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: 1559198
• 负责人: Stefan Sievert
• 金额: $ 77.33万
• 依托单位: Woods Hole Oceanographic Institution
• 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=1559198&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.

深海热液喷口于 1977 年首次发现，是典型的生态系统，其中微生物化学合成而非光合作用是有机碳的主要来源。化学合成微生物利用氧化喷口流体中所含还原无机化学物质（如硫化氢或氢气）产生的能量。气体，将二氧化碳（CO2）转化为电池材料，通过这样做，它们可以有效地将能量从地热源转移到更高的温度。营养级，在支持以高生产力为特征的独特而迷人的生态系统的过程中——原本贫瘠的深海景观中的绿洲虽然已经建立了对这些生态系统功能的总体看法，但我们对它们的理解仍然存在重大差距。这些系统的微生物学和生物地球化学特别缺乏测量原位微生物活动率的研究，而这些研究最终是了解这些生态系统的生产并评估其对全球生物地球化学循环的影响所必需的。通气潜水孵化装置（Vent-SID）是一种机器人微型实验室，最近在现场开发和测试，该仪器首次可以确定原位压力和温度下的碳固定率，从而带来革命性的变化。我们在深海热液喷口进行微生物生物地球化学研究的方式，这是美国和外国两个机构之间的跨学科合作努力，为建立网络和促进国际合作创造了独特的机会。参与该项目的研究生将接触到广泛的仪器和科学领域，促进他们的跨学科教育。与 Sage 学院学术院长 Nitzan Resnick 博士合作，将制定一个小学推广计划并进行推广。此外，还将建立一个邮轮博客网站，向学校和更广泛的公众传播研究成果，并将其纳入现有的课程和网页中。要么在PI 的实验室或机构内。该项目使用最近开发的机器人微型实验室 Vent-SID 来测量化学自养生产速率，并确定氧气和硝酸盐在深海热液喷口驱动化学合成中的相对重要性原位压力和温度，并解决以下当前未解决的科学目标：1）获得原位化学自养碳固定速率，2）获得原位硝酸盐还原率测量，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相关联，尽管最近的数据表明硝酸盐还原为N2（反硝化）或NH4+（硝酸盐异化还原为铵）可能。由于化学自养产生的很大一部分由NO3还原率负责，因此研究人员从未在热液喷口现场测量过NO3还原率，研究人员认为化学自养生长与硝酸盐呼吸有关。在该项目大约 12 个月（~2017 年 2 月）进行的巡航期间，研究人员将总共进行 4 次 Vent-SID 部署以及在北纬 46 度的辅助采样采集。他们将重点关注东太平洋海隆至北纬 9°53 段的两个扩散流喷口地点，“Crab Spa”和“Teddy Bear”是一个扩散流。喷口位点（温度：25°C）已被用作模型系统，以深入了解化能自养过程，并且在过去几年中经常进行采样，该喷口位点在地球化学和微生物学方面都得到了很好的表征，提供了出色的性能。拟议的面向过程的研究的背景数据。“泰迪熊”是 2014 年 1 月发现的扩散流站点，它的温度较低（T：12°C），使其成为一个很好的比较站点。研究人员将进行多次短期时间过程孵化，以评估已被确定为可能的关键变量（例如 O2、温度、NO3-）的不同环境参数的作用，并将这些过程速率测量值与表达式联系起来这项研究将是首次尝试在关键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。预计 Vent-SID 将成为海洋学界的常规应用，用于测量热液喷口在原位压力和喷口流体温度下相关代谢过程的时间序列速率。