| Coral reefs are bioherms whose structure comprises a dynamic mixture of geologically inherited and environmentally forced morphologies. The major debate of coral reef history is over the relative importance of antecedent, erosional and recent, constructional processes in controlling the pattern and pace of reef growth. Landscape scale studies of reef morphology enable us to distinguish between these two morphological lineages on modern reefs. This thesis quantifies empirical relationships among spatial patterns of coral reef growth, geomorphology and environmental forcing in the archetypal atoll nation of the Maldives. The main hypothesis is that asymmetric ocean wave forcing interacts with antecedent reef platform structure to produce characteristic growth configurations and predictable reef morphologies during the Holocene (at least). The hypothesis is tested by regressing a set of reef growth morphometrics derived for every single coral reef larger than 1 ha on impinging wave energy for the entire archipelago (n = 2041). The methods involved the classification of eight Landsat-7 Enhanced Thematic Mapper Plus (ETM+) satellite images covering all reefs of the Maldives, and the calculation of morphometric indices using a geographical information system (GIS). The spatial pattern of coral reef growth, as defined by the distributions of distinct reef geomorphologies, was quantified by multiple morphometrics of well-defined geomorphic zones: reef slope, reef crest, coral rubble, sand flats, reef lagoons and reef islands. These features were delineated with an overall accuracy of 81%. The total area all coral reef and lagoon habitats that comprise Maldives is 21,372.72 km2. A total of 2,041 ± 10 distinct coral reef structures larger than 0.01 km2 occupy a vertically-projected surface area of 4,493.85 km2. Smaller areas of coral reef substratum cover another 19.3 km2, bringing the total area of coral reef to 4,513.14 ± 135.40 km2. Islands occupy only 5.1% of the total reef area. Spatial gradients in environmental forcing (i.e., southern ocean swell and monsoon wind-wave fields) were characterized and quantified along the same dimensions as the reef geomorphology, and statistically related to the reef morphometrics. Non-parametric Multidimensional Scaling (MDS) and Analysis of Similarities (ANOSIM) procedures identified statistically significant differences among groups of reefs located on atoll rims that were exposed to nine differing hydrodynamic regimes.* (Abstract shortened by UMI.); *This dissertation is compound (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Microsoft Office. |
