Investigating the contribution of carotenoid degradation products to refractory dissolved organic matter (DOM)

该研究项目将确定负责碳在海洋中长期储存的生物来源和化学结构。每年，微小的海洋植物从大气中去除的二氧化碳与陆地植物一样多。呼吸作用将这些碳中的大部分以二氧化碳的形式返回海洋，但也有一些被锁在生物体的残余物中。这些剩余的化合物通过涉及细菌，阳光，化学反应和其他过程的途径进行修饰，这些过程导致碳储存数千年至数百万年。有些化合物最终会形成石油储层。基于以前的结果，该项目将研究一组特定的生物化学物质（称为类胡萝卜素）的反应和海洋寿命，作为一种可能的有机碳储存途径。类胡萝卜素在许多海洋生物中含量丰富，增加了它们是长期碳储存和石油形成的一部分的可能性。这些化合物还具有独特的化学性质，使其易于发生特定的化学反应。由于这个原因，它们被作为强大的抗氧化剂销售。因此，这项关于类胡萝卜素化学研究的科学成果不仅将为海洋碳循环提供信息，而且还将有助于研究它们作为抗氧化剂的特性。该项目将确定类胡萝卜素及其在海水中的降解产物的寿命，以提供新的见解，了解通过生物群将碳从大气转移到长期储存库的途径。研究生和代表性不足的本科生将参与这项研究。以前的工作已经确定了广泛分布在海洋溶解有机物（DOM）水库中的化合物的特定化学骨架。结合核磁共振（NMR）光谱和综合气相色谱-质谱（GC-MS）的高分辨率分析方法检测到了与类胡萝卜素密切相关的具有独特结构的DOM化合物。在实验室实验中，代表性的类胡萝卜素的光化学反应进一步将海水中检测到的化合物与类胡萝卜素降解产物（CDP）联系起来。这些初步研究表明，这里资助的工作将能够确定特定的CDP结构，并建立海水中CDP积累的定量意义，寿命和时间尺度。该项目将结合联合收割机实验室实验、高分辨率分析和化学合成方法，以确定CDP的化学成分及其在海水中的丰度。通过这项研究开发的新分析方法将与石油形成，土壤化学以及食品化学中的其他类胡萝卜素研究相关。斜坡热解氧化（PyrOx）耦合放射性碳测量将用于确定CDP富集DOM的放射性碳含量，并寻求估计这些溶解分子在环境中的累积时间尺度，据推测，更深，更老的海水将包含相对较高比例的放射性碳贫化CDP。从北太平洋不同深度收集样品，其中富含CDP的DOM将按照既定的样品处理方法分离，将提供有关控制地球碳再分配的数量和时间尺度的机制的见解和新信息？各种水库。

This research project will identify biological sources and chemical structures that are responsible for the long-term storage of carbon in the ocean. Each year, microscopic marine plants remove about as much carbon dioxide from the atmosphere as do land plants. Respiration returns much of this carbon to the ocean as carbon dioxide, but some is locked in the remnants of living organisms. These remaining compounds are modified by pathways that involve bacteria, sunlight, chemical reactions, and other processes that lead to storage of carbon for thousands to millions of years. Some compounds eventually contribute to the petroleum reservoir. Building on previous results, this project will study the reactions and oceanic lifetime of a particular set of biochemicals, called carotenoids, as a possible organic carbon storage pathway. Carotenoids are abundant in very many marine organisms, increasing the likelihood that they are part of this long-term carbon storage and petroleum formation. These compounds also have unique chemical properties that make them subject to specific chemical reactions. For this reason, they have been marketed as powerful antioxidants. Therefore, scientific outcomes from this research on carotenoid chemistry will not only inform ocean carbon cycles but could also benefit studies of their properties as antioxidants. The project will determine the lifetime of carotenoids and their degradation products in seawater to provide new insights into pathways that transfer carbon from the atmosphere through biota and into long-term storage reservoirs. Graduate students and underrepresented undergraduate students will be engaged in the research.Previous work has identified specific chemical backbones of compounds that are broadly distributed within the marine dissolved organic matter (DOM) reservoir. A high-resolution analytical approach that combines nuclear magnetic resonance (NMR) spectroscopy with comprehensive gas chromatography-mass spectrometry (GC-MS) has detected DOM compounds with unique structures closely related to carotenoids. Photochemical reactions of a representative carotenoid in laboratory experiments has further linked compounds detected in seawater to carotenoid degradation products (CDP). These preliminary studies show promise that the work funded here will be able to identify specific CDP structures and establish the quantitative significance, lifetimes, and timescales of CDP accumulation in seawater. The project will combine laboratory experiments, high resolution analyses, and chemical synthesis methods to determine the chemical composition of CDP and their abundance in seawater. The novel analytical methods developed through this research will be relevant for other carotenoid-focused studies in petroleum formation, soil chemistry, as well as food chemistry. Ramped pyrolysis oxidation (PyrOx) coupled to radiocarbon measurements will be used to determine the radiocarbon content of CDP-enriched DOM and seek to estimate the accumulation timescale of these dissolved molecules in the environment, and it is hypothesized that deeper, older ocean water will contain a relatively higher proportion of radiocarbon-depleted CDP. Collecting samples from different depths in the North Pacific Ocean where CDP-enriched DOM will be isolated following established sample processing methods will provide insights and new information on the mechanisms that control the amount and timescale of carbon redistribution among Earth?s various reservoirs.