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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

Indicators of physio-chemical conditions at the site of calcification in corals in the four pH treatments.(a) Aragonite crystal morphology imaged by scanning electron microscopy. Scale bar, 5 μm. pH treatment indicated above each image. (b) Calcifying fluid pH in corals under light and dark conditions at seawater pH 7.2 and pH 8.0. Data are means±s.e.m. CF=calcifying fluid; SW=seawater surrounding the colonies.
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f2: Indicators of physio-chemical conditions at the site of calcification in corals in the four pH treatments.(a) Aragonite crystal morphology imaged by scanning electron microscopy. Scale bar, 5 μm. pH treatment indicated above each image. (b) Calcifying fluid pH in corals under light and dark conditions at seawater pH 7.2 and pH 8.0. Data are means±s.e.m. CF=calcifying fluid; SW=seawater surrounding the colonies.

Mentions: We endeavoured to determine the cause of increasing skeletal porosity, one possibility being that dissolution is responsible for such an effect. To investigate whether dissolution could occur in the coral's internal calcifying fluid where skeletal aragonite crystals form, we used confocal microscopy to measure calcifying fluid pH 111920. Our calcifying fluid pH measurements were consistent with our earlier work on S. pistillata11, showing that, although seawater acidification depresses pH in the calcifying fluid to a certain extent, calcifying fluid pH remains high relative to the surrounding seawater (Fig. 2). Here we show for the first time, that calcifying fluid pH remains elevated in darkness as well as in light under conditions of seawater acidification (Fig. 2). These data are entirely consistent with our published estimates of Ωaragonite of the calcifying fluid at similar pH values11, and indicate that the calcifying environment in S. pistillata is supersaturated with respect to aragonite in corals from pH 8 and 7.2 treatments in light and darkness. Dissolution due to decreases in pH at the site of calcification would therefore not be expected to be responsible for increases in skeletal porosity.


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)

Indicators of physio-chemical conditions at the site of calcification in corals in the four pH treatments.(a) Aragonite crystal morphology imaged by scanning electron microscopy. Scale bar, 5 μm. pH treatment indicated above each image. (b) Calcifying fluid pH in corals under light and dark conditions at seawater pH 7.2 and pH 8.0. Data are means±s.e.m. CF=calcifying fluid; SW=seawater surrounding the colonies.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Indicators of physio-chemical conditions at the site of calcification in corals in the four pH treatments.(a) Aragonite crystal morphology imaged by scanning electron microscopy. Scale bar, 5 μm. pH treatment indicated above each image. (b) Calcifying fluid pH in corals under light and dark conditions at seawater pH 7.2 and pH 8.0. Data are means±s.e.m. CF=calcifying fluid; SW=seawater surrounding the colonies.
Mentions: We endeavoured to determine the cause of increasing skeletal porosity, one possibility being that dissolution is responsible for such an effect. To investigate whether dissolution could occur in the coral's internal calcifying fluid where skeletal aragonite crystals form, we used confocal microscopy to measure calcifying fluid pH 111920. Our calcifying fluid pH measurements were consistent with our earlier work on S. pistillata11, showing that, although seawater acidification depresses pH in the calcifying fluid to a certain extent, calcifying fluid pH remains high relative to the surrounding seawater (Fig. 2). Here we show for the first time, that calcifying fluid pH remains elevated in darkness as well as in light under conditions of seawater acidification (Fig. 2). These data are entirely consistent with our published estimates of Ωaragonite of the calcifying fluid at similar pH values11, and indicate that the calcifying environment in S. pistillata is supersaturated with respect to aragonite in corals from pH 8 and 7.2 treatments in light and darkness. Dissolution due to decreases in pH at the site of calcification would therefore not be expected to be responsible for increases in skeletal porosity.

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