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Title: The environmental geochemistry of Porites lutea coral skeletons from Phuket, south Thailand
Author: Allison, Nicola
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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The geochemical compositions of Porites lutea coral skeletons were determined in specimens collected from a range of different reef environments in Phuket, South Thailand. Specimens were analysed for stable carbon and oxygen isotopes and trace and minor elements. Geochemical variations between colonies from the same site equalled those observed between different sites. This possibly reflects genetic or growth rate differences between corals. Large variations in the trace element concentration ranges between colonies led to widely varying estimates of distribution coefficients between seawater and coral. No seasonal variations in Mg, Rb, Sr, Ba and U were found in any of the corals analysed by ion microprobe or XRF. Corals are very heterogeneous with respect to these elements on a sub-millimetre scale and the entire concentration range of an element is frequently observed over a skeletal distance corresponding to less than one months growth. This heterogeneity far exceeded the Sr range expected from the Sr palaeothermometer. Heterogeneity may reflect variations in the composition and/or quantity of the organic matrix or regulation of coral tissue metal levels by the zooxanthellae. Anomalous high concentrations of magnesium and barium were observed on microborings and centres of calcification which permeate the coral skeletons. These may relate to organic materials, precipitates or sedimentary particles. Thorough cleaning of skeletal material prior to analysis is essential to remove this contamination of the coral aragonite. δ18O is inversely related to coral growth rate and may drive the annual oxygen isotopic trend. No evidence of the isotropic trends expected from seawater temperature data were found. δ13C and coral tissue chlorophyll a content are positively related, reflecting the impact of the algal symbiants on the dissolved inorganic carbon pool available for calcification.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available