Collaborative Research: Do benthic feedbacks couple sulfur, nitrogen and carbon biogeochemistry during transient deoxygenation?

合作研究：在瞬态脱氧过程中，底栖生物反馈是否耦合硫、氮和碳的生物地球化学？蒂娜·特鲁德和大卫·瓦伦丁这项研究的重点是发生在世界大陆边缘缺氧水域的化学过程。这些过程受到微生物活动的影响，并控制着沉积到这些地区沉积物中的关键元素的命运，包括碳、氮和硫。因此，它们是海洋健康和功能的关键。这项研究的智力价值在于，通过将机器人技术与海底和船上实验室进行的实验相结合，研究这些环境中发生的耦合化学和微生物过程。该项目的更广泛影响将为本科生和研究生提供海上培训和教育机会，其结果将广泛分发给利益相关者和感兴趣的各方。这项研究的结果有望确定和量化与大陆相邻的海洋环境中碳、氮和硫耦合的关键过程的速率。该项目涉及海洋环境变化的一个重要方面（即由于变暖和营养物富集导致氧气减少）及其对化学和生物循环及海洋生态系统的影响。沿大陆边缘的氧最小带的动态及其未来扩展的潜力是重要的，因为它们与全球生物地球化学循环相交，并对海洋生态系统产生深远的影响。然而，瞬态脱氧对海底碳、氮、硫生物地球化学循环的影响尚不明确，是本研究的重点。这项研究将测试一个重要的假设，即脱氧触发了海底消耗硫化氢的细菌垫和产生硫化氢的潜在细菌群落之间的正反馈循环。硫化氢是一种对高等生物有毒的硫物种。根据这一假设，依靠无机氮源进行硫代谢的海底垫的建立，加速了脱氧后最上层沉积物层的氮循环。加速的氮循环允许产生硫化物的细菌向上扩张，这反过来又提供了硫化物的浅层来源作为基质，进一步支持海底垫中的氮循环。本研究的结果将使人们能够理解水柱中的氧动力学与海底生物地球化学过程之间的关系，这些过程将碳、氮和硫的转化联系起来。这项研究的结果有望确定硫和氮循环耦合并在海底受到强正反馈的环境条件，以及它们解耦的条件。这项研究为四名研究生和几名本科生提供了研究和创新分析实验技术的培训。本科生将在两个机构从事研究，其中一个最近被指定为西班牙裔服务机构。大约10名本科生（总共20名）将参加两次拟议的海洋考察，通过一门名为“海洋生物地球化学实地研究”的既定课程。本课程为学生提供了一个机会，让他们在远征之前制定一个独立的研究项目，参与远征，并在海上进行研究项目。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。

Collaborative Research: Do benthic feedbacks couple sulfur, nitrogen and carbon biogeochemistry during transient deoxygenation?Tina Treude and David ValentineThis study focuses on chemical processes that occur in oxygen-limited waters along the world's continental margins. These processes are influenced by the activities of microbes and control the fate of key elements that are deposited to sediments in these areas including carbon, nitrogen and sulfur. As a result, they are key to the health and function of the ocean. The intellectual merit of this research is to study the coupled chemical and microbial processes that occur in these environments by combining robotic technology with experiments that will be conducted at the ocean floor and in the shipboard laboratory. The broader impacts of this project will provide at-sea training and educational opportunities to undergraduate and graduate students and the results will be broadly distributed to stakeholders and interested parties. Results from this research promise to identify and quantify rates for key processes that couple carbon, nitrogen and sulfur in marine environments adjacent to the continents. The project addresses an important aspect of environmental change in the ocean (i.e., decreased oxygen due to warming and nutrient enrichment) and its influence on chemical and biological cycles and ocean ecosystems.The dynamics of oxygen minimum zones along continental margins, and their potential for future expansion, are important because of their intersection with global biogeochemical cycles and because of their far-reaching impacts on ocean ecosystems. However, the impacts of transient deoxygenation on biogeochemical cycles of carbon, nitrogen and sulfur at the sea floor are not well established and are the focus of this study. This study will test the overarching hypothesis that deoxygenation triggers a positive feedback loop between bacterial mats at the sea floor that consume hydrogen sulfide, a sulfur species that can be toxic to higher organisms, and an underlying community of bacteria that produce hydrogen sulfide. By this hypothesis, the establishment of sea floor mats, which depend on inorganic nitrogen sources to run their sulfur metabolism, accelerates nitrogen cycling in the uppermost sediment horizon following deoxygenation. The accelerated nitrogen cycling allows for upward expansion of the sulfide-producing bacteria, which in-turn provide a shallow source of sulfide as substrate to further support nitrogen cycling in the sea floor mat. The results of this study will enable understanding of the relationship between oxygen dynamics in the water column and the biogeochemical processes at the sea floor that link the transformations of carbon, nitrogen and sulfur. The results of this study promise to define the environmental conditions under which the sulfur and nitrogen cycles are coupled and subject to strong positive feedbacks at the seafloor, as well as the conditions under which they are decoupled. This study provides training in research and innovative analytical and experimental techniques to four graduate students and several undergraduates. Undergraduates will be engaged in research at two institutions, one of which has recently been designated as a Hispanic serving institution. Approximately 10 undergraduate students (20 in total) will participate in each of the two proposed oceanographic expeditions, through an established course entitled: Field Studies in Marine Biogeochemistry. This course provides an opportunity for students to develop an independent research project in advance of the expedition, to participate on the expedition, and to conduct research projects while at sea.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.