Collaborative Research: Does Calcification By Paleoceanographically Relevant Benthic Foraminifera Provide A Record Of Localized Methane Seepage?

合作研究：古海洋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: 1634469
• 负责人: Joan Bernhard
• 金额: $ 21.84万
• 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: 2016-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1634469&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.

甲烷在大陆边缘大量存在，作为海底沉积物中的固体气体水合物。它也是一种强大的温室气体，当从沉积物中的天然气水合物释放出来时，有可能大大加剧全球变暖。不幸的是，甲烷水合物是一种短暂的矿物，在岩石记录中没有留下直接的证据。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中甲烷释放影响的有用工具，这可以帮助我们估计我们目前正在变暖的海洋如何可能导致未来甲烷气体释放，海洋可能会破坏海底甲烷水合物沉积物的稳定并导致它们释放气体。 这项研究的重点是探索使用微小的沉积物生活的单细胞生物称为有孔虫（即，有孔虫），以实现过去海底甲烷渗漏环境出现的这种替代。 这项研究将研究有孔虫测试是否记录甲烷的渗漏，方法是检查构成它们测试的碳酸钙是否记录甲烷中碳的同位素特征，这与从海水中沉淀出来的甲烷有很大不同。这项工作的更广泛影响包括为马萨诸塞州沃特敦一所学校的视障K-12学生开发有孔虫教学单元。课程将包括多感官介绍（冷，声音，嗅觉，触觉和热）。它将包括由3D打印机从具有已知生态学和细胞生物学的有孔虫的微CT扫描生成的3D模型。该模块还将被纳入马萨诸塞州伍兹霍尔当地高中和佛罗里达自然历史博物馆的课程。这项研究的目标是看看有孔虫是否在活跃的渗漏环境中钙化它们的测试，以及渗漏甲烷中碳的特征是否记录在生物体沉积的碳酸钙中。将研究从挪威斯瓦尔巴特群岛西部韦斯特内萨海岭1200米深的甲烷渗漏点采集的大约40至50只有孔虫。将采用多种尖端分析技术。个体有孔虫试验将进行三步调查，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）稳定同位素质谱法，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，以确定生物体的生存能力和通过共生体对甲烷渗漏栖息地的适应。将对从其中提取有孔虫的同一沉积物岩心中的共存孔隙沃茨进行无机碳同位素组成和其他地球化学环境物种分析。这项工作的更广泛影响包括为马萨诸塞州沃特敦一所学校的视障K-12学生开发有孔虫教学单元。课程将包括多感官介绍（冷，声音，嗅觉，触觉和热）。它将包括由3D打印机从具有已知生态学和细胞生物学的有孔虫的微CT扫描生成的3D模型。