Larger benthic foraminifera (LBF) are unicellular eukaryotic calcifying organisms and an important component of tropical and subtropical modern and ancient oceanic ecosystems. They are major calcium carbonate producers and important contributors to primary production due to the photosynthetic activity of their symbiotic algae. Studies investigating the response of LBF to seawater carbonate chemistry changes are therefore essential for understanding the impact of climate changes and ocean acidification (OA) on shallow marine ecosystems. In this study, calcification, respiration, and photosynthesis of the widespread diatom‐bearing LBF Operculina ammonoides were measured in laboratory experiments that included manipulation of carbonate chemistry parameters. pH was altered while keeping dissolved inorganic carbon (DIC) constant, and DIC was altered while keeping pH constant. The results show clear vulnerability of O. ammonoides to low pH and CO₃²⁻ under constant DIC conditions, and no increased photosynthesis or calcification under high DIC concentrations. Our results call into question previous hypotheses, suggesting that mechanisms such as the degree of cellular control on calcification site pH/DIC and/or enhanced symbiont photosynthesis in response to OA may render the hyaline (perforate and calcitic‐radial) LBF to be less responsive to OA than porcelaneous LBF. In addition, manipulating DIC did not affect calcification when pH was close to present seawater levels in a model encompassing the total population size range. In contrast, larger individuals (>1,200 μm, >1 mg) were sensitive to changes in DIC, a phenomenon we attribute to their physiological requirement to concentrate large quantities of DIC for their calcification process.

中文翻译：

---

分离的DIC-pH实验中含共生有孔虫对海水碳酸盐化学的差分敏感性

较大的底栖有孔虫（LBF）是单细胞真核钙化生物，是热带和亚热带现代和古代海洋生态系统的重要组成部分。由于它们的共生藻类具有光合作用，它们是碳酸钙的主要生产者和初级生产的重要贡献者。因此，调查LBF对海水碳酸盐化学变化的响应的研究对于理解气候变化和海洋酸化（OA）对浅海生态系统的影响至关重要。在这项研究中，广泛地携带硅藻的LBF小单胞菌Amperides的钙化，呼吸作用和光合作用在包括碳酸盐化学参数操作在内的实验室实验中进行了测量。在保持溶解无机碳（DIC）恒定的同时改变pH，在保持pH恒定的同时改变DIC。结果表明，O。ammonoides对低pH和CO ₃ ^2-的明显脆弱性在恒定DIC条件下，在高DIC浓度下光合作用或钙化没有增加。我们的结果质疑先前的假设，表明机制如钙化位点pH / DIC上的细胞控制程度和/或响应OA增强共生光合作用可能使透明（穿孔和钙-径向）LBF反应性降低。 OA比猪LBF要大。此外，在涵盖总人口规模范围的模型中，当pH值接近当前海水水平时，操作DIC不会影响钙化。相反，较大的个体（> 1,200μm，> 1 mg）对DIC的变化敏感，这是我们将其生理需要集中到钙化过程中浓缩大量DIC的现象。