Beyond the unsaturation ratios (UK37' or UK37) of long chain alkenones: unlocking the hidden treasure trove of alkenone-producing haptophytes

拟议的研究旨在带来和校准一套新的分子工具，以便更深入和定量地了解驱动气候变化的潜在机制。新的分子工具将克服现有方法的问题，这些方法在靠近大陆边缘和河口的海洋环境中由于纠缠的分子信号而非常困难。一旦校准，新的分子指数将以前所未有的细节提供研究过去温度变化的新方法。这项研究还具有建立新的分子方法的巨大潜力，这些方法可以定量评估海面盐度的变化——这是区域水文变化的一个非常重要的指标。这项研究也将极大地促进我们对在广泛的海洋和大陆环境中，等chrysidales（一类触生藻类，是全球海洋中最主要的光合生物之一）中脂质生物合成的生物化学和遗传控制的理解。具体来说，像烯酮和烯酸酯这样的脂质是由等chrysidales产生的独特的生物标志物，不仅可以定量地重建过去的气候和环境，而且在不久的将来也被认为是使用藻类生物质生产生物柴油的最佳候选物之一。此外，基金亦会资助研究生与专业人士一起，积极参与各种影响广泛的活动，例如在本地小学至高中的学校教授科学课程，这些学校中有许多少数族裔人数较少。本研究的技术优点可以概括如下。长链烯烃（LCAs）的不饱和比（UK37′或UK37）是迄今为止开发的最成功的古海表温度（SST）代用指标之一，已被广泛应用了30多年。然而，PI最近的一项研究表明，这类重要生物标志物的真正力量尚未得到充分释放。例如，一种新发现的淡水/低盐栖植物具有不同于海洋和咸水同类植物的烯酮特征，为定量大陆古气候研究开辟了新的机会。近年来，研究小组在烯酮/烯酸酯的气相和液相色谱分离方面取得了重要进展，可以准确，全面和同时定量多达32种烯酮，烯酸酯及其结构异构体（比旧分析方法多5 - 10倍的化合物）和相应的基于异构体比例和非c37烯酮的新SST代理。这些发展有望将烯酮代理扩展到以前无法进入的区域，包括：1)烯酮由开放海洋和沿海物种贡献的边缘海；2)高纬度地区烯烃浓度低，传统的烯烃-温度关系失效。综合生物标志物分析具有很大的潜力，可以改进不同类群/种类的产烯酮触觉植物的化学分类分化，对混合水生环境中物种输入的定量分配和评估过去海面盐度（SSS）的变化具有重要意义。本研究旨在系统分析一套大型核心表层海洋沉积物，培养选定的触生菌物种/关键菌株品种，校准新的SST和SSS代理，建立高质量的生物标志物图谱，用于化学分类。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The proposed research aims to bring and calibrate a new set of molecular tools that permit a more in-depth and quantitative understanding of underlying mechanism driving climate variations. The new molecular tools will overcome the problems of the existing methods that are extremely problematic in ocean settings close to continental margins and estuaries because of entangled molecular signals. Once calibrated, the new molecular indices will provide new ways to study past temperature variations at unprecedented details. The research also has great potential to establish novel molecular approaches that allow quantitative assessment of changes in sea surface salinity - a very important indicator of regional hydrological changes. The study will also greatly advance our understanding of biochemistry and genetic control of lipid biosynthesis in isochrysidales (a class of haptophyte algae that are among the most dominant photosynthetic organisms in the global oceans) in a wide range of ocean and continental environments. Specifically, lipids like alkenones and alkenoates are unique biomarkers produced by isochrysidales that not only permit quantitative past climate and environmental reconstructions, but are also regarded as among the top candidates for biodiesel production using algal biomass in the near future. The funds will also support graduate students who, together with the PIs, actively participate in a wide range of broad-impact activities such as teaching science at local GK-12 schools, many of which have substantial population of underrepresented minorities. The technical merit of the research can be summarized as follows. The unsaturation ratios (UK37' or UK37) of long chain alkenones (LCAs) are among the most successful paleo-sea surface temperature (SST) proxies ever developed, and have been widely applied for over three decades. A recent study by the PI, however, suggests that the true power of this important class of biomarkers has yet to be fully unleashed. For example, a newly discovered freshwater/oligosaline haptophyte species with characteristic alkenone profiles distinct from marine and saline water counterparts open up new opportunities for quantitative continental paleoclimate studies. Important recent progress made by the research team in both gas and liquid chromatographic separation of alkenones/alkenoates permits accurate, comprehensive and simultaneous quantification of up to 32 alkenones, alkenoates and their structural isomers (~5 - 10 times more compounds than old analytical methods) and a corresponding new suite of SST proxies based on isomeric ratios and non-C37 alkenones. These developments promise to extend alkenone proxies to previously inaccessible regions, including: 1) marginal seas where alkenones are contributed by both open-ocean and coastal species; 2) high latitude regions where alkenone concentrations are low and the traditional alkenone-temperature relationship fails. Comprehensive biomarker profiling has great potential to refine chemotaxonomic differentiation of different groups/species of alkenone-producing haptophytes, with implications for quantitative apportionment of species inputs in mixed aquatic settings and assessing past sea surface salinity (SSS) changes. This proposal aims to systematically analyze a large suite of core top ocean sediments, and to culture selected haptophyte species/key strain varieties, to calibrate the new SST and SSS proxies and to establish high quality biomarker profiles for chemotaxonomy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.