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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

Schematic summary of the impact of ocean acidification on skeletal growth in Stylophora pistillata.Environmental change in the form of seawater acidification depresses pH and Ωaragonite at the site of calcification. Coral physiology responds by increasing proton removal from the calcifying fluid to maintain elevated pH and Ωaragonite that favours calcification. S. pistillata also increases production of organic matrix proteins (OM=organic matrix) per unit mass of CaCO3. In these conditions, corals continue to calcify, and dissolution of the skeleton does not occur, even when seawater Ωaragonite <1. However, with lower saturation states in the calcifying fluid and increased energy expenditure for calcification, S. pistillata changes its skeleton phenotype to a morphology characterized by larger corallite calyxes. The resulting skeleton is more porous. ‘OM'=organic matrix. ‘Ions' represent both transcellular and paracellular transport of ions needed for the steps of calcification. White circles in skeleton represent corallites. ‘Steps of calcification' encompass steps of skeleton precipitation and assembly outlined in Tambutté et al.15.
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f6: Schematic summary of the impact of ocean acidification on skeletal growth in Stylophora pistillata.Environmental change in the form of seawater acidification depresses pH and Ωaragonite at the site of calcification. Coral physiology responds by increasing proton removal from the calcifying fluid to maintain elevated pH and Ωaragonite that favours calcification. S. pistillata also increases production of organic matrix proteins (OM=organic matrix) per unit mass of CaCO3. In these conditions, corals continue to calcify, and dissolution of the skeleton does not occur, even when seawater Ωaragonite <1. However, with lower saturation states in the calcifying fluid and increased energy expenditure for calcification, S. pistillata changes its skeleton phenotype to a morphology characterized by larger corallite calyxes. The resulting skeleton is more porous. ‘OM'=organic matrix. ‘Ions' represent both transcellular and paracellular transport of ions needed for the steps of calcification. White circles in skeleton represent corallites. ‘Steps of calcification' encompass steps of skeleton precipitation and assembly outlined in Tambutté et al.15.

Mentions: We synthesized the results of our study to describe the phenotypic response of S. pistillata to seawater acidification (Fig. 6). Exposure of corals to seawater acidification results in increased rates of proton removal from the calcifying fluid to maintain pH elevated at the site of calcification11. Nevertheless, as the proton gradient with the surrounding seawater becomes less favourable, calcifying fluid pH (and therefore Ωaragonite) decreases slightly11. At the same time, S. pistillata increases production of OM proteins per unit mass of CaCO3. In these conditions, corals continue to calcify and dissolution of the skeleton does not occur, even when seawater Ωaragonite <1. However, pH upregulation and OM production are energy-requiring processes; thus, calcification becomes more difficult and energetically more costly under seawater acidification. Rates of CaCO3 production decrease and S. pistillata changes the morphology of the skeleton, shifting to a skeletal phenotype characterized by larger corallite calyxes and thinner septae and thecae. The resulting skeleton is more porous and less dense, but rates of linear extension are maintained.


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)

Schematic summary of the impact of ocean acidification on skeletal growth in Stylophora pistillata.Environmental change in the form of seawater acidification depresses pH and Ωaragonite at the site of calcification. Coral physiology responds by increasing proton removal from the calcifying fluid to maintain elevated pH and Ωaragonite that favours calcification. S. pistillata also increases production of organic matrix proteins (OM=organic matrix) per unit mass of CaCO3. In these conditions, corals continue to calcify, and dissolution of the skeleton does not occur, even when seawater Ωaragonite <1. However, with lower saturation states in the calcifying fluid and increased energy expenditure for calcification, S. pistillata changes its skeleton phenotype to a morphology characterized by larger corallite calyxes. The resulting skeleton is more porous. ‘OM'=organic matrix. ‘Ions' represent both transcellular and paracellular transport of ions needed for the steps of calcification. White circles in skeleton represent corallites. ‘Steps of calcification' encompass steps of skeleton precipitation and assembly outlined in Tambutté et al.15.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f6: Schematic summary of the impact of ocean acidification on skeletal growth in Stylophora pistillata.Environmental change in the form of seawater acidification depresses pH and Ωaragonite at the site of calcification. Coral physiology responds by increasing proton removal from the calcifying fluid to maintain elevated pH and Ωaragonite that favours calcification. S. pistillata also increases production of organic matrix proteins (OM=organic matrix) per unit mass of CaCO3. In these conditions, corals continue to calcify, and dissolution of the skeleton does not occur, even when seawater Ωaragonite <1. However, with lower saturation states in the calcifying fluid and increased energy expenditure for calcification, S. pistillata changes its skeleton phenotype to a morphology characterized by larger corallite calyxes. The resulting skeleton is more porous. ‘OM'=organic matrix. ‘Ions' represent both transcellular and paracellular transport of ions needed for the steps of calcification. White circles in skeleton represent corallites. ‘Steps of calcification' encompass steps of skeleton precipitation and assembly outlined in Tambutté et al.15.
Mentions: We synthesized the results of our study to describe the phenotypic response of S. pistillata to seawater acidification (Fig. 6). Exposure of corals to seawater acidification results in increased rates of proton removal from the calcifying fluid to maintain pH elevated at the site of calcification11. Nevertheless, as the proton gradient with the surrounding seawater becomes less favourable, calcifying fluid pH (and therefore Ωaragonite) decreases slightly11. At the same time, S. pistillata increases production of OM proteins per unit mass of CaCO3. In these conditions, corals continue to calcify and dissolution of the skeleton does not occur, even when seawater Ωaragonite <1. However, pH upregulation and OM production are energy-requiring processes; thus, calcification becomes more difficult and energetically more costly under seawater acidification. Rates of CaCO3 production decrease and S. pistillata changes the morphology of the skeleton, shifting to a skeletal phenotype characterized by larger corallite calyxes and thinner septae and thecae. The resulting skeleton is more porous and less dense, but rates of linear extension are maintained.

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