Barium isotopes in cold-water corals

Hemsing, Freya and Hsieh, Yu-Te and Bridgestock, Luke and Spooner, Peter T. and Robinson, Laura F. and Frank, Norbert and Henderson, Gideon M. (2020) Barium isotopes in cold-water corals. Earth and Planetary Science Letters, 491. pp. 183-192. ISSN 0012 821X DOI doi.10.1016/j.epsl.2018.03.040

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Abstract

Recent studies have introduced stable Ba isotopes (delta(138)/Ba-134) as a novel tracer for ocean processes. Ba isotopes could potentially provide insight into the oceanic Ba cycle, the ocean's biological pump, water-mass provenance in the deep ocean, changes in activity of hydrothermal vents, and land-sea interactions including tracing riverine inputs. Here, we show that aragonite skeletons of various colonial and solitary cold-water coral (CWC) taxa record the seawater (SW) Ba isotope composition. Thirty-six corals of eight different taxa from three oceanic regions were analysed and compared to delta(138)/Ba-134 measurements of co-located seawater samples. Sites were chosen to cover a wide range of temperature, salinity, Ba concentrations and Ba isotope compositions. Seawater samples at the three sites exhibit the well-established anti-correlation between Ba concentration and delta(138)/Ba-134. Furthermore, our data set suggests that Ba/Ca values in CWCs are linearly correlated with dissolved Ba] in ambient seawater, with an average partition coefficient of D-CWC/SW = 1.8 +/- 0.4 (2SD). The mean isotope fractionation of Ba between seawater and CWCs Delta(138)/Ba-134(CWC-SW) is -0.21 +/- 0.08 parts per thousand (2SD), indicating that CWC aragonite preferentially incorporates the lighter isotopes. This fractionation likely does not depend on temperature or other environmental variables, suggesting that aragonite CWCs could be used to trace the Ba isotope composition in ambient seawater. Coupled Ba] and delta(138)/Ba-134 analysis on fossil CWCs has the potential to provide new information about past changes in the local and global relationship between Ba] and delta(138)/Ba-134 and hence about the operation of the past global oceanic Ba cycle in different climate regimes. (C) 2018 Elsevier B.V. All rights reserved.

Item Type:	Article
Uncontrolled Keywords:	NILAREP
Subjects:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title:	Earth and Planetary Science Letters
Volume:	491
Page Range:	pp. 183-192
Identification Number:	doi.10.1016/j.epsl.2018.03.040
Depositing User:	Sarah Humbert
Date Deposited:	04 Nov 2020 13:52
Last Modified:	04 Nov 2020 16:04
URI:	http://eprints.esc.cam.ac.uk/id/eprint/4906

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