Collaborative Research: Does calcification by paleoceanographically relevant benthic foraminifera provide a record of localized methane seepage?

合作研究：古海洋学相关的底栖有孔虫的钙化是否提供了局部甲烷渗漏的记录？

• 批准号: 1634248
• 负责人: Jonathan Martin
• 金额: $ 8.59万
• 依托单位: University of Florida
• 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: 2016-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1634248&HistoricalAwards=false
• 关键词: Collaborative; Research; Does; calcification; paleoceanographically

Methane occurs in great quantities on continental margins as solid gas hydrates in seafloor sediments. It is also a powerful greenhouse gas that has the potential, when released from sediment-hosted gas hydrates, to dramatically increase global warming. Unfortunately, methane gas hydrates are ephemeral minerals that leave no direct evidence in the rock record. A long-lived indicator of past methane-rich marine environments would be a useful tool for assessing the impact of methane release from marine sediments in the past, which could help us estimate how our presently warming oceans, which can destabilize seafloor methane hydrate deposits and cause them to release their gases, may induce methane gas releases in the future. This research is focused on exploring the use of the carbon isotopic composition of calcareous tests of tiny sediment-living single-celled organisms called foraminifera (i.e., forams) to realize such a proxy for the occurrence of past seafloor methane seep environments. This research will study whether foram tests record the seepage of methane by examining whether the calcium carbonate that makes up their tests records the isotopic signature of carbon in methane, which is significantly different from that precipitated from seawater. Broader impacts of the work include the development of teaching units on foraminifera for visually impaired K-12 students at a school in Watertown MA. The curriculum will consist of a multisensory presentation (cold, sound, smell, touch, and heat). It will include 3D models generated by a 3Dprinter from micro-CT scans of foraminifera with known ecology and cell biology. This module will also be included in the curriculum of a local high school in Woods Hole MA and at the Florida Museum of Natural History. Goals of the research will be to see if forams calcify their tests in active seep environments and if the signature of the carbon in the seeping methane is recorded in the calcium carbonate the organism deposits. Approximately 40 to 50 forams taken from a 1200 meter deep methane seep site on the Vestnesa Ridge west of Svalbard, Norway will be studied. Multiple cutting-edge analytical techniques will be employed. Individual foram tests will undergo a three-step investigation that consists of (1) micro-computed tomography analysis to determine presence of authigenic carbonate overgrowths, (2) stable isotope mass spectrometry to determine stable carbon isotope values of the calcite, and (3) transmission electron microscopy of the decalcified cell body to establish the organism's viability and adaptation to methane seep habitats via symbionts. Coexisting pore waters from the same sediment cores from which the forams were extracted will be analyzed for inorganic carbon isotopic composition and other geochemical environmental species. Broader impacts of the work include the development of teaching units on foraminifera for visually impaired K-12 students at a school in Watertown MA. The curriculum will consist of a multisensory presentation (cold, sound, smell, touch, and heat). It will include 3D models generated by a 3Dprinter from micro-CT scans of foraminifera with known ecology and cell biology.

在大陆边缘，甲烷以固体气体水合物的形式大量存在于海底沉积物中。它也是一种强大的温室气体，当从沉积物托管的气体水合物中释放出来时，有可能大幅加剧全球变暖。不幸的是，甲烷气体水合物是短暂的矿物，在岩石记录中没有留下直接证据。一个关于过去富含甲烷的海洋环境的长期指标将是评估过去海洋沉积物释放甲烷的影响的有用工具，这可以帮助我们估计我们目前正在变暖的海洋可能会破坏海底甲烷水合物沉积的稳定并导致它们释放气体，这可能会在未来导致甲烷气体释放。这项研究的重点是探索利用被称为有孔虫(即有孔虫)的微小沉淀物生活的单细胞生物的钙质测试的碳同位素组成来实现过去海底甲烷渗漏环境的这种替代。这项研究将研究Foram测试是否记录了甲烷的渗漏，方法是检查组成测试的碳酸钙是否记录了甲烷中碳的同位素特征，这与从海水中沉淀的碳有显著不同。这项工作的更广泛影响包括在马萨诸塞州沃特敦的一所学校为视力受损的K-12学生开发有孔虫教学单元。课程将包括多感官演示(冷、声、闻、触和热)。它将包括3D打印机从已知生态和细胞生物学的有孔虫的微型CT扫描中生成的3D模型。这一单元还将被纳入马萨诸塞州伍兹霍尔当地一所高中和佛罗里达自然历史博物馆的课程。这项研究的目标将是观察有孔虫是否在活跃的渗漏环境中钙化它们的测试，以及渗出的甲烷中碳的特征是否记录在有机体沉积的碳酸钙中。从挪威斯瓦尔巴群岛以西的韦斯特内萨山脊1200米深的甲烷渗漏点采集的大约40到50个有孔虫将被研究。将采用多种尖端分析技术。单个孔洞测试将经历三个步骤的调查，包括(1)微型计算机断层扫描分析，以确定自生碳酸盐过度生长的存在，(2)稳定同位素质谱仪，以确定方解石的稳定碳同位素值，以及(3)脱钙细胞体的透射电子显微镜，以确定有机体的生存能力和通过共生体适应甲烷渗漏生境。从提取有孔虫的同一沉积物岩心中共存的孔隙水将被分析无机碳同位素组成和其他地球化学环境物种。这项工作的更广泛影响包括在马萨诸塞州沃特敦的一所学校为视力受损的K-12学生开发有孔虫教学单元。课程将包括多感官演示(冷、声、闻、触和热)。它将包括3D打印机从已知生态和细胞生物学的有孔虫的微型CT扫描中生成的3D模型。