Nitrogen isotopic (d15N) composition of carbonate-bound organic nitrogen in Deep Sea Corals: A new, high resolution proxy for N cycle studies

深海珊瑚碳酸盐结合有机氮的氮同位素 (d15N) 组成：氮循环研究的新高分辨率代理

• 批准号: 1234664
• 负责人: Maria Prokopenko
• 金额: $ 35.57万
• 依托单位: Pomona College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1234664&HistoricalAwards=false
• 关键词: Nitrogen; isotopic; d15N; composition; carbonate

The history of the nitrogen (N) cycle provides insight into the links between past climate and marine biogeochemical cycles. Interpretations of the history of the N cycle rely on the nitrogen isotopic composition (del15N) of Particulate Organic Nitrogen (del15N-PON) preserved in sedimentary "archives" such as: bulk organic nitrogen (ON) buried under suboxic/anoxic conditions in rapidly accumulating, organic-rich sediments; skeletal-bound ON in diatom frustules and foraminiferal tests, and organic skeletons of deep-sea proteinaceous corals. As is often is the case with paleo-proxies, these archives have distinct advantages and limitations, the latter including the restricted geographic occurrence of suboxic/anoxic sediments, limited temporal resolution due to bioturbation of sediments containing diatoms and foraminifera, and the limited time span for survival of the soft tissues of corals. Therefore, a multi-proxy approach is highly desirable for better understanding the patterns and causes of N cycle variability in the past. To improve upon the geographic and temporal resolution of del15N paleo-records, a scientist from Pomona College, collaborating with research groups from Claremont-McKenna College and Princeton University, will evaluate a new proxy for the history of the marine N cycle-- del15N of ON bound within the mineral lattice of deep-sea corals. Deep-sea corals can record both short-term regional and longer-term global variability in the N cycle. These organisms grow slowly, can be dated with a precision of 100 years, and have broad geographic distribution. Moreover, as demonstrated by previous research, the ON bound within the carbonate lattice is protected from diagenetic alteration. By analyzing coral specimens from disparate oceanographic environments, each chosen to represent a distinct del15N signature of PON exported from the euphotic zone, the researchers will determine whether the del15N of coral-bound ON reflects N isotopic composition of PON exported from the surface ocean. Furthermore, time-resolved records of del15N of coral-bound ON will be generated in fossil scleractinian deep-sea corals of established ages and compared to published del15N records based on more traditional proxies on decadal to millennial time scales. Much uncertainty currently exists as to which of the pools of exported PON (suspended vs. sinking) is the main food source for deep-sea corals. This issue will be addressed by comparing the del15N of modern corals from variable depths to the del15N of both suspended and sinking PON pools collected during several one-day cruises to San Pedro basin, one of the California Borderland basins.Funding for this project will support two early career female scientists and several undergraduate student research assistants from Pomona College and the new Climate Science lab in the Keck Science Department (including Claremont McKenna, Scripps, and Pitzer Colleges). Students will have an opportunity to participate in short research cruises to the San Pedro basin, to be trained in advanced analytical techniques, and present research at conferences. The results of this study will be used as topics for senior theses and independent study projects, extending the educational experience by exposing undergraduate students to both practical and intellectual aspects of climate-focused research.

氮（N）周期的历史提供了对过去气候与海洋生物地球化学周期之间联系的见解。 N周期病史的解释依赖于保留在沉积“档案”中的颗粒有机氮（DEL15N-PON）的氮同位素组成（DEL15N），例如：散装在亚油/缺氧条件下的散装有机氮（ON），在快速积累的有机有机物，有机富含有机物，富含有机含量的含量下；在硅藻瓣和有孔虫测试中骨骼结合，以及深透蛋白蛋白质珊瑚的有机骨骼。古老的档案经常是这种情况，这些档案具有明显的优势和局限性，后者包括地理上的地理/缺氧沉积物的地理限制，由于含有硅藻的沉积物的生物扰动而导致的时间分辨率有限，以及含有有孔虫的沉积物以及核心软组织生存时间的有限时间。 因此，高度需要多种方法的方法，以更好地理解过去N周期变异性的模式和原因。为了改善波莫纳学院的科学家Del15N古唱片的地理和时间分辨率，与Claremont-Mckenna学院和普林斯顿大学的研究小组合作，将评估海洋N周期历史的新代理 - DEL15N的Del15n的深层矿物质矿物质核心矿物质的矿物质。深海珊瑚可以在N周期记录短期区域和长期全球变异性。这些生物的生长缓慢，可以用100年的精度进行日期，并且具有广泛的地理分布。此外，正如先前研究所证明的那样，碳酸盐晶格内的ON绑定受到了成岩化的影响。通过分析来自不同海洋学环境的珊瑚标本，每个都选择代表从舒适区导出的独特的DEL15N特征，研究人员将确定珊瑚束缚的DEL15N是否反映了从表面海洋中导出的N同位素组成的N同位素组成。此外，将在化石巩膜的深海珊瑚中产生的珊瑚与珊瑚的DEL15N的时间分辨记录将产生，并将其与已发表的Del15N记录相比，基于更传统的DEL15N记录，基于对十分decadal到千年时间量表的更传统的代理。目前存在许多不确定性，即出口pon的哪个池（悬浮与沉没）是深海珊瑚的主要食物来源。该问题将通过将现代珊瑚的Del15n从可变深度与DEL15N进行比较，以悬挂和下沉的pon池的DEL15N与加利福尼亚州居住地盆地之一的San Pedro Basin收集的暂停和下沉的pon池。 McKenna，Scripps和Pitzer学院）。学生将有机会参加前往圣佩德罗盆地的简短研究巡游，接受高级分析技术的培训，并在会议上进行研究。这项研究的结果将用作高级论文和独立研究项目的主题，通过使本科生接触到以气候为中心的研究的实践和智力方面来扩展教育经验。