Role of phytoplankton in marine silicon cycling

浮游植物在海洋硅循环中的作用

• 批准号: RGPIN-2016-05791
• 负责人: Varela, Diana
• 金额: $ 2.11万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=709872
• 关键词: Role; phytoplankton; marine; silicon; cycling

Marine phytoplankton are key components of the Earth system. They contribute half of the world's annual photosynthetic fixation of carbon and play a fundamental role in nutrient cycling in the ocean. Of all phytoplankton groups, diatoms account for 20% of Earth's photosynthesis and are the main biological drivers of processes involved in the cycling of silicon, carbon, nitrogen and other nutrients. Production of silica cell walls by diatoms in surface waters, dissolution of this biogenic silica through the water column, and export of biogenic silica and associated carbon from surface to deep waters are some of the most important fluxes in the oceanic silicon and carbon cycles. This proposal describes an integrated field and laboratory program that will advance our understanding of these critical, but poorly known, processes of the silicon cycle. During the next 5 years, my objectives are to quantify: (A) the linkage between diatom silicon use in surface waters and the natural silicon isotopic composition of suspended and sinking particles in Subarctic waters and in Pacific source waters into the Arctic, (B) the impact of the structure of Subarctic and Arctic diatom assemblages on the silicon cycle, evaluated under natural conditions and under simulated greenhouse scenarios, (C) the coupling between silicon, nitrogen, carbon and phosphorus in marine particulate and dissolved pools, from pelagic to benthic environments. These short-term objectives will contribute to the long-term goal of my research program, which is to better understand the links between phytoplankton eco-physiology and biogeochemical cycling in the ocean. Field work will be conducted in high-latitude oceans where phytoplankton and nutrient dynamics are currently poorly described. Climate variability is disproportionally affecting these regions, which are experiencing dramatic changes in sea-ice cover, water mass circulation, temperature and seawater chemistry. It is therefore critical to experimentally evaluate phytoplankton responses and biogeochemical processes in Subarctic and Arctic seas of the NE Pacific and western Arctic. Experimental work will employ leading-edge methodologies, such as high-resolution inductively coupled plasma mass spectrometry for measuring silicon isotopic abundance, and low-level beta counting of radioactive silicon and fluorescence imaging techniques for measuring silica production and dissolution. The projects described in this proposal will provide excellent training opportunities for graduate and undergraduate students who will be exposed to interdisciplinary science. This research will fill critical gaps in our current knowledge of biologically mediated processes of the silicon cycle, and will advance our understanding of variations in marine paleoproductivity, controls on biogeochemical cycles, and the magnitude of carbon export in high-latitude oceans.

海洋浮游植物是地球系统的关键组成部分。它们贡献了世界每年光合固碳的一半，并在海洋营养循环中发挥着根本作用。在所有浮游植物中，硅藻占地球光合作用的20%，是硅，碳，氮和其他营养物质循环过程的主要生物驱动力。表层沃茨中的硅藻产生二氧化硅细胞壁，这种生物二氧化硅通过水柱溶解，以及生物二氧化硅和相关碳从表层输出到深层沃茨是海洋硅和碳循环中最重要的通量。该提案描述了一个综合的现场和实验室计划，将促进我们对这些关键的，但鲜为人知的硅循环过程的理解。在未来五年，我们的目标是量化： (A)表层沃茨中硅藻硅的使用与亚北极沃茨和进入北极的太平洋源沃茨中悬浮和下沉颗粒的天然硅同位素组成之间的联系， (B)在自然条件下和模拟温室情景下评估的亚北极和北极硅藻群落结构对硅循环的影响， (C)海洋颗粒物和溶解池中的硅、氮、碳和磷之间的耦合，从远洋到海底环境。 这些短期目标将有助于我的研究计划的长期目标，这是为了更好地了解浮游植物生态生理学和海洋地球化学循环之间的联系。 实地工作将在高纬度海洋进行，那里的浮游植物和营养物动态目前描述得很差。气候多变性对这些地区产生了不利影响，这些地区的海冰覆盖、水团循环、温度和海水化学性质都发生了巨大变化。因此，在东北太平洋和北极西部的亚北极海和北极海，通过实验评估浮游植物的响应和生态地球化学过程是至关重要的。 实验工作将采用先进的方法，如测量硅同位素丰度的高分辨率电感耦合等离子体质谱法，以及测量二氧化硅生产和溶解的放射性硅的低水平β计数和荧光成像技术。本提案中描述的项目将为研究生和本科生提供极好的培训机会，他们将接触跨学科科学。 这项研究将填补我们目前对生物介导的硅循环过程的认识中的关键空白，并将促进我们对海洋古生产力变化、对地球化学循环的控制以及高纬度海洋碳输出量的理解。