RAPID: A Unique Cruise Opportunity to Test the Effect of Trace Metal Limitation on Oxidative Stress and Coral Bleaching

RAPID：测试微量金属限制对氧化应激和珊瑚白化影响的独特游轮机会

• 批准号: 1039583
• 负责人: Mark Wells
• 金额: $ 10.41万
• 依托单位: University of Maine
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-06-01 至 2011-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1039583&HistoricalAwards=false
• 关键词: RAPID; Unique; Cruise; Opportunity; Test

Intellectual Merit. Coral bleaching has increased dramatically in frequency, severity, and geographic extent since the 1980's and this trend is anticipated to continue, causing major environmental and economic impacts in tropical regions. This bleaching, or loss by corals of their photosynthetic endosymbiotic dinoflagellates (zooxanthellae; Symbiodinium spp.), appears to result from increased oxidative stress arising from the combined effects of elevated temperature at high light intensities. However, the mechanisms underlying this failure are not understood. The premise of the PIs' current project entitled "Effects of Trace Metal Limitation on Oxidative Stress in Zooxanthellae and Its Role in Coral Bleaching" (OCE - 0648478) is that the necessary up-regulation of zooxanthellae antioxidant defenses is restricted by low concentrations of dissolved Fe, Zn and Cu; metals essential for antioxidant enzyme function (Cu, Zn-, Mn-, and Fe-SOD; catalase [Fe]; ascorbate peroxidase [Fe]). Findings from their laboratory and field manipulation experiments show that restricting Fe, and Cu/Zn availability to coral hosts under high (but not low) temperature and light intensity indeed can significantly decrease both photosynthetic efficiency of symbionts in-hospite and ROS enzyme activities, while increasing non-photosynthetic quenching of their photosystems; each indicators of the onset of bleaching conditions. However, although there is high integrity within each experiment, they have found this pattern is not consistent with all coral colonies. Based on limited sampling, it appears that corals collected from the outer shelf region normally (but not always) display indications of oxidative stress under conditions of decreased metal availability, while those collected nearshore, or maintained in coastally-derived flowing seawater (where dissolved metal concentrations are higher), often show little discernable effect. Excess metal uptake and storage is well described in the marine phytoplankton literature, which suggests that the history of the coral metal exposure is a critical factor, both with respect to our experiments as well as to the distribution of coral bleaching observed. The PIs have an unique and unforeseen opportunity to test this hypothesis by joining an Australian Institute for Marine Sciences research cruise to Flinders Reef; an offshore atoll in the Coral Sea that is substantially more distant from sporadic terrestrial metal inputs that our previous study sites. They will participate in this cruise to run on-deck incubations testing the effect of reduced and marginally elevated Fe, Cu, Zn and Mn concentrations on coral photosynthetic efficiency, ROS enzyme activities, symbiont pigment composition, and ROS enzyme and other gene expression. This geographical site will provide the ideal test site for verifying their findings of metal effects on oxidative stress in zooxanthellae, and identify some of the key mechanisms and nutritional factors contributing to the increasingly frequent and severe coral bleaching events in tropical waters.Broader Impacts: This project will provide a unique research opportunity for two graduate students and a junior female Ph.D. scientist, who will use aspects of the work for their thesis and career development. The research addresses the fundamental unknowns of the controls of coral bleaching, one of the leading threats to marine biodiversity and economic stability of tropical nations. The findings will provide a key test of laboratory- and field-developed hypotheses of the role of trace metal limitation as a contributor to oxidative stress of zooxanthellae and their coral hosts; a precursor to coral bleaching. A modular series of lectures and demonstrations targeting both upper K-12 and undergraduates will be developed and will be incorporated into existing outreach programs and undergraduate courses in Marine Science at the University of Maine. The phototrophic symbiosis between zooxanthellae and corals, and its disruption by physical environmental factors, provides an inherently powerful case study for the integration of chemistry, physics, and biology that will illustrate to marine science undergraduates the need for rigorous training in the quantitative physical sciences. The findings will provide key insights to the factors that influence the severity of bleaching events, and possibly suggest realistic mitigation strategies to minimize bleaching events in localized environmentally or economically sensitive regions.

智力优点。自 20 世纪 80 年代以来，珊瑚白化的频率、严重程度和地理范围急剧增加，预计这一趋势将持续下去，对热带地区造成重大环境和经济影响。珊瑚的这种白化或光合作用内共生甲藻（虫黄藻；共生藻属）的损失似乎是由于高光强度下温度升高的综合影响所引起的氧化应激增加所致。然而，这种失败背后的机制尚不清楚。 PI 目前的题为“微量金属限制对虫黄藻氧化应激的影响及其在珊瑚白化中的作用”（OCE - 0648478）的前提是，虫黄藻抗氧化防御的必要上调受到低浓度溶解的铁、锌和铜的限制；抗氧化酶功能所必需的金属（Cu、Zn-、Mn- 和 Fe-SOD；过氧化氢酶 [Fe]；抗坏血酸过氧化物酶 [Fe]）。他们的实验室和现场操作实验的结果表明，在高温（但不是低温）和光强度下限制珊瑚宿主对铁和铜/锌的利用确实可以显着降低共生体的光合作用效率和ROS酶活性，同时增加其光系统的非光合作用猝灭；每一项指标都表明白化状况的发生。然而，尽管每个实验都有很高的完整性，但他们发现这种模式并不与所有珊瑚群落一致。根据有限的采样，从外陆架区域采集的珊瑚通常（但并非总是）在金属可用性下降的情况下显示出氧化应激的迹象，而在近岸采集的珊瑚或在沿海衍生的流动海水中（其中溶解的金属浓度较高）保存的珊瑚通常表现出很少的可辨别的影响。海洋浮游植物文献充分描述了过量金属的吸收和储存，这表明珊瑚金属暴露的历史是一个关键因素，无论是对于我们的实验还是对于观察到的珊瑚白化的分布都是如此。 PI 有一个独特且不可预见的机会通过参加澳大利亚海洋科学研究所前往弗林德斯礁的研究巡航来检验这一假设；珊瑚海的一个近海环礁，距离我们之前研究地点的零星陆地金属输入地要远得多。他们将参加这次航行，在甲板上进行孵化，测试铁、铜、锌和锰浓度降低和略微升高对珊瑚光合效率、ROS 酶活性、共生体色素组成以及 ROS 酶和其他基因表达的影响。该地理位置将提供理想的测试地点，以验证金属对虫黄藻氧化应激的影响的发现，并确定导致热带水域珊瑚白化事件日益频繁和严重的一些关键机制和营养因素。 更广泛的影响：该项目将为两名研究生和一名低年级女博士提供独特的研究机会。科学家，他们将利用工作的某些方面来完成他们的论文和职业发展。该研究解决了珊瑚白化控制的基本未知问题，珊瑚白化是对海洋生物多样性和热带国家经济稳定的主要威胁之一。这些发现将为实验室和现场提出的假设提供关键测试，即痕量金属限制对虫黄藻及其珊瑚宿主的氧化应激有促进作用；珊瑚白化的前兆。将开发针对 K-12 高年级学生和本科生的模块化系列讲座和演示，并将其纳入缅因大学现有的外展计划和海洋科学本科课程。虫黄藻和珊瑚之间的光养共生及其受到物理环境因素的破坏，为化学、物理和生物学的整合提供了一个内在强大的案例研究，这将向海洋科学本科生说明在定量物理科学方面进行严格训练的必要性。研究结果将为影响白化事件严重程度的因素提供重要见解，并可能提出现实的缓解策略，以最大限度地减少局部环境或经济敏感地区的白化事件。