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

氧气最少区(OMZ)是指在海平面以下100至1000米深的大片海洋中发现的自然存在的低氧区域。海洋保护区在生物地球化学循环和生态系统功能方面发挥着重要作用，其低氧水域面积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影响。海洋氧合作用在多个时间尺度上对全球气候变化的反应是可变的，最近的观察表明，海洋氧合作用在过去半个世纪里扩大了。该项目将探索适用于浮游有孔虫Globorotaloides六角浮游有孔虫低氧环境的有前景的新的地球化学和形态替代物，这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水柱中过去的低氧环境。该项目将把重点放在东热带太平洋广阔的OMZ上。第一个目标是评估和校准在浮游生物拖网中生活收集的现代六角藻的定向测量结果。第二个目标是将这些替代物应用于沉积岩芯中的化石标本，以产生冰川-全新世变化的记录。结果将是可用于生成OMZ环境记录的替代指标，并更好地了解一个主要的区域OMZ在最近一段快速气候变化期间是如何变化的。这两个结果都代表着在理解海洋和海洋保护区的自然振荡以及在面对全球气候扰动的情况下为变化的海洋和海洋保护区进行建模和规划方面取得的重要进展。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合作用的最有前途的档案。然而，可用于低氧海洋环境的替代品存在重大限制。该项目旨在通过评估和应用一系列与浮游有孔虫Globorotaloides六角浮游有孔虫低氧环境有关的有前景的地球化学元素(微量元素和稳定同位素)和形态(面密度和孔隙度)指标来满足这一需要。该项目将根据以前在东太平洋深度分布的MOCNESS(多开/闭合网和环境传感系统)拖网中收集的六角螺壳的形态和地球化学特征，开发可行的替代方案。现代贝壳的这一替代发展的结果将被地面证实，并应用于墨西哥边缘和巴拿马盆地的两个已经具有良好特征的沉积岩芯，这些沉积岩芯横跨从最后一次冰盛期到全新世。沉积物记录将被用来重建东太平洋热带OMZ的过去状况，那里关于冰川-间冰期氧化作用的重大问题仍然存在。这项研究将导致对OMZ如何更广泛地应对气候的更机械的理解。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.