RUI: Collaborative Proposal: Using Organic Carbon Isotopes of Single Microfossils to Illuminate Proterozoic Eukaryotic Ecosystems

地球上生命的早期进化在很大程度上仍然是一个谜，尽管近几十年来取得了进展，但主要问题仍然存在，特别是关于生物与地球大气中氧气含量增加之间的关系。我们的提议将测量微观化石的有机碳同位素，这是我们了解动物出现之前生命进化的最佳窗口。这些测量将帮助我们弄清楚海洋中早期生物生活的地方，以及早期生命是否能在几乎没有氧气的水中茁壮成长。这项工作将涉及到本科生的研究、分析和写作的各个方面。我们将为K-12和大学教育工作者创建新的地球化学和古生物学教育模块，开发创新的有机地球化学技术，与更广泛的科学界共享，并将早期化石生命的信息添加到开放访问的古生物学数据库中。虽然在过去的几十年里，我们已经对元古代地球系统有了相当多的了解，但主要的问题仍然存在，特别是关于生物与大气中氧气增加之间的相互作用。研究元古代生物记录的一个窗口是通过有机碳同位素，它跟踪了固定碳的同位素系统。然而，这些测量几乎总是在代表整个生物群落时间平均到沉积样本的大块样本上完成的，这限制了我们使用这些测量来重建短期碳循环动力学和探测古代生态系统结构的能力。NanoEA-IRMS的最新进展现在使我们能够可靠地测量单个有机微化石的碳同位素组成，并将该值与整体13C进行比较。我们试图利用这项新技术来探索有机碳同位素如何阐明元古代地球生命系统中两个长期存在的未知数：1)早期真核生物的栖息地和代谢是什么？2)单个微化石碳同位素对元古代地层记录中整体碳同位素的控制作用有何启示？这些记录对元古代地球系统有何启示？我们将通过分析四个丰富化石单元的大块、干酪根和化石有机碳样本来解决这些问题，这些化石单元跨越了元古代真核生物的历史。该提案的广泛影响包括继续发展和完善稳定同位素分析技术，并将元古代微化石记录整合到开放访问的古生物数据库中。提案团队将让本科生参与研究的各个方面，本科生将有意义地参与数据收集和解释。该团队还将为高中和大学观众开发新的教育活动。建议的工作将包括一名博士后，他将由三位PI在研究，专业发展和教学方面进行指导。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Much about the early evolution of life on earth still remains a mystery, and while advances have been made in recent decades, major questions remain, especially about the relationships between biology and the rise of oxygen in the earth's atmosphere. Our proposal will measure organic carbon isotopes of microscopic fossils that represent our best window into the evolution of life before the rise of animals. These measurements will help us figure out where in the oceans early organisms were living and if early life could thrive in waters with little to no oxygen. This work will involve undergraduate students in every aspect of the research, analysis, and writing. We will create new geochemical and paleontological educational modules for K-12 and college educators, develop innovative organic geochemistry techniques that will be shared with the broader scientific community and add information on early fossil life to the open-access Paleobiology Database. While we have learned a significant amount about the Proterozoic Earth system in the last few decades, major questions remain, especially about the interplay between biology and the rise of atmospheric oxygen. One window into the biological record of the Proterozoic is via organic carbon isotopes, which track the isotope systematics of fixed carbon. However, these measurements are almost always done on bulk samples that represent the entire biological community time averaged into a sedimentary sample, which limits our ability to use these measurements to reconstruct short-term carbon cycle dynamics and to probe the structure of ancient ecosystems. Recent advances in NanoEA-IRMS now allow us to reliably measure the carbon isotopic composition of a single organic microfossil and compare that value to the bulk 13C. We seek to use this new technique to explore how organic carbon isotopes can illuminate two persistent unknowns in the Proterozoic Earth-life system: 1) What were the habitats and metabolisms of early eukaryotes? and 2) What can single microfossil carbon isotopes reveal about the controls on bulk carbon isotopes in the Proterozoic stratigraphic record and what do these records tell us about the Proterozoic Earth system?. We will approach these questions by analyzing bulk, kerogen and fossil organic carbon samples from four richly fossiliferous units that span the history of Proterozoic eukaryotes. The broader impacts of this proposal include continued development and refining of stable isotope analysis techniques, and integration of the Proterozoic microfossil record into the open-access Paleobiology Database. The proposal team will involve undergraduate students in all aspects of the research, and undergraduates will be meaningfully involved in data collection and interpretation. The team will also develop new educational activities for both high school and college-level audiences. The proposed work will include a postdoctoral fellow who will be mentored by all three PI's on research, professional development, and teaching.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.