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首页> 外文期刊>Paleoceanography >Vital effects in foraminifera do not compromise the use of δ~(11)B as a paleo-pH indicator: Evidence from modeling
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Vital effects in foraminifera do not compromise the use of δ~(11)B as a paleo-pH indicator: Evidence from modeling

机译:有孔虫的重要作用不影响使用δ〜(11)B作为古pH指示剂:来自建模的证据

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摘要

The stable boron isotope composition (δ~(11)B) of fossil foraminiferal shells is used as a paleo-pH recorder and is therefore one of the most promising paleocarbonate chemistry proxies ("paleoacidimetry"). One crucial question regarding this proxy is whether foraminifera record the pH of the bulk seawater or the pH of the microenvironment (diffusive boundary layer, ~500 μm), which is strongly influenced by life processes. Here we present a novel theoretical approach to address this question by using a diffusion-reaction model. Model results indicate that the δ~(11)B in planktonic foraminifera is primarily controlled by the pH of the microenvironment. We therefore predict that the δ~(11)B of different species (e.g., symbiont-bearing versus symbiont-barren) or of foraminifera grown in the dark and in the light should be offset from the δ~(11)B of inorganic calcite. This theoretical prediction was experimentally confirmed while this paper was written [Honisch et al., 2003]. Most importantly, the model predicts that this offset is constant over a wide pH range. Thus the use of δ~(11)B as a paleo-pH indicator is not compromised through vital effects as modeled here.
机译:化石有孔虫壳的稳定硼同位素组成(δ〜(11)B)用作古pH记录仪,因此是最有希望的古碳酸盐化学代表物之一(“古酸度法”)。关于这种替代物的一个关键问题是,有孔虫是否记录了海水的pH值或微环境的pH值(扩散边界层,〜500μm),这受到生命过程的强烈影响。在这里,我们提出一种新颖的理论方法,通过使用扩散反应模型来解决这个问题。模型结果表明,浮游有孔虫中的δ〜(11)B主要受微环境pH值的控制。因此,我们预测在黑暗和光线下生长的不同物种(例如,共生与贫瘠的共生物种)或有孔虫的δ〜(11)B应该与无机方解石的δ〜(11)B相抵消。 。在撰写本文时,这一理论预测在实验上得到了证实[Honisch et al。,2003]。最重要的是,该模型预测该偏移在很宽的pH范围内是恒定的。因此,δ〜(11)B作为古pH指示剂的使用不会因此处模拟的重要影响而受到损害。

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