Natural Variations in Silicon Isotopes in Seawater Silicic Acid and Marine Diatoms: A New Tool for Studying the Marine Silica Cycle

[9729996]布热津斯基在这个项目中，研究人员将测试一种全新的化学海洋学示踪剂的效用。开发了测量硅藻生物源二氧化硅和海水溶解硅酸中硅同位素天然丰度的分析工具，并首次用于证明海洋硅藻在蛋白石生物矿化过程中对硅同位素的分馏。分馏的程度在物种之间是恒定的，并且不随温度的变化而变化，这表明单一的分馏因子可以用来描述由于硅藻生长在海洋中的硅同位素比率的变化。我们建议获取数据集I)严格评估生物分馏在控制海洋中硅同位素分布中的作用，ii)评估硅同位素自然丰度，作为海洋表面二氧化硅生产的测量。第一个目标将通过分析从许多海洋盆地收集的溶解二氧化硅和颗粒二氧化硅样本来实现。将获得更多的样品来确定通过深海热液喷口和河流进入海洋的Si的同位素特征。所得数据将与数值模拟相结合，以检验生物分馏、生物泵和全球热盐环流之间的相互作用决定海洋中硅同位素分布的假设。通过比较出口到深海的二氧化硅的时间序列，将检查地表水中溶解二氧化硅和颗粒二氧化硅产量的同位素组成的响应。用于拟议比较的地表水和沉积物陷阱的样本已经或将通过现有的研究工作收集，使我们能够以低成本提出广泛的研究。成功将为研究现代海洋中的硅藻活动提供一个强大的新工具，并有能力利用沉积物岩心中硅同位素的变化来研究地质时间尺度上二氧化硅生产的变化。

9729996 Brzezinski In this project, researcher will test the utility of an entirely new tracer for chemical oceanography. Analytical tools for measuring silicon isotope natural abundance in biogenic silica from diatoms and dissolved silicic acid from seawater have been developed and have been used to demonstrate for the first time silicon isotope fractionation by marine diatoms during opal biomineralization. The extent of fractionation is constant among species, and does not vary measurably with temperature, suggesting a single fractionation factor can be used to describe variations in silicon isotopic ratios due to diatom growth in the sea. We propose to obtain data sets I) to assess rigorously the role of biological fractionation in controlling the distribution of silicon isotopes in the sea and ii) to evaluate silicon isotope natural abundance as a measure of silica production in the surface ocean. The first goal will achieved by analyzing samples of dissolved and particulate silica gathered from a number of ocean basins. Additional samples will be obtained to define the isotopic signature of the Si entering the sea through deep-sea hydrothermal vents and rivers. The resulting data will be combined with numerical modeling to test the hypothesis that the interplay among biological fractionation, the biological pump and global thermohaline circulation governs the distribution of Si isotopes in the sea. The response of the isotopic composition of dissolved and particulate silica production in the surface water will be examined by comparing time series of silica exported to depth. The samples from surface waters and sediment traps for the proposed comparisons have been, or will be, collected through existing research efforts allowing us to propose an extensive study at low cost. Success will provide a powerful new tool for examining diatom activity in the modern ocean and the ability to use variations in Si isotopes in sediment cores to examine changes in silica production on geologic time scales.