Trace element and isotope partitioning in carbonates in simulated biological environments

许多海洋生物产生碳酸钙结构，例如珊瑚产生骨骼，双壳类产生贝壳，有孔虫（单细胞生物）产生测试。这些矿物结构为生物体提供组织支持和/或保护免受捕食者和物理环境的侵害。碳酸钙的化学性质受环境的影响。特别是海水温度影响微量元素替代钙的方式和矿物结构中氧同位素（不同质量的氧形式）的比例。因此，碳酸钙结构的地球化学信息提供了生物生存和生长时海水的温度和化学信息。矿物结构在生物死后被保存下来，例如珊瑚礁，对化石标本的分析为重建过去环境条件的记录提供了一个很好的途径。这些记录有助于我们了解过去全球气候的变化和相互作用，并预测21世纪的气候变化。了解其他因素如何影响贝壳和珊瑚礁的化学成分是准确解释化石标本中记录的气候信息的关键。珊瑚骨骼和有孔虫测试在生物内部或附近的特殊钙化部位形成。钙化位点包含可溶性和不溶性有机生物分子（如蛋白质、脂类），它们控制和引导矿物的沉淀和生长。这些生物分子也影响矿物的化学性质。在这项研究中，我们将分析现代和化石珊瑚和有孔虫，以确定钙化部位有机生物分子的浓度和组成如何随时间变化。然后，我们将在复制过去和现在钙化位点的条件下体外沉淀CaCO3矿物，以确定生物分子的变化如何影响矿物化学。特别是，我们将探索生物分子如何在一定温度范围内与钙化部位的其他离子相互作用以控制矿物化学。我们将计算珊瑚骨架和有孔虫测试化学和海水温度之间的关系如何随时间变化。通过将这些计算应用于化石，我们将优化过去海水温度估计的准确性。我们还将使用先进的显微镜技术来可视化不同条件下沉淀的矿物的结构，并实时观察矿物的形成。这些观察结果将有助于我们了解钙化环境的变化如何影响碳酸钙中微量元素和同位素的掺入。

Many marine organisms produce calcium carbonate structures e.g. corals produce skeletons, bivalves produce shells and foraminifera (single-celled organisms) produce tests. These mineral structures provide organisms with tissue support and/or protection from predators and the physical environment. The chemistry of calcium carbonate is affected by environment. In particular seawater temperatures affect how trace elements substitute in place of calcium and the ratio of oxygen isotopes (forms of oxygen with different masses) in the mineral structure. Thus the geochemistry of the calcium carbonate structures provides information on the temperature and chemistry of seawater at the time the organism lived and grew. The mineral structures are preserved after the death of the organism e.g. as coral reefs, and the analysis of fossil specimens offers an excellent route to reconstruct records of past environmental conditions. Such records help us to understand past changes and interactions in global climate and to predict 21st century climate change. Understanding how other factors affect the chemistry of the shells and reefs is key to accurate interpretation of the climate information recorded in fossil specimens. Coral skeletons and foraminifera tests form at specialist calcification sites, either in or adjacent to the organism. The calcification sites contain both soluble and insoluble organic biomolecules (e.g. proteins, lipids), which control and guide the precipitation and growth of the mineral. These biomolecules also affect the chemistry of the mineral. In this research we will analyse modern and fossil corals and foraminifera to determine how the concentrations and compositions of organic biomolecules at the calcification site have varied throughout time. We will then precipitate CaCO3 minerals in vitro under conditions replicating those of past and present calcification sites to determine how variations in biomolecules affect mineral chemistry. In particular we will explore how biomolecules interact with other ions at the calcification site over a range of temperature to control mineral chemistry. We will calculate how relationships between coral skeleton and foraminifera test chemistry and seawater temperature have varied throughout time. By applying these calculations to fossils, we will optimise the accuracy of past seawater temperature estimates. We will also use advanced microscopy techniques to visualise the structure of the mineral precipitated under different conditions and to watch the formation of minerals in real time. These observations will help us to understand how variations in the calcification environment affect the incorporation of trace elements and isotopes in calcium carbonate.