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

作为世界海洋中三个拥有永久性缺氧区(ODZ)的区域之一，阿拉伯海对海洋中固定氮的损失和海洋向大气中一氧化二氮(N2O)的通量的影响比其大小所预测的要大得多。最近，人们普遍接受的典型反硝化作用对这两种通量的影响受到了挑战，因为发现厌氧氨氧化(Anammox)甚至可能主导反硝化作用产生氮气。由于这两个过程是由不同的生物体执行的，它们具有完全不同的生理特征，对环境因素的响应也不同，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循环中的通量。虽然常规的Anammox培养表明Anammox是ODZ中产生氮气的唯一途径，但这与化学计量限制或观察到的ODZ中亚硝酸盐和N2O的分布不一致，后者强烈表明反硝化作用。此外，根据分子数据得出的群落组成和动态表明，反硝化细菌必须发挥重要作用。在这项研究中，普林斯顿大学和华盛顿大学的研究人员假设，传统的孵化方法倾向于人为地偏向其中一个过程，因为它们改变了各自限制因素的浓度。为了验证这一假设，他们将使用气体不透气袋中的大量培养来调查厌氧氨氧化和反硝化对氧气、氨氮、亚硝酸盐和有机碳的响应，以获得对厌氨氧化和反硝化真实速率的真实估计。这些实验将在阿拉伯海的一艘邮轮上与印度同事合作进行。这项研究的更广泛影响的一个重要组成部分是普林斯顿大学和威斯康星大学的团队及其在印度的合作者之间的强有力的合作。这一合作将提供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的机会。在普林斯顿，该项目将雇用并为本科生提供暑期和高级论文研究机会，并将在本科生海洋学课程中通过经验和范例转化为课堂。这两个机构都支持部门和机构一级的教师培训和学生研究外展方案，所有的私人投资机构都将继续在各自的机构参加这些方案。

OCE-0648026As 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.