Collaborative Research: Iron Regulation of the Food Quality of Phytoplankton in Acidified Eastern Boundary Upwelling Systems

由于大气中二氧化碳的增加，东部边界流上升流系统预计将经历极端酸化（pH值降至7.3或更低），而东部边界流上升流系统是世界上一些主要渔业的家园，为人类提供了支持。可能会对微量金属（特别是铁）和氮的生物利用度产生影响，因此浮游植物的物种组成和生理也会发生变化。海洋酸化的一个未被充分研究的方面是它对浮游植物脂类和多不饱和脂肪酸（PUFA）的产生的影响，如二十碳五烯酸（EPA）和二十二碳六烯酸（DHA）以及其他必需脂肪酸（EFA），这些必需脂肪酸是高营养水平所依赖的。在这个项目中，来自旧金山州立大学、夏威夷大学和缅因大学的一个研究小组将研究极端海洋酸化（OA）在充满铁和耗尽上升流条件下对物种组成、总脂质产生和PUFAs特定产生的影响。有两种指导假设：(1)海洋极端酸化会通过碳吸收和氮吸收的不平衡增加浮游植物的脂质合成和EFA的产生；(2)由于酸化海水对细胞生理的直接影响或浮游植物群落组成的显著变化，自然上升流区海洋极端酸化将改变PUFA和EFA的数量和组成。为了说明这些影响，将对加利福尼亚上升流区目前的富铁和缺铁上升流区进行研究。该团队将使用受控的实验室单克隆、半连续培养实验，对具有代表性的沿海浮游植物分离物进行不同pH值和铁可用性的培养，以表征在极端pH环境条件下的耐受性/成功性，并量化细胞对综合应激源的生理反应。在项目的第三年，将研究社区对同一组压力源的反应。更广泛的影响：由于海洋渔业在全球的重要性和迄今为止对海洋酸化潜在威胁的适度理解，本研究的主题跨越了各种学科，机构，学术政府和国家边界。这三个参与机构的研究人员将领导各种各样的公共教育推广活动，为K-12学生和整个社会带来好处。研究生和本科生也将是研究工作的重要组成部分。

Within the next century, Eastern Boundary Current upwelling systems, which are home to some of the major fisheries that support humans worldwide, are expected to undergo extreme acidification (pH falling to 7.3 or lower) because of increasing atmospheric CO2. Impacts on trace metal (especially iron) and nitrogen bioavailability are likely, and consequently changes in phytoplankton species composition and physiology are also to be expected. One understudied aspect of ocean acidification is its impact on the production of phytoplankton lipids and polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and other essential fatty acids (EFA) upon which higher trophic levels depend.In this project a research team from San Francisco State University, University of Hawaii, and University of Maine will study the effect of extreme ocean acidification (OA) under iron replete and deplete upwelling conditions in regard to changes in species composition, total lipid production, and the specific production of PUFAs. There are two guiding hypotheses: (1) Extreme ocean acidification will increase lipid synthesis and EFA production in phytoplankton through the imbalance between carbon uptake and decreased nitrogen uptake; and (2) Extreme ocean acidification in natural upwelling regions will change the amount and composition of PUFA and EFA produced due either the direct effects of acidified seawater on cell physiology or to marked shifts in phytoplankton community composition. Current Fe-replete and Fe-deplete upwelling zones in the California upwelling region will be investigated to illustrate these impacts. The team will use controlled laboratory monoclonal, semi-continuous culture experiments to subject representative coastal phytoplankton isolates to varying pH and Fe availability to characterize tolerance/success under extreme pH environmental conditions and to quantify cellular physiological response to the combined stressors. In the third year of the project, community-level responses to the same set of stressors will be studied.Broader Impacts: Because of the global importance of marine fisheries and the as-yet modest understanding of the potential threats of ocean acidification, the topic of this study spans a variety of disciplinary, institutional, academic-government, and national boundaries. Researchers at all three participating institution will lead a variety of public educational outreach activities for the benefit of K-12 students and for society at-large. Graduate and undergraduate students will also be an important part of the research effort.