results from a controlled bleaching experiment conducted on the Caribbean corals Porites divaricata, Porites astreoides, and Orbicella faveolata. Stable boron (δ11B), carbon (δ13C), oxygen (δ18O) isotopes, Sr/Ca, Mg/Ca, U/Ca, and Ba/Ca ratios, as well as chlorophyll a concentrations and calcification rates were measured on coral skeletal material corresponding to the period during and immediately after the elevated temperature treatment and again after 6 weeks of recovery on the reef. We show that under these conditions, coral bleaching did not affect the boron isotopic signature in any coral species tested, despite significant changes in coral physiology. This contradicts published findings from coral cores, where significant decreases in boron isotopes were interpreted as corresponding to times of known mass bleaching events. In contrast, δ13C and δ18O exhibited major enrichment corresponding to decreases in calcification rates associated with bleaching. Sr/Ca of bleached corals did not consistently record the 1.2°C difference in seawater temperature during the bleaching treatment, or alternatively show a consistent increase due to impaired photosynthesis and calcification. Mg/Ca, U/Ca, and Ba/Ca were affected by coral bleaching in some of the coral species, but the observed patterns could not be satisfactorily explained by temperature dependence or changes in coral physiology. This demonstrates that coral boron isotopes do not record short-term bleaching events, and therefore cannot be used as a proxy for past bleaching events. The robustness of coral boron isotopes to changes in coral physiology, however, suggests that reconstruction of seawater pH using boron isotopes should be uncompromised by short-term bleaching events.http://europepmc.org/articles/PMC4232377?pdf=render |
| spellingShingle | Verena Schoepf Malcolm T McCulloch Mark E Warner Stephen J Levas Yohei Matsui Matthew D Aschaffenburg Andréa G Grottoli Short-term coral bleaching is not recorded by skeletal boron isotopes. PLoS ONE |
| title | Short-term coral bleaching is not recorded by skeletal boron isotopes. |
| title_full | Short-term coral bleaching is not recorded by skeletal boron isotopes. |
| title_fullStr | Short-term coral bleaching is not recorded by skeletal boron isotopes. |
| title_full_unstemmed | Short-term coral bleaching is not recorded by skeletal boron isotopes. |
| title_short | Short-term coral bleaching is not recorded by skeletal boron isotopes. |
| title_sort | short term coral bleaching is not recorded by skeletal boron isotopes |
| url | http://europepmc.org/articles/PMC4232377?pdf=render |
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