Mechanisms controlling the production and fate of DOM during diatom blooms

硅藻华期 DOM 产生和命运的控制机制

• 批准号: 0850857
• 负责人: Craig Carlson
• 金额: $ 68.96万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-04-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0850857&HistoricalAwards=false
• 关键词: Mechanisms; controlling; production; fate; DOM

Intellectual Merit: The residence time of DOM in surface waters of marine systems is the main factor determining its contribution to the efficiency and magnitude of the biological carbon pump. There is growing evidence that the export of DOM from the surface ocean represents a highly efficient pathway for the sequestration of organic carbon in the deep sea in some ocean regions. Current estimates are that 20% of the carbon transported to depth by the biological pump globally occurs via the export of DOC. Effective export of DOM requires that the DOM produced by phytoplankton persist in surface waters until vertical exchange processes transport the material to depth. The mechanisms controlling the time scale for the accumulation and persistence of DOM in surface waters are dominated by biological processes that influence the amount and chemical character of the DOM produced and its consumption and decomposition by microbes. This project addresses these two coupled biological processes to examine controls on the accumulation of DOM during temperate diatom blooms. Diatom blooms are known to produce prodigious quantities of DOM upon entering nutrient stress with a chemical composition that varies with the type of nutrient limitation (Si or N). This variable composition likely influences the nutritional value of DOM to microbes driving species successions towards functional groups of heterotrophic prokaryotes that are best able to metabolize particular forms of DOM. To date each side of this coupled system of production/consumption has been examined independently. A few studies have examined how limitation by different limiting nutrients affects the chemical character of the DOM produced by phytoplankton, while others have focused on the fate of DOM without detailed understanding of the mechanisms influencing its initial chemical composition. This research project will examine both sides of this coupled process simultaneously to see how different forms of nutrient limitation drive the chemical character of DOM and the subsequent microbial response which together determine the fate of DOM produced during diatom blooms. The investigators will employ a combination of laboratory and field based approaches to: 1) Investigate how limitation by either N or Si impacts the chemical composition of the DOM released by diatom blooms. 2) Determine how differences in the composition of DOM produced by diatoms experiencing different nutrient stresses affects it susceptibility to heterotrophic microbial processing through changes in the productivity, growth efficiency and community structure of bacterioplankton. The research will focus on diatom blooms for two reasons. Diatom blooms are a regular feature in regions of the ocean where DOC export is known to be significant, i.e. such as the North Atlantic, making the fate of the DOM produced during blooms a potentially significant mechanism of C export. In addition, the direct release of DOM from phytoplankton is the best studied of numerous DOM production process providing the background for formulating hypotheses on how changes in DOM production and composition affect the bacterial response that drives its consumption. Preliminary data indicates that waters of the Santa Barbara Channel, California are an ideal model system for conducting this research because the spring diatom bloom is sufficiently predictable and amenable to the types of manipulations required for these studies, and ambient DOM concentrations are low for coastal waters allowing small changes in DOM concentrations to be resolved in both laboratory and field experiments.Broader Impacts: This research will contribute to the greater scientific goal of understanding the role of upper ocean food webs in carbon cycling. The findings will improve our basic understanding of DOM dynamics aiding modelers in the development of improved representations of key processes in ecosystem models. The project will enable the education of the next generation of biological oceanographers by training graduate students, and it will be leveraged to introduce oceanography into the curriculum of local K- 12 students to make them aware of the importance of the oceans to their lives and of the possibility of oceanography as a career choice.

智力优点：DOM在海洋系统地表水中的停留时间是决定其对生物碳泵效率和幅度的贡献的主要因素。越来越多的证据表明，从表面海洋中出口DOM代表了一些海洋地区深海有机碳的高效途径。目前的估计是，全球生物泵将20％的碳通过DOC的出口出现。有效的DOM出口要求浮游植物产生的DOM持续存在在地表水中，直到垂直交换过程将材料传递到深度。控制DOM在地表水中积累和持久性的时间尺度的机制由影响DOM产生的DOM的数量和化学特征及其消耗和分解微生物的生物过程主导。该项目介绍了这两个耦合的生物学过程，以检查温带硅藻花朵期间DOM积累的控制。已知硅藻开花会在进入营养胁迫下以与营养限制的类型不同（SI或N）而产生大量的DOM。该变量的组成可能会影响DOM向微生物驱动物种继任的营养价值向官能核原核生物的功能群体，这些原核生物最好能够代谢特定形式的DOM。迄今为止，已经独立研究了这种生产/消费耦合系统的每一方面。一些研究已经研究了不同限制营养素的限制如何影响浮游植物产生的DOM的化学特征，而其他人则专注于DOM的命运，而没有详细了解影响其初始化学成分的机制。该研究项目将同时检查该耦合过程的两侧，以查看不同形式的营养限制如何驱动DOM的化学特征以及随后的微生物反应，这共同确定了在硅藻开花过程中产生的DOM的命运。研究人员将采用基于实验室和现场的方法的组合来：1）研究N或SI的限制如何影响硅藻Blooms释放的DOM的化学成分。 2）确定经历不同营养应力的硅藻产生的DOM组成的差异如何通过改变细菌浮游生物的生产力，生长效率和社区结构来影响异构微生物加工的易感性。该研究将集中于硅藻花朵，原因有两个。硅藻开花是海洋地区的常规特征，那里已知DOC出口很重要，例如北大西洋，使Bloom期间产生的DOM的命运成为C出口的潜在重要机制。此外，从浮游植物中直接释放DOM是众多DOM生产过程中最好的研究，该过程为制定了关于DOM生产和组成的变化如何影响驱动其消耗的细菌反应的假设提供了背景。 Preliminary data indicates that waters of the Santa Barbara Channel, California are an ideal model system for conducting this research because the spring diatom bloom is sufficiently predictable and amenable to the types of manipulations required for these studies, and ambient DOM concentrations are low for coastal waters allowing small changes in DOM concentrations to be resolved in both laboratory and field experiments.Broader Impacts: This research will contribute to the greater scientific goal of understanding the role of碳循环的上海食品网。这些发现将改善我们对DOM动力学建模者在开发生态系统模型中关键过程的改进表示方面的基本理解。该项目将通过培训研究生对下一代生物海洋学的教育进行教育，并将利用将海洋学引入当地K-12学生的课程中，以使他们意识到海洋对生活的重要性以及将海洋学作为职业选择的可能性。