Goals of this investigation were: 1) Differentiate between the effects of turbidity and sedimentation on corals. 2) Differentiate the effects of carbonate and terrigenous sediments on coral growth and metabolism. 3) Develop a predictive model relating increased sediment loading to the photosynthetic rate, growth and survival of corals. 4) Evaluate the validity of the widely cited "10 mg cut-off point" and determine the levels of turbidity and sedimentation that are tolerated by corals. Earlier studies suggest that coral reefs decline when sediment loading levels exceed a sediment trapping rate of 10 mg cm-2 d-1 or a turbidity of 10 mg I-1. An integrated experimental design linked field and laboratory experiments. In the field, corals were transplanted to sites with varying levels of sedimentation. Turbidity, as linked to reduced light availability, had a significant affect on coral growth and metabolism in laboratory experiments but not coral growth or survival in field experiments. Turbidity in the field was highly variable and influenced greatly by wind velocity and rainfall. Terrigenous (or land-derived) sediments influenced light extinction more than carbonate (reef-derived) sediments. In laboratory experiments turbidity was more important than sediment trapping rate in affecting the photosynthetic ability and growth rates of corals. The predictive model stated that the lower the light level (as caused by increased turbidity) the lower the photosynthetic production of corals. The model was supported by results of laboratory experiments where conditions were precisely controlled and monitored. Under field conditions, the predictive model did not hold due to extreme natural variability in sediment loading and variation in a wide range of other environmental factors encountered at the experimental sites. Corals tolerated turbidity exceeding 120 mg I-1 and sediment trapping rates in excess of 11 mg cm2 d-1. Sediment loading is correlated with other environmental factors such as nutrient loading and reduced salinity. Composition of sediment varies widely between different locations. The "10 mg cutoff may prove to be useful in setting limits to vigorous coral reef development, although individual corals or coral assemblages may be able to survive and grow at levels exceeding this value. / Thesis (Ph. D.)--University of Hawaii at Manoa, 2001. Includes bibliographical references (leaves 235-264).

The reef corals Pocillopora damicornis and Montipora verrucosa were cultured under various controlled temperatures and light conditions at Ulupau Head Microcosm facility. The skeletal carbonate deposited under different experimental regimes was analyzed for 13C and 18O. Coral skeletal 013C values varied with light dose and correlated with changes in zooxanthellar pigment. The o13C value of skeletal aragonite seems to be controlled by oxidation of photosynthetically produced organic matter. Functionally significant relationships between coral skeletal o18O values and temperature have been determined. The temperature coefficients of the o18O values (-4.20) are the same as the first order coefficient in the equilibrium paleotemperature equation, but the o18O values have species-specific offsets from equilibrium. These offsets may be attributed to the activity of the coral's zooxanthellae. Based upon the results of this study a model of coral skeletal isotopic incorporation is presented. / Typescript. Thesis (M. S.)--University of Hawaii at Manoa, 1979. Bibliography: leaves 94-102.

Twenty-seven species of known or suspected coral skeletal borers were identified from shallow Hawaiian reefs. In comnarison to inventories of the borer communities collected from other tropical areas Hawaiian corals had an abundance of polychaetous annelids, fewer species of sipunculans,and acrothoracican barnacles, and far fewer boring sponges. Polychaetes were responsible for the majority of the bioerosion of dead coral in Kaneohe Bay, Oahu. Comparisons of living and dead sections of coral colonies indicated that the borer community was more diverse and abundant in areas of the skeletons lacking living tissue. Skeletal densities of three common coral species with branching growth form were found to influence the abundance of coral borers. The least dense skeletons had greater population densities of borers. It is suggested that these three species of corals can coexist in close proximity due, in part, to the development of varying abilities to withstand invasion by skeletal borers. In order to determine rates, si te preference and seasona.li.ty of settlement a series of settlement plates were cut from coral and placed in the field at ten sites in Kaneohe Bay, Oahu. Extrapolating from the surface area of the settlement plates, mean recruitment rates of coral borers were found to be 10,000 - 50,000 individuals m-2 month-1. The recruitment rates and species composition of epibiotic and borer faunas settling; on the dead coral plates differed dramatically between areas in Kaneohe Bay due to the effects of differences in physical and biological factors caused by sewage and slltation. The larvae of coral borers generally lacked clear seasonal settlement periods, suggesting that one or more mechanisms (e.g. continuous reproduction, long pelagic phase, etc.) functioned to assure the presence of larvae throughout the year. The ultimate cause for the development of such a strategy may be that the time and location of the production of suitable settlement sites on the reef surface is. unpredictable. Some of the larvae of both epibiotic and borer species exhibited settlement selectivity with respect to the position of the settlement surface. This finding indicates that the distribution of borers in coral skeletons might be due, in part, to active selection by the laryae for particular conditions. Development of the epibiotic and borer communities of dead coral was monitored using sequentially collected blocks cut from the coral Porites lobata. The abundance and species composition of these communities were found to differ between sites in Kaneohe Bay because of several biological and physical factors. In the south bay increased food supplies (in the form of plankton and plankton-derived detrital material). due to sewage enrichment, support extensive populations of filter and deposit-feeding invertebrates including coral borers. Sewage diversion did not appear to have had any dramatic effect on these communities by the end of the study period. In the north bay, where food availability is lower, fewer borers and epibiotic organisms were collected. The effects of fish grazing are considered to be another important factor determining the species composition and abundance of the coral borer community. Grazing fish were rare in south Kaneohe Bay during the study period, which may help to explain the abundance of sessile epifaunal species. In the north bay fish grazing is extensive and contributes to the growth of encrusting coralline algae on the test blocks and the benthos. Based on the results of the long term block study it was found that in Hawaii sessile filter-feeding invertebrates do not exclude coral borers from the substratum or inhibit their growth. In south Kaneohe Bay, where conditions caused increased abundances and growth rates of filter and depositfeeding invertebrates, bioerosion rates were accelerated. Encrusting coralline algae, which flourish on reefs exposed to fish grazing (eg. north Kaneohe Bay), inhibit settlement of borers and grow over burrow apertures, thus reducing the population of borers within the dead coral. Bioerosion rates of exposed, coralline algal covered, dead coral substrata are very low on pristine shallow Hawaiian reefs. / Bibliography: leaves 181-192.

Scleractinian corals increasingly are studied as geochemical archives of modern- and palaeoclimate, but microsampling for geochemical data is complicated by: 1) the microstructural complexity and spatial variability in skeletal growth in different coral genera; and 2) the rapidity and scale of diagenetic alteration that occurs in living coralla. Geochemical sampling techniques now have spatial resolution into the sub-micrometer to tens of micrometers range, and it is hoped that the spatial resolution can be translated to temporal resolution. This study investigated the effects on geochemical analyses imposed by microstructure and diagenesis in different live-collected coral genera representing somewhat different depositional environments. Suites of samples of four reef-building genera (Acropora, Pocillopora, Goniastrea and Porites) were collected from three adjacent environments in intertidal and subtidal positions near the reef edge at Heron Reef, Great Barrier Reef and studied by means of optical and scanning electron microscopy, combined with vibrational and energy dispersive spectroscopy. The first section of this study compares and documents the microstructure of the four coral genera. Each genus was found to have very different three-dimensional arrangements of microstructural elements, and a new general growth model was proposed for Acropora, to take into account differences in the timing of precipitation of trabeculae and thickening deposits. The results highlight the complexity and spatial variability of skeletal growth in different coral genera. Because microstructural patterns vary in different genera, direct observation of microstructural elements and growth lines are necessary to allow geochemical microsamples to be placed into series that represent temporal sequences with known degrees of time averaging. Coral growth rates (i.e., rates of extension) are discussed to determine the range of temporal relationships that exist between closely spaced skeletal microstructural elements. Such data are necessary in order for coral skeletogenesis to be understood and are critical for constraining microsampling strategies aimed at developing true time series geochemical data at very fine spatial and temporal scales. The second part of the study focused on early diagenetic alteration of the corals, which is an equally important concern for geochemical analysis. Early marine diagenesis was documented in the same live-collected samples of the four common reef-building coral genera. Samples show extensive early marine diagenesis where parts of the coralla less than three years old contain abundant macro- and microborings (sponges, algae, cyanobacteria and fungi) and significant amounts of aragonite, high-Mg calcite, low-Mg calcite and brucite [Mg(OH)2] cements. Many of the cements are associated with microendoliths and endobionts that inhabit recently abandoned parts of the skeleton. The cements are problematic for palaeoclimate reconstruction because geochemical proxies used for paleoclimate studies are meant to reflect ambient seawater chemistry and conditions, but the occurrence of brucite and low-Mg calcite demonstrates how far fluid chemistry in microenvironments within the corals has evolved from ambient seawater. Some Porites lobata specimens have had as much as 60% of the most recently deposited skeletal aragonite (i.e., the part of the skeleton that projects into the layer of living polyps) bored and replaced by low-Mg calcite cement. The low-Mg calcite cement has significantly different trace element ratios (Sr/Ca(mmol/mol) = 6.3 ± 1.4; Mg/Ca(mmol/mol) = 12.0 ± 5.1) than the host coral skeletal aragonite (Sr/Ca(mmol/mol) = 9.9 ± 1.3; Mg/Ca(mmol/mol) = 4.5 ± 2.3), thus providing a serious challenge for Sr/Ca or Mg/Ca based sea surface temperature calculations. This study illustrates that many diagenetic changes that can radically alter important geochemical characteristics of coral skeleton occur very early on the sea floor (i.e., while corals are still alive). Documented cements altered trace element inventories (e.g., Sr and Mg), thus, interfering with the use of those elements in palaeotemperature calculations. Hence, significant diagenetic changes that jeopardise palaeoclimate data do not require long-term diagenesis or meteoric exposure. Some of the diagenetic changes (e.g., calcite filled borings) occur at scales that are very difficult to detect short of visual inspection using SEM. Hence, vetting of coral samples with SEM is required before any sample is subjected to geochemical analysis.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy). Appendices : leaves 141-146. Bibliography : leaves 147-169. Also available in an electronic version via the Internet.

Thesis (M.S.)--University of North Carolina Wilmington, 2009. / Vita. Title from PDF title page (January 15, 2010) Includes bibliographical references (p. 67-70)

Thesis (M.S.)--University of California, Santa Cruz, 1988. / Typescript. Includes bibliographical references.

Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.