Doctoral Dissertation Research: Development of Geochemical Proxies for Bleaching Events and the Associated Stressors in the Great Barrier Reef

在过去的几十年里，世界各地的珊瑚礁生态系统受到越来越多的自然和人为干扰。许多这些压力源对珊瑚礁造成的负面影响之一是珊瑚虫与珊瑚虫组织中含有的光合藻类虫黄藻之间的共生关系破裂。这会导致珊瑚失去色素沉着，或漂白。大多数漂白事件是由于虫黄藻的损失和/或虫黄藻色素的损失造成的。如果白化事件的规模和持续时间足够大，将导致珊瑚死亡，并可能发生珊瑚礁生态系统的持久变化。本博士论文研究项目旨在评估珊瑚白化事件的频率是否在增加，并评估白化事件的致病环境因素。该项目的目的是开发和校准一种方法，利用稳定同位素和微量元素分析在珊瑚核中识别漂白事件。为了实现这一目标，将开发一个15年的时间序列，测量氧和碳的稳定同位素，同时测量从潘多拉礁和大堡礁（GBR）的吉宝尔群岛获得的Porites珊瑚岩心的锶/钙比率的微量元素。1991年和1998年在这两个地区发生的大规模白化事件可能是由于洪水导致盐度降低，随后海温升高造成的。为了校准方法，学生将比较1991年和1998年漂白和未漂白珊瑚的稳定同位素和微量元素数据与GBR上的海温和盐度的现场测量和观测结果。校准工作将有助于开发和解释大堡礁两个地区（潘多拉岛和吉宝群岛）以及法属波利尼西亚珊瑚白化事件的连续长期记录。太平洋珊瑚礁生态系统受到大规模白化事件的严重影响，因此，珊瑚礁生态系统的死亡和变化可能对该地区的人民和国家产生巨大影响。该项目生成的地球化学记录将为研究GBR长期历史白化事件提供重要信息。这些数据将使我们能够对白化事件的频率增加是人类造成的气候和环境条件的结果，还是一种自然现象进行更明智的分析。拟议中的研究将使科学家、资源管理者和政策制定者更好地了解珊瑚礁的长期历史和漂白事件的潜在灾难性影响。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

Coral reef ecosystems worldwide have been subjected to increasing natural and human-caused disturbances over the last few decades. One of the negative effects many of these stressors have on coral reefs is the breakdown of the symbiotic relationship between coral polyps and the photosynthetic algae, zooxanthellae, contained in the polyp tissues. This leads to loss of pigmentation, or bleaching, of the corals. Most bleaching events result from the loss of the zooxanthellae and/or the loss of the pigments of the zooxanthellae. If the magnitude and duration of the bleaching event are great enough, coral mortality will result, and lasting changes in the reef ecosystem may occur. This doctoral dissertation research project aims to assess whether coral bleaching events are increasing in frequency and to evaluate causative environmental factors for the bleaching events. The objective of this project is to develop and calibrate a methodology for identifying bleaching events using stable isotopic and trace element analysis in coral cores. To achieve this objective, a 15-year time series will be developed of oxygen and carbon stable isotopic measurements along with trace element measurements of strontium/calcium ratios on Porites coral cores obtained from Pandora Reef and the Keppel Islands on Great Barrier Reef (GBR). Large-scale bleaching events in 1991 and 1998 around both regions were probably caused by decreased salinity due to flooding, followed by elevated sea surface temperatures (SST). To calibrate methods, the student will compare the stable isotopic and trace element data from bleached and unbleached corals during the 1991 and 1998 events with in situ measurements and observations of SSTs and salinity on the GBR. The calibration effort will aid in the development and interpretation of continuous, long-term records of coral bleaching events for two regions of the Great Barrier Reef (Pandora Island and the Keppel Islands) as well as French Polynesia.Coral reef ecosystems in the Pacific have been severely affected by mass bleaching events, and as a result, the mortality and changes in the reef ecosystems could have a dramatic effect on the people and countries in the region. The geochemical records generated as a result of this project will provide important information about the long-term history bleaching events on the GBR. These data will allow a more informed analysis of whether bleaching events are increasing in frequency as a result of human-caused climatic and environmental conditions or whether they are a natural phenomenon. The proposed research will provide scientists, resource managers, and policy makers with a better understanding of the long-term history of reefs and the potentially catastrophic impact of bleaching events. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.