Evaluating the Environmental Influences on D/H Fractionation in Algal Lipids

在生物地球化学和古气气学中使用脂质D/H比值的兴趣日益增长，导致这种新工具的应用比我们对藻类中控制D/H分选过程的理解发展得更快。目前仍缺乏一个定量框架来评估测量的D/H值。在这个项目中，华盛顿大学的研究人员将在硝酸盐和光照限制的生长速率、温度和盐度范围内，对海洋硅藻海硅藻和球石藻赫克斯利进行连续培养实验，以确定这些环境条件如何影响脂质中D/H的分离。与批量培养不同，恒温器允许在受控的实验室条件下在稳定状态下对细胞进行评估。这些结果将在三个野外实验中以浮游植物的自然种群进行验证。本研究将在北太平洋亚极地和亚热带的强光区进行原位培养实验，以评估光限和营养限生长速率对赫胥黎蛤脂质D/H分异的影响。温度对天然浮游植物种群D/H分值的影响将通过在一年的时间里每月对华盛顿湖取样来评估。D/H分馏将通过比较单个脂质和生长水之间的同位素差异来确定。在每个实验中都将分析丙酮（线性）和类异戊二烯（支链）脂质。来自不同生物合成途径的脂质中D/H分离的差异将为制定和测试D/H分离机制的假设提供手段。更广泛的影响：本研究将促进高中生、大学生、女性和公众的环境教育。在去年与首席研究员一起工作的10名实验室成员中，有4名是女性，3名是本科生。2009年夏天，两名本科生参加了首席研究员对马绍尔群岛和科斯雷岛的考察。最近几个月，该实验室网站平均每天的访问量超过2000次。

A growing interest in using lipid D/H ratios in biogeochemistry and paleoclimatology has resulted in the application of this new tool advancing more rapidly than our understanding of the processes that control D/H fractionation in algae. A quantitative framework in which to evaluate measured D/H values is still lacking. In this project, researchers at the University of Washington will conduct continuous culture experiments with the marine diatom Thalassiosira psuedonana and the coccolithophorid Emiliania huxleyi at a range of nitrate- and light-limited growth rates, temperatures and salinities to determine how these environmental conditions affect D/H fractionation in lipids. Unlike batch cultures, chemostats permit the evaluation of cells at steady state, under controlled laboratory conditions. These results will be validated with natural populations of phytoplankton in three field experiments. In situ incubation experiments will be conducted in the euphotic zone of subpolar and subtropical North Pacific Ocean sites to evaluate the influence of light- and nutrient-limited growth rate on D/H fractionation in lipids from E. huxleyi. The influence of temperature on D/H fractionation in a natural phytoplankton population will be evaluated by monthly sampling of Lake Washington over the course of a year. D/H fractionation will be determined by comparing the isotopic difference between individual lipids and growth water. Both acetogenic (linear) and isoprenoid (branched) lipids will be analyzed in every experiment. Differences in D/H fractionation in lipids from different biosynthetic pathways will provide the means to formulate and test hypotheses of D/H fractionation mechanisms. Broader Impacts: The environmental education of high school students, undergraduates, women and the public will be advanced by this research. Of 10 lab group members working with the principal investigator during the last year, 4 were women and 3 were undergraduates. Two undergraduates joined the principal investigator's expedition to the Marshall Islands and Kosrae in Summer 2009. The lab website has averaged more than 2000 hits per day in recent months.