Glacial-Interglacial Changes in Oxygen Minimum Zones Using Deep-Dwelling, Low-Oxygen Planktic Foraminifera

最小含氧区（OMZ）是在海洋表面以下100至1000米深处的大片海域中自然存在的低氧区域。有机MZ在海洋地球化学循环和生态系统功能中起着重要作用，其低氧沃茨范围的任何变化都可能对海洋生物和宝贵的渔业资源产生深远的影响。海洋氧合在多个时间尺度上因全球气候变化而变化，最近的观测表明，在过去的半个世纪中，海洋氧合区已经扩大。该项目将探索适用于南极有孔虫Globorotaloides hexagonus低氧环境的有前途的新的地球化学和形态学代用指标，Globorotaloides hexagonus是一种单细胞钙化生物，其海底沉积物中的化石记录非常适合重建过去水柱中的低氧环境。该项目将侧重于热带太平洋东部广阔的外保区。第一个目标是评估和校准现代G.六角藻生活在浮游生物中。第二个目标是将这些替代物应用于沉积物岩心中的化石标本，以记录冰川-全新世变化。这些结果将成为生成OMZ环境记录的有用代理，并更好地了解在最近的快速气候变化期间主要区域OMZ的变化。这两项成果都代表了在理解OMZ的自然振荡以及在全球气候扰动下对OMZ变化进行建模和规划方面的重要进展。该项目将为本科生研究人员提供机会，并支持一名女性早期职业研究人员。海洋沉积记录是重建长期海洋氧化作用的最有前途的档案。然而，现有的低氧海洋环境替代指标存在很大的局限性。该项目旨在通过评估和应用一系列与南极有孔虫Globorotaloides hexagonus低氧环境相关的有前景的地球化学（微量元素和稳定同位素）和形态学（面积密度和孔隙度）指标来满足这一需求。该项目将根据G.六角贝以前收集的深度分布MOCNESS（多开/关网和环境传感系统）拖从东太平洋。从现代贝壳代理开发的结果，然后将地面truthed和应用到两个已经很好地表征从墨西哥边缘和巴拿马盆地，跨越末次冰盛期到全新世的沉积物岩心。沉积物记录将被用来重建过去的条件在热带太平洋东部OMZ，在那里的冰川间冰期氧化的重大问题仍然存在。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Oxygen minimum zones (OMZs) are naturally occurring regions of low oxygen found across large swaths of the ocean at depths of 100 to 1000 meters below the surface. OMZs play an important role in biogeochemical cycling and ecosystem function and any change in the expanse of their low oxygen waters can have far reaching implications for marine life and valuable fisheries resources. Marine oxygenation is variable on multiple timescales in response to global climate change, with recent observations showing that OMZs have expanded over the past half century. This project will explore promising new geochemical and morphologic proxies applicable to low-oxygen environments in the planktic foraminifer Globorotaloides hexagonus, a unicellular calcifying organism whose fossil record in seafloor sediments is well suited to reconstructing past low-oxygen environments in the water column. The project will focus on the extensive OMZ of the eastern tropical Pacific. The first goal is to evaluate and calibrate the targeted measurements for modern G. hexagonus collected live in plankton tows. The second goal is to apply these proxies to fossil specimens in sediment cores to generate records of glacial-Holocene change. The outcomes will be useable proxies for generating records of the OMZ environment, and a better understanding of how a major regional OMZ changed during the most recent period of rapid climate change. Both outcomes represent important progress towards understanding natural oscillations in the OMZ as well as modeling and planning for a changing OMZ in the face of global climate perturbations. The project will provide opportunities for undergraduate researchers as well as support a female early career researcher.The marine sedimentary record is the most promising archive from which to reconstruct long term marine oxygenation. However, significant limitations exist in the available proxies for low oxygen marine environments. This project aims to address this need by evaluating and applying a range of promising geochemical (trace element and stable isotope) and morphologic (area-density and porosity) proxies relevant to low oxygen environments in the planktic foraminifer Globorotaloides hexagonus. The project will develop viable proxies based on the morphology and geochemistry of G. hexagonus shells previously collected in depth-distributed MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System) tows from the eastern Pacific. The results from this proxy development in modern shells will then be ground-truthed and applied to two already well characterized sediment cores from the Mexican Margin and Panama Basin that span from the Last Glacial Maximum through the Holocene. The sediment records will be used to reconstruct past conditions in the eastern tropical Pacific OMZ, where significant questions about glacial-interglacial oxygenation persist. This research will lead to a more mechanistic understanding of how OMZs respond to climate more broadly.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.