Collaborative Research: Isotopic Indicators for Mechanisms of Organic Matter Degradation in the Northeast Pacific (EXPORTS)

生物泵在很大程度上负责有机碳从表面到海洋内部的垂直运输。然而，只有一小部分表层沃茨中产生的有机物质被封存在深海中。其余的被细菌和更大的有机体消耗或呼吸。拟议工作的总体目标是表征细菌与较大生物体对有机材料随深度降解的相对影响。在亚热带太平洋最近结果的指导下，研究人员将使用不同氨基酸中氮的稳定同位素的测量结果（氨基酸的化合物特异性同位素分析，称为AA-CSIA），沿着不同形式氨基酸丰度的测量，以及从这些分析中得出的其他参数，以确定大小颗粒的分配和通量如何受到不同的降解过程。通过提高AA-CSIA技术的解释能力，研究人员建议确定：1）微生物和浮游动物消耗对亚北极东北太平洋生物碳泵效率的相对重要性，以及2）微生物改变的小颗粒为中层浮游动物的代谢提供了多少燃料。这项工作利用了现有的综合实地项目（NASA EXPORTS），专门致力于建立一个将海洋表面特性与有机碳垂直通量联系起来的预测框架。作为EXPORTS计划的一部分，将收集关于生物泵各个方面的大量数据，这将有助于研究人员开发和解释氨基酸同位素工具。将通过制作和分发几集“海洋之声”节目广泛宣传成果，这是一个地方电视节目，将在夏威夷和许多太平洋岛屿播出。埃普雷蒂安还将在网上发布，并通过社交媒体向南佛罗里达社区宣传。该项目将支持博士学位。一名是迈阿密大学的学生，一名是本科生，该大学为25%的西班牙裔人口提供服务。一名学生和一名本科生在夏威夷大学，这是一个指定的少数民族服务机构。拟议的工作介绍了一个新的地球化学框架，以区分微生物与浮游动物的海洋有机质的变化。从亚热带太平洋的样本进行试点，这种方法直接询问未经修改的下沉材料，使用氨基酸化合物特异性同位素分析（AA-CSIA），以确定微生物和浮游动物降解途径的渐进，累积的影响。拟议的工作（1）将扩展这一解释框架，以明确定义端元签名，如粪便颗粒，并将这一改进的方法应用于亚北极东北太平洋的一个研究地点，以（2）确定海洋学位置的降解机制的垂直进展，对比生产力和通量衰减的垂直长度尺度，（3）确定微生物是否-降解的生物质对于在对比碳通量条件下为中层水后生动物提供燃料是重要的。拟议的工作将在海洋站Papa时间序列站点与NASA EXPORTS计划合作进行。与该计划合作提供了一个独特的机会，可以在完善AA-CSIA解释的同时，进行密集的数据收集，以确定生产率，粒度分布和通量以及众多生物参数。在比较亚热带和亚北极太平洋地区，拟议的工作将测试生产力和浮游生物群落结构的差异如何影响微生物和浮游动物从表层到中层深度的消费和改变植物碎屑的垂直模式。该奖项反映了NSF的法定使命，并被认为值得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来支持。

The biological pump is largely responsible for the vertical transport of organic carbon from the surface to the ocean interior. However, only a small fraction of organic material produced in surface waters is sequestered in the deep ocean. The rest is consumed, or respired, by bacteria and larger organisms. The overarching goal of the proposed work is to characterize the relative influences of bacteria versus larger organisms on the degradation of organic material with depth. Guided by recent results from the subtropical Pacific, the investigators will use measurements of stable isotopes of nitrogen in different amino acids (compound-specific isotopic analysis of amino acids, known as AA-CSIA), along with measurements of the abundances of different forms of amino acids, and other parameters derived from these analyses to identify how the partitioning and flux of large and small particles are affected by different degradation processes. By improving the interpretive power of the AA-CSIA technique the investigators propose to determine: 1) the relative importance of microbial and zooplankton consumption on the efficiency of the biological carbon pump in the subarctic northeast Pacific, and 2) how much microbially-altered small particles fuel the metabolisms of mid-water zooplankton. This work capitalizes on an existing, comprehensive field program (NASA EXPORTS) specifically focused on building a predictive framework relating surface ocean properties to the vertical flux of organic carbon. The tremendous amount of data to be collected on all aspects of the biological pump as part of the EXPORTS program will aid the development and interpretation of the investigators' amino acid isotopic tool. Results will be broadly communicated via production and distribution of several episodes of Voice of the Sea, a local television program that will air in Hawaii and across many Pacific islands. Episodes also will be posted online and publicized through social media to the south Florida community. This project will support a Ph.D. student and an undergraduate student at University of Miami, which serves a 25% Hispanic population, and an M.S. student and an undergraduate student at University of Hawaii, which is a designated minority-serving institution.The proposed work introduces a new geochemical framework to distinguish microbial versus zooplankton alteration of marine organic matter. Piloted on samples from the subtropical Pacific, this approach interrogates unamended sinking material directly, using amino acid compound-specific isotopic analysis (AA-CSIA) to determine the progressive, cumulative impact of microbial and zooplankton degradative pathways. The proposed work (1) will extend this interpretive framework to explicitly define end-member signatures such as fecal pellets and will apply this refined method to a study site in the subarctic northeast Pacific to (2) determine the vertical progression of degradative mechanisms in an oceanographic location with contrasting productivity and vertical length scales of flux attenuation and (3) determine whether microbially- degraded biomass is important for fueling midwater metazoans under contrasting carbon flux conditions. The proposed work will be conducted in collaboration with the NASA EXPORTS program at the Ocean Station Papa time-series site. Teaming with this program presents a unique opportunity to refine AA-CSIA interpretation in parallel with intensive data collection defining productivity, particle size distribution and flux, and numerous biological parameters. In comparing subtropical and subarctic Pacific locations, the proposed work will test how differences in productivity and plankton community structure influence vertical patterns of consumption and alteration of phytodetritus by microbes and zooplankton, from surface to mesopelagic depths.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.