OCE-PRF: Windows into Cretaceous diatom paleobiology: Seasonal responses in laminated sediments and survivability and response to the Cretaceous-Paleogene extinction event

硅藻是一种光合藻类，是生物圈和地球气候系统的重要组成部分。虽然新生代的记录表明了它们对原始生物和化学循环的影响，但对白垩纪硅藻的描述和应用研究缺乏。这种描述性工作的缺乏限制了它们在理解白垩纪温室气候等古代全球生态系统方面的应用。因此，更好地了解在白垩纪末期大灭绝事件中硅藻是如何对显著的环境扰动作出反应的，以及它们对白垩纪早期季节变化的反应；对于了解地球气候系统在地质时期的演变至关重要，并有助于限制未来的气候变化。统一的研究主题是更好地了解硅藻对古环境变化响应的控制因素，并提高其作为白垩纪地质研究工具的实用性。PI Coenen将研究现代和古代层状沉积物，以更好地了解海洋钻探项目693点的古环境和硅藻分类。这项工作将提供对白垩纪早期季节性气候变化的关键理解，这将有助于理解温室世界中的地球气候系统。此外，PI Coenen将研究白垩纪-古近纪（K/Pg）大灭绝前后的硅藻和硅鞭毛藻，以了解硅质微化石对环境扰动的反应，并了解导致硅藻在这次大灭绝事件中存活的因素。作为NSF博士后研究员，PI Coenen将指导本科生项目，学习如何指导研究生项目，并与Harwood博士一起管理一个研究实验室。此外，PI Coenen将为在线南极地球科学课程和古近系和白垩纪硅质微化石生物地层学研讨会开发模块。PI Coenen还将在当地图书馆和k-12学校举办外联活动，并与联合国大学密切合作，促进扩大地球科学参与的努力。该研究旨在开发南半球两个地点的硅藻古生物学和古生态学的新信息，时间范围从早白垩纪到K/Pg大灭绝事件。PI Coenen将评估现代生态学方法是否可以应用于古代古生物记录。核心假设是白垩纪硅藻与现代硅藻共享许多生活策略，允许应用“生物均变论”来解释硅藻化石记录。这项研究将在内布拉斯加大学林肯分校进行，哈伍德博士将在那里指导PI Coenen研究白垩纪硅藻系统学、生物地层学和古生态学。Drs。Harwood和Coenen将与Leventer博士合作，为Coenen提供有关南极东部边缘现代硅藻层状沉积物的培训，以建立他的技能，从ODP Site 693层状沉积物中解释早白垩纪硅藻的季节变化。这项工作将为研究早白垩纪温室气候期间的高分辨率海洋-大气强迫提供难得的机会。此外，南极半岛Seymour岛和Vega岛的硅质微化石将记录在K/Pg大灭绝事件之前约150 kyr的大型动物群中确认的前体灭绝，并记录事件后的恢复。硅藻和硅藻对极端环境扰动的反应将被详细研究，以记录硅藻的逆行进化，并更好地了解硅藻是如何在K/Pg灭绝中幸存下来的，这种灭绝导致其他浮游植物化石大量灭绝。对硅藻组合的研究，重点关注与德干圈闭相关的潜在前体灭绝中硅藻休眠孢子的丰度和体积变化，将为解决这些问题提供数据。此外，对新形成的南大洋的研究对认识晚白垩世古气候和古海洋学具有重要意义。这两项提议的研究都有可能限制建模工作，并在这些各自的区间提供更好的古环境感觉。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。

Diatoms are photosynthetic algae that are an essential part of the biosphere and Earth’s climate system. While Cenozoic records indicate their impact on primary biological and chemical cycles, there is a lack of descriptive and applied research on Cretaceous diatoms. This lack of descriptive work limits their application for understanding ancient global ecosystems such as the Cretaceous greenhouse climates. Therefore, developing a better understanding of how diatoms responded to significant environmental perturbations during the end-Cretaceous mass extinction event and their response to seasonal changes in the early Cretaceous; is critical for understanding how Earth’s climate system has evolved through geologic time and helps constrain future climate variability. The unifying research theme is to better understand the controls on diatom responses to paleoenvironmental changes and improve their utility as tools for Cretaceous geological studies. PI Coenen will study modern and ancient laminated sediments to better understand Ocean Drilling Project Site 693 paleoenvironments and diatom taxonomy. This work will provide a critical understanding of early Cretaceous climate variability on a seasonal timescale, which will aid in the understanding of Earth’s climate system in a greenhouse world. Additionally, PI Coenen will study diatoms and silicoflagellates both before and after the Cretaceous-Paleogene (K/Pg) mass extinction to see how siliceous microfossils respond to environmental perturbations and understand what factors led to survivability in diatoms through this mass extinction event. As an NSF Postdoctoral Researcher, PI Coenen will mentor undergraduate student projects and learn how to mentor graduate level projects and run a research lab with Dr. Harwood. Additionally, PI Coenen will develop modules for an online Antarctic Geosciences course and a Paleogene and Cretaceous siliceous microfossil biostratigraphy workshop. PI Coenen will also host outreach activities at local libraries and k-12 schools and work closely with UNL to foster efforts to broaden participation in the geosciences.The proposed research seeks to develop new information on diatom paleobiology and paleoecology from two locations in the Southern Hemisphere, ranging in time from the early Cretaceous through the K/Pg mass extinction event. PI Coenen will evaluate whether modern ecological approaches can be applied to ancient paleontological records. The central hypothesis is that Cretaceous diatoms shared many life strategies with modern diatoms, allowing for the application of ‘biological uniformitarianism’ to interpret fossil diatom records. This research will be conducted at the University of Nebraska-Lincoln, where Dr. Harwood will mentor PI Coenen on Cretaceous diatom systematics, biostratigraphy, and paleoecology. Drs. Harwood and Coenen will collaborate with Dr. Leventer to provide Coenen training on modern diatom-bearing laminated sediments from the East Antarctic margin to build his skill set to interpret early Cretaceous diatom seasonal changes from ODP Site 693 laminations. This work will provide a rare opportunity to study high-resolution ocean-atmospheric forcing during early Cretaceous greenhouse climates. Additionally, siliceous microfossils from Seymour and Vega islands, Antarctic Peninsula, will be documented across a precursor extinction recognized in the macrofauna ~150 kyr prior to the K/Pg mass extinction event, as well as document the post-event recovery. The response of both silicoflagellates and diatoms to extreme environmental perturbations will be studied in detail to document silicoflagellate retrograde evolution and better understand how diatoms survived the K/Pg extinction that decimated other fossil phytoplankton. Study of diatom assemblages, with a focus on abundance and volume changes of diatom resting spores across a potential precursor extinction related to the Deccan Traps will provide data to resolve these questions. Additionally, this research on the newly forming Southern Ocean has important implications for understanding late Cretaceous paleoclimate and paleoceanography. Both proposed studies have the potential to constrain modeling efforts and provide a better sense of paleoenvironments in these respective intervals.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.