Nasser Saja, Cohen-Taguri Gili, Mass Tali, Pinkas Iddo, Goobes Gil
Department of Chemistry and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 5290002, Israel.
Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa 3498838, Israel.
Heliyon. 2024 Aug 22;10(17):e36648. doi: 10.1016/j.heliyon.2024.e36648. eCollection 2024 Sep 15.
The ratio of Sr/Ca ions in marine biogenic minerals is considered advantageous for tracking geochemical and biomineralization processes that occur in the oceans. It is debatable, though, whether the ratio in biominerals such as coral skeleton is simply related to values in the seawater environment or controlled by the organism. Recent data show that coral larvae produce partially disordered immature aragonite in Mg-containing Sr-poor calcifying fluids, which transforms into well-ordered aragonite in Mg-depleted Sr-enriched environments, upon animal metamorphosis into the sessile polyp state. Inspired by the process in young coral, we explored substitution of Ca by Sr in aragonite by exposing aragonite crystals precipitated to Sr solutions with variable concentrations. The resulting biphasic material, comprised of Sr-doped aragonite and Ca-doped strontianite, was carefully analyzed for foreign cation substitution in each polymorph. This allowed to establish a linear correlation between Sr levels in mineralizing solutions and Sr in aragonite as well as Ca in strontianite. It indicated that 5-fold higher Sr solution concentration is needed for substitution in the crystal to reach the level found in corals. It also provided with Sr levels required for a putative strontianite phase to form.
海洋生物源矿物质中锶/钙离子的比例被认为有利于追踪海洋中发生的地球化学和生物矿化过程。然而，珊瑚骨骼等生物矿物质中的这一比例是仅仅与海水环境中的值相关，还是受生物体控制，仍存在争议。最近的数据表明，珊瑚幼虫在含镁贫锶的钙化液中产生部分无序的不成熟文石，当动物变态为固着的水螅体状态时，在贫镁富锶的环境中转变为有序的文石。受年轻珊瑚这一过程的启发，我们通过将沉淀的文石晶体暴露于不同浓度的锶溶液中，探索了文石中钙被锶取代的情况。对所得的由掺锶文石和掺钙天青石组成的双相材料，仔细分析了每种多晶型物中的外来阳离子取代情况。这使得能够在矿化溶液中的锶含量与文石中的锶以及天青石中的钙之间建立线性关系。这表明，晶体中的取代需要比珊瑚中发现的水平高5倍的锶溶液浓度。它还提供了假定的天青石相形成所需的锶含量。
