Journal
QUATERNARY GEOCHRONOLOGY
Volume 23, Issue -, Pages 35-45Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.quageo.2014.05.002
Keywords
U-Th dating; MC-ICP-MS; Coral mortality; Acropora; Great Barrier Reef
Funding
- Marine and Tropical Science Research Facility (MTSRF) Project [1.1.4]
- Australian Research Council (ARC) [LE0989067]
- Australian Research Council Centre of Excellence (ARC CoE) in Coral Reef Studies grant
- Australian Postgraduate Award (APA)
- IPRS
- NERP Tropical Ecosystems Hub Project [1.3]
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To assist with our understanding of reef dynamics prior to modern monitoring programs and recent observations of coral decline, a robust dating technique is required to place coral mortality events and historical changes in community structure in an accurate chronological framework. In this study we adopted a refined Uranium-Thorium (U-Th) isotope measurement protocol using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for rapid, precise and accurate age determination of a large branching Acropora coral death assemblage from an inshore reef of the Great Barrier Reef (GBR) where the timing of mortality is independently constrained. To achieve this, we developed a vigorous sample cleaning/treatment procedure to remove most non-carbonate detritus from the coral skeleton, and a correction scheme that accounts for initial Th-230 sources in the dead coral skeletons. Using this method, the Th-230 ages (with 2 sigma errors of 1-5 years) from 41 individual dead Acropora branches precisely bracket the timing of a documented similar to 100% loss of hard coral cover, primarily Acropora, that was caused by increased sea-surface temperatures during the 1997-1998 mass bleaching event. Our results demonstrate the applicability of U-Th dating in accurately determining the timing of previous disturbance events in coral reef communities, as well as identifying potential drivers. This approach provides a powerful tool to researchers and managers in assessing the current status of reefs and identifying areas vulnerable to degradation where long-term monitoring data are absent or too recent. (C) 2014 Elsevier B.V. All rights reserved.
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