Accomplishment Based Renewal: An iron limitation mosaic within the central California Current System

东部边界上升流系统长期以来因其高浮游植物生产力而被公认。Carr和Kearns(2003)在对东部边界流系统进行详细比较时报告说，大西洋东部边界流系统中给定的常量营养素浓度所维持的生物量是太平洋边界流系统的两倍。作者总结道：“目前尚不清楚有效营养支持的生物量的明显差异是由于浮游植物群落效率的差异，可能与铁的可获得性有关，还是与放牧压力有关。”他们提出，搁板的宽度可以被认为是衡量底栖动物铁有效性的一个指标。对于给定的常量营养素浓度，生物量最低的是秘鲁-洪堡洋流和加利福尼亚洋流系统的加利福尼亚州北部地区，这两个地区的灰尘输入都很少，大陆架也相对狭窄。在这个以成就为基础的更新项目中，加州大学圣克鲁斯分校的一位海洋痕量金属地球化学家和他的学生及同事将继续数十年的探索，以了解铁在加州中部电流系统(CCCS)中的作用。实地工作将把地表水中持续进行的铁和营养数据以及一系列垂直剖面结合起来。重点将包括CCCS内的三个区域：各种活跃的富铁和贫铁的沿海上升流制度，富铁的加利福尼亚州海流过渡区，其硝酸盐含量较高，但叶绿素浓度相对较低和均匀，以及近海营养较少的加利福尼亚州海流。他们将绘制铁和其他微量和常量营养素的表面和深度分布图。有四个具体的目标涉及表征与有机Fe(III)结合的有机配体，测定大陆架上低氧水中Fe(II)和Fe(III)的浓度，检查颗粒和溶解形式Fe之间的交换，以及研究涡流在CCCS富涡流过渡水域中的作用。更广泛的影响对科学的直接好处：CCS引起了人们的极大兴趣，因为它在浮游植物生产力和支持更高的营养水平方面具有重要意义。到目前为止，CCS的研究重点一直是物理学和生物学之间的关系。这项研究将把微量营养素化学的重要作用加入到这幅图中。它还将在提前确保船期和为其他合作研究提供后勤支持方面发挥重要作用。这对于合作的科学家来说是非常有价值和成本效益的，因为有了提供的水文、营养和痕量金属数据，他们可以专注于他们免费的研究工作。推广和教育：该项目将为加州大学洛杉矶分校的两名现有研究生提供资金，他们还将在那里接受课程培训，课程包括i)科学交流，ii)海洋科学职业，和iii)补助金撰写。该项目的一个更广泛的影响目标是，通过将研究目标转化为广泛分发的教材供课堂使用，促进与海洋科学有关的专题的教与学。为了实现这一目标，该团队将与加州大学朗姆海洋实验室的西摩发现中心合作。探索中心每年接待14,000名游客，该项目将提供资金，在CCS开发一个关于限制营养物质和浮游植物水华发育的互动展示。

Eastern boundary upwelling systems have long been recognized for their high phytoplankton productivity. Carr and Kearns (2003), in a detailed comparison of eastern boundary current systems, reported that biomass sustained by a given macronutrient concentration in Atlantic eastern boundary current systems was twice as large as those systems in the Pacific. The authors concluded "It is not clear whether the apparent difference in biomass supported by available nutrients is due to differences in the efficiency of the phytoplankton community, perhaps related to the availability of iron, or to grazing pressure." They suggested that the width of the shelf might be considered a proxy for the benthic availability of iron. The lowest biomass for a given macronutrient concentration was in the Peru-Humboldt Current and in the northern California region of the California Current System, both areas with low dust inputs and a relatively narrow shelf. In this Accomplishment Based Renewal project, a marine trace metal geochemist at the University of California - Santa Cruz and his students and colleagues will continue a decades-old quest to understand the role of iron in the central California Current System (cCCS). Field efforts will combine continuous underway iron and nutrient data in surface waters and a series of vertical profiles. The focus will include three regions within the cCCS: a variety of active Fe-replete and Fe-deplete coastal upwelling regimes, the eddy-rich California Current transition zone that is Fe-limited and has elevated nitrate but relatively low and uniform chlorophyll concentrations, and the offshore, oligotrophic California Current. They will map surface and depth distributions of Fe and other micro- and macronutrients. There are four specific goals dealing with characterizing the organic Fe(III)-binding organic ligands, determining Fe(II) and Fe(III) concentrations in hypoxic waters over the shelf, examining the exchange between particulate and dissolved forms of Fe, and studying the roles of eddies in the eddy-rich transition waters of the cCCS. Broader ImpactsDirect Benefits to Science: There is a great deal of interest in the CCS because of its importance in terms of phytoplankton productivity and the support of higher trophic levels. Until now, the emphasis in studies of the CCS has been on relationships between physics and biology. This study will insert the important role of micronutrient chemistry into the picture. It will also serve an important role in securing ship time in advance and providing logistical support for other collaborative studies. This is extremely valuable and cost effective for collaborating scientists since with the hydrography, nutrient and trace metal data provided, they can focus on their complimentary research efforts.Outreach and Education: The project will provide funding for two current graduate students at UCSC, where they will also receive course training in a curriculum that includes i) scientific communication, ii) careers in marine science, and iii) grant writing. A broader impact goal of this project is to facilitate teaching and learning on marine science-related topics through translating research objectives into widely distributed educational materials for classroom use. To accomplish this, the team will partner with the Seymour Discovery Center at the Long Marine Lab, UCSC. The Discovery Center receives 14,000 visitors each year, and the project will provide funds to develop an interactive display on limiting nutrients and phytoplankton bloom development in the CCS.