A new boron isotope-pH calibration for Orbulina universa, with implications for understanding and accounting for 'vital effects'
A new boron isotope-pH calibration for Orbulina universa, with implications for understanding and accounting for 'vital effects'
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DOI：
10.1016/j.epsl.2016.09.024
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发表时间：
2016-11-15
影响因子：
5.3
通讯作者：
Wilson, Paul A.
中科院分区：
文献类型：
--
作者：
Henehan, Michael J.;Foster, Gavin L.;Wilson, Paul A.
在南极有孔虫中测得的硼同位素比值可以作为过去海洋pH值的有用示踪剂，因此有助于辨别古代大气中的CO2浓度。然而，不同种类的浮游有孔虫表现出不同的硼同位素随环境海水pH值的变化模式。因此，当将该替代物应用于过去地质问题时，最好进行特定种类的校准。除了一个校准物种的进化历史，我们必须依赖于我们对现代海洋中观察到的“重要影响”的原因的理解，以及这种理解对灭绝物种的适用性。在这里，我们提出了一个新的开放海洋校准的南极有孔虫Orbulina universa，通过多接收器电感耦合质谱（MC-ICPMS）测量。与其它共生有孔虫不同，O. universa记录的δ B-11（因此pH值）低于其周围海水，但pH敏感性大致等于含水硼酸根离子。我们讨论了这一意义的硼同位素代理在深时间的应用，最佳实践和未来的研究方向的建议。(C)2016作者由爱思唯尔公司出版
Boron isotope ratios, as measured in planktic foraminifera, can be a useful tracer of past ocean pH, and hence help to discern the concentration of CO2 in the ancient atmosphere. However, different species of planktic foraminifera demonstrate different patterns of boron isotope variation with ambient seawater pH. Therefore when applying the proxy to questions in the geological past, species-specific calibrations are preferable. Beyond the evolutionary history of a calibrated species, we must rely on our understanding of the causes of the observed "vital effects" in the modern ocean, and the applicability of that understanding to extinct species. Here we present a new open-ocean calibration of the planktic foraminifera Orbulina universa, measured via Multi-Collector Inductively Coupled Mass Spectrometry (MC-ICPMS). Unlike other symbiont-bearing foraminifera, O. universa record a delta B-11 (and hence pH) that is lower than its surrounding seawater, but with a pH-sensitivity roughly equal to that of aqueous borate ion. We discuss the significance of this for application of the boron isotope proxy in deep time, with recommendations for best practice and future research directions. (C) 2016 The Authors. Published by Elsevier B.V.