published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

The purpose of this study was to integrate the principles of marine geotechnical engineering, underwater acoustic and optical observation techniques into studying the distribution of seafloor sediments and engineering stability of artificial reefs off Yong-an Harbor, Kaohsiung County, south-western coast of Taiwan. The artificial reefs were deployed to the testing site in November 9th, 1996. The goal of this study was intended to describe the engineering status of this reef site and to investigate whether these reefs were moved and buried or not; as well as, to predict whether additional reefs should be deployed to this site in the future. Long-term monitoring of underwater targets was conducted by using of side-scan sonar system, echo sounder, sub-bottom profiler, and underwater video camera. The utility of side-scan sonar system was to depict the topography and terrain features of the seabed. The other equipments were used to complement and cross correlate the results of side-scan sonar observations. In this study, wave forces against reef were estimated by Morison¡¦s equation(ex. Huang, 1995), scouring depth was calculated by Silvester¡¦s experience equation (Silvester, 1974), and the settlement of reefs by theoretical consolidation equation(ex. Das, 1990). The topography of Yung-an reef site is generally gentle and monotonous. The major texture of surficial sediments in this site was sandy silt, and some gravel was distributed at the southern part of the site. In terms of the stability on the artificial reefs project, Typhoon was the main factor which causes the reef to slide or roll. Verified by theoretical analysis and monitoring, the study area of the original stacked reefs has tumbled during the research period, while the remaining non-stacked reef shows insignificant displacement and quantity of the settlement found no cases being buried. To sum up, Yong-an artificial reef district in Kaohsiung county, respectively as A, B, C; the stacked reef under normal condition has found no significant reef being buried and moving traces and artificial reefs can fully elaborate by the gathers of the fish. According to the viewpoint of this project , "Direct contact with the reef and the body of the sea-bed " both the forces of the waves and ocean currents when a typhoon strikes is not easy for the reefs to glide. The "stacked reef" which causes the reef to slide or roll when typhoon occurs was caused by both the forces of the waves and ocean currents. "Direct contact with the reef and the body of the sea-bed " in the case of wave period of 10 sec, analysis shows that the wave height must be greater than 5.8 m in order to make the reef slide. "Stacked reef" in the case of wave period of 10 sec, analysis shows that the wave height must be greater than 4.5 m in order to make the reef roll.

The purpose of this study is to incorporate the knowledge and technique of marine geotechnical engineering, underwater acoustic surveying and hydraulic experiment into studying the problems of artificial reefs off Ling-yang, Kaohsiung Country, South-western part of Taiwan deployed in March 1996. Based on hydraulic experiment, we try to observe the scouring mechanism of artificial reefs. Beside, two other reefs Yung-an, Fang-lio reef were surveyed in this study .The ultimate goal of this investigate was intended to deduce ways to solve the problem of excessive scouring and subsidence, and decide the appropriate environment of the seafloor to deploy artificial reefs for promoting fishing developing. The topography of Ling-yang is generally gentle. Based on the test of physics and mechanics, most surficial sediments at the surface was cohesiveless sand sediments including a lot of seashell. Therefore, we deduced that the surficial sediments are easier to drift caused by monsoon and typhoon in summer. The phenomenon indicated that the surface of sediments is unstable when the sediments are cohesiveless or were loaded by other forces. This study showed that there were obvious scouring effect occurred in and around the reefs, Ling-yang, Yung-an and Fang-lio. The most serious scouring area was occurred in Ling-yang, and a majority of reefs have been buried there. Therefore, the major factors, which could induce excessive subsidence or undermining of the artificial reefs in the testing site, were proposed to be scouring effects. Compared with other reef areas, the scouring effect was related to the grain distribution on the seafloor and the velocity of currents. In the aspect of preventing subsidence of reefs, the reefs closely deployed were better than that loosely deployed.

Thesis (M.S.)--Rutgers University, 2008. / "Graduate Program in Ecology and Evolution." Includes bibliographical references (p. 73-77).

Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Restricted until October 2003. Bibliography: leaves 93-103.

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

Artificial reefs may enhance the biological production of reef-associated flora and fauna, but their trophic structure relative to that of natural reefs remains understudied. We assessed trophic dynamics by comparing δ13C and δ15N in 43 fish species from artificial and natural reef tracts of Broward County, Florida. We tested the effect of sampling location (artificial, first, and second reef), general feeding strategy (herbivore, omnivore, planktivore, invertivore, and carnivore), phylogeny, and standard length. For all samples, δ13C and δ15N ranged from -19.5 to -13.1‰ and 6.7 to 13.3‰, respectively. Lower trophic level feeding behavior resulted in more depleted δ13C and δ15N and higher trophic level feeding behavior resulted in more enriched δ13C and δ15N. We detected significant effects of both general feeding strategy and phylogeny. We also detected significant differences in δ13C and δ15N profiles between artificial and natural reefs; however, these differences were not great enough to suggest changes in the feeding strategy or trophic dynamics of individual fish taxa.