AUTHOR=Yoshimura Toshihiro , Wakaki Shigeyuki , Iwasaki Nozomu , Ishikawa Tsuyoshi , Ohkouchi Naohiko 

TITLE=Stable Sr isotope (88Sr/86Sr) fractionation in calcite precious corals

JOURNAL=Frontiers in Marine Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.1045909

DOI=10.3389/fmars.2022.1045909

ISSN=2296-7745

ABSTRACT=<p>Stable isotope ratios of Sr (<sup>88</sup>Sr/<sup>86</sup>Sr) are a novel indicator for identifying terrestrial and oceanic Sr cycling and biological processes. Here we evaluate the temperature dependence of stable Sr isotope ratios (δ<sup>88</sup>Sr) in the calcite skeletons of precious corals, known as octocorals. High-precision Sr isotope measurements by double spike thermal ionization mass spectrometry were applied to different precious corals (<italic>Corallium japonicum</italic>, <italic>Pleurocorallium elatius</italic>, <italic>P. konojoi</italic>, <italic>Corallium</italic> sp., <italic>Keratoisis</italic> sp., and Coralliidae sp.) collected from water depths of 30–1500 m in the Pacific Ocean, corresponding to annual mean water temperatures of 2.5 to 19.5°C. The precious corals showed mean δ<sup>88</sup>Sr values of 0.101 ± 0.023‰. The magnitude of Sr isotope fractionation between the skeleton and ambient seawater (Δ<sup>88</sup>Sr) is −0.291 and is about −0.1‰ lower than the value predicted from the precipitation of inorganic calcite. This fractionation is not affected by changes in skeletal Sr/Ca ratio and associated biological effects on δ<sup>88</sup>Sr are negligible. δ<sup>88</sup>Sr of precious coral skeleton is an excellent recorder of ambient seawater.</p>