Collaborative Research: Environmental Drivers of Chemoautotrophic Carbon Production at Deep-Sea Hydrothermal Vents - Comparative Roles of Oxygen and Nitrate

合作研究：深海热液喷口化学自养碳生产的环境驱动因素 - 氧气和硝酸盐的比较作用

• 批准号: 1559042
• 负责人: Jeremy Rich
• 金额: $ 20.74万
• 依托单位: University of Maine
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-05-01 至 2020-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1559042&HistoricalAwards=false
• 关键词: Collaborative; Research; Environmental; Drivers; Chemoautotrophic

Deep-sea hydrothermal vents, first discovered in 1977, are exemplary ecosystems where microbial chemosynthesis rather than photosynthesis is the primary source of organic carbon. Chemosynthetic microorganisms use the energy generated by oxidizing reduced inorganic chemicals contained in the vent fluids, like hydrogen sulfide or hydrogen gas, to convert carbon dioxide (CO2) into cell material. By doing so, they effectively transfer the energy from a geothermal source to higher trophic levels, in the process supporting the unique and fascinating ecosystems that are characterized by high productivity - oases in the otherwise barren deep ocean landscape. While the general view of the functioning of these ecosystems is established, there are still major gaps in our understanding of the microbiology and biogeochemistry of these systems. Particularly lacking are studies measuring rates of microbial activity in situ, which is ultimately needed to understand production of these ecosystems and to assess their impact on global biogeochemical cycles. This project makes use of the Vent-Submersible Incubation Device (Vent-SID), a robotic micro-laboratory that was recently developed and tested in the field. This instrument makes it possible for the first time to determine rates of carbon fixation at both in situ pressures and temperatures, revolutionizing the way we conduct microbial biogeochemical investigations at deep-sea hydrothermal vents. This is an interdisciplinary and collaborative effort between two US and foreign institutions, creating unique opportunities for networking and to foster international collaborations. This will also benefit two graduate students working in the project, who will get exposed to a wide range of instrumentation and scientific fields, facilitating their interdisciplinary education. In collaboration with Dr. Nitzan Resnick, academic dean of The Sage School, an elementary school outreach program will be developed and a long-term partnership with the school established. Further, a cruise blog site to disseminate the research to schools and the broader public will be set up. The results will be the topic of media coverage as well as be integrated into coursework and webpages existing either in the PI's labs or at the institution.This project is using a recently developed robotic micro-laboratory, the Vent-SID, to measure rates of chemoautotrophic production and to determine the relative importance of oxygen and nitrate in driving chemosynthesis at deep-sea hydrothermal vents at in situ pressures and temperatures and to tackle the following currently unresolved science objectives: 1) obtain in situ rates of chemoautotrophic carbon fixation, 2) obtain in situ nitrate reduction rate measurements, and 3) directly correlate the measurement of these processes with the expression of key genes involved in carbon and energy metabolism. Although recent data suggests that nitrate reduction either to N2 (denitrification) or to NH4+ (dissimilatory reduction of nitrate to ammonium) might be responsible for a significant fraction of chemoautotrophic production, NO3-reduction rates have never been measured in situ at hydrothermal vents. The researchers hypothesize that chemoautrophic growth is strongly coupled to nitrate respiration in vent microbial communities. During a cruise that will take place approximately 12 months into the project (~Feb 2017), the researchers will carry out a total of 4 deployments of the Vent-SID as well as ancillary sampling collection at the 9°46N to 9°53N segment of the East Pacific Rise. They will focus efforts on two diffuse-flow vent sites, "Crab Spa" and "Teddy Bear". "Crab Spa" is a diffuse flow vent site (T: 25°C) that has been used as a model system to gain insights into chemoautotrophic processes and has been frequently sampled over the last several years. This vent site has been very well characterized, both geochemically and microbiologically, providing excellent background data for the proposed process oriented studies. "Teddy Bear" is a diffuse-flow site that was discovered in Jan 2014, and it has a lower temperature (T: 12°C), making it a good comparative site. The researchers will perform a number of short duration time-course incubations to assess the role of different environmental parameters that have been identified as likely key variables (e.g., O2, temperature, NO3-), and to link these process rate measurements to the expression of functional genes using metatranscriptomic analyses. This study will be the first attempt to measure critical metabolic processes of hydrothermal vent microbial assemblages under critical in situ conditions and to assess the quantitative importance of electron donor and acceptor pathways in situ. In the future, it is envisioned that the Vent-SID will become a routine application by the oceanographic community for measuring time series rates of relevant metabolic processes at hydrothermal vents under in situ pressures and vent fluid temperatures.

1977年首次发现的深海热液喷口是典型的生态系统，其中微生物化学合成而不是光合作用是有机碳的主要来源。化学合成微生物利用通过氧化排出流体中所含的还原无机化学物质（如硫化氢或氢气）产生的能量将二氧化碳（CO2）转化为细胞材料。通过这样做，它们有效地将能量从地热源转移到更高的营养水平，在此过程中支持独特而迷人的生态系统，其特点是高生产力-否则贫瘠的深海景观中的绿洲。虽然这些生态系统的功能的一般观点是建立，仍然存在重大差距，我们的理解这些系统的微生物学和地球化学。特别缺乏的是原位测量微生物活动率的研究，这是最终需要了解这些生态系统的生产和评估其对全球生物地球化学循环的影响。该项目使用了Vent-SID（Vent-Submersible Incubation Device），这是一个最近开发并在现场测试的机器人微型实验室。该仪器首次使人们有可能确定在原地压力和温度下的碳固定率，彻底改变了我们在深海热液喷口进行微生物生物地球化学调查的方式。这是两个美国和外国机构之间的跨学科和合作努力，为建立网络和促进国际合作创造了独特的机会。这也将使两名在该项目中工作的研究生受益，他们将接触到广泛的仪器和科学领域，促进他们的跨学科教育。 在与Nitzan Resnick博士，圣人学校的学术院长，小学推广计划将开发和建立与学校的长期合作伙伴关系。此外，还将建立一个游轮博客网站，向学校和广大公众传播研究成果。研究结果将成为媒体报道的主题，并被整合到PI实验室或机构现有的课程和网页中。该项目使用最近开发的机器人微型实验室Vent-SID，测量化能自养生产的速率，并确定氧气和硝酸盐在驱动深层化学合成中的相对重要性，在原地压力和温度下对海洋热液喷口进行研究，并解决以下目前尚未解决的科学目标：1）获得化能自养碳固定的原位速率，2）获得原位硝酸盐还原速率测量，以及3）将这些过程的测量与参与碳和能量代谢的关键基因的表达直接关联。虽然最近的数据表明，硝酸盐还原为N2（反硝化）或NH 4+（异化还原硝酸盐铵）可能是负责一个显着的部分化能自养生产，NO3还原率从未被测量原位热液喷口。研究人员假设，化能自养生长与喷口微生物群落中的硝酸盐呼吸密切相关。在项目开始后约12个月（约2017年2月）的巡航期间，研究人员将在东太平洋海隆的9° 46 N至9° 53 N部分进行总共4次Vent-SID部署以及辅助采样收集。他们将集中精力在两个扩散流喷口地点，“螃蟹温泉”和“泰迪熊”。“螃蟹温泉”是一个扩散流喷口（温度：25°C），已被用作模型系统，以深入了解化能自养过程，并在过去几年中经常取样。该喷口地点的地球化学和微生物特征都很清楚，为拟议的面向过程的研究提供了极好的背景数据。“泰迪熊”是2014年1月发现的一个扩散流站点，它具有较低的温度（T：12°C），使其成为一个很好的比较站点。研究人员将进行一些短时间的孵育，以评估不同环境参数的作用，这些参数已被确定为可能的关键变量（例如，O2，温度，NO3-），并使用元转录组学分析将这些过程速率测量与功能基因的表达联系起来。这项研究将是首次尝试在关键的原位条件下测量热液喷口微生物组合的关键代谢过程，并评估原位电子供体和受体途径的定量重要性。今后，预计Vent-SID将成为海洋学界的一项常规应用，用于测量在原地压力和喷口流体温度下热液喷口相关代谢过程的时间序列速率。