Collaborative Research: Diatoms, Food Webs and Carbon Export - Leveraging NASA EXPORTS to Test the Role of Diatom Physiology in the Biological Carbon Pump

合作研究：硅藻、食物网和碳输出 - 利用 NASA EXPORTS 测试硅藻生理学在生物碳泵中的作用

• 批准号: 1756442
• 负责人: Mark Brzezinski
• 金额: $ 51.22万
• 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: 2018
• 资助国家: 美国
• 起止时间: 2018-03-01 至 2024-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1756442&HistoricalAwards=false
• 关键词: Collaborative; Research; Diatoms; Food; Webs

This project focuses on a group of microscopic single-celled photosynthetic organisms in the ocean called diatoms. Diatoms float in the surface ocean as part of a group of organisms collectively called phytoplankton. There are thousands of different species of diatoms distributed across the global ocean. A famous oceanographer Henry Bigelow once said "All fish is diatoms" reflecting the importance of diatoms as the base of the food chain that supports the world's largest fisheries. Despite their small size, diatom photosynthesis produces 20% of the oxygen on earth each year. That's more than all of the tropical rainforests on land. The major objective of the research is to understand how the metabolic differences among diatom species affects the amount of diatom organic carbon that is carried, or exported, from the surface ocean to the deep ocean. As diatoms are photosynthesizers like green plants, their biological carbon comes from converting carbon dioxide dissolved in seawater from the atmosphere into organic forms. Diatoms also require a series of other nurtrients supplied by the ocean such as nitrogen and phosphorous and, uniquely for diatoms, the silicon used to construct their glass shells. This research will investigate how genetic and physiological differences among diatoms influence how each species react to changes in nutrient levels in the ocean and how those shifts affect the export of diatom carbon to the deep sea. The link between diatoms' physiological response and their carbon export comes about because shifts in physiology affect diatom attributes like how fast they sink and how tasty they are to predators. So if we can relate the physiological condition of different diatoms to the food-web pathways followed by different species, we can ultimately use knowledge of diatom physiological status and food web structure to predict how much diatom carbon gets to the deep sea. The research involves investigators with expertise in the physiology and genomics of diatoms and in the ocean's chemistry. The work will initially take place in the subarctic North Pacific in conjunction with the NASA Export Processes in the Ocean from RemoTe Sensing (EXPORTS) field program. The EXPORTS program is using a wide variety of methods to quantify the export and fate of photosynthetically fixed carbon in the upper ocean. The research supports the training of undergraduate students, graduate students and a postdoctoral scholar. The research will also serve as the basis for activities aimed at K-12 and junior high school students. The research will broadly impact our understanding of the biology of the biological pump (the transport of photosynthetically fixed organic carbon to the deep sea) by forming a mechanistic basis for predicting the export of diatom carbon. It is hypothesized that the type and degree of diatom physiological stress are vital aspects of ecosystem state that drive export. To test this hypothesis, the genetic composition, rates of nutrient use and growth response of diatom communities will be evaluated and supported with measurements of silicon and iron stress to evaluate stress as a predictor of the path of diatom carbon export. The subarctic N. Pacific ecosystem is characterized as high nutrient low chlorophyll (HNLC) due to low iron (Fe) levels that are primary controllers constraining phytoplankton utilization of other nutrients. It has been a paradigm in low Fe, HNLC systems that diatoms grow at elevated Si:C and Si:N ratios and should be efficiently exported as particles significantly enriched in Si relative to C. However, Fe limitation also alters diatoms species composition and the high Si demand imposed by low Fe can drive HNLC regions to Si limitation or Si/Fe co-limitation. Thus, the degree of Si and/or Fe stress in HNLC waters can all alter diatom taxonomic composition, the elemental composition of diatom cells, and the path cells follow through the food web ultimately altering diatom carbon export.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目重点研究海洋中一组称为硅藻的微观单细胞光合生物。硅藻漂浮在海洋表层，是统称为浮游植物的生物体的一部分。全球海洋中分布着数千种不同的硅藻。 著名海洋学家亨利·毕格罗曾说过“所有的鱼都是硅藻”，反映出硅藻作为支持世界最大渔业的食物链基础的重要性。尽管硅藻体积很小，但其光合作用每年产生地球上 20% 的氧气。这比陆地上所有的热带雨林还要多。该研究的主要目的是了解硅藻物种之间的代谢差异如何影响从表层海洋携带或输出到深海的硅藻有机碳量。由于硅藻与绿色植物一样都是光合作用的，它们的生物碳来自于将大气中溶解在海水中的二氧化碳转化为有机形式。 硅藻还需要海洋提供的一系列其他营养物质，例如氮和磷，以及硅藻特有的用于构造其玻璃壳的硅。 这项研究将调查硅藻之间的遗传和生理差异如何影响每个物种对海洋营养水平变化的反应，以及这些变化如何影响硅藻碳向深海的输出。硅藻的生理反应与其碳输出之间存在联系，因为生理学的变化会影响硅藻的属性，例如它们下沉的速度以及它们对捕食者的美味程度。因此，如果我们能够将不同硅藻的生理状况与不同物种遵循的食物网路径联系起来，我们最终可以利用硅藻生理状态和食物网结构的知识来预测有多少硅藻碳进入深海。这项研究涉及具有硅藻生理学和基因组学以及海洋化学专业知识的研究人员。这项工作最初将与美国宇航局遥感海洋出口过程（EXPORTS）现场计划一起在北太平洋亚北极地区进行。出口计划正在使用多种方法来量化上层海洋光合固定碳的出口和归宿。该研究支持本科生、研究生和博士后学者的培养。该研究还将作为针对 K-12 和初中学生的活动的基础。该研究将通过形成预测硅藻碳输出的机制基础，广泛影响我们对生物泵（将光合作用固定的有机碳输送到深海）生物学的理解。据推测，硅藻生理应激的类型和程度是驱动出口的生态系统状态的重要方面。为了检验这一假设，将评估硅藻群落的遗传组成、养分利用率和生长反应，并通过硅和铁压力的测量来支持，以评估压力作为硅藻碳输出路径的预测因子。由于铁 (Fe) 水平较低，亚北极北太平洋生态系统的特点是高营养低叶绿素 (HNLC)，而铁 (Fe) 水平是限制浮游植物利用其他营养物质的主要控制因素。在低 Fe、HNLC 系统中，硅藻以较高的 Si:C 和 Si:N 比率生长，并且应该以相对于 C 显着富集 Si 的颗粒形式有效地输出。然而，Fe 的限制也会改变硅藻的物种组成和低 Fe 带来的高 Si 需求可能会导致 HNLC 区域受到 Si 限制或 Si/Fe 共同限制。因此，HNLC 水中的 Si 和/或 Fe 胁迫程度都会改变硅藻分类组成、硅藻细胞的元素组成以及细胞通过食物网的路径，最终改变硅藻碳输出。该奖项反映了 NSF 的法定使命和通过使用基金会的智力优点和更广泛的影响审查标准进行评估，该项目被认为值得支持。

项目成果

The upper ocean silicon cycle of the subarctic Pacific during the EXPORTS field campaign

• DOI: 10.1525/elementa.2021.00087
• 发表时间: 2022
• 期刊: Elementa: Science of the Anthropocene
• 作者: M. Brzezinski;D. Varela;B. Jenkins;K. Buck;Sile M. Kafrissen;Janice L. Jones