CAREER: Understanding biosphere-geosphere coevolution through carbonate-associated phosphate, community archives, and open-access education in rural schools

磷是生命必需的营养物质。今天，磷在海洋中的丰度极低，限制了生物圈的生产力。大部分磷来自大陆磷矿物的风化作用。然而，在地球历史的最初10到20亿年里，没有大陆可以风化。在第一批大陆出现在海平面以上后不久（约32亿至26亿年前，Ga），微生物进化出了进行含氧光合作用的能力，这导致了富氧大气和初级生产力的大幅增加。海洋和大气的氧化作用与地球第一批大陆的风化作用有直接关系吗？本研究将记录2 ~ 0.5 Ga古代海洋中磷的浓度，以检验海洋微生物的进化是否与地球被冰覆盖时早期大陆的风化有关。最终，磷的丰富可能促成了有氧生物和多细胞生物的进化。这项研究将与当地高中教师为邻近农村地区开发的新的地球科学课程相结合。该项目将开发开放式教室和基于实地的学习模块，以及虚拟实地考察，将学生与宾夕法尼亚景观中的寒武纪大爆发——宏观动物的进化——联系起来。新课程的效果将通过前后实施的一系列知识评估和随后几年的“知识提升”来评估。中大西洋高中的教师将接受培训，了解将在课堂上使用的各种资源。自生命开始以来，微生物就与碳酸盐矿物和地球表面的化学演化密切相关。20亿年前的含氧光养代谢创新促进了氧气的增加，提高了全球初级生产力，并永久地改变了生物地球化学循环。然而，为什么微生物进化出光合作用的能力相对较晚，以及是什么控制了随后的微生物进化的步伐，我们知之甚少。CAREER奖的主要目标是评估磷酸盐的有效性，磷酸盐是所有生命必需的营养物质，在承载原始微生物和新兴代谢的结构和地球化学证据的环境中。中元古代生产力的降低是富氧光养生物耗尽磷酸盐储层的症状吗？冠群真核生物和后生动物的进化是否受到新元古代全球冰川作用和超大陆分裂的风化磷酸盐的影响？本项目通过在元古宙全球冰川、构造和现有时间和成岩框架的背景下，利用碳酸盐岩相关磷酸盐（CAP）在现有的前寒武纪样品集上重建海水，验证了磷酸盐可用性对真核生物和后生动物进化至关重要的假设。该研究将通过(1)分析具有丰富成岩和地球化学数据的相同前寒武纪样品中的CAP，以及(2)进行生长实验以开发矿物特异性CAP-[P]海水校准，提高我们对CAP及其在地球和天体生物学中的应用的理解。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。

Phosphorus is an essential nutrient for life. Today, phosphorus exists in extremely low abundance in the oceans limiting the productivity of the biosphere. The majority of phosphorus is derived from weathering of phosphate minerals from continents. However, for the first one to two billion years of Earth history, there were no continents to weather. Shortly after the first continents emerged above sea level (~3.2 to 2.6 billion years ago, Ga), microbes evolved the ability to perform oxygenic photosynthesis, which led to an oxygen-rich atmosphere and massive increase in primary productivity. Was the oxygenation of the oceans and atmosphere directly related to weathering of Earth’s first continents? This study will develop a record of the concentration of phosphorus in ancient oceans ~2 to 0.5 Ga to examine if the evolution of marine microorganisms was linked to weathering of early continents when the Earth was covered in ice. Ultimately, phosphorus abundance may have enabled the evolution of aerobic and multicellular organisms. The research will be integrated into new Earth sciences curricula developed with local high school teachers for neighboring rural districts. The project will develop open-access classroom and field-based learning modules and virtual field trips that connect students to the Cambrian explosion—the evolution of macroscopic animals—in the Pennsylvania landscape. The efficacy of the new curricula will be assessed through serial knowledge assessments implemented before and after exposure and “knowledge boosts” in subsequent years. Mid-Atlantic high school teachers will be trained in various resources to be implemented in their classrooms.Microbes have been intimately linked to carbonate minerals and the chemical evolution of Earth’s surface since life began. The metabolic innovation of oxygenic phototrophy 2 billion years ago contributed to the rise of oxygen, increased global primary productivity, and permanently changed biogeochemical cycles. However, little is known about why microbes evolved the ability to photosynthesize relatively late in the history of life, and what controlled the pace of subsequent microbial evolution. The primary goal of this CAREER award is an assessment of phosphate availability—an essential nutrient for all life—in the environments that host textural and geochemical evidence for primitive microbes and emergent metabolisms. Was the reduced productivity of the Mesoproterozoic a symptom of a phosphate reservoir depleted by oxygenic phototrophs? Was the evolution of crown group eukaryotes and metazoans fertilized by weathering-derived phosphate from Neoproterozoic global glaciations and the breakup of supercontinents? This project tests the hypothesis that enhanced phosphate availability was essential to the evolution of eukaryotes and metazoans by reconstructing seawater [P] via carbonate-associated phosphate (CAP) on existing Precambrian sample sets within the context of Proterozoic global glaciations, tectonics, and existing temporal and diagenetic frameworks. The research will improve our understanding of CAP and its utility for geo- and astrobiology by (1) analyzing CAP in the same Precambrian samples that have a wealth of existing diagenetic and geochemical data, and (2) performing growth experiments to develop mineral-specific CAP-[P]seawater calibrations.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.