Collaborative Research: New Approaches to New Production

合作研究：新生产的新方法

• 批准号: 1740538
• 负责人: Alyson Santoro
• 金额: $ 10.15万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1740538&HistoricalAwards=false
• 关键词: Collaborative; Research; New; Approaches; Production

Coastal marine ecosystems are seasonally dynamic and highly productive. Phytoplankton populations shift from nutrient replete conditions in the spring to nutrient poor conditions in other seasons. The San Pedro Ocean Time-series (SPOT), located 17 km offshore between Los Angeles Harbor and Catalina Island, is a representative and accessible model coastal system with regular sampling and a substantial archive of relevant observations. The SPOT program has cataloged the dynamics, diversity, and productivity of microbial populations since 2000. With rising carbon dioxide (CO2) concentrations and resulting decreases in surface pH, it is critically important to understand the nutrient controls on primary production in coastal waters and the capacity of coastal ecosystems to sequester CO2. This project will examine rates of primary production, nitrogen uptake associated with primary production, and the oxidation of ammonium to nitrate (nitrification), at SPOT over two seasonal cycles. It will also contribute to the development of human resources in the marine sciences through the training of undergraduate and graduate students at the University of Southern California and the University of Maryland. The researchers participate in education outreach activities (e.g. through the Centers for Ocean Sciences Education Excellence programs), and will incorporate findings from this study in those presentations.This project will investigate primary production and nitrogen (N) dynamics at SPOT and specifically implement an analysis of new production. The new production conceptual model has been a powerful organizing principle in biological oceanography and provides a means to constrain the amount of primary production that may be exported or "sequestered" from the system. Despite qualifications to the definitions of new and regenerated forms of N as originally articulated, the concept has, for the most part, been narrowly applied, specifying nitrate as the primary form of new N, and ammonium as the predominant recycled form. Evidence continues to accumulate that these definitions may warrant expansion. N fixation can be at times a substantial source of new N; similarly, forms of dissolved organic N (e.g., urea) may contribute significantly to recycled production, but the specific organisms taking part in these transformations are still uncertain. Nitrification in the upper water column may also compromise the strict definitions of new and recycled N. Scientists can now probe more deeply into new and regenerated production, and directly identify major agents of these processes using new molecular techniques. This project will quantify new and regenerated production in a coastal ecosystem, illuminating the predominant compounds involved. Rates of primary production, nitrate, ammonium and urea assimilation, N2 fixation, and nitrification will be determined in the upper water column in concert with monthly SPOT cruises. In tandem, two stable isotope probing (SIP) approaches (conventional SIP for nitrate, ammonium and urea uptake coupled to high throughput sequencing and microarray based Chip-SIP for N2 fixation) will be used to directly identify the major agents involved in these processes, along with the uptake of 13C-urea into nitrifier biomass. The following two hypotheses will be tested:1. N2 fixation is a substantial source of new N in coastal waters of Southern California supporting export production. 2. Forms of dissolved organic N, and specifically urea, can be substrates for nitrification and contribute substantially to regenerated production.

沿海海洋生态系统具有季节性动态且生产力高。浮游植物种群从春季营养丰富的条件转变为其他季节营养贫乏的条件。圣佩德罗海洋时间序列 (SPOT) 位于洛杉矶港和卡塔利娜岛之间近海 17 公里处，是一个具有代表性和可访问的沿海系统模型，定期采样并拥有大量相关观测档案。自 2000 年以来，SPOT 计划对微生物种群的动态、多样性和生产力进行了编目。随着二氧化碳 (CO2) 浓度的上升和导致表面 pH 值的下降，了解沿海水域初级生产的营养控制和沿海生态系统封存二氧化碳的能力。 该项目将在两个季节周期的 SPOT 上检查初级生产率、与初级生产相关的氮吸收率以及铵到硝酸盐的氧化（硝化）。它还将通过培训南加州大学和马里兰大学的本科生和研究生，为海洋科学人力资源的开发做出贡献。 研究人员参与教育推广活动（例如通过海洋科学教育卓越计划中心），并将本研究的结果纳入这些演示中。该项目将调查 SPOT 的初级生产和氮 (N) 动态，并具体实施一项分析新生产。新的生产概念模型已成为生物海洋学中强大的组织原则，并提供了一种限制可能从系统中输出或“隔离”的初级生产量的方法。尽管对最初阐明的新氮和再生形式氮的定义有限制，但该概念在很大程度上被狭隘地应用，指定硝酸盐为新氮的主要形式，铵为主要的回收形式。越来越多的证据表明这些定义可能值得扩展。氮固定有时可能是新氮的重要来源；同样，溶解有机氮（例如尿素）的形式可能对回收生产做出重大贡献，但参与这些转化的具体生物体仍然不确定。 上层水体中的硝化作用也可能损害新氮和再生氮的严格定义。科学家现在可以更深入地探讨新氮和再生氮的生产，并使用新的分子技术直接识别这些过程的主要因素。该项目将量化沿海生态系统中的新生产和再生生产，阐明所涉及的主要化合物。初级生产、硝酸盐、铵和尿素同化、N2 固定和硝化的速率将在上层水柱中与每月的 SPOT 巡航相结合来确定。同时，两种稳定同位素探测 (SIP) 方法（用于硝酸盐、铵和尿素吸收的传统 SIP 结合高通量测序和用于 N2 固定的基于微阵列的 Chip-SIP）将用于直接识别参与这些过程的主要试剂，随着硝化菌生物质吸收 13C-尿素。将检验以下两个假设： 1．固氮是南加州沿海水域新氮的重要来源，支持出口生产。 2. 溶解的有机氮，特别是尿素，可以作为硝化作用的底物，对再生生产有很大贡献。