Control of aragonite deposition in colonial corals by intra-skeletal macromolecules

Falini, Giuseppe; Reggi, Michela; Fermani, Simona; Sparla, Francesca; Goffredo, Stefano; Dubinsky, Zvy; Levi, Oren; Dauphin, Yannicke; Cuif, Jean‐Pierre

doi:10.1016/j.jsb.2013.05.001

Cited by 51 publications

(79 citation statements)

References 53 publications

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“…This is perhaps to be expected. Corals do not precipitate randomly but exert exquisite control over both the sites of precipitation and the crystal morphology 24 . Our findings have implications for predicting the effects of ocean acidification on coral reefs.…”

Section: Resultsmentioning

confidence: 99%

Corals concentrate dissolved inorganic carbon to facilitate calcification

et al. 2014

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The sources of dissolved inorganic carbon (DIC) used to produce scleractinian coral skeletons are not understood. Yet this knowledge is essential for understanding coral biomineralization and assessing the potential impacts of ocean acidification on coral reefs. Here we use skeletal boron geochemistry to reconstruct the DIC chemistry of the fluid used for coral calcification. We show that corals concentrate DIC at the calcification site substantially above seawater values and that bicarbonate contributes a significant amount of the DIC pool used to build the skeleton. Corals actively increase the pH of the calcification fluid, decreasing the proportion of DIC present as CO 2 and creating a diffusion gradient favouring the transport of molecular CO 2 from the overlying coral tissue into the calcification site. Coupling the increases in calcification fluid pH and [DIC] yields high calcification fluid [CO 3 2 À ] and induces high aragonite saturation states, favourable to the precipitation of the skeleton.

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Section: Resultsmentioning

confidence: 99%

Corals concentrate dissolved inorganic carbon to facilitate calcification

et al. 2014

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“…6) we calculated a valueof 17.05±0.85‰ for a virtual 100%-calcite end-memberwith a constant seawater δ 11 B value of 39.61‰ .This would correspond to a calculatedpH solution of about 7.87 ± 0.11. It can be noted that such low δ 11 B value was recently observed for calcite cold-water octocorals (Farmer et al, 2015;McCulloch et al, 2012) which calcifying fluid pH fallingwithin 7.6-8.0.Nevertheless, in a biologically-controlled biomineralization, aragonite and calcite precipitation strictly results from the control of the organic matrix compounds,in the scleractinian coral case synthesized by the calicoblastic epithelium (Falini et al, 1996;Falini et al, 2013;Mass et al, 2013;Puverel et al, 2005;Rahman et al, 2011;. To date, no coral specieshasbeen found to produce both CaCO 3 polymorphsin natural modern seawater conditions, even in the primary skeleton formed by coral post-larvae (Clode et al, 2011).…”

Section: Origin Of the Intra-skeletal Calcite: Biogenic Vs Early Diamentioning

confidence: 88%

Intra-skeletal calcite in a live-collected Porites sp.: Impact on environmental proxies and potential formation process

Lazareth

Soares-Pereira

Douville

et al. 2016

Geochimica et Cosmochimica Acta

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Geochemical proxies measured in the carbonate skeleton of tropical coral Porites sp. have commonly been used to reconstruct sea surface temperature (SST) and more recently seawater pH. Nevertheless, both reconstructed SST and pH depend on the preservation state of the skeleton, here made of aragonite; i.e., diagenetic processes and its related effects should be limited. In this study, we report on the impact of the presence of intra-skeletal calcite on the skeleton geochemistry of a live-collected Porites sp..The Porites skeleton preservation state was analyzed using X-ray diffraction and scanning electron microscopy. Sr/Ca, Mg/Ca, U/Ca, Ba/Ca, Li/Mg, and B/Ca ratios were measured at a monthly and yearly resolution using solution ICP-MS and multi-collector ICP-MS. Theδ 11 B signatures and the calcite percentages were acquired at a yearly timescale. The coral colony presents two parts, one with less than 3% calcite (referred to as "no-calcite" skeleton), the other one, corresponding to the skeleton formed during the last 4 yrs. of growth,with calcite percentages varying from 13 to 32% (referred to as "with calcite" skeleton). This intra-skeletal calcite replaces partly or completely numerouscenter of calcification (COCs). All geochemical tracers investigated are significantlyimpacted by the presence of calcite. Thereconstructed SSTdecreasesby about0.1°C per calcite-percent as inferred fromthe Sr/Ca ratio. Such impact reaches up to 0.26°C per calcite-percent for temperature deduced from the Li/Mg ratio. So, less than 5% of such intra-skeletal calcite does not prevent SST reconstructions using Sr/Ca ratio, but the percentage and type of calcite have to be determined before fine SST interpretation. Seawater pH reconstruction inferredfrom boron isotopes drop by about -0.011 pH-unit per calcitepercent. Such sensitivity to calcite presence is particularly dramatic for fine paleo-pH reconstructions. Here we suggest that after being brought to shallow waters following a cyclone, the studied coral was seasonally subjected to rainfall-related water freshening that could have mimicked a vadose environment like can be encountered on raised fossil coral reefs. Nevertheless, the process of calcite precipitation remains to be determined.

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“…First, organic matter coats aragonite crystals in the skeleton (Clode and Marshall, 2002), and elevated organic matter content is closely associated with the relatively disordered centers of calcification (COCs; also called "rapid accretion deposits" or RADs) (Benzerara et al, 2011;Falini et al, 2013;Von Euw et al, 2017). Second, organic molecules extracted from the skeleton have been attributed to certain roles in crystal growth (Constantz and Weiner, 1988;Weiner and Addadi, 1991;Allemand et al, 1998;Goldberg, 2001;Cuif et al, 2008;Reggi et al, 2014;Takeuchi et al, 2016), with some proteins even capable of inducing spontaneous aragonite precipitation from seawater .…”

Section: Introductionmentioning

confidence: 99%

“…It is for this reason that studies of the organic matrix have relied heavily on characterizing its composition and location within the skeleton (in which it composes less than 0.1% by mass), rather than by direct observations during crystal growth (Allemand et al, 2004;Reggi et al, 2014;Wang et al, 2015). Techniques for observing and mapping the distribution of the SOM include scanning electron microscopy (Clode and Marshall, 2002), helium ion microscopy (Von Euw et al, 2017), transmission electron microscopy (Benzerara et al, 2011;Falini et al, 2013), and fluorescence as detected by a Raman spectrometer (Jolivet et al, 2008;Nehrke et al, 2011;Wall and Nehrke, 2012;Von Euw et al, 2017). Of these, Raman spectroscopy is advantageous in that it can potentially identify certain organic bonds, and the same spectra provide information regarding the chemical composition of the aragonite crystals (Bischoff et al, 1985;Nehrke et al, 2011;Wall and Nehrke, 2012;DeCarlo et al, 2017;Von Euw et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

The Origin and Role of Organic Matrix in Coral Calcification: Insights From Comparing Coral Skeleton and Abiogenic Aragonite

DeCarlo¹,

Ren²,

Farfán³

2018

Front. Mar. Sci.

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Understanding the mechanisms of coral calcification is critical for accurately projecting coral reef futures under ocean acidification and warming. Recent suggestions that calcification is primarily controlled by organic molecules and the biological activity of the coral polyp imply that ocean acidification may not affect skeletal accretion. The basis for these suggestions relies heavily on correlating the presence of organic matter with the orientation and disorder of aragonite crystals in the skeleton, carrying the assumption that organic matter observed in the skeleton was produced by the polyp to control calcification. Here we use Raman spectroscopy to test whether there are differences in organic matter content between coral skeleton and abiogenic aragonites precipitated from seawater, both before and after thermal annealing (heating). We measured the background fluorescence and intensity of C-H bonding signals in the Raman spectra, which are commonly attributed to coral polyp-derived skeletal organic matrix (SOM) and have been used to map its distribution. Surprisingly, we found no differences in either fluorescence or C-H bonding between abiogenic aragonite and coral skeleton. Annealing reduced the molecular disorder in coral skeleton, potentially due to removal of organic matter, but the same effect was also observed in the abiogenic aragonites. The presence of organic molecules in the abiogenic aragonites is further supported by measurements of N content and δ 15 N. Together, our data suggest that some of what has been interpreted in previous studies as polyp-derived SOM may actually be seawater-sourced organic matter or some other signal not unique to biogenic aragonite. Finally, we create a high-resolution Raman map of a Pocillopora skeleton to demonstrate how patterns of fluorescence and elevated calcifying fluid aragonite saturation state ( Ar ) along centers of calcification are consistent with both biological and physico-chemical controls. Our aim is to advance discussion on biological mediation of calcification and the implications for coral resilience in a high-CO 2 world.

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Control of aragonite deposition in colonial corals by intra-skeletal macromolecules

Cited by 51 publications

References 53 publications

Corals concentrate dissolved inorganic carbon to facilitate calcification

Corals concentrate dissolved inorganic carbon to facilitate calcification

Intra-skeletal calcite in a live-collected Porites sp.: Impact on environmental proxies and potential formation process

The Origin and Role of Organic Matrix in Coral Calcification: Insights From Comparing Coral Skeleton and Abiogenic Aragonite

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