Trace element cycling in upwelling filaments in the California Current System

锰、铁、镍、钴、铜、锌等微量元素在海洋生物过程中发挥着重要作用。在浮游植物生长并支撑海洋食物网基础的表层水域，微量元素的存在浓度往往小得惊人。这给海洋生物带来了巨大的挑战，微量元素可能是浮游植物生产力的限制因素。海洋系统中的生物过程，如浮游植物生长、放牧、溶解有机质生产和沉积，反过来可以对微量元素在海洋中的循环产生重要影响。这些相互关系是复杂的，并没有得到很好的理解，但它们对生态系统生产力和全球养分循环具有重要的影响。这项研究旨在研究加利福尼亚州沿海洋流系统中具有动态和生态意义的上升丝状环境中微量元素分布与化学和生物过程之间的关系。实地研究将利用正在进行的加州当前生态系统长期生态研究(CCE-LTER)网站，该网站已经为计划于2019年和2021年进行的邮轮提供资金。该项目将支持研究生的教育和培训，以及通过CCE-LTER项目开展的教育和外展活动，包括指导本科生参与研究项目，并通过斯克里普斯白桦水族馆促进公共教育和外展。人们日益认识到，微量元素的供应对海洋浮游植物群落的生产力和结构具有重要影响。痕量元素本身在海洋系统中的停留时间、化学形态和循环等方面都受到生物过程的强烈影响。现场过程研究充分表征了上层海洋系统的生物和物理动力学，并在现场同时测定多种微量元素，这有可能极大地帮助我们了解微量元素与生物群之间的耦合作用，但由于其跨学科的复杂性和成本，此类研究相对较少。该提案寻求通过利用正在进行的加州当前生态系统长期生态研究计划(CCE-LTER)来进行此类研究的支持。即将在2019年和2021年资助的两次LTER过程巡航将通过结合勘测绘图、详细采样和拉格朗日过程测量来表征上升细丝在向近海移动时的生物地球化学和生态演变。该项目为购置和建立海洋FAST微微浓缩系统和电感耦合等离子体质谱分析时间提供资金，这将使在这些航行中研究多种微量元素成为可能。这种类型的中尺度特征很少从微量元素生物地球化学的角度来描述，我们预计我们的发现将引起海洋界的广泛兴趣。在拟议的工作中，将检验一些关于上升流丝中微量元素的来源、汇和循环的假设。该项目还将利用CCE-LTER正在进行的研究合作，将多元素微量元素数据集与关于群落结构和功能以及溶解有机物组成的分子级信息结合起来。这将有助于探索生物群落对多因素共同限制的反应，有机分子在调节痕量金属循环中的作用，以及痕量金属循环与碳、氮和硅循环的耦合。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Trace element micronutrients such as manganese, iron, nickel, cobalt, copper and zinc play important roles in biological processes in the ocean. In surface waters where phytoplankton grow and support the base of the marine food web, trace elements are often present at vanishingly small concentrations. This presents great challenges to marine life, and trace elements can be limiting factors for phytoplankton productivity. Biological processes in marine systems like phytoplankton growth, grazing, dissolved organic matter production, and sedimentation can in turn have important impacts on how trace elements cycle through the ocean. These inter-relationships are complex and not very well understood, but they have important ramifications for ecosystem productivity and global nutrient cycling. The research proposed here seeks to study the relationships between trace element distributions and chemistry and biological processes in a dynamic and ecologically significant environment - upwelling filaments in the coastal California Current System. Field studies will take advantage of the ongoing California Current Ecosystem Long Term Ecological Research (CCE-LTER) site, which already has funded cruises planned for 2019 and 2021. This project will support the education and training of graduate students, and the participation of both the PI and graduate students in education and outreach activities carried out through the CCE-LTER project, including mentoring undergraduates in research projects and contributing to public education and outreach through the Birch Aquarium at Scripps.The availability of trace element micronutrients is increasingly recognized as an important influence on the productivity and structure of marine phytoplankton communities. Trace elements themselves are strongly influenced by biological processes in terms of their residence time, chemical speciation, and cycling in marine systems. Field process studies which fully characterize the biological and physical dynamics of upper ocean systems with simultaneous determination of multiple trace elements in situ have the potential to greatly inform our understanding of the coupled interactions between trace elements and biota, but such studies are comparatively rare due to their interdisciplinary complexity and expense. This proposal seeks support to perform such a study by leveraging the ongoing California Current Ecosystem Long Term Ecological Research program (CCE-LTER). Two upcoming funded LTER process cruises in 2019 and 2021 will characterize the biogeochemical and ecological evolution of upwelling filaments as they move offshore via a combination of survey mapping, detailed sampling and Lagrangian process measurements. This project funds the acquisition and setup of a seaFAST pico preconcentration system and ICP-MS analytical time which will enable the study of multiple trace elements in the context of these cruises. This type of mesoscale feature has rarely been characterized from the standpoint of trace element biogeochemistry, and we anticipate that our findings will be of broad interest to the oceanographic community. A number of hypotheses regarding the sources, sinks and cycling of trace elements in an upwelling filament will be examined in the proposed work. This project will also take advantage of ongoing research collaborations within CCE-LTER to couple multi-elemental trace element data sets with molecular-level information on community structure and function and dissolved organic matter composition. This will facilitate exploration of the response of biological communities to multi-factorial co-limitation, the role of organic molecules in mediating trace metal cycles, and the coupling of trace metal cycles with the cycles of carbon, nitrogen, and silica.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.