CAREER: Organic Matter Cycling in the Upper Ocean: Insights from time-series measurements of d15N and D14C in the California Current System

海洋溶解有机质(DOM)储集层通常被认为是碳的“电容器”，因为它具有储存和与其他活跃储集层交换的潜力。然而，尽管DOM的规模和潜在重要性尚未得到充分评估，因此这个储存库在全球和海洋碳和氮循环中的最终作用仍有待确定。为了解决复杂的DOM储集层的动力学问题，加州大学圣地亚哥分校的一位年轻的研究人员将开发DOM组分特定d15N和D14C测量的空间分辨时间序列。这一时间序列将被放在加州当前系统中，该系统在各种时间尺度上经历物理/气候变化(例如，季节、年际、年代际)。与气候有关的扰动(加深/变浅温跃层或北温线，风场的变化)预计将导致地表无机溶解的二氧化碳和NO3-水池的同位素组成出现可测量的漂移。这些漂移最终是由最近在地表水中产生的有机物质组分记录的；当被置于时间序列的背景下时，组分特定的同位素变异性将首次直接确定DOM在年度到数十年的时间尺度上的循环。此外，时间序列还将有助于确定地表水中耐火和年轻DOM组分的相对比例，并勾勒出控制DOM水库大小和年龄的一些物理和生物过程。作为这一职业奖项的一部分，将开设一门新的、以探究为基础的本科课程，将气候-海洋-大气等大尺度现象与海洋物理-化学-生物学等小尺度现象之间的理论耦合置于具体的、特定地区的现实世界框架内。这门课程的一个基本目标是让学生亲身体验科学是如何“工作”的；学生将设计使用存档的时间序列数据来探索上述联系的课堂项目，并在4-7天的加州现代系统教育邮轮上收集海洋数据。在更广泛的影响中，这项研究将是关于气候和生物地球化学之间相互关系的最全面、最长期的研究之一。该区域正在进行的大型科学计划的基础设施将提供背景，并通过基于网络的工具以及书面和口头交流，加强将收集的科学数据作为该提案的一部分向广大受众传播。通过教育和外联计划的四个具体目标，PI将教授和指导约100名本科生，指导~8名高中生，使两个学生群体成为更关键、更好的环境决策者，为~8名教育工作者提供宝贵的科学经验，以便带回自己的课堂，从而接触到更多的学生，并为约100,000名公民提供一个宝贵的窗口，了解他们自家后院的海洋生态系统。此外，将成为目标的高中生代表了圣地亚哥县一些最缺乏服务的年轻人。

The marine dissolved organic matter (DOM) reservoir is often conceptualized as a "capacitor" for carbon because of its potential for storage and exchange with the other active reservoirs. Yet, despite its size and potential importance, the dynamics of DOM have not been fully assessed, and therefore the ultimate role of this reservoir for the global and marine carbon and nitrogen cycle remains to be established. To resolve the dynamics of the complex DOM reservoir, a young investigator from the University of California San Diego will develop a spatially resolved time-series of fraction-specific d15N and D14C measurements of DOM. This time series will be placed within the California Current System which experiences physical/climate variability on a variety of timescales (e.g. seasonal, interannual, decadal). The climate-associated disturbances (deepening/shoaling thermocline or nutricline, changes in wind field) are expected to lead to measurable excursions in the isotopic composition of surface inorganic dissolved CO2 and NO3-pools. These excursions are ultimately recorded by organic matter fractions that are recently produced in surface waters; and when placed within the context of a time series, fraction-specific isotopic variability will, for the first time, directly identify DOM cycling on annual to multidecadal timescales. In addition, the time series will also help identify relative proportions of refractory and young DOM components in surface waters and delineate some of the physical and biological processes that control the size and age of the DOM reservoir. As part of this CAREER award, a new, inquiry based, undergraduate course will be created to place the theoretical coupling between large scale phenomena such as climate-ocean-atmosphere and smaller scale phenomena such as ocean physics-chemistry-biology within a tangible, region-specific, real-world framework. A fundamental goal of this course will be for students to learn experientially how science "works"; students will design class projects that use archived time-series data to explore the above connections and collect oceanographic data on a 4-7 day educational cruise to the California Current System. Among the broader impacts, this study will be one of the most comprehensive, long-term investigations of the interrelation between climate and biogeochemistry. The infrastructure of the larger, ongoing scientific programs in the region will provide context, and enhance the dissemination of scientific data collected as part of this proposal to a broad audience through both web-based tools and written and verbal communication. Through the four specific goals of the Education and Outreach plan, the PI will teach and mentor ~100 undergraduates, mentor ~8 high school students, empower both student groups to be more critical, better environmental decision-makers, provide ~8 educators with valuable scientific experience to take back to their own classrooms and so reach even a larger number of students, and also provide ~100,000 citizens with a valuable window into the marine ecosystem in their own backyards. In addition, the high school students that will be targeted represent some of the most under-served youths in San Diego County.