Dimensions: Diversity, assembly and function of microbial communities on suspended and sinking particles in a marine Oxygen Deficient Zone

海洋缺氧区（ODZs）是指功能上缺氧的水域。在没有氧气的情况下，一些微生物能够将水中的氮转化为氮气，然后氮气离开海洋进入大气。海洋中一种重要营养物质的流失对浮游植物的生长和海洋食物网产生了影响。虽然缺氧区只占海洋的很小一部分，但它们占海洋中N和N2损失的一半之多。此外，由于气候变化，预计这些地区的规模将在本世纪扩大。能够产生氮气的微生物种类繁多，并使用几种不同的生化途径来完成这一过程。它们既可以自由漂浮在水中，也可以附着在从地表水中悬浮或下沉的小颗粒上，为它们提供碳源。然而，就海洋氮流失的贡献而言，这两种生活方式（自由生活与颗粒附着）的重要性尚未得到很好的理解。该项目将确定在悬浮颗粒和下沉颗粒上产生N2气的主要生物，它们进行的化学反应，以及这种反应发生的速度。这些信息将用于改进全球气候模型，以更好地预测未来海洋中氮的损失率。参加科学教师硕士项目的中小学教师将参与该项目，该项目支持的研究生和博士后研究人员将有机会参与他们的课堂。通过一系列暑期实习，服务不足的人群也将纳入本科和中学水平的研究。odz具有非常复杂的元素循环，这意味着微生物多样性很大。与ODZ区域的微生物复杂性交织在一起的是自由生活的细菌和生活在悬浮或下沉颗粒上的细菌之间相对未被探索的相互作用。确定这些社区和生态位如何相互作用和联系是当今ODZ系统研究中最具挑战性的组成部分之一。目前的气候模式通过规定的函数来描绘臭氧臭氧区和整个深海中的颗粒动力学，这些函数基于来自含氧海洋的稀疏数据，微生物仅由群落的净化学反应来表示。然而，在现实中，一个系统发育和代谢多样化的微生物群，可能在联合体中起作用，负责氮转化，最终导致N2的产生。为探索N损失过程中遗传多样性和功能冗余的维持过程，将整合四个研究领域：群落系统发育多样性（分类学和基因组多样性）、执行关键氮转化过程的蛋白质的遗传多样性（通过定量蛋白质组学观察）、由此产生的生物地球化学功能（15N标记氮转化速率测量）以及对这种多样性和相应功能如何响应气候变化的预测（生物地球化学模型）。该方法将分析系统发育（16S rRNA标签测序）和功能遗传多样性（基因组学）对大容量沉淀池收集的下沉颗粒。系统发育和基因组学研究将与活性测量密切相关——谁在进行关键的生物地球化学转化（蛋白质组学），以及他们进行这些转化的原位速率是多少（使用新的孵化系统）。然后，数据将用于模拟多样性和相应的功能如何在时间和空间尺度范围内变化，从单个粒子的下沉到季节周期。为了了解悬浮粒子和下沉粒子对群落多样性和功能的影响，将在东热带北太平洋ODZ进行一系列的三次巡航。

Marine oxygen deficient zones (ODZs) are waters that are functionally devoid of oxygen. Without oxygen, some microbes are capable of converting nitrogen in the water into N2 gas, which then leaves the ocean and enters the atmosphere. This loss of an important nutrient from the ocean has impacts on phytoplankton growth and marine food webs. While oxygen deficient zones occupy a very small percentage of the ocean, they account for as much as half of the oceanic loss of N as N2. Moreover, the size of these regions is predicted to expand during this century due to climate change. The microbes that are capable of producing N2 gas are extremely diverse, and use several different biochemical pathways to carry out this process. They may occur both free-floating in the water and attached to small particles that are suspended or sinking from the surface waters and providing them a carbon source. However the importance of these two lifestyles (free-living vs particle attached) in terms of contributions to N loss from the oceans is not well understood. This project will identify the major organisms that result in N2 gas production on both suspended and sinking particles, the chemical reactions they carry out, and the rates at which this occurs. This information will be used to improve global climate models to better predict rates of N loss in a future ocean. Elementary and middle school teachers enrolled in a Masters in Science for Science Teachers program will be involved in the project and the graduate students and post-doctoral researchers supported by the project will have opportunities to participate in their classrooms. Underserved populations will also be integrated into the research at the undergraduate and middle school level through a series of summer internships.ODZs have very complex elemental cycles, implying great microbial diversity. Intertwined with the microbial complexity of ODZ regions is the relatively unexplored interplay between free-living bacteria and those living on either suspended or sinking particles. Determining how these communities and niches interact and relate is one of the most challenging components of ODZ system studies today. Current climate models portray the dynamics of particles in the ODZs and throughout the deep ocean through prescribed functions based on sparse data from the oxic ocean with microbes represented only by the net chemical reactions of the community. However, in reality a phylogenetically and metabolically diverse group of microbes, likely acting in consortia, are responsible for the nitrogen transformations that ultimately result in the production of N2. To explore the processes maintaining the genetic diversity and functional redundancy in N loss processes, four research areas will be integrated: the community phylogenetic diversity (both taxonomic and genomic diversity) the genetic diversity of the proteins that carry out key N transformation processes (as seen through quantitative proteomics), the resulting biogeochemical functions (15N labeled nitrogen transformation rate measurements) and predictions about how this diversity and corresponding function may change in response to climate change (biogeochemical modeling). The approach will be to assay both phylogenetic (16S rRNA tag sequencing) and functional genetic diversity (genomics) on sinking particles collected using large-volume sediment traps. Phylogenetic and genomic studies will be intimately tied to measurements of activity - who is doing key biogeochemical transformations (proteomics) and what are the in situ rates at which they are doing them (using novel incubation systems). Data will then be used to model how diversity and corresponding function change on a range of time and space scales, from the sinking of a single particle to seasonal cycles. To understand the relationship of community diversity and function on suspended and sinking particles, a series of three cruises will be conducted in the Eastern Tropical North Pacific ODZ.