Biomineralization in Deep-sea Corals: Empirical Tracer Calibration Coupled to a Mechanistic Model of Skeletal Growth

我们对气候如何变化的直接记录仅限于相对较近的一段时间，校准仪器（温度计，湿度计，风向标等）已经部署。 这些仪器记录涵盖了过去的100-150年。 如果我们想利用过去气候的巨大变化来更好地了解系统是如何工作的，我们需要能够记录我们所关心的变量的“代理”的档案。 迄今为止，最成功的海洋气候档案来自碳酸钙分泌生物的外壳。 有孔虫和球壳虫等远洋生物的贝壳在海底沉积物中占很大比例。 档案中还包括每年一次的珊瑚和软体动物的骨骼。 然而，所有这些都通过生物矿化的过滤器结合了过去气候的代理（例如Mg/Ca作为温度计）。 这些生物以仅部分已知的方式改变其骨骼的化学成分，这些“重要影响”阻碍了我们解码过去气候变化的能力。 这个项目的目的是更好地了解这一生物矿化过程，通过一个良好的观察和一个新的成功的钙化过程模型相结合。 该项目将重点关注深海珊瑚，因为这些动物生活在今天的环境中，变化不大。 这使它们成为一个很好的“实验室老鼠”，因为我们可以在野外研究现代生物，并且仍然有受控实验。 这一项目的更广泛影响包括支持一名研究生直接从事研究工作，并通过公开讲座和视频进行宣传，以接触到广泛的受众。石竹具有规则的带型和跟随带型的相关地球化学示踪物值。 这些模式，以及无处不在和有用的档案，使这个物种的一个理想的目标，进一步示踪剂的发展。 在几乎恒定的条件下生长，这种珊瑚骨骼中稳定同位素和Me/Ca比率的变化只能是由于“生命效应”。 该项目将开发更好的温度计和碳酸盐岩系统代理。dianthus石竹using运用a two-pronged双管齐下approach方法. 现有的现代样本收集包含41个个体，来自广泛的温度，碳酸盐和磷酸盐浓度。 使用多元素ICP-MS方法对Li、B、Mg、Ca、Sr、Ba和U进行的大量测量将给出骨架和海水之间的经验关系。 使用西姆斯和NanoSIMS对单个骨骼进行微量分析，将阐明地球化学的内部结构并添加del 11B。 珊瑚细胞外钙化液中生物矿化过程的一个新模型表明，该模型能正确地预测D.石竹和各种海洋钙化物。 该项目将扩展该模型，以包括Me/Ca比率，并根据西姆斯和批量分析观察结果对其进行测试。 该项目的目标是通过改进生物矿化过程的表征来创建更好的示踪剂。 虽然该模型已经显示出其价值，但收集经验现代样本校准数据集的计划确保它也可以改进现代校准。

Our direct record of how the climate has changed is limited to the relatively recent period of time where calibrated instruments (thermometers, hygrometers, wind vanes, etc.) have been deployed. This instrumental record covers the last 100-150 years. If we want to exploit the large changes in past climate to better understand how the system works, we need archives capable of recording 'proxies' of the variables we care about. Far and away the most successful archive of past climate from the oceans comes from the shells of calcium carbonate secreting organisms. Shells from open ocean dwellers like foraminifera and coccoliths make up a large percentage of the seafloor sediments. Archives also include the annually banded skeletons of corals and mollusks. However, all of these incorporate proxies for past climate (Mg/Ca as a thermometer for instance) through the filter of biomineralization. These organisms modify the chemistry of their skeletons in only partially known ways, and these 'vital effects' hinder our ability to decode how climate has changed in the past. This project aims to better understand this biomineralization process through a combination of well-posed observations and a newly successful model of the calcification process. This project will focus on deep-sea corals because these animals live in an environment today that does not change very much. This makes them a good 'lab rat' since we can study a modern organism in the wild and still have controlled experiments. The broader impacts of this project include support for a graduate student to work directly on the research and outreach through public lectures and videos to reach a wide range of audiences.The deep-sea coral D. dianthus has a regular banding pattern and correlated geochemical tracer values that follow the banding. These patterns, and the ubiquity and usefulness of the archive, make this species an ideal target for further tracer development. Growing in near constant conditions, variations in stable isotopes and Me/Ca ratios within this coral's skeleton can only be due to 'vital effects'. This project will develop better thermometers and carbonate system proxies in D. dianthus using a two-pronged approach. The existing modern sample collection contains 41 individuals from a wide range of temperature, carbonate and phosphate concentrations. Bulk measurements of Li, B, Mg, Ca, Sr, Ba, and U using a multi-element ICP-MS method will give the empirical relationship between skeleton and seawater. Microanalysis of individual skeletons using SIMS and NanoSIMS will elucidate the internal structure of the geochemistry and add del11B. A new model of the biomineralization process in the coral's Extracellular Calcifying Fluid shows that it can correctly predict the linear relationship between del18O and del13C seen in D. dianthus and a wide array of marine calcifiers. This project will expand this model to include Me/Ca ratios and to test it against the SIMS and bulk analysis observations. The goal of the project is to create better tracers through improved characterization of the biomineralization process. While the model is already showing its worth, the plan to collect an empirical modern sample calibration dataset ensures that it can also improve modern calibrations.