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

有色溶解有机物（CDOM）是海洋碳库中一个很小但很重要的部分，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，海洋CDOM形成的化学基础仍然不清楚。CDOM可以由两种可能的来源形成：1）初级生产力的异养细菌转化（来自于南极洲），或2）来自于陆地。该项目将研究浮游植物作为海洋中CDOM来源的作用，方法是利用一种强大的新技术来测量颗粒有机物的吸收率和荧光，对可能的CDOM前体进行离散化学测量，并进行酶分析。本研究结果将为深入了解异养菌对CDOM的转化和CDOM的产生提供新的思路。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分享，并将船上活动的实时反馈流到小学教室。陆地和海洋溶解有机物（DOM）的化学成分不同。实验室和开放的海洋观测表明，细菌转化浮游植物DOM产生腐殖类CDOM信号，在视觉上类似于陆地CDOM。然而，以前的研究海洋CDOM使用吸光度和荧光适合电子相互作用（EI）模型的供体和受体分子之间的分子内电荷转移（CT）反应常见的部分氧化的陆地分子中发现的腐殖物质。该项目将测试浮游植物和细菌提供微生物转化和连接的供体和受体来源的假设，使它们之间的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，包括海洋雪的形成。一种新的技术，用于测量碱提取POM（BEPOM）的吸光度和荧光将被用来将CDOM的结果纳入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的产生如何与非线性CDOM形成的光学和化学相联系的理解。确定浮游植物POM和DOM转化的时间过程和程度的异养细菌在相同的浮游植物生长实验将提供一个深入的了解如何细菌转化海洋雪相关的浮游有机物驱动整个海洋的CDOM生产。

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.