Collaborative Research: Planktonic Sources of Chromophoric Dissolved Organic Matter in Seawater

显色性溶解有机物（CDOM）是海洋碳库中很小但很重要的一部分，它与太阳辐射相互作用，从而影响海洋中的许多光化学和生物过程。尽管它很重要，但海洋CDOM形成的化学基础仍不清楚。CDOM可能有两个可能的来源：1)异养细菌转化初级生产力（浮游生物来源），或2)陆地来源。该项目将利用一种强大的新技术来测量颗粒有机物的吸光度和荧光，对浮游生物CDOM可能前体的离散化学测量，以及酶分析，研究浮游植物作为海洋中CDOM来源的作用。本研究结果将为了解浮游CDOM的来源、产生及其在异养菌中的转化提供新的思路。这项关于CDOM的研究将通过北卡罗莱纳水族馆的一个模块广泛分享，并将船上活动的实况转播给小学教室。陆地和海洋溶解有机物（DOM）的化学组成不同。实验室和远洋观测表明，浮游植物DOM的细菌转化产生腐殖质样的CDOM信号，在视觉上与陆地上的CDOM相似。然而，先前利用吸光度和荧光对海洋CDOM进行的研究，符合腐殖质中部分氧化的陆生分子常见的供体和受体分子之间分子内电荷转移（CT）反应的电子相互作用（EI）模型。这个项目将测试这样一个假设，即浮游植物和细菌提供了供体和受体的来源，这些供体和受体通过微生物转化和连接，使它们之间能够进行CT接触，并产生海洋CDOM。为了解决这个问题，研究人员将系统地研究浮游植物的生长，包括海洋雪的形成。一种测量碱基萃取POM （BEPOM）吸光度和荧光的新技术将用于将浮游CDOM结果纳入EI模型，并补充其可能的化学前体的测量。这些实验将提高对海洋中CDOM的产生如何与浮游CDOM形成的光学和化学联系在一起的理解。在同一浮游植物生长实验中，确定异养细菌对浮游植物POM和DOM转化的时间过程和程度，将有助于深入了解海洋雪相关浮游有机物的细菌转化如何驱动整个海洋CDOM的产生。

Chromophoric dissolved organic matter (CDOM) is a small but important fraction of the marine carbon pool that interacts with solar radiation and thus affects many photochemical and biological processes in the ocean. Despite its importance, the chemical basis for the formation of oceanic CDOM remains unclear. CDOM may be formed from two possible sources: 1) heterotrophic bacterial transformations of primary productivity (plankton-derived), or 2) terrestrially-derived. This project will examine the role of phytoplankton as a source of CDOM in the ocean by utilizing a powerful, new technique to measure particulate organic matter absorbance and fluorescence, discrete chemical measurements of probable precursors to planktonic CDOM, and enzymatic assays. Results of this research will provide new insights into the origin and production of planktonic CDOM and its transformation by heterotrophic bacteria. This research on CDOM will be shared broadly through a module at a North Carolina Aquarium, and streaming live feeds of shipboard activities to elementary school classrooms.Terrestrial and oceanic dissolved organic matter (DOM) differ in their chemical composition. Laboratory and open-ocean observations suggest that bacterial transformation of phytoplankton DOM produces humic-like CDOM signals that are visually similar to those in terrestrial CDOM. However, prior studies of oceanic CDOM using absorbance and fluorescence fit an electronic interaction (EI) model of intramolecular charge transfer (CT) reactions between donor and acceptor molecules common to partially-oxidized terrestrial molecules found in humic substances. This project will test the hypothesis that phytoplankton and bacteria provide a source of donors and acceptors that are microbially-transformed and linked, enabling CT contacts between them and creating oceanic CDOM. To address this, researchers will systematically study phytoplankton growth, including marine snow formation. A new technique for measuring base-extracted POM (BEPOM) absorbance and fluorescence will be used to incorporate planktonic CDOM results into the EI model, and supplemented with measurements of its probable chemical precursors. These experiments will improve understanding of how the production of CDOM in the ocean is linked to the optics and chemistry of planktonic CDOM formation. Determining the time course and extent of phytoplankton POM and DOM transformation by heterotrophic bacteria during the same phytoplankton growth experiments will provide an in-depth understanding as to how bacterial transformation of marine snow-associated planktonic organic matter drives CDOM production throughout the ocean.