Publication Date:
2022-05-26
Description:
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Chemical Geology 437 (2016): 67-76, doi:10.1016/j.chemgeo.2016.05.007.
Description:
Measurements of B/Ca ratios in marine carbonates have been suggested to record
seawater carbonate chemistry, however experimental calibration of such proxies based on
inorganic partitioning remains limited. Here we conducted a series of synthetic aragonite
precipitation experiments to evaluate the factors influencing the partitioning of B/Ca
between aragonite and seawater. Our results indicate that the B/Ca ratio of synthetic
aragonites depends primarily on the relative concentrations of borate and carbonate ions
in the solution from which the aragonite precipitates; not on bicarbonate concentration as
has been previously suggested. The influence of temperature was not significant over the
range investigated (20 – 40°C), however, partitioning may be influenced by saturation
state (and/or growth rate). Based on our experimental results, we suggest that aragonite
B/Ca ratios can be utilized as a proxy of [CO32-]. Boron isotopic composition (δ11B) is an
established pH proxy, thus B/Ca and δ11B together allow the full carbonate chemistry of
the solution from which the aragonite precipitated to be calculated. To the extent that
aragonite precipitation by marine organisms is affected by seawater chemistry, B/Ca may
also prove useful in reconstructing seawater chemistry. A simplified boron purification
protocol based on amberlite resin and the organic buffer TRIS is also described.
Description:
This work
was supported by the Australian Research Council (ARC) Centre of Excellence for Coral
Reef Studies. Research conducted at WHOI was supported by NSF grant OCE-1338320.
M.H. was supported by an ARC Super Science Fellowship and an NSF International
Postdoctoral Fellowship. T.D. was supported by a NSF Graduate Research Fellowship.
M.M. was supported by a Western Australian Premiers Fellowship and an ARC Laureate
Fellowship.
Keywords:
Boron
;
Aragonite
;
Coral
;
Proxy
;
Carbonate
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
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