Biomineralization of giant clam shells (tridacna gigas): implications for paleoclimate applications

dc.contributorAndrus, C. Fred T.
dc.contributorDimova, Natasha T.
dc.contributorOlson, Julie B.
dc.contributor.advisorPerez-Huerta, Alberto
dc.contributor.advisorAharon, Paul
dc.contributor.authorGannon, Michelle E.
dc.contributor.otherUniversity of Alabama Tuscaloosa
dc.date.accessioned2017-03-01T17:44:19Z
dc.date.available2017-03-01T17:44:19Z
dc.date.issued2016
dc.descriptionElectronic Thesis or Dissertationen_US
dc.description.abstractThe giant clam, Tridacna gigas, is an important faunal component of Indo-Pacific reef ecosystems, for which its shell is often used as an environmental archive for modern and past climates. This thesis is a study of the shell microstructure of modern specimens from Palm Island, Great Barrier Reef (GBR), Australia and Huon Peninsula, Papua-New Guinea (PNG), using a combination of petrography, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and Raman spectroscopy, as well as a microstructural comparison of fossil T. gigas through 200 ka from PNG. Daily growth increments are recognizable in all specimens through ontogeny within the internal layer. For modern T. gigas from PNG, increments are composed of pairs of organized aragonitic needles and compact, oblong crystals, whereas modern specimens from GBR are composed of shield-like crystals. The combination of nutrient availability and rainfall are likely the most significant factors controlling shell growth and it may explain the observed differences in microstructure. The external layers are composed of a dendritic microfabric, significantly enriched in 13C compared to the internal layer, suggesting a different metabolic control on layer secretion. The internal and external layers are likely mineralized independent from each other, associated with the activity of a specific mantle organ. Furthermore, needles similar to those of modern T. gigas from PNG, are observed and the widths are measured in the set of fossil T. gigas. An exception includes two mid-Holocene-aged individuals, composed of elongated crystals, oblique to the outside of the shell. The results show that widths follows a cyclic pattern, similar to those of solar radiation variability, suggesting there is a relationship between solar activity and the width of aragonitic needles. Differences between modern and mid-Holocene T. gigas, are likely associated with fundamental environmental differences. The results of this study, pointing to locality and environmental dependence, layer specific mantle biomineralization, and co-variation between needle width and solar modulation, advance the potential of giant clam shells to assist in the reconstruction of many climate parameters that were previously limited to chemical analyses. Microstructural results are additionally applicable in engineering and medical research fields.en_US
dc.format.extent154 p.
dc.format.mediumelectronic
dc.format.mimetypeapplication/pdf
dc.identifier.otheru0015_0000001_0002339
dc.identifier.otherGannon_alatus_0004M_12795
dc.identifier.urihttps://ir.ua.edu/handle/123456789/2668
dc.languageEnglish
dc.language.isoen_US
dc.publisherUniversity of Alabama Libraries
dc.relation.hasversionborn digital
dc.relation.ispartofThe University of Alabama Electronic Theses and Dissertations
dc.relation.ispartofThe University of Alabama Libraries Digital Collections
dc.rightsAll rights reserved by the author unless otherwise indicated.en_US
dc.subjectPaleontology
dc.titleBiomineralization of giant clam shells (tridacna gigas): implications for paleoclimate applicationsen_US
dc.typethesis
dc.typetext
etdms.degree.departmentUniversity of Alabama. Department of Geological Sciences
etdms.degree.disciplineGeology
etdms.degree.grantorThe University of Alabama
etdms.degree.levelmaster's
etdms.degree.nameM.S.
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