Ocean Acidification: Collaborative Research: The response of calcareous nannoplankton to ocean acidification during the Paleocene-Eocene thermal maximum

海洋酸化：合作研究：古新世-始新世热最大值期间钙质超小型浮游生物对海洋酸化的响应

• 批准号: 1415958
• 负责人: James Zachos
• 金额: $ 25.56万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1415958&HistoricalAwards=false
• 关键词: Ocean; Acidification; Collaborative; Research; response

One of the most significant threats for marine organisms is acidification as a result of unabated anthropogenic CO2 emission. On a global scale, acidification has the potential to impact biota that make their shells out of the minerals aragonite and calcite, that have a hard time forming shells in low pH waters. One such group, the calcareous nannoplankton (haptophyte algae including coccolithophores that build shells of the mineral calcite), are a vital part of the open-ocean food chain. Laboratory experiments suggest that coccolithophores can adapt to more acidic conditions, but whether the group can adapt in the natural environment is uncertain. The geological record contains a series of natural experiments that allow us to address the biological response of nannoplankton to greenhouse gas perturbations. The Paleocene-Eocene thermal maximum (PETM), a ~200,000 year long transient warming event 56 million years ago, is likely the best ancient model for the impact of massive greenhouse gas on marine ecosystems. Studies of nannoplankton from deep-sea sites show new taxa during the PETM including an increase in malformed morphotypes that could signify adaptation to lower calcite saturation. Moreover, geochemical evidence suggests a similar magnitude pH decline during the initial stages of the event as projected to occur in the 21st century. The insight gained from this study will complement modern experimental and ecological studies, allowing mapping of the impact of progressive carbonate undersaturation on the ancestors of modern nannoplankton through space and time. In addition to better understanding the long-term consequences of ocean acidification, broader impacts include training of students at the graduate and undergraduate level, support of a postdoctoral researcher, and outreach to K-12 classrooms.Much of the information on the PETM derives from the study of cores drilled in the deep sea. However, as the deep ocean also acidified during the event, the key early stage of the PETM and likely when the maximum surface ocean acidification took place, calcium carbonate has been dissolved in most deep-sea locations. Thus to study the full impact of ocean acidification on nannoplankton, this research focuses on nannoplankton contained within sedimentary sections deposited at continental shelf water depths. A superb opportunity to explore the impact of ocean acidification on PETM plankton exists in cores from the shelf on the Atlantic Coastal Plain where some of the shallowest and most expanded records of the event are found. These core sections offer high temporal resolution and preserve a high-fidelity record of the early part of the PETM. This project will use new and existing cores from Maryland and New Jersey to study the development and impact of acidification on the coastal ocean over millennial time scales. The goal is to address the following hypotheses: (1) Surface ocean carbonate saturation reached a minimum within the first twenty thousand years of the PETM then slowly recovered; (2) The response of nannoplankton to surface acidification was systematic with existing species tolerant of low saturation increasing in abundance followed by the evolution of new species and morphotypes; and (3) Eutrophication in the coastal ocean amplified the impact of acidification locally and played a critical role in drawing down CO2 during the early stages of the PETM. These hypotheses will be addressed using closely integrated: (a) nannoplankton assemblage studies to determine how species composition and morphology changed; (b) a suite of inorganic and organic proxies to elucidate the nature of environmental changes and particularly to unravel acidification from temperature signals; and (c) models to simulate the temporal variability of pH, saturation state and eutrophication on the shelf.

海洋生物面临的最重大威胁之一是人为二氧化碳排放量有增无减导致的酸化。 在全球范围内，酸化有可能影响用文石和方解石矿物制造贝壳的生物群，而这些矿物在低 pH 值水中很难形成贝壳。 其中一个类群是钙质超微浮游生物（触生藻类，包括形成矿物方解石壳的颗石藻），是公海食物链的重要组成部分。实验室实验表明，颗石藻可以适应更酸性的条件，但该群体是否能适应自然环境尚不确定。 地质记录包含一系列自然实验，使我们能够解决纳米浮游生物对温室气体扰动的生物反应。古新世-始新世最热期 (PETM) 是 5600 万年前长达约 20 万年的短暂变暖事件，可能是研究大量温室气体对海洋生态系统影响的最佳古代模型。对深海超微浮游生物的研究表明，PETM期间出现了新的类群，包括畸形形态类型的增加，这可能意味着对较低方解石饱和度的适应。 此外，地球化学证据表明，在该事件的初始阶段，pH 值下降的幅度与预计在 21 世纪发生的情况类似。从这项研究中获得的见解将补充现代实验和生态研究，从而可以绘制出渐进的碳酸盐饱和度在空间和时间上对现代超小型浮游生物祖先的影响。 除了更好地了解海洋酸化的长期后果外，更广泛的影响还包括对研究生和本科生的学生培训、博士后研究员的支持以及对 K-12 课堂的推广。有关 PETM 的大部分信息来自对深海钻取岩心的研究。 然而，由于深海在该事件期间也发生酸化，这是PETM的关键早期阶段，也可能是最大表面海洋酸化发生的时候，碳酸钙已在大多数深海位置溶解。因此，为了研究海洋酸化对超小型浮游生物的全面影响，本研究重点关注大陆架水深沉积部分中包含的超小型浮游生物。大西洋海岸平原大陆架的岩芯中存在着一个绝佳的机会来探索海洋酸化对 PETM 浮游生物的影响，那里发现了该事件的一些最浅和最扩展的记录。 这些核心部分提供高时间分辨率并保留 PETM 早期部分的高保真记录。 该项目将利用马里兰州和新泽西州的新的和现有的岩心来研究酸化在千年时间尺度上对沿海海洋的发展和影响。 目标是解决以下假设：（1）表面海洋碳酸盐饱和度在PETM的前两万年内达到最低值，然后缓慢恢复； (2) 超微浮游生物对表面酸化的响应是系统性的，现有的耐低饱和度的物种数量增加，随后新物种和形态类型的进化； (3)近海富营养化加剧了局部酸化的影响，对PETM早期CO2的减少起到了关键作用。 这些假设将通过紧密结合的方式来解决： (a) 超微浮游生物组合研究，以确定物种组成和形态如何变化； (b) 一套无机和有机替代物，用于阐明环境变化的性质，特别是从温度信号中揭示酸化现象； (c) 模拟陆架 pH 值、饱和状态和富营养化随时间变化的模型。