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

合作研究：季节性、硅化和蚀变在氮和硅同位素古代理变异中的作用

• 批准号: 2218705
• 负责人: Mark Brzezinski
• 金额: $ 90万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2218705&HistoricalAwards=false
• 关键词: Collaborative; Research; Roles; Seasonality; Silicification

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.

化石硅藻（浮游生物的一种）的化学成分，特别是它们的氮和硅成分，反映了过去地表水养分的变化以及植物吸收的沉积硅藻氮和硅值与南大洋记录的变化程度。随着时间的推移，生物消耗了表层海洋中的营养物质，这些记录被解释为记录了大规模垂直海洋环流以及铁刺激的生物生产的变化，这些过程可能共同促进了海洋和大气之间的碳交换。拟议的工作将解决以下方面的差距：具体来说，我们对硅藻代理如何记录表面营养条件的理解包括检查环境控制对硅藻生理学的影响，这些影响会导致硅藻改变其外壳的形成方式，以及在下沉和埋葬过程中对氮和元素组成的潜在影响。研究结果将改善过去养分减少的重建，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。最终将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下。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作业来影响教育，并转化科学方法，通过艺术向新观众展示该项目的目标和结果。拟议的工作将研究：1）硅藻氮和硅同位素值与南大洋春季水华期间表面养分吸收之间的关系，2）对空间的主要控制观察到之间关系的变异性硅藻结合营养物同位素代理、常量营养物和生物量，以及 3) 在传输到沉积物过程中可能发生的同位素信号变化。现场部分包括南纬 67° 至南纬 54° 的横断面，用于对水和颗粒进行广泛的采样。结合同位素和新型荧光标记技术的船上孵化将测量硅化程度如何影响硅藻氮和二氧化硅同位素的损失。硅藻壳溶解过程中的轻硅化类群和/或分馏将通过国内机构的实验室孵化进行评估，我们将在罗德岛大学扩大对 STEM 的参与。通过参与海洋学研究生院的本科生研究经验和夏季本科生海洋学研究奖学金计划，以及在该项目的研究生职位和加州大学的招聘中优先考虑代表性不足的群体圣巴巴拉通过专注于服务不足的 K-12 学生的研究经验和教育设施。该奖项反映了 NSF 的法定使命，并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，被认为值得支持。