Influence of continental margin iron on phytoplankton species composition and production in the northern Gulf of Alaska

大陆边缘铁对阿拉斯加湾北部浮游植物物种组成和生产的影响

• 批准号: 0726858
• 负责人: Raphael Kudela
• 金额: $ 37.5万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0726858&HistoricalAwards=false
• 关键词: Influence; continental; margin; iron; phytoplankton

The northern Gulf of Alaska (GOA) is among the ocean's most productive ecosystems and supports a rich coastal fisheries. Although strong cross-shelf gradients in phytoplankton (chlorophyll decreasing offshore) have been identified, yet the specific factors that regulate and control primary production have only been hypothesized. Cross-shelf patterns in primary production/species composition are consistent with a gradient of iron availability (Strom et al., in press), but this has yet to be rigorously tested. In collaboration with the NSF-funded project Mixing of iron-rich coastal waters with nutrient-rich HNLC waters leading to enhanced phytoplankton biomass: a focus on the northwest Gulf ofAlaska (K. Bruland), this project will examine the influence of cross-shelf exchange and physico-chemical gradients on phytoplankton distributions, physiology, and assemblage structure in the northern GOA, making use of complementary high-resolution iron data and building on the results from previous studies. The proposed work directly complements studies accomplished by the US GLOBEC Coastal Gulf of Alaska (CGOA) program, and is essential to link Bruland's study of trace metal dynamics and speciation to key biological processes. Bruland's project seeks to quantify the inputs of iron from the Copper River, AK, and to characterize and assess the interactions among river inputs and shelf/offshore systems. The quasi-synoptic sampling scheme enables characterization at the mesoscale, the dominant scale of variability in the region. The station grid allows quasi-synoptic sampling while remaining flexible to take advantage of interesting mesoscale features. Should a mesoscale eddy be present, the study will focus on the role that eddy circulation plays in facilitating the offshore transport (suggested by Stabeno et al., 2004) of bio-active trace metals. This project aims to provide a detailed examination of the phytoplankton rates, assemblage structure, and response to cross-shelf transport/ mixing across gradients in iron and light to better parameterize satellite observations and future modeling efforts. Specific questions include: 1) Do cross-shelf gradients in iron correspond to patterns of carbon assimilation, nutrient uptake, new production, and species composition of phytoplankton in the northern GOA? 2) Do iron and light interact to structure species assemblages and patterns of carbon assimilation? 3) How do frontal regions influence phytoplankton distributions and physiology? 4) What bio-optical properties characterize the different water masses (inshore/offshore), and how well do satellite observations describe phytoplankton standing stocks and rates? 5) What chemical characteristics define the deep Fe-source identified by Lam et al. (2006), and what is the bioavailability of this material when mixed with near-surface waters? This study will provide the first concurrent measurements of iron concentration and phytoplankton physiological parameters in the waters of the northern GOA. Broader Impacts. The proposed work will be extremely valuable in testing hypotheses arising from many years of effort by GLOBEC CGOA. Data from this study will further our understanding of ocean-climate interactions in an economically and ecologically important region. The results could have far-reaching implications for our basic understanding of coupled biogeochemical cycles in shelf ecosystems. This will have both direct and indirect impacts on our understanding of carbon cycling, as well as how other researchers parameterize regional and global biogeochemical models. Undergraduate, graduate and post-doctoral education will be furthered through active participation in lab, field, and data synthesis activities. Two full time graduate students and a post-doc (this proposal and an NSERC Fellowship) will receive a unique educational background in multidisciplinary oceanography, spanning physical, chemical, and biological processes.

阿拉斯加北方海湾（果阿）是海洋中最具生产力的生态系统之一，并支持丰富的沿海渔业。虽然已经确定了浮游植物的强烈跨大陆架梯度（近海叶绿素减少），但调节和控制初级生产的具体因素只是假设。初级生产/物种组成的跨大陆架模式与铁可用性的梯度一致（Strom等人，但这还有待严格检验。与NSF资助的项目“将富含铁的沿海沃茨与富含营养的HNLC沃茨混合，导致浮游植物生物量增加：重点关注阿拉斯加湾西北部（K。Bruland），该项目将利用补充性高分辨率铁数据并在以往研究结果的基础上，研究跨大陆架交换和物理化学梯度对北方果阿浮游植物分布、生理和群落结构的影响。拟议的工作直接补充了美国GLOBEC阿拉斯加沿海海湾（CGOA）计划完成的研究，并且对于将Bruland的痕量金属动力学和物种形成研究与关键生物过程联系起来至关重要。Bruland的项目旨在量化来自AK铜河的铁输入，并描述和评估河流输入和大陆架/近海系统之间的相互作用。准天气抽样方案能够在中尺度上进行表征，这是该区域变化的主要尺度。站网格允许准天气采样，同时保持灵活，以利用有趣的中尺度功能。如果存在中尺度涡旋，则研究将侧重于涡旋环流在促进近海输送方面所起的作用（Stabeno等人建议，2004）的生物活性微量金属。该项目的目的是提供一个详细的检查浮游植物率，组合结构，并响应跨货架运输/混合跨梯度的铁和光，以更好的参数化卫星观测和未来的建模工作。具体问题包括：1）铁的跨陆架梯度与北方果阿的碳同化、营养吸收、新生产和浮游植物的物种组成模式相对应吗？2)铁和光的相互作用对结构物种组合和碳同化模式有影响吗？3)锋区如何影响浮游植物的分布和生理？4)不同水团（近岸/离岸）的生物光学特性是什么？卫星观测对浮游植物现存量和比率的描述如何？5)Lam等人（2006年）确定的深层铁源的化学特征是什么？这种物质与近地表沃茨混合后的生物利用度是什么？这项研究将首次同时测量北方果阿沃茨的铁浓度和浮游植物生理参数。更广泛的影响。拟议的工作将是非常有价值的测试假设所产生的GLOBEC CGOA多年的努力。这项研究的数据将进一步加深我们对这一具有重要经济和生态意义的地区的海洋-气候相互作用的理解。这些结果可能会对我们对陆架生态系统中耦合地球化学循环的基本理解产生深远的影响。这将直接和间接地影响我们对碳循环的理解，以及其他研究人员如何参数化区域和全球地球化学模型。本科，研究生和博士后教育将通过积极参与实验室，现场和数据合成活动得到进一步发展。两名全日制研究生和一名博士后（该提案和NSERC奖学金）将获得多学科海洋学的独特教育背景，涵盖物理，化学和生物过程。