François Daniel, Reichart Gert-Jan, de Nooijer Lennart J
Department of Ocean Systems, NIOZ Royal Netherlands Institute for Sea Research and Utrecht University, Texel, Netherlands.
Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands.
Sci Adv. 2025 May 2;11(18):eadq8425. doi: 10.1126/sciadv.adq8425.
Marine calcifying organisms precipitate their shells either in equilibrium with seawater or under strict biological control. Here, we show that these two options represent two ends of a spectrum. In species with a more "closed" system, rates of H removal and Ca uptake are high and exceed the amount of ions required for calcification. This explains the relatively low Mg/Ca of the calcite of this species by dilution of the [Mg] in the calcifying fluid. Conversely, in species with a more open system, the H and Ca fluxes are lower, with more seawater exchanged between the environment and calcifying fluid, explaining the relatively high Mg/Ca in these foraminifera. In either of these species, mitochondria were found to be located at the site where the Ca/H exchange takes place and the mitochondrial density aligned with the rate of pumping. These findings highlight the crucial role of transmembrane transporters and mitochondria in foraminifera calcification and explain the species-specific elemental signatures.
海洋钙化生物要么在与海水平衡的状态下沉淀其外壳，要么在严格的生物控制下进行。在此，我们表明这两种情况代表了一个连续谱的两端。在具有更“封闭”系统的物种中，氢离子去除率和钙离子摄取率很高，超过了钙化所需的离子量。这通过钙化液中镁离子浓度的稀释，解释了该物种方解石相对较低的镁钙比。相反，在具有更开放系统的物种中，氢离子和钙离子通量较低，环境与钙化液之间交换的海水更多，这解释了这些有孔虫相对较高的镁钙比。在这两种物种中，都发现线粒体位于钙离子/氢离子交换发生的部位，线粒体密度与泵浦速率一致。这些发现突出了跨膜转运蛋白和线粒体在有孔虫钙化中的关键作用，并解释了物种特异性的元素特征。
