All Title Author
Keywords Abstract

PLOS ONE  2011 

Live Tissue Imaging Shows Reef Corals Elevate pH under Their Calcifying Tissue Relative to Seawater

DOI: 10.1371/journal.pone.0020013

Full-Text   Cite this paper   Add to My Lib


The threat posed to coral reefs by changes in seawater pH and carbonate chemistry (ocean acidification) raises the need for a better mechanistic understanding of physiological processes linked to coral calcification. Current models of coral calcification argue that corals elevate extracellular pH under their calcifying tissue relative to seawater to promote skeleton formation, but pH measurements taken from the calcifying tissue of living, intact corals have not been achieved to date. We performed live tissue imaging of the reef coral Stylophora pistillata to determine extracellular pH under the calcifying tissue and intracellular pH in calicoblastic cells. We worked with actively calcifying corals under flowing seawater and show that extracellular pH (pHe) under the calicoblastic epithelium is elevated by ~0.5 and ~0.2 pH units relative to the surrounding seawater in light and dark conditions respectively. By contrast, the intracellular pH (pHi) of the calicoblastic epithelium remains stable in the light and dark. Estimates of aragonite saturation states derived from our data indicate the elevation in subcalicoblastic pHe favour calcification and may thus be a critical step in the calcification process. However, the observed close association of the calicoblastic epithelium with the underlying crystals suggests that the calicoblastic cells influence the growth of the coral skeleton by other processes in addition to pHe modification. The procedure used in the current study provides a novel, tangible approach for future investigations into these processes and the impact of environmental change on the cellular mechanisms underpinning coral calcification.


[1]  Wilkinson C, editor. (2008) Status of Coral Reefs of the World. Townsville: Global Coral Reef Monitoring Network and Reef and Rainforest Research Center, Townsville, Australia.
[2]  Weis VM, Davy SK, Hoegh-Guldberg O, Rodriguez-Lanetty M, Pringle JR (2008) Cell biology in model systems as the key to understanding corals. Trends Ecol Evol 23: 369–376.
[3]  Weis V, Allemand D (2009) What determines Coral Health? Science 324: 1153–1155.
[4]  Hoegh-Guldberg O, Mumby P-J, Hooten AJ, Steneck RS, Greenfield P, et al. (2007) Coral reefs under rapid climate change and ocean acidification. Science 318: 1737–1742.
[5]  Allemand D, Tambutté é, Zoccola D, Tambutté S (2010) Coral reefs an ecosystem in transition. Dubinsky Z, Stambler N, editors. (Springer).
[6]  Johnston IS (1980) The ultrastructure of skeletogenesis in zooxanthellate corals. Int Rev Cytol 67: 171–214.
[7]  Barnes DJ (1970) Coral skeletons: an explanation of their growth and structure. Science 170: 1305–1308.
[8]  Constantz BR (1986) Coral skeleton construction: a physiochemically dominated process. Palaios 1: 152–157.
[9]  Cohen AL, McConnaughey TA (2003) Biomineralization, Rev Mineral Geochem. Dove PM, Weiner S, Yoreo JJ, editors. pp. 151–187.
[10]  Holcomb M, Cohen AL, Gabitov RI, Hutter JL (2009) Compositional and morphological features of aragonite precipitated experimentally from seawater and biogenically by corals. Geochim Cosmochim Acta 73: 4166–4179.
[11]  Marshall AT, Clode PL, Russell R (2007) Electron and ion microphobe analysis of calcium distribution and transport in coral tissues. J Exp Biol 210: 2453–2463.
[12]  McConnaughey TA, Whelan JF (1997) Calcification generates protons for nutrient and bicarbonate uptake. Earth Sci Rev 42: 95–117.
[13]  Allemand D, Ferrier-Pagès C, Furla P, Houlbrèque F, Puverel S, et al. (2004) Biomineralisation in reef-building corals: from molecular mechanisms to environmental control. C R Paleoevol 3: 453–467.
[14]  Sinclair D, Risk M (2006) A numerical model of trace element coprecipitation in a physicochemical calcification system: Application to coral biomineralization and trace element vital effects. Geochimica and Cosmochimica Acta 70: 3855–3868.
[15]  Cohen A, Holcomb M (2009) Why corals care about ocean acidification: Uncovering the mechanism. Oceanography 22:
[16]  Al-Horani FA, Al-Moghrabi SM, de Beer D (2003) The mechanism of calcification and its relation to photosynthesis and respiration in the scleractinian coral Galaxea fascicularis. Mar Biol 142: 419–426.
[17]  Reynaud S, Hemming NG, Juillet-Leclerc A, Gattuso J-P (2004) Effect of pCO2 and temperature on the boron isotopic composition of the zooxanthellate coral Acropora sp. Coral Reefs 23: 539–546.
[18]  Gaillardet J, Allègre C (1995) Boron isotopic compositions of corals: Seawater or diagenesis record? Earth Planet Sci Lett 136: 665–676.
[19]  Pelejero C, Calvo E, McCulloch , Marshall JF, Gagan MK, et al. (2005) Preindustrial to Modern Interdecadal Variability in Coral Reef pH. Science 309: 2204–2207.
[20]  Honisch B, Hemming NG, Grottoli AG, Amat A, Hanson GN, et al. (2004) Assessing scleractinian corals as recorders for paleo-pH: Empirical calibration and vital effects. Geochim Cosmochim Acta 68: 3675–3685.
[21]  Roos A, Boron WF (1981) Intracellular pH. Physiol Rev 61: 296–434.
[22]  Allemand D, Furla P, Bénazet-Tambutté S (1998) Mechanisms of carbon acquisition for endosymbiont photosynthesis in Anthozoa. Can J Bot 76: 925–941.
[23]  Venn AA, Tambutté E, Lotto S, Zoccola D, Allemand D, Tambutté S (2009) Intracellular pH in Symbiotic Cnidarians. Proc Natl Acad Sci USA 106: 16574–16579.
[24]  Muscatine L, Tambutté é, Allemand D (1997) Morphology of coral desmocytes, cells that anchor the calicoblastic epithelium to the skeleton. Coral Reefs 16: 205–213.
[25]  Raz-Bahat M, Erez J, Rinkevich B (2006) In vivo light-microscopic documentation for primary calcification processes in the hermatypic coral Stylophora pistillata. Cell Tissue Res 325: 361–368.
[26]  Vandermeulen JH, Watabe N (1973) Studies on Reef Corals. I. Skeleton Formation by Newly Settled Planula Larva of Pocillopora damicornis. Mar Biol 23: 47–57.
[27]  Shashar N, Cohen Y, Loya Y (1993) Extreme diel fluctuations of oxygen in diffusive boundary layers surrounding stony corals. Biol Bull 185: 455–461.
[28]  De Beer D, Kühl M, Stambler N, Vaki L (2000) A microsensor study of light enhanced Ca2+ uptake and photosynthesis in the reef-building hermatypic coral Favia sp. Mar Ecol Prog Ser 194: 75–85.
[29]  Mass T, Genin A, Shavit U, Grinstein M, Tchernov D (2010) Flow enhances photosynthesis in marine benthic autotrophs by increasing the efflux of oxygen from the organism to the water. Proc Natl Acad Sci U S A 107: 2527–2531.
[30]  Ip YK, Lim ALL, Lim RWL (1991) Some properties of calcium-activated adenosine triphosphatase from the hermatypic coral Galaxea fascicularis. Mar Biol 111: 191–197.
[31]  Zoccola D, Tambutté é, Kulhanek E, Puverel S, Scimeca J-C, Allemand D, Tambutté S (2004) Molecular cloning and localization of a PMCA P-type calcium ATPase from the coral Stylophora pistillata. Biochim et Biophys Acta 1663: 117–126.
[32]  Allison N, Finch AA (2010) δ11B, Sr, Mg and B in a modern Porites coral : then relationship between calcification site pH and skeletal chemistry. Geochim et Cosmochim Acta 74: 1790–1800.
[33]  Krief S, Hendy E, Fine M, Yam R, Meibom A, et al. (2010) Physiological and isotopic responses of scleractinian corals to ocean acidification. Geochim and Cosmochim Acta 74: 4988–5001.
[34]  Pelletier G, Lewis E, Wallace D (2007) CO2Sys.xls: A calculator for the CO2 system in seawater for microsoft excel/VBA. Washington State Department for Ecology/Brookhaven National Laboratory, Olympia, WA/Upton, NY, USA.
[35]  Mehrbach C, Culberson C, Hawley J, Pytkowicz R (1973) Measurements of the apparent dissociation constants of carbonic acid in seawater at atmospheric pressure. Limnol and Oceanog 18: 897–907.
[36]  Dickson A, Millero F (1987) A comparison of the equilibrium constants for the dissociation of carbonic acid in seawater media. Deep Sea Research 34: 1733–1743.
[37]  Dickson A, Weslowski D, Palmer D, Mesmer R (1990) The dissociation constant of bisulfate ion in aqueous sodium chloride solutions to 250°C. Journal of Physical Chemistry 94: 7978–7985.
[38]  Adkins JF, Boyle EA, Curry WB, Lutringer A (2003) Stable isotopes in deep-sea corals and a new mechanism for ‘vital effects”. Geochim Cosmochim Acta 67: 1129–1143.
[39]  Furla P, Galgani I, Durand I, Allemand D (2000) Sources and mechanisms of inorganic carbon transport for coral calcification and photosynthesis. J Exp Biol 203: 3445–3457.
[40]  Marubini F, Ferrier-Pagès C, Furla P, Allemand D (2008) Coral calcification responds to seawater acidification: a working hypothesis towards a physiological mechanism. Coral Reefs 27: 491–499.
[41]  Bentov S, Brownlee C, Erez J (2009) The role of seawater endocytosis in the biomineralization process in calcareous foraminifera. Proc Natl Acad Sci U S A 51: 21500–21504.
[42]  de Nooijer J, Toyofuku T, Kitazato H (2009) Foraminifera promote calcification by elevating their intracellular pH. Proc Nat Acad Sci USA 106: 15374–15378.
[43]  Moya A, Tambutté S, Bertucci A, Tambutté é, Lotto S, et al. (2008) Carbonic anhydrase in the scleractinian coral Stylophora pistillata: characterization, localization, and role in biomineralization. J Biol Chem 283: 25475–25484.
[44]  Le Tissier MDAA (1988) Patterns of formation and the ultrastructure of the larval skeleton of Pocillopora damicornis. Mar Biol 98: 493–501.
[45]  Isa Y (1986) An electron microscope study on the mineralization of the skeleton of the staghorn coral Acropora hebes. Mar Biol 93: 91–101.
[46]  Barnes DJ (1972) The structure and formation of growth-ridges in scleractinian coral skeletons. Proc Roy Soc Lond 182: 331–350.
[47]  Clode PL, Marshall AT (2002) Low temperature FESEM of the calcifying interface of a scleractinian coral. Tissue Cell 34: 187–198.
[48]  Tambutté é, Allemand D, Zoccola D, Meibom A, Lotto S, et al. (2007) Observations of the tissue-skeleton interface in the scleractinian coral Stylophora pistillata. Coral Reefs 26: 517–529.
[49]  Dewitt S, Hallett MB (2011) Optical complexities of living cytoplasm –implications for live cell imaging and photo-micromanipulation techniques. J Microscopy 241: 221–224.
[50]  Whitaker JE, Haugland RP, Prendergast FG (1991) Spectral and photophysical studies of Benzo(c)xanthene dyes: dual emission pH sensors. Anal Biochem 194: 330–344.


comments powered by Disqus