Collaborative Research: Control of Denitrification and Anammox in the Oxygen Deficient Waters of the Eastern Tropical North and South Pacific

基本问题仍然对氧氮(N)周期最小区域的相对贡献(OMZ)和脱氮和氨的损失固定N .最近的工作由华盛顿大学的科学家和普林斯顿大学的显示发生厌氧氨氧化和反硝化作用在OMZ的阿拉伯海,表明,反硝化作用主导固定N的去除与报告OMZ南太平洋东部热带(ESTP)。观察到的差异归因于提供给OMZ水域的有机碳的性质和时间。在这个项目中，科学家们建议通过记录反硝化与地表水的有机碳通量有关，而厌氧氨氧化并不直接响应有机碳输入，而是取决于有机物质分解过程中释放的可溶性副产物，如铵和亚硝酸盐的通量，来解释在omz中对反硝化的有限观察。将进行一项包括两次单独巡航的实地计划，一次前往东部热带北太平洋，另一次前往东部热带北太平洋。之所以选择这些位点，是因为ESTP是三种主要的OMZ中研究最多的，而ETNP是体积最大的OMZ，在联合脱氮方面可能在数量上最重要。实现上述目标的实验计划包括：(1)利用广泛的空间覆盖代替高分辨率的时间覆盖，获得反硝化和厌氧氨氧化速率的多个测量值；(2)利用操作实验研究了反硝化和厌氧氨氧化速率对特定扰动（如有机物添加量和瞬态氧扰动）的响应；(3)在培养实验中采用新的示踪测量方法区分反硝化、异化硝态氮还原为铵态氮和厌氧氨氧化；(4)利用DNA/RNA微阵列研究转化速率与反硝化菌组合之间的关系，以解决颗粒在刺激反硝化速率中的作用；(5)在示踪剂孵育过程中，使用高灵敏度氧探针来确定氧的分布并跟踪低水平下的氧动力学。就更广泛的影响而言，华盛顿大学计划在R/V汤普森号上贡献时间，以便本科生可以参加巡航，学习开展海洋学研究所涉及的方法和技术，特别是与本研究有关的方法和技术。作为该项目的一部分，华盛顿大学的一名研究生、普林斯顿大学的一名博士后、一名研究生和一名本科生将得到支持和培训。

Fundamental question remain on how nitrogen (N) cycles in oxygen minimum zones (OMZs) and on the relative contribution of denitrification and anammox to the loss of fixed N. Recent work by scientists at the University of Washington and Princeton University showed the occurrence of anammox and denitrification in the OMZ of the Arabian Sea and indicated that denitrification dominated the fixed N removal in contrast to reports for the OMZ in the Eastern Tropical South Pacific (ESTP). The observed difference was attributed to the nature and timing of organic carbon supplied to the OMZ waters. In this project, the scientists propose to explain the limited observations of denitrifications in the OMZs by documenting that denitrification is linked to the flux of organic carbon from surface waters whereas anammox does not respond directly to organic C inputs but depends on the flux of soluble byproducts such as ammonium and nitrite released during the breakdown of organic matter. A field program involving two separate cruises, one to the ETSP and one to the Eastern Tropical North Pacific (ETNP) will be carried. These sites were selected because the ESTP is the most studied of the three major OMZs whereas the ETNP is the largest OMZ by volume and may be quantitatively the most important in terms of combined nitrogen removal. The experimental plan to attain their goals include the following: (1) use extensive spatial coverage as a substitute for high resolution temporal coverage to obtain many measurements of denitrification and anammox rates; (2) use manipulation experiments to investigate the response of denitrification and anammox rates to specific perturbations such as organic matter additions and transient oxygen perturbation; (3) use new tracer measurements to distinguish denitrification, dissimilatory nitrate reduction to ammonium and anammox in incubation experiments; (4) use DNA/RNA microarrays to investigate relationships between transformation rates and the denitrifier assemblage to resolve the role of particles in stimulation of denitrification rates; and (5) use high sensitivity oxygen probes to define the oxygen distribution and to follow oxygen dynamics at low levels in tracer incubation. In terms of the broader impacts, the University of Washington plans to contribute time on the R/V Thompson so that undergraduate students can participate in a cruise and learn about the methods and techniques involved in carrying out oceanographic research, especially those related to this study. One graduate student from the University of Washington and one postdoc, one graduate student and one undergraduate student from Princeton University would be supported and trained as part of this project.