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Optimising a method for aragonite precipitation in simulated biogenic calcification media
Celeste Kellock1, Maria Cristina Castillo Alvarez1, Adrian Finch1
1School of Earth and Environmental Sciences, University of St. Andrews, St. Andrews, United Kingdom.
Plos One
|December 2, 2022
Summary
This study optimized aragonite precipitation from seawater, finding that aspartic acid promotes formation at low concentrations but inhibits it at high levels. Organic content variations can affect Raman spectra, potentially confusing paleoclimate proxy interpretations.
Area of Science:
- Geochemistry
- Biomineralization
- Palaeoclimate proxy development
Background:
- Understanding factors influencing biogenic calcium carbonate (CaCO3) geochemistry and structure is key for developing reliable palaeoproxies.
- Coral skeletons, primarily aragonite, are crucial archives of past ocean conditions.
Purpose of the Study:
- To optimize a method for precipitating aragonite under controlled conditions simulating coral calcification fluids.
- To investigate the influence of aspartic acid, a common coral skeleton amino acid, on aragonite structure and morphology.
Main Methods:
- Optimized in vitro precipitation of aragonite from seawater using controlled saturation states (Ωaragonite = 6.9-19.2).
- Utilized seeded precipitation with ≥200 mg aragonite seed in 330 mL seawater for reproducible rate estimates.
- Analyzed the effect of varying aspartic acid concentrations (1-10 μM to ≥ 1 mM) on aragonite formation and structure using Raman spectroscopy.
Main Results:
- Seeded precipitation provided reproducible rates, while unseeded precipitation was highly variable.
- Low aspartic acid concentrations (1-10 μM) promoted aragonite formation, whereas high concentrations (≥ 1 mM) inhibited it.
- High aspartic acid concentrations (≥ 1 mM) increased the full width at half maxima (FWHM) of the Raman aragonite v1 peak, indicating increased rotational disorder.
Conclusions:
- The optimized method allows for reproducible aragonite precipitation and analysis of organic molecule influence.
- Aspartic acid concentration significantly impacts aragonite structure and morphology.
- Variations in organic content, like aspartic acid, can alter Raman spectral signatures, necessitating careful consideration when interpreting palaeo-saturation states from coral skeletons.
