Direct Mass Spectrometric Profiling of Water Column Particulate Organic Matter Composition

本研究涉及应用新颖的“源内”质谱（MS）技术在分子水平上表征（亚）微克数量的颗粒物有机物质（POM）。总体目标是将POM组成的变化与水柱为基础的生物地球化学过程联系起来，并评估这些过程在确定沉积有机质化学特征方面的重要性。观察到的POM组成的变化将在当前有机物保存概念的背景下进行解释。为了实现这一目标，将调查来自高生产力（秘鲁上升流区）和低营养（马尾藻海）海洋环境的浮游植物种群、颗粒物质和表层沉积物样本中的有机物组成。所采用的分析方法旨在克服目前阻碍分子标记作为海洋地球化学常规工具应用的若干限制。具体来说，源内质谱作为一种快速、高灵敏度的方法，可用于研究大范围分子大小和极性的复杂混合物的组成特征。主要重点放在POM的大分子成分的结构方面，然而，脂质组成的评估也将试图提供一个更全面的视角的POM转化。源内质谱固有的灵敏度将通过研究流式细胞术分离的聚甲醛亚组分的变化来利用。通过这种方式，化学变化可以与明确定义的颗粒特征（大小、形状、叶绿素含量）相关，从而建立浮游植物组成与POM之间的系统关系。

This research involves the application of novel "in -source" mass spectrometric (MS) techniques for the molecular-level characterization of (sub)-microgram quantities of particulate organic matter (POM). The overall objective is to relate changes in POM composition to water column-based biogeochemical processes and to assess the importance of these processes in determining the chemical characteristics of sedimentary organic matter. Observed variations in POM composition will be interpreted in the context of current concepts for organic matter preservation. This objective will be pursued by investigating the composition of organic matter in samples of phytoplankton populations, particulate matter and surface sediments from high productivity (Peru Upwelling region) and oligotrophic (Sargasso Sea) Oceanic environments. The analytical approach adopted seeks to overcome several limitations which currently prevent the application of molecular markers as routine tools in marine geochemistry. Specifically, in- source MS offers advantages as a rapid, high sensitivity method which can be used to study compositional features of complex mixtures over a wide range of molecular sizes and polarities. The major focus is placed upon structural aspects of macromolecular constituents of POM, however, an assessment of lipid composition will also be made in an attempt to provide a more holistic perspective of POM transformation. The inherent sensitivity of in- source MS will be exploited by studying compositional variations in sub-factions of POM separated by flow cytometry. In this way, chemical variations can be related to well-defined particle characteristics (size, shape, chlorophyll content), enabling systematic relationships to be established between the composition of phytoplankton and POM.