Collaborative research: Validation of the Lacustrine Branched GDGT Paleothermometer

合作研究：湖相分支 GDGT 古温度计的验证

• 批准号: 1451818
• 负责人: Jessica Tierney
• 金额: $ 22.49万
• 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: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1451818&HistoricalAwards=false
• 关键词: Collaborative; research; Validation; Lacustrine; Branched

The reconstruction of past continental temperatures provides critical insights into the Earth's climate system and its sensitivity to internal and external forcing mechanisms. Such reconstructions provide geological context for observed and projected future climate changes, and reveal the impact of diverse forcings, such as changes in solar irradiance, volcanic events, and greenhouse gas concentrations, on global climate. Organic molecules preserved in sediments provide a tool for inferring past climate that may be widely applicable in both space and time. A promising and recently developed technique based on assemblages of branched glycerol dialkyl glycerol tetraethers (brGDGTs), membrane lipids produced by bacteria, has the potential to expand understanding of past continental temperatures across a variety of climatic regimes, time scales, and depositional environments. brGDGTs represent an important climate archive because they are widespread and abundant in lakes, they exhibit structural differences related to water temperature and pH, and they can be preserved for long periods of time (millions of years) in lake sediments. However, it has not been rigorously assessed if brGDGTs provide a universal method for past temperature reconstruction and the potential influence of environmental parameters other than temperature and pH has not yet been evaluated. Through conducting fundamental field and laboratory experiments, the investigators will elucidate the structural response of the brGDGTs to environmental stresses and investigate the impacts of oxygen exposure, degradation, and microbial community structure on brGDGT distributions. This research represents necessary, fundamental work to validate the use of the brGDGT paleothermometer in lakes. Investigators will partner with the Eureka! Program of Girls, Inc. of Holyoke, MA to offer hands-on summer workshops in environmental geochemistry, as part of a month-long summer science camp designed to encourage middle and high school girls to pursue careers in STEM fields.Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are ubiquitous compounds, found in a variety of terrestrial environments includes soils, rivers, and lakes. Previous research, including work done by the investigators, has established that the degree of methylation of these compounds is sensitive to temperature, auguring the use of brGDGT distributions as a proxy for past temperature changes. However, a number of challenges and unresolved issues limit the application of a brGDGT thermometer. These include unknown biological source(s), a lack of first-principles evidence that brGDGT structures respond to environmental forcings, and evidence for diagenetic alteration and/or sensitivity to oxygen exposure. This project aims to address some of these fundamental challenges via both a field and laboratory-based approach. In a lab setting, researchers will maintain and manipulate mesocosm experiments to determine whether brGDGT methylation and cyclization responds to temperature and pH. In the field, they will monitor brGDGT fluxes in a target lake and conduct controlled degradation experiments. Lipid analyses will be paired with Illumina MiSeq sequencing in order to understand how microbial community structure influences brGDGT distributions. Finally, they will conduct exploratory statistical analyses on a set of lake sediments to study how brGDGT distributions behave in different sedimentary and climatic regimes. The results of this project will constitute a fundamental advance in the understanding of brGDGTs and improve the ability to use them as a paleothermometer.

过去大陆温度的重建提供了对地球气候系统及其对内部和外部强迫机制的敏感性的关键见解。这种重建为观察和预测的未来气候变化提供了地质环境，并揭示了各种强迫的影响，例如太阳辐照度，火山事件和温室气体浓度对全球气候的影响。保存在沉积物中的有机分子提供了一种推断过去气候的工具，该工具可能广泛适用于时空和时间。一种有前途且最近开发的技术，基于分支甘油二甲基甘油的组合（BRGDGTS），细菌产生的膜脂质具有扩展对过去大陆温度的理解，从而扩大各种气候，时间尺度，时间尺度和深度定位环境。 BRGDGTs代表着重要的气候档案，因为它们在湖泊中广泛且丰富，它们表现出与水温和pH值相关的结构差异，并且可以在湖泊沉积物中长时间（数百万年）保存它们。但是，如果BRGDGT提供了过去温度重建的通用方法以及温度和pH以外的其他环境参数的潜在影响，则尚未严格评估它。通过进行基本领域和实验室实验，研究人员将阐明BRGDGT对环境压力的结构反应，并研究氧气暴露，降解和微生物群落结构对BRGDGT分布的影响。这项研究代表了验证在湖泊中使用BRGDGT浅热量计能的必要基础工作。调查人员将与尤里卡合作！作为一个为期一个月的夏季科学训练营的一部分，旨在鼓励中学和高中女生从事STEM领域的职业。先前的研究，包括研究人员所做的工作，已经确定这些化合物的甲基化程度对温度很敏感，从而增加了将BRGDGT分布作为过去温度变化的代理。但是，许多挑战和未解决的问题限制了BRGDGT温度计的应用。其中包括未知的生物学来源，缺乏第一原则的证据表明BRGDGT结构对环境的强迫响应，以及对氧气暴露的成岩成分改变和/或敏感性的证据。该项目旨在通过基于现场和实验室的方法来应对其中一些基本挑战。在实验室环境中，研究人员将维护和操纵中验实验，以确定BRGDGT甲基化和环化是否响应温度和pH。在现场，他们将监视目标湖中的BRGDGT通量，并进行受控的降解实验。脂质分析将与Illumina Miseq测序配对，以了解微生物群落结构如何影响BRGDGT分布。最后，他们将对一组湖泊沉积物进行探索性统计分析，以研究BRGDGT分布如何在不同的沉积和气候方案中行事。该项目的结果将构成理解BRGDGTS的基本进步，并提高将其用作苍白热计的能力。