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

在生物地球化学和古气候学中使用类脂D/H比值的兴趣日益增长，导致这一新工具的应用比我们对控制藻类D/H分馏的过程的理解进展得更快。目前仍缺乏一个量化的框架来评估测量的D/H值。在这个项目中，华盛顿大学的研究人员将用海洋硅藻Psuedonana和球石藻Emily huxleyi在一系列硝酸盐和光限制的生长速度、温度和盐度下进行连续培养实验，以确定这些环境条件如何影响脂类中的D/H分级。与分批培养不同，恒化器允许在受控的实验室条件下对处于稳定状态的细胞进行评估。这些结果将在三个野外实验中用自然浮游植物种群进行验证。在北太平洋亚极区和亚热带海域的真光区进行现场培养实验，以评价光照和营养限制生长速度对虎尾龙虾脂肪D/H分级的影响。温度对自然浮游植物种群D/H分馏的影响将通过一年中华盛顿湖的每月采样来评估。D/H分馏将通过比较单个脂类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产乙酸脂(线性的)和类异戊二烯的(分支的)脂类。来自不同生物合成途径的脂类中D/H分级的不同将为建立和检验D/H分级机制的假说提供手段。更广泛的影响：这项研究将促进高中生、本科生、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名实验室小组成员中，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调查员对马绍尔群岛和科斯雷的考察。近几个月来，该实验室网站平均每天的点击量超过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.