Collaborative Proposal: Biomarkers in Diatom Frustules: Development and Application of a New Compound-Specific Isotope Analysis Method to Understand the Present and Past Ocean

硅藻是一种微小的单细胞浮游植物，在有机模板上分泌硅壁，称为硅藻壳。硅藻生长的硅藻壳和它们的有机模板记录了它们生长的环境条件。一旦硅藻壳下沉并成为沉积物，古海洋学家就能够利用它们的化学和同位素组成来研究过去的营养利用率（15 N/14 N比率）和生产力（13 C/12 C比率），以及确定沉积硅藻壳的放射性碳年龄。 目前，在分析与硅藻壳相关的大量有机物的元素和同位素组成之前，先对沉积硅藻壳进行物理隔离和化学净化。不幸的是，通过这些流行的方法进行的记录导致了对过去海洋环境的模糊重建。出于这个原因，华盛顿大学和俄勒冈州州立大学的研究人员将开发几种新的、更可靠的方法，用于分析与硅藻硅藻壳相关的有机物的分子和同位素特征。 具体而言，科学家小组将通过使用液相色谱法结合质谱法来表征来自培养物、浮游生物丝束和沉积物的硅藻细胞壳中的有机物质。 硅藻壳清洁和部分溶解对硅藻壳结合的有机化合物和生物标志物的绝对相对丰度在硅藻壳铁有限和铁充足的条件下的影响也将被检查。 此外，研究小组还将纯化个别硅藻壳结合的生物标志物。 通过改进硅藻壳有机质分子和同位素特征的分析方法，可以提高全新世富硅样品定年的准确性，正确评价岩心完整性，改进硅藻壳13 C/12 C、15 N/14 N和C/N比值的测定方法。 至于更广泛的影响，这项工作不仅将在古海洋学方面开辟全新的途径，而且还将导致更好地了解过去的气候条件和海洋对未来人为影响的生物地球化学循环反应。 该项目还将为一名女研究生和一至两名本科生提供支助和培训。

ABSTRACTOCE-0525829OCE-0525968Diatoms are microscopic, single-celled phytoplankton, that secrete walls of silica, called frustules, on an organic template. The frustules of growing diatoms and their organic template record the environmental conditions in which they grow. Once frustules sink and become sediment, paleoceanographers are able to use their chemical and isotopic composition to study past nutrient utilization (15N/14N ratio) and productivity (13C/12C ratio), as well as determine the radiocarbon age of sedimentary frustules. Currently, sedimentary frustules are physically isolated and chemically cleaned prior to the analysis of the elemental and isotopic composition of bulk organic matter associated with the frustules. Unfortunately, the records that have been through these prevailing methods have lead to ambiguous reconstructions of past oceanographic environments. For this reason, researchers at the University of Washington and Oregon State University will develop several new, more reliable methods for analyzing the molecular and isotopic signatures of organic matter associated with diatom frustules. Specifically, the team of scientists will characterize the organic matter in diatoms frustules from cultures, plankton tows and sediments by using liquid chromatography coupled to mass spectrometry. The influence of frustule-cleaning and partial dissolution on frustule-bound organic compounds and the absolute relative abundance of biomarkers in frustules under iron limited and iron replete conditions will also be examined. In addition, the team of researchers will also purify individual frustule-bound biomarkers. By improving the methods for analyzing the molecular and isotopic signature of organic matter associated with diatom frustules, the dating of diatom-rich samples of Holocene age will be more accurate, the core integrity will be properly assessed, and the methods for measuring 13C/12C, 15N/14N and C/N ratios in diatom frustules will be improved. As regards broader impacts, the work will not only open up entirely new avenues in paleoceanography, but also lead to a better understanding of past climate conditions and the ocean's biogeochemical cycles response to future anthropogenic impacts. The project will also provide for the support and training of one female graduate student and one or two undergraduate students.