Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2005. / Printout. Includes bibliographical references (leaves 63-68). Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Edward C. Theriot and Judith C. Lang. Vita. Includes bibliographical references.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1984. / Bibliography: leaves [259]-275. / Photocopy. / Microfilm. / xvii, 275 leaves, bound ill., maps 29 cm

The timing of glacial-interglacial cycles shows a clear dependence on the periodic variations in the Earth’s orbital parameters. However, the Earth’s climate is an extremely complex, non-linear system, with many internal feedback mechanisms and there are still features of the climate record for which a definitive explanation remains elusive. Understanding reef history is important due to significant predicted feedbacks between changes in global climate and carbonate production via the carbon cycle; phases of rapid reef growth in shallow water areas being associated with increased release of carbon dioxide to the atmosphere. Previous work on Pleistocene reef history, investigated via reef boreholes, shows a large global expansion of reefs between 800-400ka; approximately concurrent with one of the major unexplained alterations in the climate system, the Mid-Pleistocene Transition (MPT). Quaternary reef history is usually investigated via reef boreholes, which provide limited spatial information and are subject to dating uncertainties of the order of ±100kyrs. This means that any inferences made about the relationship between reef expansion and specific changes in the climate system are not well constrained. This thesis instead, presents a novel approach to reconstructing reef growth history, using a trial site near the island of New Caledonia, in the south west Pacific. The initiation of carbonate production on shallow shelves is known to produce a signal in the surrounding deeper basins, via sediment shedding. Therefore, this research set out to independently verify the proposed expansion of the New Caledonia Barrier Reef at ~ 400ka (Marine Isotope Stage [MIS] 11) by examining the composition of turbidites deposited in the New Caledonia Trough. Deep sea sediment core MD06-3019, was collected south west of the New Caledonia Barrier Reef (22oS, 165oE; 3,500m water depth). It is predominantly composed of pelagic carbonate ooze, into which 79 sandy turbidite layers have been deposited. These layers interrupt, but do not disturb, the background sedimentation and source material from the shallow shelf, which is carried to the deep sea via submarine canyons. A core age model based principally on orbital tuning, yields a core bottom age of 1,260ka, ~MIS38. This chronology has allowed the timing of deposition of the turbidite layers within the core to be assigned to within ±10kyr. Turbidite layers vary in width (1-35cm), grain size (φ=4 to -2) and composition, containing among other shelf derived material, well preserved coral fragments from 1.26Ma through to the present day. Patterns in turbidite timing and frequency, grain size and composition (investigated via point counting, carbonate coulometry and aragonite content) have been analysed, to assess whether there are any temporal changes which may reflect variation in shallow shelf reef extent. This included the development of XRF scanning measurements for [Sr], as a new proxy for the aragonite content of samples. A calibration line with the equation: Aragonite %=0.0011* Sr count +2.64 (R2 =0.6105, p-value < 0.001) was obtained for turbidite samples from sediment core MD06-3019. The method shows significant promise as a new proxy for quickly establishing the aragonite content of sediment samples. Corroborating the work of previous investigators, turbidites deposited since MIS11 show an increase in average bulk carbonate and aragonite content, a greater dominance of shallow water bioclasts and a higher occurrence of coral fragments. Additionally, both coarse and fine grained turbidites are present, whereas directly before this period only fine grained turbidites occur. However, there is another significant shift in depositional style further back in the record. Prior to MIS23 both coarse and fine grained turbidites are present, the average carbonate content of turbidite layers is higher and there is a greater dominance of shallow water biota. Coral abundance for turbidites at the base of the core can equal values for turbidites at the top of the core. These results challenge the assumption that the only significant evolution on the western New Caledonia margin over the last 1.2Myrs was the expansion of the barrier reef at MIS11. This suggests that the history of the western New Caledonia margin may be more complicated than initially anticipated. These temporal variations in turbidite deposition are interpreted as reflecting changes in the level of carbonate production on the shallow shelf over the course of the 1.26Myr record. Shallow water carbonate production having decreased substantially during the period MIS23-MIS11. There are many possible controls on the shallow water carbonate production; such as: sea surface temperature and salinity, sea-level and nutrient availability. However, it is hypothesised that the principal control is glacial-interglacial sea-level change. It is proposed that prior to MIS23 sea-level was high enough during certain interglacial periods for significant carbonate production to occur on the shelf. However, from MIS23 onwards the climate proceeded into a period of ‘lukewarm’ interglacials which were both cooler and had lower sea-levels. It is hypothesised that during this period sea-level did not rise enough during highstands to flood the shelf sufficiently to allow for significant shallow water carbonate production. The high sea-levels of the long, warm MIS11then allowed for the expansion of the barrier reef (perhaps on substrates provided by former siliciclastic coast lines, deposited between MIS23-11) and its continuation during subsequent interglacial periods until the current day. This pattern of shallow shelf carbonate production is similar to those proposed for the Belize margin and the Gulf of Papua over the last 1.2Myrs. This thesis provides one of the first detailed investigations of gravity deposits in the New Caledonia Trough, providing information on their composition and timing over an unprecedented 1.26Myr time period. This study demonstrates that deep sea turbidites, sourced from shallow shelf areas, can be used to help reconstruct tropical reef growth histories. The results corroborate the work of previous researchers in the area and provide new insights into the history of reefs along the western New Caledonian margin. The main advantage of this method, compared to traditional borehole techniques, is the 10-fold reduction in the age uncertainty of events, to ±10 kyr. In addition, because turbidite material is sourced from a wide area along the coast, the method is able to provide information on reef history over a larger spatial area than single reef boreholes. This method can now be extended globally to help improve knowledge of the timing and history of tropical reef growth during the Quaternary. This will enable a better understanding of how reefs have impacted on, and been affected by, changes in climate, linked by feedbacks mechanisms via the global carbon cycle.

Coral reefs worldwide are experiencing unprecedented and rapid declines. However, deeper, mesophotic coral ecosystems (MCEs; 30–150 m) may act as refuges for coral species, providing larvae to recolonize degraded shallow reefs. This study assessed the genetic connectivity of shallow and mesophotic Montastraea cavernosa populations on the Belize Barrier Reef and the community structure of their endosymbiotic algae (Family Symbiodiniaceae) across a fine-scale depth gradient (10, 16, 25, 35 m). Evaluation of nine polymorphic microsatellite markers demonstrated that relatively shallow (10 and 16 m) M. cavernosa populations were genetically distinct from relatively deep (25 and 35 m) populations. High throughput sequencing of ribosomal coding DNA from Symbiodiniaceae communities of M. cavernosa revealed differences in community structure across depth, with shallow-specialist and depth-generalist community profiles. This research provides important information for the management of distinct deep and adds to the body of research on the understudied MCEs of the Mesoamerican Reef. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

In the marine environment, relatively little is known about how the effects of climatic change will manifest into future patterns of biodiversity and community stability, with the exception of recent work on corals in tropical reef ecosystems. In this thesis, I examine quantitatively how patterns of coral reef biodiversity will respond to the impacts of climatic change and provide essential information (i) to address a critical knowledge gap in the understanding of coral reef biodiversity and (ii) predict how a wide range of sessile invertebrates from coral reef ecosystems will respond to a range of potential impacts of climatic change such as increased physical disturbance and rising sea level. An initial descriptive component of my thesis was required to determine the distribution and abundance of a diverse assemblages of sessile non-scleractinian invertebrates, found along gradients of increasing physical disturbance from wave action and increasing intertidal shore height. I also examined the source, intensity and frequency of disturbance along these environmental gradients. This information was used to derive testable hypotheses about the potential impacts of increasing physical disturbance and rising sea level associated with climatic change. I found that physical disturbance had a substantial influence on the types of species that are able to survive in these intertidal rubble habitats, with diversity decreasing at more exposed shores and further down the shore. Physical disturbance was more important for determining the composition of sessile assemblages than other biotic factors such as predation, which only had weak effects on these sessile assemblages. Increased frequency and intensity of waves and storms will increase rates of physical disturbances such as scraping and overturning of rubble plates, which will have a substantial negative impact on biodiversity in these tropical intertidal habitats. These effects may be more complicated that first thought when combined with the effects of rising sea level which will not only alter the extent of inundation, but may also allow wave energy to propagate further up the shore, which has the potential to modify interactions among species through changes to the supply and recruitment of larvae, predator-prey interactions, competition and survival in harsher environments. However, the magnitude of these impacts may depend on how increased physical disturbance and rising sea level affect established species, and whether they will have a substantial effect on larval mortality rates, which currently appears to be limited by physical disturbance. Declines in biodiversity as a result of climatic change over the next 100 years could have important implications for the future health and productivity of coral reef ecosystems, especially given the ecosystem services these organisms provide. A greater understanding of the processes that drive the distribution and abundance of many different types of organisms on coral reefs, and indeed in other ecosystems, will provide essential information that managers can use to better understand and maintain these important ecosystems for future generations.

Macroalgae are an important part of the coral reef ecosystem that has largely been overlooked. However, in the past few decades their abundances have increased and this has been attributed to combinations of coral mortality opening up space in the reef, decreased grazing and increased nutrient load in reefs. This dissertation illustrates a novel means of investigating the effect of various growth and disturbance factors on the dynamics of macroalgae at three different levels (individual, population and 3-species community). Macroalgae are modular and clonal organisms that have differing morphologies depending on the environment to which they are exposed. These traits were exploited in order to understand the factors that were acting on the dominant and common macroalgae in the Florida Reef Tract: Halimeda tuna, Halimeda opuntia and Dictyota sp. The agent-based model SPREAD (SPatially-explicit REef Algae Dynamics) was developed to incorporate the key morphogenetic characteristics of clonality and morphological plasticity. It revolves around the iteration of macroalgal module production in response to light, temperature, nutrients, and space availability, while fragmentation is the source for mortality or new individuals. These processes build the individual algae then the population. The model was parameterized through laboratory experiments, existing literature and databases and results were compared to independently collected field data from four study sites in the Florida Keys. SPREAD was run using a large range of light, temperature, nutrient and disturbance (fragmentation without survival) levels and yielded six morphological types for Halimeda tuna, and two each for Halimeda opuntia and Dictyota sp. The model morphological types that matched those measured in two inshore patch reefs (Cheeca Patch and Coral Gardens) and two offshore spur and groove reefs (Little Grecian and French Reef), were formed in conditions that were similar to the environmental (light, nutrient and disturbance) conditions in the field sites. There were also differences between species in the important factors that influenced their morphologies, wherein H. opuntia and Dictyota were more affected by disturbance than growth factors, while H. tuna morphology was affected by both. Allowing for fragmentation with survival in the model resulted in significantly higher population abundances (percent cover and density). The highest abundances were achieved under high fragment survival probabilities and a high disturbance level (but not large fragment sizes). Incorporating fragmentation with survival and simulating the variations in light, nutrients and disturbance between the inshore patch reefs and offshore spur and groove reefs in SPREAD led to comparable abundances of Halimeda in the virtual reef sites. Adding competition for space and light and epiphytism by Dictyota on the two Halimeda species suggests that it can regulate the populations of the three macroalgae. However, comparing model abundances to the field, competition may not be a strong regulating force for H. tuna in all the sites and H. opuntia in the patch reefs. H. opuntia in the offshore reefs is possibly competitively regulated. Although SPREAD was not able to capture the patterns in the population abundance of Dictyota, this points to the potential importance of other morphometrics not captured by the model, a variation in growth curves between reef habitats, or the differential contribution of sexual reproduction.

<p>Coral reef fish coexist in a state of high diversity that has not been successfully explained by niche diversification, larval supply, differential mortality, or a suite of other proposed factors. These processes are all occurring on a diverse substrate that would be expected to affect the abundance and distribution of fish by directing habitat preferences as well as affecting competitive and predatory success. I conducted correlational studies on healthy and degraded Caribbean reefs that addressed fish abundances at the levels of community, species, and age class. I also experimentally tested habitat preferences in two ways: choice experiments on adults of common species that determined preferences for live coral and rugosity in an isolated environment, and monitoring of artificial reefs differing in live coral cover that tested habitat selection of adults and juveniles in the field. These observations all show that live coral had no effect on community parameters such as abundance or diversity, but that rugosity was positively related to species richness. However, these measures of the community masked differences at the species and age class level. A handful of species exhibited positive or negative preferences for live coral, but these selections did not follow a taxonomic or trophic-level classification. Species within the genus Stegastes, for example, could either aggregate towards or avoid live coral. One species even reversed its habitat preference as it matured. Field distributions were not determined solely by these habitat preferences, but inclusion of competitive interactions into a multi-factorial model explained distribution of some species. Results suggest that changes in live coral cover, an increasingly common phenomenon, would not affect fish at a community level, but could affect a few species through changes to recruitment or alteration of competitive interactions.</p> / Dissertation

Thesis (M.S.)--University of North Carolina at Wilmington, 2003.