Barium/calcium ratios in non-spinose planktic foraminifera: a novel proxy for reconstructing paleo-productivity

无刺浮游有孔虫中的钡/钙比率：重建古生产力的新指标

• 批准号: 1737165
• 负责人: Jennifer Fehrenbacher
• 金额: $ 46.98万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1737165&HistoricalAwards=false
• 关键词: Barium; calcium; ratios; non; spinose

This project will test a novel hypothesis that deeper dwelling planktic foraminiferal barium-to-calcium ratios record surface-ocean productivity. The research will quantify the link between the barium geochemistry of deeper-dwelling planktic foraminifera (N. dutertrei and P. obliquiloculata) and established paleoproductivity proxies in marine sediments. Because export productivity is directly linked to carbon sequestration from the atmosphere and varies with climate cycles such as the El Nino-Southern Oscillation, it is a key parameter required to establish carbon cycle variability in the past ocean. A planktic foraminiferal derived productivity proxy will be particularly useful in areas where other productivity proxies are less reliable or compromised, such as in areas with low sediment accumulation rates and/or low preservation of biogenic minerals, or in coastal settings where sediments become anoxic and organic carbon accumulation rates can be biased by terrestrial sources. The broader impacts of this research include improved utility of foraminiferal calcite based climate reconstructions and the establishment of a new proxy for export productivity. The project will provide support for an early career female researcher, a graduate student, and two undergraduate students. The principal investigator (PI) will utilize her position as a Science Communication Fellow at the Oregon Museum of Science and Industry to provide public outreach.Laboratory culture experiments confirm that N. dutertrei record seawater Ba/Ca ratios during calcification. Yet, published records show that Ba/Ca is unusually high in fossil specimens of the deeper dwelling planktic foraminifera species, including N. dutertrei. The Ba/Ca ratio in fossil specimens far exceeds that which can be explained by seawater Ba/Ca ratios alone and may be due to calcification in microenvironments enriched in Ba, such as marine snow. The PI will evaluate the hypothesis that Ba/Ca in deep dwelling taxa is related to export production from surface waters by generating downcore Ba/Ca data in a suite of sediment cores that span a productivity gradient across the equatorial Pacific, compare the Ba/Ca records to existing paleo-productivity data spanning the time interval from the last glacial maximum to present from the same cores, and assess the fidelity of the proxy by completing reconstructions in well-preserved and poorly-preserved sediments. While preliminary data indicate that fossil foraminifer Ba/Ca ratios are lowered by dissolution, these data suggest that Ba/Ca ratios still reflect productivity even in the samples most heavily affected by dissolution. In addition to generating downcore Ba/Ca records, the PI will generate Mg/Ca records and stable isotope records (oxygen and carbon) from the same samples. The Mg/Ca data for N. dutertrei will be used to test a newly developed Mg-based temperature calibration for N. dutertrei. This research seeks to expand the utility of the paleoceanographically important, but underutilized, non-spinose planktic foraminifera species Neogloboquadrina dutertrei and Pulleniatina obliquiloculata and develop a new foraminifer-based proxy for productivity. High-resolution analytical techniques (laser ablation-ICP-MS, isotope ratio mass spectrometry, and solution based-ICP-MS) will be used to generate the downcore trace element and stable isotope records in this study.

该项目将测试一个新的假设，即更深的浮游有孔虫的钡钙比记录了表面海洋的生产力。该研究将量化深层浮游有孔虫（N. dutertrei 和 P. obliquiloculata）的钡地球化学与海洋沉积物中已建立的古生产力指标之间的联系。由于出口生产率与大气中的碳固存直接相关，并且随着厄尔尼诺-南方涛动等气候周期的变化而变化，因此它是确定过去海洋碳循环变化所需的关键参数。浮游有孔虫衍生的生产力指标在其他生产力指标不太可靠或受到影响的地区特别有用，例如沉积物积累率低和/或生物矿物保存率低的地区，或沉积物缺氧且有机碳积累率可能受到陆地来源影响的沿海地区。这项研究的更广泛影响包括提高基于有孔虫方解石的气候重建的效用以及建立新的出口生产力替代指标。该项目将为一名早期职业女性研究员、一名研究生和两名本科生提供支持。首席研究员 (PI) 将利用她在俄勒冈州科学与工业博物馆科学传播研究员的职位来提供公众宣传。实验室培养实验证实，杜特特雷猪笼草在钙化过程中记录了海水 Ba/Ca 比率。然而，已发表的记录显示，在深层浮游有孔虫物种（包括杜特尔特氏猪笼草）的化石标本中，Ba/Ca 含量异常高。化石标本中的 Ba/Ca 比率远远超过仅用海水 Ba/Ca 比率可以解释的值，可能是由于富含 Ba 的微环境（例如海雪）中的钙化所致。 PI 将评估深层居住类群中的 Ba/Ca 与地表水出口生产相关的假设，方法是在一组跨越赤道太平洋生产力梯度的沉积岩芯中生成岩心 Ba/Ca 数据，将 Ba/Ca 记录与跨越从末次盛冰期到同一岩芯出现的时间间隔的现有古生产力数据进行比较，并通过以下方式评估代理的保真度： 完成保存完好和保存不良的沉积物的重建。虽然初步数据表明，化石有孔虫 Ba/Ca 比率因溶解而降低，但这些数据表明，即使在受溶解影响最严重的样品中，Ba/Ca 比率仍然反映了生产力。除了生成岩心 Ba/Ca 记录外，PI 还将从同一样本中生成 Mg/Ca 记录和稳定同位素记录（氧和碳）。杜特尔特雷猪笼草的镁/钙数据将用于测试新开发的杜特尔特雷猪笼草基于镁的温度校准。本研究旨在扩大古海洋学上重要但未充分利用的非刺浮游有孔虫物种 Neogloboquadrina dutertrei 和 Pulleniatina obliquiloculata 的实用性，并开发一种新的基于有孔虫的生产力代理。在本研究中，高分辨率分析技术（激光烧蚀-ICP-MS、同位素比质谱法和基于溶液的ICP-MS）将用于生成岩心下痕量元素和稳定同位素记录。

项目成果

Preferential Loss of High Trace Element Bearing Inner Calcite in Foraminifera During Physical and Chemical Cleaning

• DOI: 10.1029/2020gc009419
• 发表时间: 2021-01-01
• 期刊: GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
• 影响因子: 3.5
• 作者: Fritz-Endres, Theresa;Fehrenbacher, Jennifer
• 通讯作者: Fehrenbacher, Jennifer