Collaborative Research: The Potential Importance of Intracellular Nitrate Cycling in the Nitrogen Cycle in Marine Sediments

合作研究：细胞内硝酸盐循环在海洋沉积物氮循环中的潜在重要性

• 批准号: 2148672
• 负责人: Anne Giblin
• 金额: $ 31.35万
• 依托单位: Marine Biological Laboratory
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-04-01 至 2025-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2148672&HistoricalAwards=false
• 关键词: Collaborative; Research; Potential; Importance; Intracellular

Nitrogen is an essential element for life. Thus, knowledge of the rates and processes that control nitrogen cycling are needed to understand marine ecosystem dynamics. Nitrogen exists in many chemical forms, and the processes that convert one form to another are mostly carried out by bacteria. However, new data suggest that nitrate stored inside the cells of more complex organisms accounts for a major pool of nitrate in marine sediments. This intracellular nitrate has not been adequately measured and integrated into an overall framework of nitrogen cycling. The investigators will address this issue in the proposed research to better understand and revise nitrogen inventories and flows in the oceans. This information can be used to increase understanding of controls on global carbon cycling and climate change feedbacks. One graduate student will be trained in using tools and techniques to solve complex marine systems issues, and three undergraduate researchers will participate in the work. The team will expand the impact of this research by 1) collaborating with the U. Maine Center for Innovation in Teaching and Learning and the Institute for Broadening Participation to produce and distribute educational videos about this research and its implications for the environment; and 2) leading summer workshops to mentor high school teachers to develop ocean sciences curricula in partnership with the Gulf of Maine Institute. Key processes that influence nitrogen cycling in marine sediments are denitrification and anammox, which lead to a net loss of biologically available nitrogen, and dissimilatory nitrate reduction to ammonium (DNRA), which diverts nitrate away from denitrification back into the system. It has traditionally been assumed that these processes are controlled by bacteria lacking intracellular nitrate and driven by porewater nitrate pools. However, more recent data indicates that large intracellular nitrate pools are widespread in marine sediments and that eukaryotic microbes, particularly benthic foraminifera and diatoms, may be responsible for these pools. The team hypothesizes that the size and flux rate of this intracellular nitrate pool needs to be sufficiently accounted for to accurately measure and understand the nitrogen cycle in marine sediments. Intracellular nitrate presents significant methodological and conceptual challenges to current understanding of the marine nitrogen cycle. The investigators propose two objectives: 1) To measure rates of intracellular nitrate cycling and other major nitrogen cycling pathways in marine sediments across a depth gradient from photic subtidal to dark continental shelf sediments in the Gulf of Maine; 2) To further examine controls on intracellular nitrate cycling by conducting physiological experiments on different microbial eukaryotic cells isolated from the proposed study sites to measure their intracellular nitrate pool sizes and cycling rates. They propose a new strategy using nitrogen-15 labeled nitrate spike experiments to measure the role that intracellular nitrate plays in overall rates of nitrogen cycling in marine sediments. Through the proposed work, they aim to develop a model system to understand and integrate intracellular nitrate cycling into the nitrogen cycle in marine sediments more broadly.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.

氮是生命的基本要素。因此，需要了解控制氮循环的速率和过程以了解海洋生态系统动力学。氮都以多种化学形式存在，而将一种形式转换为另一种形式的过程主要由细菌进行。但是，新数据表明，硝酸盐储存在更复杂的生物体内部的细胞内，这是海洋沉积物中主要的硝酸盐池。这种细胞内硝酸盐尚未得到充分测量并整合到氮循环的整体框架中。研究人员将在拟议的研究中解决这个问题，以更好地理解和修改海洋中的氮库存和流动。这些信息可用于增加对全球碳循环和气候变化反馈的控制的理解。一名研究生将接受使用工具和技术来解决复杂的海洋系统问题的培训，三名本科研究人员将参加这项工作。该团队将通过1）与美国缅因州教学创新中心以及扩大参与研究所合作，扩大参与研究所，以制作和分发有关这项研究及其对环境的影响的教育视频； 2）领导夏季讲习班指导高中教师与缅因州湾研究所合作开发海洋科学课程。影响海洋沉积物中氮循环的关键过程是反硝化和甲氧化物，这导致净损失生物学上可用的氮，而异化的硝酸盐将硝酸盐减少到铵（DNRA），从而将硝酸盐从硝酸盐中转移而成。传统上，人们认为这些过程是由缺乏细胞内硝酸盐的细菌控制的，并由孔隙水池驱动。但是，最近的数据表明，大量的细胞内硝酸盐池在海洋沉积物中广泛存在，而真核微生物，尤其是底栖有孔虫和硅藻可能是这些池的原因。该团队假设该细胞内硝酸盐池的大小和通量速率需要充分考虑到准确测量和了解海洋沉积物中的氮循环。细胞内硝酸盐对当前对海洋氮周期的理解提出了重大的方法论和概念挑战。研究人员提出了两个目标：1）测量在缅因州湾的光下至深色大陆架子沉积物的深度梯度的海洋沉积物中的细胞内硝酸盐循环和其他主要氮气循环途径的速率； 2）通过对从提议的研究地点分离的不同微生物真核细胞进行生理实验，进一步检查对细胞内硝酸盐循环的对照，以测量其细胞内硝酸盐池的大小和循环速率。他们提出了一种使用氮-15标记为硝酸盐尖峰实验的新策略，以衡量细胞内硝酸盐在海洋沉积物中氮循环总体速率中发挥的作用。通过拟议的工作，他们旨在开发一个模型系统，以更广泛地理解和整合海洋沉积物中的氮循环到氮周期中。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准来通过评估来通过评估来支持的。