Improving High Latitude Foraminiferal Paleoproxies: Insights from Northern California Current Modern and Historical Records

这个项目将提高我们重建高纬度地区过去海洋状况的能力，比如海面温度。这些地区对气候变化的反应比低纬度地区更为极端。研究过去海洋气候变化的最好方法之一是研究被称为浮游有孔虫或“有孔虫”的浮游化石。有孔虫是一种微小的浮游动物，已经存在了2亿多年，生活在海洋表面附近。随着这些生物的生长，它们会形成小壳。壳化学记录了壳形成时的条件。当生物死亡时，它的外壳沉入海底，成为地质化石记录的一部分。因此，从深海沉积物中回收的化石壳的化学成分可以用来重建过去的海洋表面条件。本研究将产生用于评估有孔虫化石记录的地球化学-环境关系（即校准方程）。从海洋表面收集的活着的和最近死去的有孔虫的壳的组成将与它们所生活的海水的条件和化学组成进行比较。这项研究的样本将包括过去十年的浮游生物拖曳样本档案。新收集的浮游生物拖和水样本来自整个北加州洋流区域的北加州海岸，俄勒冈州和华盛顿州也将被研究。尽管有孔虫在全球范围内都有发现，但这项研究将重点关注生活在中纬度到高纬度地区的物种的地球化学-环境关系，以更好地预测这些脆弱地区将如何应对我们不断变化的气候。研究小组还将调查有孔虫壳的组成在整个生物体的生命周期中是如何变化的。这项研究将有助于确保用于解释化石记录的校准方程是准确的。该项目包括对早期职业科学家和本科生的支持。研究团队将通过多次公众外展活动，与公众分享研究成果和科学过程。近半个世纪以来，通过对加利福尼亚、俄勒冈和华盛顿海岸的一系列水文样带，人们对动态的北加州洋流（NCC）系统进行了广泛的监测，形成了一个强大的浮游生物样本档案和同步的环境数据。本研究将利用历史浮游生物样本，并收集新的浮游生物样本，进一步开发一系列中高纬浮游有孔虫物种的微量元素/钙（TE/Ca）古代用物。NCC共有的物种包括温带和高纬度基因型的Globigerina bulloides， Neogloboquadrina pachyderma， N. incompta， N. dutertrei和Turborotalita quinqueloba。这些物种在高纬度地区很常见，包括北冰洋，那里的温度变化对气候变化的响应往往是最大的。研究目标是：1)建立未充分研究的温带至极地浮游有孔虫分类群的Mg/ ca -温度和Na/ ca -盐度校准，并研究其他TE/ ca -环境关系的可能性；2)研究TE在浮游有孔虫壳从生到死转变过程中的潜在重要影响和机制。3)对研究区d18O（海水）特征进行表征，建立特定物种的海水有孔虫方解石同位素偏移，以约束研究分类群的深度生境，这是建立基于“自然实验室”环境数据的校准的关键步骤。该研究将进一步开发新的和现有的浮游有孔虫TE/Ca代用物，用于古气候和古海洋重建，特别强调提高我们重建中高纬度地区过去环境条件的能力。该奖项反映了美国国家科学基金会的法定使命，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。

This project will improve our ability to reconstruct past ocean conditions, such as sea surface temperatures, in high-latitude regions. These regions experience a more extreme response to climate change than low-latitude regions. One of the best ways to study past ocean-climate change is by studying fossil plankton called planktic foraminifera or “forams”. Forams are microscopic zooplankton that have existed for over 200 million years and live near the surface of the ocean. As these organisms grow, they build small shells. The shell chemistry records the conditions at the time the shells were formed. When the organism dies, its shell sinks to the seafloor and becomes part of the geological fossil record. Thus, the chemical composition of fossil shells recovered from deep-sea sediments can be used to reconstruct the surface ocean conditions in the past. This study will generate the geochemical-environmental relationships (i.e., calibration equations) used to evaluate fossil foram records. The composition of the shells of living and recently deceased forams collected from the surface ocean will be compared to the conditions and chemical makeup of the seawater they are living in. Samples for this study will include an archive of plankton tow samples from the last decade. Newly collected plankton tow and water samples from throughout the Northern California Current region off the coast of northern California, Oregon, and Washington states will also be studied. Although forams are found globally, this study will focus on constraining geochemical-environmental relationships for species that live in intermediate- to high-latitude regions to better predict how these vulnerable regions will respond to our changing climate. The research team will also investigate how the composition of foram shells may change throughout the organism’s life cycle. This study will help ensure that the calibration equations used to interpret fossil records are accurate. The project includes support for an early career scientist and for undergraduate students. The research team will share the results and scientific process of the research with the public through several public outreach events.The dynamic Northern California Current (NCC) system has been extensively monitored for nearly half a century, through a series of hydrographic transects off the coasts of California, Oregon, and Washington, resulting in a robust archive of plankton tow samples and concurrent environmental data. This study will use historical plankton tow samples, and collect new plankton samples, to further develop a range of trace element/calcium (TE/Ca) paleoproxies for intermediate to high latitude planktic foraminiferal species living in the NCC. Species common to the NCC include temperate and high-latitude genotypes of Globigerina bulloides, Neogloboquadrina pachyderma, N. incompta, N. dutertrei, and Turborotalita quinqueloba. These species are common in higher latitude regions, including the Artic Ocean, where temperature change in response to climate change tends to be greatest. The research objectives are to: 1) establish Mg/Ca-temperature and Na/Ca-salinity calibrations for understudied temperate to polar planktic foraminiferal taxa and investigate the potential for other TE/Ca-environmental relationships, 2) investigate potential vital effects and mechanisms for TE incorporation in planktic foraminiferal shells as they transition from life to death, and 3) characterize the d18O(seawater) signature in the study region and establish species specific seawater foraminiferal calcite isotopic offsets in order to constrain the depth habitats of the study taxa, a critical step to establishing calibrations based on data in a “natural laboratory” setting. The proposed research will further develop novel and existing planktic foraminiferal TE/Ca proxies for use in paleoclimatic and paleoceanographic reconstructions, with particular emphasis on improving our ability to reconstruct past environmental conditions in intermediate to high latitude regions.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.