Thesis (Ph.D.) - James Cook University, 2004. / Typescript (photocopy). Bibliography: leaves 237-260.

Thesis (Ph.D.) -- James Cook University of North Queensland, 1992. / Typescript (photocopy) Bibliography: leaves 321-351.

Thesis (Ph.D.) - James Cook University, 2002. / Typescript (photocopy)

Thesis (Ph. D.)--University of Queensland, 2001. / Includes bibliographical references.

Thesis (M.Sc. )--Edith Cowan University, 2006. / Submitted to the Faculty of Computing, Health and Science. Includes bibliographical references.

Thesis (Ph.D.) - James Cook University, 2005. / Typescript (photocopy) Bibliography: leaves 148-167.

Thesis (Ph.D.) - James Cook University, 2006. / Appendix 2 (p. 444-454) contains the Research Agreement between the author and the Hopevale Community which governs further research or publications arising from the thesis. Typescript (photocopy). Bibliography: leaves 373-441.

Seagrass meadows are a crucial foraging habitat for marine megaherbivores. The Red Sea hosts two megaherbivore species, the green turtle Chelonia mydas and the dugong Dugong dugon, along with twelve seagrass species. Seagrass habitats in the Saudi Arabian coast of the Red Sea are currently under pressure from large scale coastal developments. I used multiple methods to assess seagrass and megaherbivore densities in Al-Wajh lagoon, a unique semi-enclosed bay on the northeastern coast of the Red Sea that is currently targeted for development. Seagrasses were assessed using quadrat surveys while megaherbivores censuses were conducted by both unmanned aerial vehicles (UAV) and boat-based observers. Both seagrass and sea turtles were patchily distributed throughout the bay. Dugongs were never encountered during surveys but feeding trails and off-effort encounters suggest at least occasional use of the area. While there were some qualitative patterns between seagrass composition and feeding trail/sea turtle abundance, there was not enough data to achieve statistical significance. The UAV generally outperformed boat-based surveys, but the inability of the drone to distinguish turtles through dense seagrass coverage is a methodological limitation that should be overcome by using hyperspectral cameras in future work. Overall, my results highlight the importance of ground truthing habitat maps, reveal interesting questions for additional study, and provide some direction for future research and conservation efforts within Al-Wajh Lagoon.

Thesis (Ph. D.)--Griffith University, 2002. / Title from PDF title page (viewed on Apr. 28, 2005). Includes bibliographical references.

The loss of large-bodied herbivores and/or top predators has been associated with large-scale changes in terrestrial, freshwater, and marine ecosystems around the world. Understanding the consequences of these declines has been hampered by a lack of studies in relatively pristine systems. To fill this gap, I investigated the dynamics of the relatively pristine seagrass ecosystem of Shark Bay, Australia. I began by examining the seagrass species distributions, stoichiometry, and patterns of nutrient limitation across the whole of Shark Bay. Large areas were N-limited, P-limited, or limited by factors other than nutrients. Phosphorus-limitation was centered in areas of restricted water exchange with the ocean. Nutrient content of seagrasses varied seasonally, but the strength of seasonal responses were species-specific. Using a cafeteria-style experiment, I found that fast-growing seagrass species, which had higher nutrient content experienced higher rates of herbivory than slow-growing species that are dominant in the bay but have low nutrient content. Although removal rates correlated well with nutrient content at a broad scale, within fast-growing species removal rates were not closely tied to N or P content. Using a combination of stable isotope analysis and animal borne video, I found that green turtles (Chelonia mydas) – one of the most abundant large-bodied herbivores in Shark Bay – appear to assimilate little energy from seagrasses at the population level. There was, however, evidence of individual specialization in turtle diets with some individuals foraging largely on seagrasses and others feeding primarily on macroalgae and gelatinous macroplankton. Finally, I used exclusion cages, to examine whether predation-sensitive habitat shifts by megagrazers (green turtles, dugongs) transmitted a behavior-mediated trophic cascade (BMTC) between sharks and seagrasses. In general, data were consistent with predictions of a behavior-mediated trophic cascade. Megaherbivore impacts on seagrasses were large only in the microhabitat where megaherbivores congregate to reduce predation risk. My study highlights the importance of large herbivores in structuring seagrass communities and, more generally, suggests that roving top predators likely are important in structuring communities - and possibly ecosystems - through non-consumptive pathways.