Collaborative research: Using individual amino acids N isotopes in sinking particles and surficial sediments to reconstruct euphotic zone N sources and trophic structure

合作研究：利用下沉颗粒和表层沉积物中的单个氨基酸N同位素重建富光带N源和营养结构

• 批准号: 1829947
• 负责人: Lin Zhang
• 金额: $ 37.51万
• 依托单位: Texas A&M University Corpus Christi
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1829947&HistoricalAwards=false
• 关键词: Collaborative; research; Using; individual; amino

Nitrogen is a limiting nutrient over most of the surface ocean. Fixed nitrogen (N) such as nitrate controls absorption of atmospheric carbon dioxide and production of organic matter by marine plants and algae. Nitrogen availability, use patterns, and biological community structure in the surface ocean help determine the amount of organic matter passed onto higher organisms. Nitrogen availability also controls how much organic matter sinks into deep waters. This project will reconstruct past sources of nitrogen, use patterns, and trophic structures in surface waters of the Gulf of California, equatorial Pacific, and Sargasso Sea. The tool employed by the principal investigators from Texas A&M University in Corpus Christi and University of Massachusetts Dartmouth is nitrogen isotope ratios of individual amino acids. The investigators will measure isotope ratios in sinking particle samples collected by sediment traps such as those used by the Ocean Flux Program in the Sargasso Sea. This study will train graduate students in stable isotope biogeochemistry and oceanography. This project will also provide research funds for students in the McNair program. McNair students come from underrepresented and economically challenged backgrounds to pursue degrees in STEM fields at Texas A&M University Corpus Christi, a Hispanic and Minority Serving Institution. Data from this project will be made available to the public through the Biological and Chemical Oceanography-Data Management Office (www.bco-dmo.org).There is great interest in reconstructing past climate-forced variations in nitrogen sources, their patterns of utilization, and euphotic zone community structure using compound specific N isotope ratios in amino acids liberated from preserved proteinaceous materials in sediments and coral skeletons. However, it has not yet been verified whether 1) the nitrogen isotope ratios of individual amino acids produced in the euphotic zone are transported with fidelity by sinking particles to deep-sea corals and sediments and 2) the nitrogen isotope ratios of individual amino acids liberated from sedimentary organic matter have been altered by diagenesis. Through analysis of sediment trap material collected over time, this project seeks to verify that nitrogen isotope ratios in individual amino acids reflect the 1) overall spatial contrast in N sources, utilization patterns, and trophic structures among the Gulf of California, equatorial Pacific, and Sargasso Sea and 2) temporal variations in nitrogen sources, utilization patterns, and trophic structures within both the Gulf of California and equatorial Pacific due to seasonal upwelling and/or El Nino-Southern Oscillation. This study will also test if the nitrogen isotope ratios of total hydrolysable amino acids in sedimentary organic matter from the three locations retain the unaltered nitrogen isotope patterns carried by sinking particles. This project will, for the first time, compare nitrogen stable isotope ratios in amino acids collected from sediment trap samples with surficial sediments from deep-sea oxic sites to verify whether total hydrolysable amino acids in deep-sea sediments preserve unaltered nitrogen isotope signals produced in overlying euphotic zone, which can provide insights on addressing diagenetic alteration of bulk N isotope ratios that have hindered paleo-nitrogen cycle reconstruction.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.

氮是大部分表层海洋的限制性营养物质。固定氮（N）如硝酸盐控制着海洋植物和藻类对大气二氧化碳的吸收和有机物的产生。表层海洋中氮的可用性、使用模式和生物群落结构有助于确定传递给高等生物的有机物的量。氮的可用性还控制着有多少有机物沉入深水中。该项目将重建加利福尼亚湾、赤道太平洋和马尾藻海表层水域过去的氮源、使用模式和营养结构。德克萨斯农工大学科珀斯克里斯蒂分校和马萨诸塞大学达特茅斯分校的主要研究人员使用的工具是单个氨基酸的氮同位素比率。研究人员将测量通过沉积物捕集器收集的下沉颗粒样本中的同位素比率，例如马尾藻海海洋通量计划使用的沉积物捕集器。这项研究将培训稳定同位素生物地球化学和海洋学方面的研究生。该项目还将为麦克奈尔项目的学生提供研究经费。麦克奈尔的学生来自代表性不足且经济困难的背景，在德克萨斯农工大学科珀斯克里斯蒂分校攻读 STEM 领域的学位，这是一所西班牙裔和少数族裔服务机构。该项目的数据将通过生物和化学海洋学数据管理办公室（www.bco-dmo.org）向公众提供。人们对利用从沉积物和珊瑚骨骼中保存的蛋白质材料中释放的氨基酸中的复合特定氮同位素比率来重建过去气候造成的氮源变化、氮源利用模式和亮光区群落结构非常感兴趣。然而，尚未证实：1）在真光带中产生的单个氨基酸的氮同位素比是否通过下沉颗粒保真地输送到深海珊瑚和沉积物；2）从沉积有机质中释放的单个氨基酸的氮同位素比是否已被成岩作用改变。通过对一段时间内收集的沉积物捕集材料进行分析，该项目旨在验证单个氨基酸中的氮同位素比率反映了 1) 加利福尼亚湾、赤道太平洋和马尾藻海之间氮源、利用模式和营养结构的整体空间对比，以及 2) 海湾内氮源、利用模式和营养结构的时间变化 由于季节性上升流和/或厄尔尼诺-南方涛动，加利福尼亚州和赤道太平洋地区发生了变化。这项研究还将测试三个地点沉积有机质中总可水解氨基酸的氮同位素比率是否保留下沉颗粒携带的未改变的氮同位素模式。该项目将首次将从沉积物陷阱样品中收集的氨基酸中的氮稳定同位素比率与深海含氧地点的表层沉积物进行比较，以验证深海沉积物中的总可水解氨基酸是否保留了上覆富光带产生的未改变的氮同位素信号，这可以为解决大量氮同位素的成岩变化提供见解。 该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。