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

智力优势。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都急剧增加，预计这一趋势将继续下去，对热带地区造成重大的环境和经济影响。这种漂白，或珊瑚失去其光合作用的内共生甲藻（虫黄藻;共生藻属），似乎是由升高的温度和高光强度的组合效应引起的增加的氧化应激引起的。然而，这种失败的机制尚不清楚。研究所目前题为“微量金属限制对虫黄藻氧化应激的影响及其在珊瑚漂白中的作用”的项目的前提（OCE - 0648478）是虫黄嘌呤抗氧化防御的必要上调受到低浓度溶解的Fe、Zn和Cu的限制;这些金属是抗氧化酶功能所必需的（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）和光照强度下限制珊瑚宿主的Fe和Cu/Zn可用性确实可以显着降低共生体的光合效率和ROS酶活性，同时增加其光系统的非光合猝灭;每个指标都是漂白条件的开始。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适用于所有的珊瑚群落。根据有限的取样，似乎从外大陆架区域采集的珊瑚通常（但并非总是）在金属可用性减少的条件下显示出氧化应激的迹象，而在近岸采集的珊瑚或在沿海流动海水（溶解的金属浓度较高）中保存的珊瑚往往没有什么明显的影响。过量的金属吸收和存储是很好地描述了海洋浮游植物文献，这表明，历史的珊瑚金属暴露是一个关键因素，无论是相对于我们的实验，以及观察到的珊瑚漂白的分布。PI有一个独特的和不可预见的机会来测试这一假设，通过加入澳大利亚海洋科学研究所的研究巡航弗林德斯礁;在珊瑚海的近海环礁，是远远更远离零星的陆地金属输入，我们以前的研究地点。他们将参加这次航行，在甲板上进行孵育，测试减少和轻微升高的Fe，Cu，Zn和Mn浓度对珊瑚光合效率，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。这个地理位置将提供一个理想的测试地点，以验证他们的发现金属对氧化应激的影响在虫黄藻，并确定一些关键机制和营养因素，导致日益频繁和严重的珊瑚漂白事件在热带沃茨。更广泛的影响：这个项目将提供一个独特的研究机会，两名研究生和一名大三女博士。科学家，谁将使用他们的论文和职业发展的工作方面。该研究解决了珊瑚漂白控制的基本未知数，这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。研究结果将提供一个关键的测试实验室和现场开发的假设的作用，微量金属限制作为一个贡献者的氧化应激zooxanthropium和他们的珊瑚宿主;珊瑚漂白的前体。一个模块化的系列讲座和演示，针对高K-12和本科生将被开发，并将被纳入现有的推广计划和本科课程在海洋科学在缅因州大学。虫黄藻和珊瑚之间的光养共生，其物理环境因素的破坏，提供了一个内在的强大的案例研究的整合化学，物理学和生物学，将说明海洋科学本科生需要严格的训练在定量物理科学。这些发现将为影响漂白事件严重程度的因素提供关键见解，并可能提出现实的缓解策略，以尽量减少局部环境或经济敏感地区的漂白事件。

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.