Reconstructing coral calcification fluid dissolved inorganic carbon chemistry from skeletal boron: An exploration of potential controls on coral aragonite B/Ca

The boron geochemistry of coral skeletons reflects the dissolved inorganic carbon (DIC) chemistry of the calcification fluid from which the skeletons precipitates and may be a valuable tool to investigate the effects of climate change on coral calcification. In this paper I calculate the predicted B/Ca of aragonite precipitating from seawater based fluids as a function of pH, [DIC] and [Ca2+]. I consider how different co-precipitating DIC species affect aragonite B/Ca and also estimate the impact of variations in the B(OH)4-/co-precipitating DIC aragonite partition coefficient (KD), which may be associated with changes in the DIC and Ca2+ chemistry of the calcification fluid. The coral skeletal B/Ca versus calcification fluid pH relationships reported previously can be reproduced by estimating B(OH)4- and co-precipitating DIC speciation as a function of pHCF and assuming that KD are constant i.e. unaffected by calcification fluid saturation state. Assuming that B(OH)4- co-precipitates with CO32-, then observed patterns can be reproduced by a fluid with approximately constant [DIC] i.e. increasing pHCF concentrates CO32-, as a function of DIC speciation. Assuming that B(OH)4- co-precipitates with HCO3- only or CO32- + HCO3- then the observed patterns can be reproduced if [DIC]CF and pHCF are positively related i.e. if DIC is increasingly concentrated in the calcification fluid at higher pHCF probably by CO2 diffusion into the calcification site

Allison N., 2017. Reconstructing coral calcification fluid dissolved inorganic carbon chemistry from skeletal boron: an exploration of potential controls on coral aragonite B/Ca. Heliyon 3(8): e00387. doi: 10.1016/j.heliyon.2017.e00387. Article.


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