Decoupled carbonate chemistry controls on the incorporation of boron into Orbulina universa
Decoupled carbonate chemistry controls on the incorporation of boron into Orbulina universa
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DOI：
10.5194/bg-14-415-2017
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发表时间：
2016-05
期刊：
影响因子：
4.9
通讯作者：
E. Howes;K. Kaczmarek;M. Raitzsch;A. Mewes;Nienke N. Bijma;I. Horn;S. Misra;J. Gattuso;J. Gattuso;J. Gattuso;J. Bijma
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文献类型：
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作者：
E. Howes;K. Kaczmarek;M. Raitzsch;A. Mewes;Nienke N. Bijma;I. Horn;S. Misra;J. Gattuso;J. Gattuso;J. Gattuso;J. Bijma
抽象。为了充分约束古碳酸盐系统，需要七个参数中的两个参数，加上温度和盐度。由于B（OH）4−取代了CO 32 −进入生物成因方解石晶格，硼酸盐和碳酸盐离子在较高pH值下更丰富，因此早期有人提出生物成因方解石中的B闪烁Ca比可以作为[CO 32 −]的替代物。虽然最近的几项研究表明，B scinCa碳酸盐系统参数的直接连接可能会被掩盖的领域中的其他环境因素，有充分的证据B scinCa和碳酸盐系统参数之间的机械关系。在这里，我们专注于调查的主要关系，发展硼吸收的机械理解。区分pH值和[CO 32 −]的影响是有问题的，因为它们在自然系统中密切相关，因此对硼掺入的主要控制仍然不清楚。为了对pH和[CO 32-]的影响进行去卷积，并研究它们对B scinCa比率和δ 11 B的影响，我们在操作培养基中对浮游有孔虫Orbulina universa进行了培养实验：恒定pH值（8.05），但改变[CO 32 −]（238、286和534 µmol kg−1 CO 32 −），以及恒定[CO 32 −]（276 ± 19.5 µmol kg−1）和变化pH值（7.7、7.9和8.05）。硼的同位素组成和B scinCa比的测量同时进行使用飞秒激光烧蚀系统耦合到MC-ICP-MS（多收集器电感耦合等离子体质谱仪）。我们的结果表明，正如预期的那样，δ 11 B受pH值控制，但也受[CO 32 −]的调节。另一方面，B scinCa比值由[HCO 3 −]驱动，与pH无关。这表明有孔虫方解石中的B scinCa比值可能用作完整的古碳酸盐系统重建的第二个独立替代物。最近的文献表明，B scinCa和[HCO 3 −]之间的主要关系可能会被其他环境参数所掩盖。
Abstract. In order to fully constrain paleo-carbonate systems, proxies for two out of seven parameters, plus temperature and salinity, are required. The boron isotopic composition (δ11B) of planktonic foraminifera shells is a powerful tool for reconstructing changes in past surface ocean pH. As B(OH)4− is substituted into the biogenic calcite lattice in place of CO32−, and both borate and carbonate ions are more abundant at higher pH, it was suggested early on that B ∕ Ca ratios in biogenic calcite may serve as a proxy for [CO32−]. Although several recent studies have shown that a direct connection of B ∕ Ca to carbonate system parameters may be masked by other environmental factors in the field, there is ample evidence for a mechanistic relationship between B ∕ Ca and carbonate system parameters. Here, we focus on investigating the primary relationship to develop a mechanistic understanding of boron uptake. Differentiating between the effects of pH and [CO32−] is problematic, as they co-vary closely in natural systems, so the major control on boron incorporation remains unclear. To deconvolve the effects of pH and [CO32−] and to investigate their impact on the B ∕ Ca ratio and δ11B, we conducted culture experiments with the planktonic foraminifer Orbulina universa in manipulated culture media: constant pH (8.05), but changing [CO32−] (238, 286 and 534 µmol kg−1 CO32−) and at constant [CO32−] (276 ± 19.5 µmol kg−1) and varying pH (7.7, 7.9 and 8.05). Measurements of the isotopic composition of boron and the B ∕ Ca ratio were performed simultaneously using a femtosecond laser ablation system coupled to a MC-ICP-MS (multiple-collector inductively coupled plasma mass spectrometer). Our results show that, as expected, δ11B is controlled by pH but it is also modulated by [CO32−]. On the other hand, the B ∕ Ca ratio is driven by [HCO3−], independently of pH. This suggests that B ∕ Ca ratios in foraminiferal calcite can possibly be used as a second, independent, proxy for complete paleo-carbonate system reconstructions. This is discussed in light of recent literature demonstrating that the primary relationship between B ∕ Ca and [HCO3−] can be obscured by other environmental parameters.