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脂质D/H比的兴趣越来越大，导致这种新工具的应用比我们对藻类中控制D/H分馏的过程的理解更快地发展。一个定量的框架，以评估测量D/H值仍然缺乏。在这个项目中，华盛顿大学的研究人员将在一系列硝酸盐和光限制的生长速率，温度和盐度下对海洋硅藻Thalassiosira psuedonana和球石藻Emiliania huxleyi进行连续培养实验，以确定这些环境条件如何影响脂质中的D/H分馏。与分批培养不同，恒化器允许在受控的实验室条件下在稳态下评价细胞。这些结果将在三个现场实验中用浮游植物的自然种群进行验证。在北太平洋亚极地和亚热带的真光区进行原位培养实验，以评估光和营养限制生长速率对E. huxleyi。温度对自然浮游植物种群D/H分馏的影响将通过一年内每月对华盛顿湖进行采样来评估。 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。将在每个实验中分析产乙酸（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分馏的差异将提供制定和测试D/H分馏机制的假设的手段。更广泛的影响： 本研究对高中生、大学生、女性及公众的环境教育有一定的促进作用。在去年与主要研究者一起工作的10名实验室成员中，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研究员对马歇尔群岛和科斯雷群岛的考察。 近几个月来，该实验室的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.