Linking phytoplankton physiology to the biogeochemistry of silicon and carbon in the ocean

海洋浮游植物是地球系统的关键组成部分。它们每年通过光合作用提供了世界上一半的固定碳，在养分循环中起着重要作用，是海洋生态系统的基础。在所有浮游植物群中，硅藻占地球光合作用的约20%，是硅、碳和其他营养物质循环过程的主要生物驱动力。在海洋硅和碳循环中，硅藻在地表水中产生二氧化硅细胞壁，这种生物源二氧化硅通过水柱溶解，以及从表层向深水输出生物源二氧化硅和伴生碳是一些最重要的通量。尽管硅是硅藻生长所必需的元素，也是地球上第二丰富的元素，但与其他营养循环相比，我们对这些过程的了解仍然有限。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但鲜为人知的硅循环过程的理解，以及它们如何与高纬度海洋中的其他元素（如碳）相结合。气候变率正不成比例地影响着加拿大周围的海洋，这些海洋正在经历海冰覆盖、水团循环、养分输入、温度、盐度和海洋酸度的变化。因此，实验评估浮游植物对变化的响应及其对亚北极和北极海洋硅和碳生物地球化学的影响至关重要。在未来5年，我们将研究：(A)硅藻硅利用与从海洋表面到沉积物的天然硅同位素信号之间的联系，这对于解决过去到现在海洋中硅和碳循环的广泛时空变化以及硅藻生产至关重要；(B)硅藻组合组成（大小和分类群）对二氧化硅生产和碳出口的影响，硅藻组合硅藻化和结构对海洋酸化的响应。以及硅化、颗粒聚集和向深海输出碳潜力之间的关系。这些短期目标将有助于我的研究计划的长期目标，即更好地了解海洋浮游植物生态生理与生物地球化学循环之间的联系。这项研究将采用领先的方法，并为学生提供优秀的培训和合作机会，他们将接触到多学科的科学。我们的数据将极大地提高计算机海洋模型的预测能力，以评估气候变率对大气-海洋碳平衡和海洋生态系统可持续性的影响。最终，决策者可以利用这些知识制定计划和政策，减轻气候对海洋资源的影响，并为加拿大人提供有益的服务。

Marine phytoplankton are key components of the Earth system. They contribute to half of the world's carbon fixed by photosynthesis annually, play a fundamental role in nutrient cycling, and are at the base of marine ecosystems. 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 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. Despite silicon being essential for diatom growth and the second most abundant element on Earth, our knowledge of these processes is still limited compared to those of other nutrient 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 and how they couple with those of other elements, such as carbon, in high-latitude oceans. Climate variability is disproportionally affecting the oceans surrounding Canada, which are experiencing changes in sea-ice cover, water mass circulation, nutrient inputs, temperature, salinity, and ocean acidity. It is therefore critical to experimentally evaluate phytoplankton responses to change and their impact on silicon and carbon biogeochemistry in sub-Arctic and Arctic Oceans. During the next 5 years we will study: (A) the linkage between diatom silicon use and natural silicon isotopic signals from the ocean surface to sediments, which is crucial to quantify for resolving broad spatial and temporal variations in silicon and carbon cycles, and diatom production from the past to the present ocean, and (B) the impact of diatom assemblage composition (size and taxa) on silica production and carbon export, the response of diatom assemblage silicification and structure to ocean acidification, and the relationships between silicification, particle aggregation and carbon export potential to the deep ocean. These short-term objectives will contribute to the long-term goals of my research program, which are to better understand the links between phytoplankton eco-physiology and biogeochemical cycling in the ocean. This research will employ leading-edge methodologies, and provide outstanding training and collaborative opportunities for students who will be exposed to multi-disciplinary science. Our data will critically improve the predictive capacity of computer ocean models to assess the effects of climate variability on the atmospheric-oceanic carbon equilibrium and sustainability of marine ecosystems. Ultimately, policy makers can use this knowledge to create plans and policies that mitigate the effects of climate on marine resources and provide services of benefit to Canadians.