The sodium-to-calcium ratio (Na/Ca) of biogenic CaCO3 has recently been introduced as a proxy for past seawater Ca2+ concentrations ([Ca2+sw]) as demonstrated by a positive correlation between seawater and shell Na/Ca with a minor influence of salinity. In the present study, we investigate the effect of carbonate chemistry on the Na/Ca proxy by conducting a set of experiments in which pH and the concentration of dissolved inorganic carbon (DIC) were independently varied. In addition to Na+, the incorporation of Li+, Mg2+, and Sr2+ into the shells of the large benthic high-Mg calcitic foraminifer Operculina ammonoides was assessed by culturing under constant DIC (∼2170 µmol kg−1) with varying pH (7.5–8.4 NBS scale), and under varying DIC (830–2470 µmol kg−1) with constant pH (∼7.9). Foraminiferal growth rate correlates linearly with calcite saturation state (Ω) of the experimental seawater (SW). The lowest pH and DIC experiments were characterized by low population growth rates, and some of these specimens died and their shells partially dissolved.

中文翻译：

---

碳酸盐化学对高镁方解石有孔虫微量元素掺入的影响


生物 CaCO3 的钠钙比 （Na/Ca） 最近被引入作为过去海水 Ca2+ 浓度 （[Ca2+sw]） 的代表，海水与贝壳 Na/Ca 之间的正相关关系证明了这一点，盐度的影响很小。在本研究中，我们通过进行一组实验来研究碳酸盐化学对 Na/Ca 代理的影响，其中 pH 值和溶解无机碳 （DIC） 的浓度独立变化。除 Na+ 外，通过在恒定 DIC （∼2170 μmol kg-1） 和不同 pH 值 （∼7.5-8.4 NBS 等级） 下培养，以及在恒定 pH 值 （∼7.9） 下培养，评估了 Li+、Mg2+ 和 Sr2+ 掺入大型底栖高镁方解石有孔虫 Operculina ammonoides 的壳中。有孔虫生长速率与实验海水 （SW） 的方解石饱和状态 （Ω） 呈线性相关。最低的 pH 值和 DIC 实验的特点是种群增长率低，其中一些标本死亡，壳部分溶解。