Hydrogen isotope response of algal lipids to variable nutrient concentrations in Swiss lakes

S. Nemiah Ladd博士获得了美国国家科学基金会地球科学博士后奖学金，研究藻类化石如何记录营养物污染。该奖学金将允许一名早期职业的美国科学家在瑞士联邦水产科学与技术研究所（Eawag）开展一项研究项目。富营养化（湖泊和其他水生生态系统的营养物污染）通常是由肥料和洗涤剂引起的。它会导致有害藻华和广泛的鱼类死亡，并降低水体的经济和美学价值。瑞士政府在减少富营养化的原因和修复被污染的湖泊方面尤其积极主动。然而，尽管在过去的35年里进行了协调一致的努力，在瑞士中部高原的湖泊中，一系列的营养物质浓度仍然存在。本项目将开发一种新的工具，从湖泊沉积物中的分子藻化石中重建湖泊过去的营养水平。它还将改进对过去气候的现有代用物的使用，这些代用物基于相同的沉积标志。在她的奖学金期间，Ladd博士将通过与eawg伙伴计划（EPP）合作创建一个指导计划来支持访问研究生，从而促进发展中国家年轻科学家的教育。由于EPP的研究员将把新磨练出来的技能带回当地的机构，并用它们来解决当地的问题，因此对EPP奖学金项目的支持将更广泛地影响非洲和亚洲的科学进步，并促进对整个发展中国家与用水和水质有关的一系列环境、经济和社会问题的研究。藻类产生的脂质不易降解，可以在沉积物中保持数百万年不变。它们通常记录藻类生长的水中的氢同位素组成，这是由温度、降雨和大气环流模式等气候变量控制的。因此，藻类脂质已被开发为过去气候的有用代用物。然而，其他几个变量可以影响藻类脂质的同位素组成。对本项目特别重要的是，在实验室研究中，海藻中的氢同位素分馏对养分有效性高度敏感。通过测量瑞士湖泊中不同磷酸盐浓度的活藻脂、下落颗粒和表面沉积物中的同位素分馏，该项目将首次确定自然环境和淡水藻类中营养物质的可用性和生长速度是否会影响氢同位素分馏。在第二阶段的工作中，将通过对沉积物岩心的校准研究结果来重建不同湖泊的环境历史。确定具有相同气候历史的湖泊之间的自然变异性将允许对正在进行的污染补救策略进行更完整的评估。该奖项得到了国际和综合活动办公室的资助。

Dr. S. Nemiah Ladd has been granted an NSF Earth Sciences postdoctoral fellowship to study how fossilized algal remains record nutrient pollution. This fellowship will allow an early career American scientist to carry out a research project at Eawag, the Swiss Federal Institute of Aquatic Science and Technology. Eutrophication (nutrient pollution of lakes and other aquatic ecosystems) is commonly caused by fertilizers and detergents. It can result in harmful algal blooms and widespread fish death, and reduces the economic and aesthetic value of water bodies. The Swiss government has been especially proactive about reducing the causes of eutrophication and remediating polluted lakes. However, despite concerted efforts over the past thirty-five years, a range of nutrient concentrations persists among lakes in the central Swiss plateau. This project will develop a novel tool to reconstruct past nutrient levels in lakes from molecular algal fossils in lake sediment. It will also refine the use of existing proxies of past climate, which are based on the same sedimentary markers. During her fellowship, Dr. Ladd will promote the education of young scientists from developing countries by collaborating with the Eawag Partnership Program (EPP) to create a mentoring program to support visiting graduate students. Because EPP fellows will take newly honed skills back to their local institutions, and use them to address local problems, support of the EPP fellowship program will more broadly impact the advancement of science in Africa and Asia, and facilitate the study of a range of environmental, economic, and social issues related to water use and quality throughout the developing world.Lipids produced by algae are resistant to degradation and can persist unchanged in sediment for millions of years. They typically record the hydrogen isotope composition of the water in which the algae grew, which is controlled by climatic variables such as temperature, rainfall, and atmospheric circulation patterns. Algal lipids have therefore been developed as a useful proxy for past climate. However, several other variables can influence the isotopic composition of algal lipids. Of particular importance for this project, in laboratory studies hydrogen isotope fractionation in marine algae is highly sensitive to nutrient availability. By measuring isotope fractionation in algal lipids from living algae, falling particles, and surface sediment in Swiss lakes with variable phosphate concentrations, this project will for the first time establish whether nutrient availability and growth rate affect hydrogen isotope fractionation in natural settings, and for freshwater algae. In the second phase of this work, the environmental histories of different lakes will be reconstructed by applying the results of the calibration study to sediment cores. Determining the natural variability among lakes with identical climate histories will permit a more complete assessment of ongoing pollution remediation strategies.This award was supported with funding from the Office of International and Integrative Activities.