Effects of Trace Metal Limitation on Oxidative Stress in Zooxanthellae and Its Role in Coral Bleaching

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

• 批准号: 0648478
• 负责人: Mark Wells
• 金额: $ 68万
• 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: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2011-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0648478&HistoricalAwards=false
• 关键词: Effects; Trace; Metal; Limitation; Oxidative

Coral bleaching has increased dramatically in frequency, severity, and geographic extent since the 1980s and this trend is anticipated to continue, causing major environmental and economic impacts in tropical regions. This bleaching - the loss by corals of their photosynthetic endosymbiotic dinoflagellates (zooxanthellae; Symbiodinium spp.) - involves increased oxidative stress arising from the combined effects of elevated temperature at high light intensities. Although the production of reactive oxygen species (ROS) in corals and phytoplankton is routine during daylight hours, the failure of antioxidant defenses in zooxanthellae becomes catastrophic under comparatively small changes in environmental temperature, because reef corals live close to their upper thermal limits. The mechanisms underlying this failure are not understood, but fall into two categories: (1) the temperature /irradiance conditions lie beyond the capacity for thermal acclimatization by corals and their endo-symbionts, or (2) the necessary enhancement of antioxidant defenses in zooxanthellae is hindered by nutrient deficiencies. In this project, the working hypothesis is that low ambient concentrations of dissolved iron, zinc, copper and perhaps manganese (Fe, Zn, Cu, and Mn) in oligotrophic tropical surface waters, combined with regulation of metal supply to zooxanthellae by the coral host, restrict the compensatory elevation of metal-dependent antioxidant enzymes with rising ROS production, and this resource limitation contributes to coral bleaching. This hypothesis will be investigated in three stages: with pure clonal cultures of zooxanthella isolates; in coral colony culture experiments; and in samples on areas of the Great Barrier Reef, Australia, observed to be susceptible or resistant to coral bleaching. The primary goals of the pure culture experiments are to 1) identify which of the known metals involved in antioxidant enzymes (Fe, Cu, Zn, Mn) are important in zooxanthellae, 2) determine the thresholds of metal nutrition (both in supply and intracellular metal quotas) below which onset of uncontrolled oxidative stress occurs in the zooxanthellae, and 3) ascertain whether these relationships differ significantly among bleaching sensitive and insensitive Symbiodinium species. In addition to verifying the findings in coral/algal symbioses, coral experiments will be used to determine whether the timing and magnitude of bleaching indicators change with metal nutrition, and whether bleaching-sensitive corals can become more resistant by increasing their metal quotas. The linkage between trace metals and antioxidant enzymes is well established in other biological systems but has not been examined in coral/zooxanthellar associations. The proposed work brings together experts in trace metal/ phytoplankton interactions, phytoplankton photo-physiology and oxidative stress, photo-oxidative defenses in reef corals, and molecular biology of marine symbioses to provide mechanistic understanding of coral bleaching, increasing predictive insights to the global trend of coral bleaching. This project will support the education and research training of two Ph.D. students who would test hypotheses integral to the work as parts of their dissertations. Two postdoctoral scientists will participate in the planning, management, and research of the project, providing opportunities to refine their professional development and their mentoring skills necessary for career success. Public lectures on "corals and global climate change" are planned. The findings will provide insights to the factors influencing the severity of bleaching events, and may suggest realistic mitigation strategies to minimize bleaching in localized environmentally or economically sensitive regions.

自1980年代以来的频率，严重程度和地理范围内，珊瑚漂白量显着增加，预计这种趋势将继续，从而在热带地区造成重大的环境和经济影响。这种漂白 - 珊瑚对光合作用性内生物植物的损失（Zooxanthelelae; Symbiodinium spp。）涉及氧化应激增加，这是由于高光强度下升高温度的综合作用而产生的。尽管珊瑚和浮游植物中的活性氧（ROS）的产生是日光下的常规，但在环境温度的相对较小的变化下，Zooxanthellae中抗氧化剂防御的失败变成了灾难性的，因为珊瑚礁珊瑚珊瑚的寿命接近其上的热极限。该故障背后的机制尚不清楚，但分为两类：（1）温度 /辐照度条件超出了珊瑚及其内部 - 伴侣的热适应能力，或（2）（2）在营养中，动物毒素中的抗氧化剂防御剂的必要增强受到营养的防御能力的阻碍。 在这个项目中，工作假设是，寡植物的热带热带地表水中溶解的铁，锌，铜，也许是锰（Fe，Zn，Cu和Mn）的含量较低，结合了对金属宿主的促进式腐烂的腐蚀，并限制了金属依赖性抗氧化剂的脉动含量，并限制了金属对ZOOXANTHELLAE的金属供应，并限制了金属依赖性抗氧化剂的脉动含量。漂白。该假设将在三个阶段进行研究：纯Zooxanthella分离株的纯克隆培养物；在珊瑚菌落培养实验中；在澳大利亚大堡礁地区的样品中，观察到易受珊瑚漂白的敏感或抗性。纯培养实验的主要目标是1）确定哪些已知金属与抗氧化酶（Fe，Cu，Zn，Mn）在动物植物中很重要，2）确定金属营养的阈值（在供应和细胞内金属中的阈值）在下面是不同的ZOOX在哪些ZOOONISS中发生了不同的ZOOX，在哪些方面发生了不同之处。在漂白敏感和不敏感的共生菌中。除了验证珊瑚/藻类共生的发现外，还将使用珊瑚实验来确定漂白指标的时间和幅度是否随着金属营养而变化，以及对漂白敏感的珊瑚是否会通过增加金属配额而变得更具抵抗力。痕量金属与抗氧化酶之间的联系已在其他生物系统中得到很好的建立，但尚未在珊瑚/Zooxanthellar关联中进行检查。拟议的工作汇集了痕量金属/植物浮游生物相互作用，浮游植物的照片生理学和氧化应激，珊瑚礁珊瑚中的光氧化防御能力以及海洋共生的分子生物学，以提供对珊瑚漏洞的机械理解，从而增加对全球式珊瑚趋势的预测洞察力的机械理解。该项目将支持两个博士学位的教育和研究培训。将在论文的一部分中检验作品不可或缺的假设的学生。两名博士后科学家将参与该项目的计划，管理和研究，提供机会来完善其职业发展和职业成功所必需的指导技能。计划了有关“珊瑚和全球气候变化”的公开演讲。这些发现将为影响漂白事件严重性的因素提供见解，并可能提出现实的缓解策略，以最大程度地减少环境或经济敏感区域的局部化漂白。