Collaborative Research: Anammox and Denitrification in the Oxygen Deficient Zone of the Arabian Sea

作为世界海洋中包含永久性缺氧区（ODZ）的三个区域之一，阿拉伯海对海洋中固定氮的损失和海洋中氧化亚氮（N2O）向大气的通量的影响比其大小所能预测的要大得多。普遍接受的范式，典型反硝化是负责这两个通量最近受到挑战的发现，厌氧氨氧化（厌氧氨氧化）甚至可能主导反硝化氮气生产。由于这两个过程是由不同的生物进行的，它们的生理机能完全不同，对环境因素的反应也不同，因此有必要准确地确定它们各自的贡献，以便了解和预测N循环的通量。虽然传统的厌氧氨氧化培养表明厌氧氨氧化是ODZ中产生N2的唯一途径，但这与化学计量学限制或观察到的ODZ中亚硝酸盐和N2O的分布不一致，这强烈表明存在反硝化作用。此外，从分子数据得出的群落组成和动态表明，反硝化菌必须发挥重要作用。在这项研究中，来自普林斯顿大学和华盛顿大学的研究人员假设，传统的孵化方法往往会人为地偏向于其中一个过程，因为它们改变了各自限制因素的浓度。为了验证这一假设，他们将研究厌氧氨氧化和反硝化对氧气、铵、亚硝酸盐和有机碳的反应，在不透气的袋子中使用大容量孵育，以获得厌氧氨氧化和反硝化的真实速率的现实估计。这些实验将在阿拉伯海的一次巡航中与印度同事合作进行。这项研究产生更广泛影响的一个重要组成部分是普林斯顿大学和华盛顿大学的研究小组及其在印度的合作者之间的强有力合作。这种合作将提供机会在稳定同位素和分子生态技术方面进行一定数量的技术转让。在普林斯顿大学，该项目将为本科生提供暑期和大四的论文研究机会，并将通过经验和例子转化为本科海洋学课程的课堂教学。这两个机构都支持系级和学院级的教师培训和学生研究外展项目，所有的pi将继续在各自的机构参与这些项目。

OCE-0647981As one of the three regions of the world ocean that contains a permanent Oxygen Deficient Zone (ODZ), the Arabian Sea is disproportionately more important to the loss of fixed N from the ocean and to the oceanic flux of nitrous oxide (N2O) to the atmosphere than its size would predict. The generally accepted paradigm that canonical denitrification is responsible for both of these fluxes has recently been challenged by the finding that anaerobic ammonium oxidation (anammox) may even dominate denitrification for N2 production. Because the two processes are performed by different organisms with completely different physiologies that respond differently to environmental factors, it is necessary to accurately resolve their respective contributions in order to understand and predict fluxes in the N cycle. Although conventional anammox incubations suggest that anammox is the sole pathway of N2 production in the ODZ, this cannot be reconciled with stoichiometric constraints or with observed distributions of nitrite and N2O in the ODZ, which strongly suggest denitrification. Additionally, community composition and dynamics derived from molecular data suggest that denitrifiers must play an important role. In this research, researchers from Princeton and University of Washington hypothesize that the conventional incubation methods tend to artificially favor one or the other process because they alter the concentrations of their respective limiting factors. To test this hypothesis, they will investigate the response of anammox and denitrification to oxygen, ammonium, nitrite and organic carbon using large volume incubations in gas impermeable bags to obtain realistic estimates of the true rates of anammox and denitrification. The experiments will be carried out on a cruise in the Arabian Sea in collaboration with Indian colleagues. An important component of the broader impacts of the research is a strong collaboration between the Princeton and UW groups and their collaborators in India. This cooperation will provide opportunities to engage in a certain amount of technology transfer in stable isotope and molecular ecological techniques. At Princeton, the project will employ and provide summer and senior thesis research opportunities for undergraduates, and will translate into the classroom by experience and example in the undergraduate oceanography curriculum. Both institutions support department and institutional level outreach programs for teacher training and student research, and all the PIs will continue to participate in these at their respective institutions.