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Morphological plasticity of the coral skeleton under CO2-driven seawater acidification.

Tambutté E, Venn AA, Holcomb M, Segonds N, Techer N, Zoccola D, Allemand D, Tambutté S - Nat Commun (2015)

Bottom Line: Ocean acidification causes corals to calcify at reduced rates, but current understanding of the underlying processes is limited.Instead, changes occur by enlargement of corallite-calyxes and thinning of associated skeletal elements, constituting a modification in skeleton architecture.We also detect increases in the organic matrix protein content of skeletons formed under lower pH.

View Article: PubMed Central - PubMed

Affiliation: 1] Marine Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine 1er, Monaco 98000, Monaco [2] Laboratoire Européen Associé 647 « BIOSENSIB », Centre Scientifique de Monaco- Centre National de la Recherche Scientifique, 8 Quai Antoine 1er, Monaco 98000, Monaco.

ABSTRACT
Ocean acidification causes corals to calcify at reduced rates, but current understanding of the underlying processes is limited. Here, we conduct a mechanistic study into how seawater acidification alters skeletal growth of the coral Stylophora pistillata. Reductions in colony calcification rates are manifested as increases in skeletal porosity at lower pH, while linear extension of skeletons remains unchanged. Inspection of the microstructure of skeletons and measurements of pH at the site of calcification indicate that dissolution is not responsible for changes in skeletal porosity. Instead, changes occur by enlargement of corallite-calyxes and thinning of associated skeletal elements, constituting a modification in skeleton architecture. We also detect increases in the organic matrix protein content of skeletons formed under lower pH. Overall, our study reveals that seawater acidification not only causes decreases in calcification, but can also cause morphological change of the coral skeleton to a more porous and potentially fragile phenotype.

No MeSH data available.


Related in: MedlinePlus

Coral skeleton morphology in the four pH treatments imaged by micro-CT.(a) Representative longitudinal sections; (b) transverse sections. pH treatment is indicated in the top left corner of each image. Scale bar, 1 mm.
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f4: Coral skeleton morphology in the four pH treatments imaged by micro-CT.(a) Representative longitudinal sections; (b) transverse sections. pH treatment is indicated in the top left corner of each image. Scale bar, 1 mm.

Mentions: An alternative explanation for the increase in skeletal porosity under acidification was found at higher levels of organization in the skeleton's architecture. We measured the size of corallite calyxes (the interior diameter of the cup-shaped openings in the skeleton that house the polyps23 (see Supplementary Fig. 2 for nomenclature of coral skeletal elements)). The size of corallite calyxes significantly increased with decreasing pH (Fig. 3a,b) and as larger corallite calyxes formed under acidification, there was a corresponding decrease in the number of corallites per unit surface area (Supplementary Fig. 3). Corallite calyx size from the four pH treatments was significantly correlated with both porosity and bulk density, indicating that the acidification-induced enlargement of corallite calyx size is a factor explaining the decrease in skeletal density and increase in porosity (Spearman' s rank-order tests: rs=0.783, P<0.01; rs=0.744, P<0.01). In addition, micro-CT images showed that enlargement of corallite calyxes at the surface of the skeleton corresponded to larger corallites extending throughout the interior of the skeleton, making it more porous (Fig. 4). Micro-CT images also revealed that corallites formed at lower pH are characterized by thinner septae, thecae and areas of coenosteum (Fig. 4), indicating that changes in the development of these features also contributed to changes in skeletal porosity. Taken together, these observations constitute an important finding: changes in calcification rate can be explained, not by physico-chemical dissolution of the skeleton, but rather by a change in skeleton phenotype.


Morphological plasticity of the coral skeleton under CO2-driven seawater acidification.

Tambutté E, Venn AA, Holcomb M, Segonds N, Techer N, Zoccola D, Allemand D, Tambutté S - Nat Commun (2015)

Coral skeleton morphology in the four pH treatments imaged by micro-CT.(a) Representative longitudinal sections; (b) transverse sections. pH treatment is indicated in the top left corner of each image. Scale bar, 1 mm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4490415&req=5

f4: Coral skeleton morphology in the four pH treatments imaged by micro-CT.(a) Representative longitudinal sections; (b) transverse sections. pH treatment is indicated in the top left corner of each image. Scale bar, 1 mm.
Mentions: An alternative explanation for the increase in skeletal porosity under acidification was found at higher levels of organization in the skeleton's architecture. We measured the size of corallite calyxes (the interior diameter of the cup-shaped openings in the skeleton that house the polyps23 (see Supplementary Fig. 2 for nomenclature of coral skeletal elements)). The size of corallite calyxes significantly increased with decreasing pH (Fig. 3a,b) and as larger corallite calyxes formed under acidification, there was a corresponding decrease in the number of corallites per unit surface area (Supplementary Fig. 3). Corallite calyx size from the four pH treatments was significantly correlated with both porosity and bulk density, indicating that the acidification-induced enlargement of corallite calyx size is a factor explaining the decrease in skeletal density and increase in porosity (Spearman' s rank-order tests: rs=0.783, P<0.01; rs=0.744, P<0.01). In addition, micro-CT images showed that enlargement of corallite calyxes at the surface of the skeleton corresponded to larger corallites extending throughout the interior of the skeleton, making it more porous (Fig. 4). Micro-CT images also revealed that corallites formed at lower pH are characterized by thinner septae, thecae and areas of coenosteum (Fig. 4), indicating that changes in the development of these features also contributed to changes in skeletal porosity. Taken together, these observations constitute an important finding: changes in calcification rate can be explained, not by physico-chemical dissolution of the skeleton, but rather by a change in skeleton phenotype.

Bottom Line: Ocean acidification causes corals to calcify at reduced rates, but current understanding of the underlying processes is limited.Instead, changes occur by enlargement of corallite-calyxes and thinning of associated skeletal elements, constituting a modification in skeleton architecture.We also detect increases in the organic matrix protein content of skeletons formed under lower pH.

View Article: PubMed Central - PubMed

Affiliation: 1] Marine Biology Department, Centre Scientifique de Monaco, 8 Quai Antoine 1er, Monaco 98000, Monaco [2] Laboratoire Européen Associé 647 « BIOSENSIB », Centre Scientifique de Monaco- Centre National de la Recherche Scientifique, 8 Quai Antoine 1er, Monaco 98000, Monaco.

ABSTRACT
Ocean acidification causes corals to calcify at reduced rates, but current understanding of the underlying processes is limited. Here, we conduct a mechanistic study into how seawater acidification alters skeletal growth of the coral Stylophora pistillata. Reductions in colony calcification rates are manifested as increases in skeletal porosity at lower pH, while linear extension of skeletons remains unchanged. Inspection of the microstructure of skeletons and measurements of pH at the site of calcification indicate that dissolution is not responsible for changes in skeletal porosity. Instead, changes occur by enlargement of corallite-calyxes and thinning of associated skeletal elements, constituting a modification in skeleton architecture. We also detect increases in the organic matrix protein content of skeletons formed under lower pH. Overall, our study reveals that seawater acidification not only causes decreases in calcification, but can also cause morphological change of the coral skeleton to a more porous and potentially fragile phenotype.

No MeSH data available.


Related in: MedlinePlus