Collaborative Research: The Roles of Seasonality, Silicification, and Alteration in Nitrogen and Silicon Isotope Paleo-proxy Variability

化石硅藻（一种浮游生物）的化学成分，特别是它们的氮和硅成分，反映了过去地表水营养物质和植物吸收的变化。来自南大洋的沉积硅藻氮和硅值的变化记录了海洋生物随着时间的推移消耗海洋表层营养物质的程度。这些记录被解释为记录了大规模垂直海洋环流的变化以及铁刺激的生物生产。这些过程可能共同作用，促进了海洋和大气之间的碳交换。拟议的工作将解决我们对硅藻代理记录表面营养状况的理解方面的差距。具体而言，这包括检查环境控制的生理影响，导致硅藻改变他们如何建立自己的外壳和改变在下沉和埋葬的氮和二氧化硅的组成的潜在影响。这些结果将改善过去营养物质下降的重建，突出稳健重建的最佳地质条件，并增加我们对现有硅藻氮和硅同位素记录中观察到的空间和时间变化的理解。这项工作将最终提高我们对过去全球规模气候变化的理解，并将未来的变化置于背景之中。该项目将促进早期职业科学家的职业生涯，通过培训学生和将项目成果纳入课程工作来影响教育，并通过艺术将科学方法，目标和该项目的结果转化为新颖的观众。1）在南大洋春季水华期间硅藻氮和硅同位素值与表面营养盐吸收之间的关系，2）主要控制的空间变异性之间的关系观察到的磷结合的营养同位素代理，常量营养素，和生物量，和3）可能发生的同位素信号在运输到沉积物的过程中的改变。实地部分包括南纬67°至54°的一条横断面，以进行广泛的水和颗粒取样。结合同位素和新型荧光标记技术的船上培养将测量硅化程度如何影响硅藻氮和硅同位素。在硅藻壳的溶解过程中，轻度硅化类群和/或分馏的损失的影响将通过在家庭机构的实验室培养进行评估。艺术与科学合作的产品将在网上和活动中公开展示。我们将通过参与海洋学研究生院的本科生研究经验和海洋学暑期本科生研究奖学金计划，扩大罗得岛大学对STEM的参与，以及在项目研究生职位和加州圣巴巴拉大学的招聘中优先考虑代表性不足的群体，通过研究经验和教育设施，重点是该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The chemistry of fossil diatoms (a type of plankton), specifically their nitrogen and silicon composition, reflects past changes in surface water nutrients and uptake by plants. Changes in sedimentary diatom nitrogen and silicon values from the Southern Ocean record to what degree ocean biology consumed nutrients in the surface ocean through time. These records have been interpreted to document changes in large-scale vertical ocean circulation as well as iron-stimulated biological production. These processes likely worked together to contribute to carbon exchange between the ocean and the atmosphere. The proposed work will address gaps in our understanding of how the diatom proxies record surface nutrient conditions. Specifically, this includes an examination of environmentally controlled effects on physiology that lead diatoms to change how they build their shells and of alteration during sinking and burial as potential influences on the composition of nitrogen and silica. The results will improve reconstructions of nutrient drawdown in the past, highlight optimal geological conditions for robust reconstructions, and increase our understanding of observed spatial and temporal variability in existing diatom nitrogen and silicon isotope records. This work will ultimately improve our understanding of global-scale climate change in the past and contextualize future change. The project will foster the careers of early career scientists, impact education through training of students and incorporation of project results into course work, and translate science methods, goals, and results of this project to novel audiences through art.The proposed work will examine: 1) the relationship between diatom nitrogen and silicon isotope values and surface nutrient uptake during a Southern Ocean spring bloom, 2) primary controls on the spatial variability observed for the relationships between diatom-bound nutrient isotope proxies, macronutrients, and biomass, and 3) possible alteration to isotopic signals occurring during transit to the sediment. The field component includes a transect from 67°S to 54°S to conduct extensive sampling of water and particles. Shipboard incubations combining isotope and novel fluorescent labeling techniques will measure how degree of silicification influences diatom Nitrogen and Silica isotopes. The influence of the loss of lightly silicified taxa and/or fractionation during the dissolution of frustules will be evaluated through laboratory incubations at home institutions. Products of an art-science collaboration will be publicly displayed online and at events. We will broaden participation in STEM at the University of Rhode Island through our participation in the Graduate School of Oceanography’s Research Experience for Undergraduates and the Summer Undergraduate Research Fellowship in Oceanography Program, as well as prioritizing underrepresented groups in recruitment for the project’s graduate student position and at University California Santa Barbara through the Research Experience and Education Facility that focuses on underserved K-12 students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.