Resolving the physiological basis for fluorescence diagnostics of iron stress in natural phytoplankton populations

解决天然浮游植物种群中铁胁迫荧光诊断的生理基础

• 批准号: 0726116
• 负责人: Michael Behrenfeld
• 金额: $ 65.91万
• 依托单位: Oregon State University
• 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: 2007-09-15 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0726116&HistoricalAwards=false
• 关键词: Resolving; physiological; basis; fluorescence; diagnostics

Phytoplankton constitute the base of nearly all ocean ecosystems and have a profound influence on the global cycling of carbon and other nutrients. The growth rate and distribution of phytoplankton reflect the distribution of growth limiting factors such as nutrients and light. Understanding the environmental factors regulating phytoplankton biomass and activity has been a foremost goal in biological oceanography. This problem has been approached from many directions (including bottle enrichment studies, molecular probes, and in situ nutrient enrichments), with each technique having unique advantages and disadvantages. Recent research in the tropical Pacific Ocean has uncovered a new set of fluorescence-based diagnostics that allow detection of particular micronutrient and macronutrient growth conditions. As the fluorescence features are truly striking and can be evaluated without the need for incubations or enrichments, they provide a path to investigate nutrient constraints in natural phytoplankton populations at a scale inaccessible to the more traditional approaches. The diagnostic fluorescence properties were resolved using over 11 years of field measurements and involve diel changes in normalized variable fluorescence, the functional absorption cross section of photosystem II, and the electron turnover time of the plastoquinone pool. An underlying mechanistic basis for the diagnostics has been proposed based on decades of directed laboratory research on iron stress effects in phytoplankton, but an outstanding issue remains: the inferred mechanisms been never demonstrated in the field and the diagnostic diel fluorescence patterns have never been reproduced in the laboratory. The lack of confirmation of the physiological mechanisms involved (and thus their specificity to specific nutrient conditions) undermines the utility of the diagnostics to describe nutrient growth conditions. This project aims at bridging the gap between physiological processes and expressions in natural phytoplankton populations. The proposed approach includes field and laboratory components, both aimed at linking the diel fluorescence characteristics to proposed (or revised) mechanisms. Ship time for the field component is being provided at no cost to the project by the NOAA TAO Program. The intellectual merit of this project resides in (1) an improved understanding of iron-stress effects in natural marine phytoplankton populations and their impacts on measured photosynthetic efficiencies, (2) resolving specific cellular stress responses in the laboratory in association with variable fluorescence attributes, and (3) if successful, the establishment of a new approach for assessing nutrient stress in the open ocean on a truly basin-scale. Broader Impacts: Broader impacts include (1) a potential significant adjustment in the contribution of HNLC regions to global ocean production if the proposed mechanisms for the fluorescence diagnostic are correct, (2) an approach to globally monitor the distribution and variability of iron-stressed phytoplankton populations using remotely-sensed natural fluorescence, (3) an important contribution toward better physiological interpretation of variable fluorescence data collected in the field. This project will contribute to training of a post doctoral fellow and every effort will be made to recruit a qualified minority for the position. The selected associate will be encouraged to regularly participate in professional meetings and society activities. In addition, continued public outreach and broad dissemination of results will be carried out.

浮游植物构成了几乎所有海洋生态系统的基础，对全球碳和其他营养物质的循环具有深远的影响。浮游植物的生长速度和分布反映了营养物质和光照等生长限制因素的分布情况。了解调节浮游植物生物量和活性的环境因素一直是生物海洋学的首要目标。人们从多个方向解决了这个问题（包括瓶富集研究、分子探针和原位营养物富集），每种技术都有独特的优点和缺点。最近在热带太平洋的研究发现了一套新的基于荧光的诊断方法，可以检测特定的微量营养素和常量营养素的生长条件。由于荧光特征确实引人注目，并且无需孵化或富集即可进行评估，因此它们提供了一种以传统方法无法达到的规模研究自然浮游植物种群营养限制的途径。诊断荧光特性通过超过 11 年的现场测量得到解决，涉及归一化可变荧光的昼夜变化、光系统 II 的功能吸收截面以及质体醌池的电子周转时间。基于几十年来对浮游植物中铁胁迫效应的定向实验室研究，提出了诊断的潜在机制基础，但仍然存在一个突出的问题：推断的机制从未在现场得到证实，并且诊断性昼夜荧光模式也从未在实验室中重现。缺乏对所涉及的生理机制的确认（以及它们对特定营养条件的特异性）破坏了诊断学描述营养生长条件的效用。该项目旨在弥合自然浮游植物种群的生理过程和表达之间的差距。所提出的方法包括现场和实验室部分，两者都旨在将柴油荧光特性与提议（或修订）的机制联系起来。 NOAA TAO 计划免费为该项目提供现场组件的运输时间。该项目的智力价值在于（1）更好地了解天然海洋浮游植物种群中的铁胁迫效应及其对测量的光合效率的影响，（2）解决实验室中与可变荧光属性相关的特定细胞胁迫反应，以及（3）如果成功，将建立一种在真正的盆地规模上评估公海营养胁迫的新方法。更广泛的影响：更广泛的影响包括（1）如果所提出的荧光诊断机制正确的话，HNLC 地区对全球海洋生产的贡献可能会发生重大调整；（2）一种利用遥感天然荧光在全球范围内监测铁胁迫浮游植物种群分布和变异性的方法；（3）对现场收集的可变荧光数据进行更好的生理解释的重要贡献。该项目将有助于培养博士后研究员，并将尽一切努力招募合格的少数人担任该职位。我们将鼓励选定的员工定期参加专业会议和社会活动。此外，还将继续开展公众宣传和广泛传播成果。