CAREER: A Triple-Isotope Approach to Unraveling Subsurface Food Webs

一个由细菌和其他微生物组成的庞大生态系统生活在你的脚下。这个生物群系延伸到地壳深处数公里，包含的有机碳与地表生物一样多。虽然科学家们对这些微生物有很多了解，但了解它们以什么为生是一个更难的问题。生态学家利用植物和动物的化学特征来绘制食物链。在这项工作中，奥斯本教授将开发一种新的工具来绘制类似的微生物食物网，重点关注那些在地下100至10000英尺处发现的微生物食物网。就像指甲上的特征区分食肉动物和素食者一样，这个工具将揭示地下浅层和超深层使用了哪些碳和氮源。地下微生物吃什么，其影响令人惊讶地遍及全球。如果它们主要吃地表植物产生的有机物质，那么它们就会大量吸收碳，并依赖于地表生态系统。如果这些微生物以无机物质为食，呼吸无机物质，利用二氧化碳，那么这些生态系统可能非常古老。这项工作背后的科学概念（食物链、微生物生态学、地球系统科学和实地调查）非常适合高中课堂。奥斯本教授将与社会科学和芝加哥公立学校合作开展以这些概念为特色的活动，最终目标是向具有不同背景和观点的学生介绍地球科学和实地调查。她还将邀请其中一些学生作为实习生，进行沉浸式的实验室体验。大陆地下蕴藏着巨大而活跃的微生物生物圈；然而，这些微生物对地表输入的净依赖性仍然未知。这项工作将询问地下微生物食物网对地表碳的依赖，在地下环境的梯度（浅到2.9公里深）。最终的问题是：地下生态系统是否依赖于地表输入，这是如何随着深度而变化的，以及它是如何随着时间而变化的？超深层大陆生态系统可能独立于表层有机质而生存，并记录了其生物量中暗初级生产力的特征。Osburn教授将开发一种新的氨基酸（AA）三重同位素指纹图谱，并将其应用于一系列深层地下环境的反卷积营养关系。为了实现这些目标，首先，她将用相关的异养和化学自养微生物校准同位素指纹（目标1），然后分析三个特征明确的地点的地下生物量，包括浅层（1-150米），中间（250-1500米）和超深（2.4-2.9公里）环境（目标2）。教育和推广活动的重点是解决地球科学多样性的严重问题，为芝加哥公立高中的多样化教室建立互动的、分析性的内容模块（目标3），并通过实习和实地考察机会为高中生创造沉浸式的实验室体验（目标4）。通过将研究成果纳入K-12课堂，并邀请高中实习生进入研究领域，她直接将研究和教育目标联系起来。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。

A vast ecosystem of bacteria and other microorganisms live beneath your feet. This biome extends kilometers deep into the Earth's crust and contains as much organic carbon as surface life. While scientists know a lot about who these microbes are, understanding what they do for a living is a harder question. Ecologists use chemical signatures of plants and animals to map food chains. In this work, Prof. Osburn will develop a new tool to similarly map microbial food webs, focusing on those found 100s to ~10,000 feet underground. Just like the signatures in fingernails distinguish carnivores from vegetarians, this tool will reveal which carbon and nitrogen sources are uses in the shallow vs. ultra-deep places underground. The implications of what subsurface microbes eat are surprisingly global. If they eat mostly organic matter made by surface plants, then they are sequestering carbon in huge amounts and depend on surface ecosystems. If these microbes instead eat and breathe inorganic materials and use CO2, then these ecosystems could be very ancient indeed. The scientific concepts underlying this work (food chains, microbial ecology, earth system science, and field-based inquiry) are well suited to be adapted for high school classrooms. Prof. Osburn will develop activities featuring these concepts in collaboration with Science in Society and Chicago Public Schools, with the ultimate goal of introducing Earth Science and field-based inquiry to students with a diversity of backgrounds and perspectives. She will also host some of these students as interns for immersive laboratory experiences.The continental subsurface harbors vast and active microbial biospheres; however, the net dependence of these microbes on surficial inputs remains unknown. This work will interrogate the dependency of subsurface microbial food webs on surface carbon, within a gradient of subsurface environments (shallow to 2.9 km deep). Ultimately the questions are: Are subsurface ecosystems dependent on surficial inputs, how does this change with depth, and how might it have changed with time? Ultra-deep continental ecosystems may live independently of surficial organic matter and record signatures of dark primary productivity in their biomass. Prof. Osburn will develop a novel amino acid (AA) triple isotope fingerprint and apply it to deconvolve trophic relationships in a range of deep subsurface environments. To accomplish these ends, first she will calibrate the isotopic fingerprint with relevant heterotrophic and chemoautotrophic microbes (Objective 1), then analyze subsurface biomass from three well-characterized localities including shallow (1-150 m), intermediate (250-1500 m), and ultra-deep (2.4-2.9 km) environments (Objective 2). Education and outreach activities center on addressing the grave problem of diversity in Geoscience by building interactive, analytical content modules for diverse Chicago public high school classrooms (Objective 3) and creating immersive laboratory experiences for high school students via internships and field opportunities (Objective 4). By incorporating research products into the K-12 classroom and inviting high school interns into research arenas, she directly links research and education objectives.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.