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.

该项目的重点是海洋中一组称为硅藻的微观单细胞光合生物。硅藻漂浮在海洋表面，是一组统称为浮游植物的生物体的一部分。有成千上万种不同种类的硅藻分布在全球海洋中。 著名的海洋学家亨利毕格罗曾经说过：“所有的鱼都是硅藻”，这反映了硅藻作为支撑世界上最大渔业的食物链基础的重要性。尽管硅藻的体积很小，但它们的光合作用每年产生地球上20%的氧气。比陆地上所有的热带雨林都多。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的数量。由于硅藻像绿色植物一样是光合作用者，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，如氮和磷，以及硅藻特有的用于构建其玻璃壳的硅。 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出口。硅藻的生理反应和它们的碳输出之间的联系是因为生理学的变化影响硅藻的属性，比如它们下沉的速度和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途径联系起来，我们最终可以利用硅藻生理状况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调查人员。这项工作最初将在亚北极北太平洋与美国航天局遥感海洋出口过程（出口）现场方案一起进行。EXPORTS计划正在使用各种各样的方法来量化海洋上层光合作用固定碳的输出和命运。该研究支持本科生，研究生和博士后学者的培训。这项研究还将作为针对K-12和初中学生的活动的基础。这项研究将通过形成预测硅藻碳出口的机制基础，广泛影响我们对生物泵（光合作用固定的有机碳向深海的运输）生物学的理解。据推测，硅藻生理压力的类型和程度是驱动出口的生态系统状态的重要方面。为了验证这一假设，硅藻群落的遗传组成，营养物质的使用率和生长反应将进行评估，并支持硅和铁应力的测量，以评估应力作为硅藻碳输出路径的预测因子。亚北极N.太平洋生态系统的特点是高营养低叶绿素（HNLC），由于低铁（Fe）水平是限制浮游植物利用其他营养盐的主要控制因素。在低Fe、HNLC系统中，硅藻在升高的Si：C和Si：N比率下生长并且应当作为相对于C显著富集Si的颗粒有效地输出已经是范例。然而，Fe限制也改变硅藻物种组成，并且由低Fe施加的高Si需求可以驱使HNLC区域进行Si限制或Si/Fe共限制。因此，硅和/或铁应力的程度在HNLC沃茨都可以改变硅藻的分类组成，硅藻细胞的元素组成，并通过最终改变硅藻碳export.This奖项细胞遵循的食物网反映NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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