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存在极大的问题。一旦校准，新的分子指数将提供以前所未有的细节研究过去温度变化的新方法。这项研究还具有很大的潜力，可以建立新的分子方法，定量评估海洋表面盐度的变化-这是区域水文变化的一个非常重要的指标。这项研究还将大大推进我们对等鞭金藻目（一类附着藻类，是全球海洋中最主要的光合生物）在广泛的海洋和大陆环境中脂质生物合成的生物化学和遗传控制的理解。具体而言，脂质，如烯酮和烯酸酯是由异鞭金藻产生的独特的生物标志物，不仅允许定量过去的气候和环境重建，但也被认为是在不久的将来使用藻类生物质生产生物柴油的最佳候选人之一。这些资金还将支持研究生，他们与PI一起积极参与广泛的广泛影响活动，例如在当地GK-12学校教授科学，其中许多学校有大量代表性不足的少数民族。本研究的技术优点可概括如下。长链烯酮（LCAs）的不饱和度比值（UK 37 '或UK 37）是迄今为止最成功的古海表温度（SST）指标之一，并已被广泛应用了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完全释放。例如，一个新发现的淡水/寡盐附着植物物种的特征烯酮配置文件不同于海洋和盐水的同行开辟了新的机会，定量大陆古气候研究。研究小组最近在烯酮/烯酸酯的气相和液相色谱分离方面取得的重要进展允许准确，全面和同时定量多达32种烯酮，烯酸酯及其结构异构体（比旧的分析方法多5 - 10倍）以及相应的基于异构体比率和非C37烯酮的一套新的SST代理。这些发展有望将烯酮替代物扩展到以前无法到达的地区，包括：1）边缘海，其中烯酮由公海和沿海物种贡献; 2）高纬度地区，其中烯酮浓度低，传统的烯酮-温度关系失效。全面的生物标志物分析有很大的潜力，完善化学分类分化的不同群体/种的烯酮生产的附着植物，在混合水生环境中的物种投入的定量分配和评估过去的海面盐度（SSS）的变化的影响。该项目旨在系统地分析大量的核心表层海洋沉积物，培养选定的附着植物物种/关键菌株品种，校准新的SST和SSS代理，并建立高质量的化学分类生物标志物档案。该奖项反映了NSF的法定使命，并被认为值得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来支持。

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.