Pathways and regulation of transformation of low molecular weight carbon compounds in subseafloor sediments from the Guaymas Basin (Gulf of California)

这项研究将探索地球上最大的碳储存库之一——位于海底的海洋沉积物中的碳循环。随着时间的推移，这些碳通过地质、化学和生物过程的相互作用逐渐循环。该项目将记录这些过程如何转化来自瓜伊马斯盆地（加利福尼亚湾）的海洋沉积物中的碳。这种设置提供了在大范围的化学和温度梯度中研究碳循环的机会，提供了梳理海洋沉积物中调节碳循环的因素的机会。这个项目将调查海洋沉积物在全球碳循环中的作用。这些研究目标代表了全球环境变化时期的关键科学优先事项。在推广活动方面，这位科学家将与吉姆·图米教育公司合作，继续制作“扎克和莫莉的冒险”系列教育视频。在这种情况下，视频将记录这项研究的结果及其更广泛的意义。这位科学家还将为教师创建一个学习指南。录像带和学习指南都将分发给教育工作者。作为该项目的一部分，将支持和培训一名研究生和一名本科生。瓜伊马斯盆地（加利福尼亚湾）的地下沉积物为研究动态但易处理的海洋环境中的碳循环提供了一个可访问的窗口。这项工作将研究地下沉积物的加热如何影响低分子量溶解有机碳的产生、消耗和命运。这项研究将追踪关键碳物种的命运，包括甲酸盐、醋酸盐和甲醇，因为它们经过一系列微生物介导的过程。样品是在2019年9月至10月的国际海洋发现计划第385次探险期间收集的。一些实验是在科考船上进行的，另外一些实验将在实验室进行。该研究将结合直接速率、池大小、稳定同位素测量以及热力学模型和验证性实验室实验来限制低分子量碳基质的转化幅度和命运。重点研究课题包括：(1)地下沉积物中有机化合物的主要生产方式是什么？(2)沿地球化学和温度梯度，产甲烷的主要途径是什么？(3)微生物驱动碳循环过程的温度极限是什么？(4)有机化合物的命运如何沿着地球化学和/或温度梯度变化？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。

This research will explore carbon cycling in one of the largest carbon reservoirs on Earth, marine sediments, located at bottom of the ocean. This carbon is recycled gradually over time through interacting geological, chemical, and biological processes. This project will document how each of these processes transforms carbon in marine sediments from the Guaymas Basin (Gulf of California). This setting offers the chance to study carbon cycling across a broad range of chemical and temperature gradients, providing an opportunity to tease apart the factors regulating carbon cycling in marine sediments. This project will investigate the role of ocean sediments in the global carbon cycle. These research objectives represent key science priorities in a time of global environmental change. For outreach activities, the scientist, in collaboration with Jim Toomey Education, would continue the “Adventures of Zack and Molly” educational video series. In this instance, the video would document results from this study and its broader significance. The scientist also would create a learning guide for teachers. Both the video and the learning guide would be disseminated to educators. One graduate and one undergraduate student would be supported and trained as part of this project. Subsurface sediments in the Guaymas Basin (Gulf of California) offer an accessible window for investigating carbon cycling in a dynamic, yet tractable, marine environment. This work will study how heating of subsurface sediments affects the production, consumption, and fate of low molecular weight dissolved organic carbon. The research will track the fate of key carbon species – including formate, acetate, and methanol – as they are processed through a gauntlet of microbial-mediated processes. Samples were collected during Expedition 385 of the International Ocean Discovery Program in September-October 2019. Some experiments were conducted on the research vessel and additional experiments will be conducted in the laboratory. The study will constrain the magnitudes of transformation and the fate of low molecular weight carbon substrates using a combination of direct rate, pool size, and stable isotopic measurements coupled to thermodynamic modeling and probative laboratory experiments. Key topics for investigation include: (1) What is the dominant production mode for organic compounds in subsurface sediments? (2) What are the dominant pathways of methanogenesis along geochemical and temperature gradients? (3) What are the temperature limits of microbially-driven carbon cycling processes? (4) How does the fate of organic compounds change along geochemical and/or temperature gradients?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.