Factors affecting B/Ca ratios in synthetic aragonite

Holcomb, Michael; DeCarlo, Thomas M.; Gaetani, G. A.; McCulloch, Malcolm T.

doi:10.1016/j.chemgeo.2016.05.007

Cited by 90 publications

(220 citation statements)

References 56 publications

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“…These analyses require >20 mg of aragonite powder, which exceeds the amount of material remaining for most of the abiogenic samples after previous measurements (DeCarlo et al, 2015;Holcomb et al, 2016). Therefore, we chose to mix three abiogenic samples (f02, f03, and f06) that had enough material remaining and that precipitated across the full range of Ar .…”

Section: N Content and δ 15 Nmentioning

confidence: 99%

“…Raman spectroscopy was used to analyze abiogenic aragonites precipitated from 0.2-µm filtered Vineyard Sound (Massachusetts, USA) seawater (described in DeCarlo et al, 2015;Holcomb et al, 2016) and the JCp-1 Porites coral skeleton (Okai et al, 2002), both before and after thermal annealing. Briefly, the abiogenic aragonites were precipitated by addition of NaHCO 3 and Na 2 CO 3 solutions to seawater, combined with air/CO 2 bubbling, which together increases Ar and induces crystal nucleation.…”

Section: Samples Analyzed With Raman Spectroscopymentioning

confidence: 99%

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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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Section: N Content and δ 15 Nmentioning

confidence: 99%

Section: Samples Analyzed With Raman Spectroscopymentioning

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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“…De Carlo et al (2018) (Balan et al, 2016). Allison (2017) replotted the combined datasets of Mavromatis et al (2015) and Holcomb et al (2016) for synthetic aragonites precipitated at 25°C to show that KD is highly dependent on precipitating fluid saturation state. This may reflect enhanced incorporation of B during rapid crystal extension, as in calcite (Gabitov et al, 2014).…”

Section: Calculation Of Calcification Fluid Dic Parametersmentioning

confidence: 99%

“…KD have been calculated for aragonite under a range of different scenarios (Allison et al, 2014, 2017, Holcomb et al 2016and De Carlo et al, 2018. While it is likely that B(OH)4 -substitute for CO3 2-in aragonite (Balan et al, 2016), it is unknown which aqueous DIC species are involved in aragonite precipitation.…”

Section: Calculation Of Calcification Fluid Dic Parametersmentioning

confidence: 99%

The effect of ocean acidification on tropical coral calcification: insights from calcification fluid DIC chemistry

Allison¹

2018

Preprint

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Ocean acidification typically reduces calcification in tropical marine corals but the mechanism for this process is not understood. We use skeletal boron geochemistry (B/Ca and δ 11 B) to reconstruct the calcification fluid DIC of corals cultured over both high and low seawater pCO2 (180, 400 and 750 μatm). We observe strong positive correlations between calcification fluid pH and concentrations of the DIC species potentially implicated in aragonite precipitation (be they CO3 ). Similarly, with the exception of one outlier, the fluid concentrations of precipitating DIC species are strongly positively correlated with coral calcification rate. Corals cultured at high seawater pCO2 usually have low calcification fluid pH and low concentrations of precipitating DIC, suggesting that a reduction in DIC substrate at the calcification site is responsible for decreased calcification. The outlier coral maintained high pHCF and DICCF at high seawater pCO2 but exhibited a reduced calcification rate indicating that the coral has a limited energy budget to support proton extrusion from the calcification fluid and meet other calcification demands. We find no evidence that increasing seawater pCO2 enhances diffusion of CO2 into the calcification site. Instead the overlying [CO2] available to diffuse into the calcification site appears broadly comparable between seawater pCO2 treatments, implying that metabolic activity (respiration and photosynthesis) generates a similar [CO2] in the vicinity of the calcification site regardless of seawater pCO2.

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“…In surface waters of the tropical oceans, carbonate ion concentrations ([CO 5254 T. M. DeCarlo et al: Raman proxy for aragonite saturation state sions continue unabated, by the end of the 21st century the [CO 2− 3 ] of surface seawater is projected to decline to ∼ 50 % of pre-industrial levels (Hoegh-Guldberg et al, 2014). This rapid change in ocean carbonate chemistry, likely unprecedented for hundreds of millions of years (Hönisch et al, 2012;Zeebe et al, 2016), has sparked concerns for coral growth. Indeed, laboratory experiments repeatedly demonstrate that coral calcification rates decrease in response to lower or [Ca 2+ ] (Gattuso et al, 1998;Chan and Connolly, 2013;Comeau et al, 2017), leading to projections that as CO 2 levels continue to rise calcification will decline to unsustainable levels, such that there is net reef erosion (HoeghGuldberg et al, 2007;Pandolfi et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Coral calcifying fluid aragonite saturation states derived from Raman spectroscopy

DeCarlo¹,

D’Olivo²,

Foster³

et al. 2017

Biogeosciences

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Abstract. Quantifying the saturation state of aragonite ( Ar ) within the calcifying fluid of corals is critical for understanding their biomineralization process and sensitivity to environmental changes including ocean acidification. Recent advances in microscopy, microprobes, and isotope geochemistry enable the determination of calcifying fluid pH and [CO ]/K sp ) has proved elusive. Here we test a new technique for deriving Ar based on Raman spectroscopy. First, we analysed abiogenic aragonite crystals precipitated under a range of Ar from 10 to 34, and we found a strong dependence of Raman peak width on Ar with no significant effects of other factors including pH, Mg/Ca partitioning, and temperature. Validation of our Raman technique for corals is difficult because there are presently no direct measurements of calcifying fluid Ar available for comparison. However, Raman analysis of the international coral standard JCp-1 produced Ar of 12.3 ± 0.3, which we demonstrate is consistent with published skeletal Mg/Ca, Sr/Ca, B/Ca, δ 11 B, and δ 44 Ca data. Raman measurements are rapid (≤ 1 s), high-resolution (≤ 1 µm), precise (derived Ar ± 1 to 2 per spectrum depending on instrument configuration), accurate ( ±2 if Ar < 20), and require minimal sample preparation, making the technique well suited for testing the sensitivity of coral calcifying fluid Ar to ocean acidification and warming using samples from natural and laboratory settings. To demonstrate this, we also show a high-resolution time series of Ar over multiple years of growth in a Porites skeleton from the Great Barrier Reef, and we evaluate the response of Ar in juvenile Acropora cultured under elevated CO 2 and temperature.

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Factors affecting B/Ca ratios in synthetic aragonite

Abstract: aragonite precipitation by marine organisms is affected by seawater chemistry, B/Ca may 36 also prove useful in reconstructing seawater chemistry. A simplified boron purification 37 protocol based on amberlite resin and the organic buffer TRIS is also described. 38 39

Cited by 90 publications

References 56 publications

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

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

The effect of ocean acidification on tropical coral calcification: insights from calcification fluid DIC chemistry

Coral calcifying fluid aragonite saturation states derived from Raman spectroscopy

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