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

这项拟议的研究旨在带来和校准一套新的分子工具，使人们能够更深入和定量地了解推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因分子信号纠缠而存在极大问题。一旦校准，新的分子指数将提供新的方法，以前所未有的细节研究过去的温度变化。这项研究还具有建立新的分子方法的巨大潜力，能够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。这项研究还将极大地促进我们对广泛海洋和大陆环境中异菊科(一类超植物藻类，是全球海洋中最主要的光合作用生物之一)中脂肪生物合成的生物化学和遗传控制的理解。具体地说，烯酮和烯酸酯等脂类是异菊科产生的独特生物标志物，不仅可以定量地重建过去的气候和环境，而且被认为是近期利用藻类生物质生产生物柴油的首选对象之一。这笔资金还将支持研究生，他们与私人投资机构一起，积极参与各种影响广泛的活动，例如在当地GK-12学校教授科学，其中许多学校有大量代表不足的少数民族人口。这项研究的技术价值可以概括为以下几点。长链烷酮(LCA)的不饱和度比(UK37‘或UK37)是迄今开发的最成功的古海洋表面温度(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，新发现的淡水/低盐上生植物物种具有不同于海洋和咸水的特征烯酮轮廓，这为定量研究大陆古气候开辟了新的机会。该研究小组最近在烯烃/烯酸盐气相和液相色谱分离方面取得的重要进展，使得能够准确、全面和同时定量多达32种烯酮、烯烃及其结构异构体(比旧分析方法多5-10倍的化合物)以及相应的基于异构体比和非C37烯烃的SST新替代物。这些发展有望将烯烃替代品扩展到以前无法进入的地区，包括：1)边缘海，其中的烯烃既有远洋物种，也有沿海物种；2)高纬度地区，那里的烯酮浓度低，传统的烯酮-温度关系失效。全面的生物标记物分析对于完善不同类群/物种的产烯酮类植物的化学分类分化具有很大潜力，这对于定量分配混合水生环境中的物种输入和评估过去的海面盐度变化具有重要意义。这项提议旨在系统地分析一大套岩心顶端海洋沉积物，培养选定的触生生物物种/关键菌株品种，校准新的SST和SSS替代指标，并为化学分类建立高质量的生物标记物轮廓。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.