CAREER: Cryptic sulfur cycling and organic matter preservation in marine oxygen deficient zones

职业：以颗粒为宿主的硫循环和有机物埋藏在海洋的缺氧区，没有溶解氧的区域被称为缺氧区。由于人类活动和气候变化，这些环境正在增加。大量有机碳埋藏在缺氧区以下的沉积物中。然而，我们并不完全理解为什么有机碳被保存在这些区域。这个项目试图了解一种新发现的过程，该过程可能有助于在缺氧区保存碳。这一过程被称为有机物硫化。通过这个过程，有机物质被转化，并通过与硫化物的反应有效地‘酸洗’。首次在下沉的海洋颗粒中发现了快速硫化反应，并可能对沉积物中的碳埋藏产生比之前认为的更大的影响。该项目将首次对现代缺氧区有机物快速硫化的规模和意义进行测量。该项目包括实地和实验室研究。这项研究将涉及一个学生团队，其中包括一名研究生和六名本科生，他们将通过同伴指导计划得到支持。本科生研究人员将从加州大学圣巴巴拉分校新开发的实用研究技能课程(地球101a)的首届班级中招募。这门课程的目的是使地球科学系的本科生研究机会更具包容性，更容易为小规模学生所接受。它旨在帮助本科生培养具有广泛适用性的批判性思维和观察技能。该项目将启动一个自给自足的、充满活力的海洋生物地球化学研究计划，在本科研究教育上投入巨资，其影响将超过其五年的持续时间。该项目的总体研究目标是评估硫化反应对缺氧环境下有机碳保存的贡献。在建造并测试了一套定制的颗粒捕集器后，将对墨西哥海岸外的海洋缺氧区进行探险。下沉颗粒、悬浮物和表层沉积物将在墨西哥陆架和斜坡上的三个地点收集，这些地点通常具有较高的当地生产力和底层水氧浓度的梯度。在野外，将使用稳定和放射性同位素示踪剂测量微生物硫酸盐还原和有机硫形成的速率和同位素分馏。随后，来自天然样品和实验室实验的有机硫源将使用质谱仪、X射线吸收光谱和其他地球化学技术进行表征。总之，这项工作的结果将确定该环境中有机物硫化的时间和位置，这对模拟海洋碳通量和解释地质记录都具有重要意义。这项研究将首次对缺氧海区有机质硫化的规模、其对沉积碳埋藏的贡献以及其对环境变化的敏感性进行定量估计。同时，该项目将通过开发一种明确、支持和可访问的机制，让来自不同背景的学生参与研究，来改进加州大学圣巴巴拉分校的地球科学本科课程。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

CAREER: Particle-Hosted Sulfur Cycling and Organic Matter Burial in Oxygen Deficient Zones Areas of the ocean without dissolved oxygen are called anoxic zones. These environments are increasing due to human activities and climate change. Large amounts of organic carbon are buried in sediments below anoxic zones. However, we do not fully understand why organic carbon is preserved in these zones. This project seeks to understand a newly discovered process that may contribute to carbon preservation in anoxic zones. The process is called organic matter sulfurization. Through this process, organic matter is transformed and effectively ‘pickled’ by reacting with sulfide. Rapid sulfurization reactions were identified for the first time in sinking marine particles and may have larger effect on carbon burial in sediments than previously thought. This project will be the first to provide measurements of the scale and significance of rapid organic matter sulfurization in modern anoxic zones. This project includes field and laboratory studies. The research will involve a team of students, including a graduate student and six undergraduates, who will be supported through a peer mentorship program. Undergraduate researchers will be recruited from the inaugural class of a newly developed Practical Research Skills course (Earth 101A) at the University of California Santa Barbara. This course aims to make undergraduate research opportunities in the Earth Science Department more inclusive and accessible to minoritized students. It seeks to help undergraduates develop critical thinking and observational skills that have broad applicability. This project will launch a self-sustaining and vigorous research program in marine biogeochemistry, heavily invested in undergraduate research education, with impacts that will outlast its five-year duration.The overarching research goal of this project is to assess the contribution of sulfurization reactions to organic carbon preservation in anoxic environments. After constructing and testing a set of customized particle traps, an expedition will be conducted to the marine anoxic zone off the coast of Mexico. Sinking particles, suspended materials, and surface sediments will be collected at three sites on the Mexican shelf and slope, that have generally high local productivity and gradients in bottom-water oxygen concentration. In the field, the rates and isotopic fractionation of microbial sulfate reduction and organic sulfur formation will be measured with stable and radioactive isotope tracers. Subsequently, organic sulfur sources from both natural samples and laboratory experiments will be characterized using mass spectrometry, X-ray absorption spectroscopy, and other geochemical techniques. Together, the results of this work will identify the timing and location of organic matter sulfurization in this environment, which have substantial implications for both modeling marine carbon fluxes and interpreting the geologic record. This study will provide the first quantitative estimates of the scale of organic matter sulfurization in anoxic marine zones, its contribution to sedimentary carbon burial, and its sensitivities to environmental change. Simultaneously, this project will improve the Earth Science undergraduate curriculum at the University of California Santa Barbara through the development of a clear, supportive, and accessible mechanism for including students from diverse backgrounds in research.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.