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

合作研究：海水中发色溶解有机物的浮游来源

• 批准号: 1459294
• 负责人: Thomas Bianchi
• 金额: $ 23.11万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-01 至 2018-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1459294&HistoricalAwards=false
• 关键词: Collaborative; Research; Planktonic; Sources; Chromophoric

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.

发色溶解有机物（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。尽管其重要性，但海洋 CDOM 形成的化学基础仍不清楚。 CDOM 可能由两种可能的来源形成：1) 初级生产力的异养细菌转化（源自浮游生物），或 2) 源自陆地。该项目将通过利用强大的新技术测量颗粒有机物吸光度和荧光、对浮游 CDOM 的可能前体进行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。这项研究的结果将为浮游 CDOM 的起源和生产及其异养细菌的转化提供新的见解。这项关于 CDOM 的研究将通过北卡罗来纳州水族馆的一个模块广泛共享，并将船上活动的实时直播传输到小学教室。陆地和海洋溶解有机物 (DOM) 的化学成分不同。实验室和公海观察表明，浮游植物 DOM 的细菌转化产生了类似腐殖质的 CDOM 信号，这些信号在视觉上与陆地 CDOM 中的信号相似。然而，先前使用吸光度和荧光对海洋 CDOM 的研究符合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，这种反应对于腐殖质中发现的部分氧化的陆地分子很常见。该项目将检验这样的假设：浮游植物和细菌提供了通过微生物转化和连接的供体和受体的来源，从而使它们之间能够进行 CT 接触并创建海洋 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，包括海洋积雪的形成。一种测量碱基提取 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。这些实验将加深对海洋中 CDOM 的产生如何与浮游 CDOM 形成的光学和化学联系起来的理解。在相同的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的 CDOM 产生。