RAPID: Does dinitrogen fixation occur in oxygen minimum zones?

最近的多条证据表明，氮的固定和反硝化作用在空间上可能比先前提出的更紧密地耦合，并且已经在阿拉伯海的氧气最小区(OMZ)内发现了nifH基因及其表达。在这个OMZ中，同位素证据和氮的过饱和表明，氮的固定是一个重要的过程。然而，尽管有关于阿拉伯海固定氮的位置和大小的地球化学推断，以及该盆地通过反硝化作用从海洋中去除固定氮的重要性，但人们认为OMZ不含有重氮菌(固氮菌)。老道明大学的一组研究人员认为，OMZ可能是活跃的氮气固定地点，在快速反应研究补助金(RAPID)的资助下，他们将参加东热带北太平洋(ETNP)的一次机会巡航，以确定固定氮气是否是这个OMZ内或附近的一个重要过程。他们希望更好地了解相对于OMZ的氮气固定发生在哪里，以及活跃的反硝化区域。与船上的其他海洋氮循环同事合作，他们希望能够同时比较反硝化和固氮的速率，同时还可以检查ETNP OMZ内反硝化和固氮生物的多样性、群落结构和并置情况。随着对反硝化和氮气固定相对于OMZ的分布有了更全面的了解，应该会对OMZ内的N循环有一个更现实的看法。更广泛的影响。这些结果将有助于目前对海洋氮气固定控制的总体理解，以及氮素输入和来自OMZ的损失之间的平衡。有理由认为，该项目将改变我们对海洋N循环的看法，特别是在N投入方面。

Recent and multiple lines of evidence suggest that dinitrogen (N2) fixation and denitrification may be more closely coupled in space than previously suggested and nifH genes and their expression have been identified from within the oxygen minimum zone (OMZ) of the Arabian Sea. In this OMZ, isotopic evidence and N2 supersaturation suggests N2 fixation is a significant process. However, despite the geochemical inferences regarding the location and magnitude of N2 fixation in the Arabian Sea, and the importance of this basin in removing fixed N from the ocean via denitrification, it is thought that OMZs do not harbour diazotrophs (nitrogen fixing bacteria). A team of researchers at Old Dominion University believe that OMZs may be sites of active N2 fixation, and with funding from this Rapid Response Research Grant (RAPID) they will participate in a cruise of opportunity in the Eastern Tropical North Pacific (ETNP) to determine whether N2 fixation is an important process within or adjacent to this OMZ. They expect to achieve a better understanding of where N2 fixation occurs with respect to the OMZ and areas of active denitrification. In collaboration with other marine nitrogen cycle colleagues onboard, they expect to be able to simultaneously compare rates of denitrification and N2 fixation while also examining the diversity, community structure, and juxtaposition of denitrifying and N2 fixing organisms within the ETNP OMZ. Armed with this more comprehensive understanding of the distribution of denitrification and N2 fixation with respect to the OMZ, a more realistic view of the N cycle within should be gained. Broader Impacts. Results will contribute to current understanding of the controls on marine N2 fixation in general, as well as the balance between N inputs and losses from OMZs. IT is reasonable to think that this project will be transformative in shaping our view of the marine N cycle, particularly as regards to N inputs.