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

在过去几十年里，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。许多应激源对珊瑚礁的负面影响之一是珊瑚虫和珊瑚虫组织中包含的光合藻--虫黄藻之间的共生关系被破坏。这会导致珊瑚色素的丧失或漂白。大多数漂白事件是由于虫黄藻的丢失和/或虫黄藻的色素的丢失引起的。如果白化事件的规模和持续时间足够大，就会导致珊瑚死亡，珊瑚礁生态系统可能会发生持久的变化。这项博士论文研究项目旨在评估珊瑚漂白事件的频率是否在增加，并评估导致漂白事件的环境因素。该项目的目标是开发和校准一种方法，以便利用珊瑚岩芯中的稳定同位素和微量元素分析来确定漂白事件。为实现这一目标，将制定一个为期15年的时间序列，对从潘多拉礁和大堡礁上的凯佩尔群岛获得的Porites珊瑚岩芯进行氧和碳稳定同位素测量，以及对锶/钙比进行微量元素测量。1991年和1998年在这两个地区发生的大规模漂白事件可能是由于洪水导致盐度下降，随后是海洋表面温度(SST)上升造成的。为了校准方法，学生将把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SST和盐度的现场测量和观测进行比较。校准工作将有助于制定和解释大堡礁两个区域(潘多拉岛和吉佩尔群岛)以及法属波利尼西亚珊瑚白化事件的连续长期记录。太平洋的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区域的人民和国家产生重大影响。该项目产生的地球化学记录将提供有关GBR上长期历史漂白事件的重要信息。这些数据将使我们能够更充分地分析漂白事件是否由于人为的气候和环境条件而增加，或者它们是否是一种自然现象。这项拟议的研究将使科学家、资源经理和政策制定者更好地了解珊瑚礁的长期历史以及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.