Coral skeletal B/Ca (effectively B/CO), in combination with boron isotopic composition (δB), has been used to reconstruct the dissolved inorganic carbon chemistry of coral calcification media and to explore the biomineralisation process and its response to ocean acidification. This approach assumes that B(OH), the B species incorporated into aragonite, competes with dissolved inorganic carbon species for inclusion in the mineral lattice. In this study we precipitated aragonite from seawater under conditions that simulate the compositions of the calcification media used to build tropical coral skeletons. To deconvolve the effects of pH and [CO] on boron incorporation we conducted multiple experiments at constant [CO] but variable pH and at constant pH but variable [CO], both in the absence and presence of common coral skeletal amino acids. Large changes in solution [CO], from < 400 to >1000 µmol kg, or in precipitation rate, have no significant effect on aragonite B/Ca at pH of 8.20 and 8.41. A significant inverse relationship is observed between solution [CO] and aragonite B/Ca at pH = 8.59. Aragonite B/Ca is positively correlated with seawater pH across precipitations conducted at multiple pH but this relationship is driven by the effect of pH on the abundance of B(OH) in seawater. Glutamic acid and glycine enhance the incorporation of B in aragonite but aspartic acid has no measurable effect. Normalising aragonite B/Ca to solution [B(OH)] creates K which do not vary significantly between pH treatments. This implies that B(OH) and CO do not compete with each other for inclusion in the aragonite lattice at pH 8.20 and 8.41. Only at high pH (8.59), when [B(OH)] is high, do we observe evidence to suggest that the 2 anions compete to be incorporated into the lattice. These high pH conditions represent the uppermost limits reliably measured in the calcification media of tropical corals cultured under present day conditions, suggesting that skeletal B/Ca may not reflect the calcification media dissolved inorganic carbon chemistry in all modern day corals.

中文翻译：

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在 pHtotal 8.20 和 8.41 的合成沉淀中，B(OH)4− 和 CO32− 不会竞争掺入文石，但在 pHtotal 8.59 时会竞争


珊瑚骨骼 B/Ca（实际上是 B/CO）与硼同位素组成 (δB) 相结合，已被用来重建珊瑚钙化介质的溶解无机碳化学，并探索生物矿化过程及其对海洋酸化的响应。该方法假设 B(OH)（文石中掺入的 B 物质）与溶解的无机碳物质竞争包含在矿物晶格中。在这项研究中，我们在模拟用于构建热带珊瑚骨骼的钙化介质成分的条件下从海水中沉淀文石。为了消除 pH 值和 [CO] 对硼掺入的影响，我们在不存在和存在常见珊瑚骨骼氨基酸的情况下，在恒定 [CO] 但可变 pH 和恒定 pH 但可变 [CO] 下进行了多项实验。溶液 [CO] 的较大变化（从 < 400 到 >1000 µmol kg 或沉淀速率）对 pH 值 8.20 和 8.41 的文石 B/Ca 没有显着影响。在 pH = 8.59 时，溶液 [CO] 和文石 B/Ca 之间存在显着的反比关系。在多个 pH 值下进行的沉淀中，文石 B/Ca 与海水 pH 值呈正相关，但这种关系是由 pH 值对海水中 B(OH) 丰度的影响驱动的。谷氨酸和甘氨酸增强文石中 B 的掺入，但天冬氨酸没有可测量的效果。将文石 B/Ca 标准化为溶液 [B(OH)] 产生的 K 值在 pH 处理之间不会发生显着变化。这意味着在 pH 8.20 和 8.41 时，B(OH) 和 CO 不会相互竞争进入文石晶格。仅在高 pH (8.59) 下，当 [B(OH)] 较高时，我们观察到证据表明 2 个阴离子竞争并入晶格中。 这些高 pH 条件代表了在当今条件下培养的热带珊瑚钙化介质中可靠测量的最高限值，表明骨骼 B/Ca 可能无法反映所有现代珊瑚中钙化介质溶解的无机碳化学。