Collaborative Research: Chemoautotrophy in Antarctic Bacterioplankton Communities Supported by the Oxidation of Urea-derived Nitrogen

合作研究：尿素氮氧化支持的南极浮游细菌群落的化能自养

• 批准号: 1643345
• 负责人: Brian Popp
• 金额: $ 16.45万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-10-01 至 2020-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1643345&HistoricalAwards=false
• 关键词: Collaborative; Research; Chemoautotrophy; Antarctic; Bacterioplankton

Part 1: Nitrification is the conversion of ammonium to nitrate by a two-step process involving two different guilds of microorganisms: ammonia- and nitrite-oxidizers. The process is central to the global nitrogen cycle, affecting everything from retention of fertilizer on croplands to removal of excess nitrogen from coastal waters before it can cause blooms of harmful algae. It also produces nitrous oxide, an ozone-destroying, greenhouse gas. The energy derived from both steps of nitrification is used to convert inorganic carbon into microbial biomass. The biomass produced contributes to the overall food web production of the Southern Ocean and may be a particularly important subsidy during winter when low light levels restrict the other major source of biomass, primary production by single-celled plants. This project addresses three fundamental questions about the biology and geochemistry of polar oceans, with a focus on the process of nitrification. The first question the project will address concerns the contribution of chemoautotrophy (based on nitrification) to the overall supply of organic carbon to the food web of the Southern Ocean. Previous measurements indicate that it contributes about 9% to the Antarctic food web on an annual basis, but those measurements did not include the additional production associated with nitrite oxidation. The second question to be addressed is related to the first and concerns the coupling between the steps of the process. The third seeks to determine the significance of the contribution of other sources of nitrogen, (specifically organic nitrogen and urea released by other organisms) to nitrification because these contributions may not be assessed by standard protocols. Measurements made by others suggest that urea in particular might be as important as ammonium to nitrification in polar regions.This project will result in training a postdoctoral researcher and provide undergraduate students opportunities to gain hand-on experience with research on microbial geochemistry. The Palmer LTER (PAL) activities have focused largely on the interaction between ocean climate and the marine food web affecting top predators. Relatively little effort has been devoted to studying processes related to the microbial geochemistry of nitrogen cycling as part of the Palmer Long Term Ecological Research (LTER) program, yet these are a major themes at other sites. This work will contribute substantially to understanding an important aspect of nitrogen cycling and bacterioplankton production in the PAL-LTER study area. The team will be working synergistically and be participating fully in the education and outreach efforts of the Palmer LTER, including making highlights of the findings available for posting to their project web site and participating in any special efforts they have in the area of outreach.Part 2: The proposed work will quantify oxidation rates of 15N supplied as ammonium, urea and nitrite, allowing us to estimate the contribution of urea-derived N and complete nitrification (ammonia to nitrate) to chemoautotrophy and bacterioplankton production in Antarctic coastal waters. The project will compare these estimates to direct measurements of the incorporation of 14C into organic matter the dark for an independent estimate of chemoautotrophy. The team aims to collect samples spanning the water column: from surface water (~10 m), winter water (50-100 m) and circumpolar deep water (150 m); on a cruise surveying the continental shelf and slope west of the Antarctic Peninsula in the austral summer of 2018. Other samples will be taken to measure the concentrations of nitrate, nitrite, ammonia and urea, for qPCR analysis of the abundance of relevant microorganisms, and for studies of related processes. The project will rely on collaboration with the existing Palmer LTER to ensure that ancillary data (bacterioplankton abundance and production, chlorophyll, physical and chemical variables) will be available. The synergistic activities of this project along with the LTER activities will provide a unique opportunity to assess chemoautotrophy in context of the overall ecosystem?s dynamics- including both primary and secondary production processes.

第1部分：硝化是通过涉及两个不同的微生物公会的两步过程将铵转化为硝酸盐的转化：氨和亚硝酸盐氧化剂。 该过程对于全球氮周期至关重要，从而影响从农田上的肥料到去除沿海水域过多的氮才能引起有害藻类之前的所有事物。 它还产生一氧化二氮，破坏臭氧的温室气体。 源自两个硝化步骤的能量用于将无机碳转化为微生物生物量。产生的生物质有助于南大洋的整体食品网络生产，在冬季，低光水平限制了另一个主要的生物质来源，单细胞植物的一级生产。 该项目解决了有关极地海洋生物学和地球化学的三个基本问题，重点是硝化过程。 该项目将解决的第一个问题涉及化学杂志（基于硝化）对有机碳对南大洋食品网的总体供应的贡献。 先前的测量表明，它每年对南极食品网的贡献约为9％，但这些测量值不包括与亚硝酸盐氧化相关的额外产生。 要解决的第二个问题与第一个问题有关，并涉及过程步骤之间的耦合。 第三个试图确定其他氮来源（特别是其他生物体释放的有机氮和尿素）对硝化作用的重要性，因为这些贡献可能无法通过标准方案来评估。 其他人进行的测量表明，尿素尤其可能与极地地区的硝化铵一样重要。该项目将导致培训博士后研究人员，并为本科生提供机会获得有关微生物地球化学研究的手段经验。 Palmer lter（PAL）活动主要集中在海洋气候与影响顶级捕食者的海洋食品网之间的相互作用上。作为Palmer长期生态研究（LTER）计划的一部分，研究与氮循环微生物地球化学有关的过程相对较少的努力，但这些过程在其他地点是主要主题。这项工作将有助于理解氮循环和细菌性研究领域的氮气循环和细菌产生的重要方面。 The team will be working synergistically and be participating fully in the education and outreach efforts of the Palmer LTER, including making highlights of the findings available for posting to their project web site and participating in any special efforts they have in the area of​​ outreach.Part 2: The proposed work will quantify oxidation rates of 15N supplied as ammonium, urea and nitrite, allowing us to estimate the contribution of urea-derived N and complete nitrification （硝酸盐氨）到南极沿海水域的化学自由营养和细菌产生。 该项目将将这些估计值与将14C掺入有机物中的黑暗中直接测量，以实现化学自由营养的独立估计。 该团队的目标是收集跨越水柱的样品：从地表水（〜10 m），冬季水（50-100 m）和圆形深水（150 m）；在巡航比赛中，在2018年澳大利亚夏季的南极半岛以西的大陆架和斜坡上。将采用其他样品来测量硝酸盐，亚硝酸盐，氨和尿素的浓度，以qpcr分析相关微生物的丰度，以及相关过程的研究。该项目将依靠与现有的Palmer lter的合作，以确保将提供辅助数据（细菌丰度和生产，叶绿素，物理和化学变量）。该项目的协同活动以及批量活动将提供一个独特的机会，以评估整个生态系统的动力学（包括初级和二级生产过程）的背景下。