Dissertations / Theses on the topic 'Coral reefs and islands – Barbados'

Both local and global threats are affecting the health of coral reefs worldwide. In addition to endangering the livelihoods and source of food for millions of people, threats to coral reefs may result in flattening reefs, which reduce habitat complexity and the ability of reefs to protect shorelines from erosion. This could be particularly detrimental to low-lying Pacific atolls like those found in the Republic of the Marshall Islands (RMI). I examined the influence of local human disturbance and heat stress on coral and algal community composition in Majuro and Arno Atolls in the RMI to explore how human disturbance affects coral and algal communities, and how to best characterize those communities. With a population of approximately 30,000 people, Majuro is home to the largest population of all of the RMI's 29 atolls and underwent extensive human modifications after American occupation during World War II. By contrast, Arno is home to fewer than 2,000 people and has remained relatively undisturbed. In June of 2016, I conducted benthic surveys at 25 sites along a gradient of human impacts across the two atolls. At each site at 10m depth, I measured percent cover of coral and algae genera and size-frequency of coral. I also utilized limited historical data to explore how reefs had recovered after a thermal stress event in 2014. In order to estimate human disturbance, I used the mean normalized difference vegetation index (NDVI) of the nearby coastline, which measures vegetation intensity. The coral and macroalgae composition of sites differed by atoll, mean NDVI, and wind and wave exposure, but not by sea surface temperature. The most degraded sites had low macroalgae cover and were dominated by turf algae, sponges, and cyanobacteria. One genus of macroalgae, Halimeda, was associated with sites that had low disturbance, while another, Hypnea, was correlated with higher disturbance. These results suggest that using macroalgae as an indicator of degradation may mask the influence of local human disturbance on reef community composition. Instead, it is important to consider identifying other indicator taxa and to measure coral and macroalgae cover to at least the genus level.
Arts, Faculty of
Geography, Department of
Graduate

Coral reef resources are under threat globally from liuman-induced changes including; development, pollution, fishing, over-use and climatic change. Here I consider the ecological and economic effects of the scuba diving and snorkelling industries on the coral reefs of the British Virgin Islands (BVI). I begin examining the current ecological impacts of scuba diving and snorkelling across reefs in the BVI; I also look at diver behaviour, and the recovery of hard corals following exposure to diver damage. The intensity of dive and snorkelling use currently appears sustainable. However, there are several sites based on wrecks that are subject to extremely high levels of use, thus the benthic organisms situated at these sites are under significantly greater levels of stress than those situated at other sites. All corals monitored following simulated diver damage showed rapid recovery. However, there were differences in recovery times between hard coral species and types of damage. Coral reef ecosystems are particularly important to the economies of many island nations and help attract tourists as well as providing the basis for excursion industries such as scuba diving and snorkelling. In the later chapters of this thesis I focus on the current and potential value of coral reefs to the BVI by conducting several choice experiments with visual aids. I found a significant consumer surplus related to the guided scuba diving and snorkelling industries of the BVI, both of which were influenced by changes in environmental quality. Finally, ecological and economic methodologies were applied to a specific ecosystem threat. I used the 2005 Caribbean wide bleaching as an example of a catastrophic event experienced by the reefs of the BVI. The ensuing economic and ecological losses were measured and found to be significant. These results demonstrate the strength of a combined ecological and economic approach to reef management.

Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2009.
Committee Chair: Weiss, Howard; Committee Member: Cvitanovic , Predrag; Committee Member: Goldman, Daniel; Committee Member: Schatz, Michael; Committee Member: Wiesenfeld, Kurt. Part of the SMARTech Electronic Thesis and Dissertation Collection.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior
As assembleias de peixes em ambientes recifais estÃo entre as mais diversas dos oceanos, sendo o estudo destes animais indispensÃvel para um melhor entendimento do ecossistema como um todo. Recentemente foi publicado um volume considerÃvel de trabalhos a respeito da ictiofauna recifal brasileira. Contudo, algumas regiÃes, como o estado do CearÃ, apresentam grande carÃncia de informaÃÃes bÃsicas. A presente pesquisa encontra-se dividida em dois tÃpicos principais, sÃo eles: 1. Estruturas das assembleias de peixes em trÃs ambientes recifais do Parque Estadual Marinho da Pedra da Risca do Meio (PRM), 2. Uma anÃlise zoogeogrÃfica dos peixes em ambientes recifais do Nordeste brasileiro. Para discutir ambos os assuntos, foram utilizados dados qualitativos (listas das espÃcies) e quantitativos (abundÃncia das espÃcies) obtidos em aproximadamente 210 mergulhos autÃnomos (SCUBA) em 13 ambientes recifais da costa cearense entre 16 e 35 metros de profundidade. As amostragens quantitativas foram realizadas em trÃs ambientes recifais dentro do PRM (Pedra Nova, Risca, AviÃo) entre outubro de 2002 e setembro de 2003 e foram baseadas em 63 censos visuais estacionÃrios, 21 em cada ponto. Para o PRM foram inventariadas 129 espÃcies de peixes sendo 6 elasmobrÃnquios e 123 teleÃsteos. Baseado em registros fotogrÃficos, foi elaborado um guia preliminar contendo 83 espÃcies de peixes do PRM. Foram registradas nos censos 11.140 ocorrÃncias de peixes sendo: 4.755 na Pedra Nova, 2.222 na Risca e 4.163 no AviÃo. As trÃs assembleias analisadas apresentaram padrÃes de ictiofauna significativamente diferenciados que provavelmente estÃo relacionados Ãs peculiaridades ambientais de cada local. TambÃm foram constatadas diferenÃas significativas nas assembleias dos trÃs locais, entre os dois perÃodos climÃticos existentes na regiÃo (seco e chuvoso). A anÃlise zoogeogrÃfica comparou ambientes recifais do CearÃ, Parcel do Manuel LuÃs (MaranhÃo), Risca do Zumbi (Rio Grande do Norte) ParaÃba (PA), Abrolhos (Bahia) e as ilhas oceÃnicas Atol das Rocas e ArquipÃlago de SÃo Pedro e SÃo Paulo. Foi observado que a composiÃÃo da ictiofauna recifal do Cearà apresenta considerÃvel semelhanÃa as dos estados prÃximos (Rio Grande do Norte e ParaÃba). Alem disso, os ambientes recifais continentais da regiÃo nordeste do Brasil suportam um nÃmero semelhante de espÃcies.
Meetings of fish in reef environments are among the most diverse of the oceans, and the study of these essential for a better understanding of the ecosystem as a whole animal. Recently published a considerable volume of studies regarding the Brazilian reef fish populations. However, some regions, such as the state of CearÃ, show great lack of basic information. This research is divided into two main topics are: 1. Structures of the Assemblies of fish in three reef environments of Pedra da Risca do Meio State Marine Park (PRM), 2. A zoogeographical analysis of fish in reef environments Northeast Brazil. Were used qualitative data (list of species) and quantitative (species abundance) obtained in approximately 210 scuba dives (SCUBA) in 13 reef environments of Cearà coast between 16 and 35 feet deep to discuss both matters. Quantitative samples were taken from three reef environments within the PRM (New Stone, Risca, Airplane) between October 2002 and September 2003 and were based on stationary visual census 63, 21 in each point. PRM to 129 species of fish and 6 elasmobranch and teleost 123 were inventoried. Based on photographic records, we designed a preliminary guide containing 83 fish species from the PRM. 11,140 occurrences of fish were being recorded in the censuses: 4755 New Stone, in 2222 and 4163 in Risca Airplane. The three assemblies analyzed showed significantly different patterns of fish populations that are probably related to the environmental characteristics of each site. Significant differences were also found in the assemblies of the three sites, existing between the two climatic periods in the region (dry and wet). A zoogeographical analysis compared reef environments of CearÃ, Parcel Manuel LuÃs (MaranhÃo), Risca Zombie (Rio Grande do Norte) ParaÃba (PA) Abrolhos (Bahia) and oceanic islands Archipelago and Rocas Atoll St Peter and St Paul . It was observed that the composition of the reef fish fauna of Cearà has considerable similarity to the nearby states (Rio Grande do Norte and ParaÃba). Moreover, the continental reef environments of northeastern Brazil support a similar number of species.

Thesis (MTech (Oceanography))--Cape Peninsula University of Technology, 2009
A collaborative study between Marine and Coastal Management (MCM) and the Oceanographic Research Institute (ORI) was initiated in March 2001 to investigate the physical oceanography of Sodwana Bay, South Africa, and the affects on coral communities resident to the area. A bottom-mounted Acoustic Doppler Current Profiler (ADCP) and three Underwater Temperature Recorders (UTR) were deployed to complement the long-term monitoring UTR deployed on Nine-Mile Reef (NMR) in 1994. The study was terminated after 30 months, whereby all instruments were removed except for the long-term monitoring UTR.

Thesis (MTech (Oceanography))--Cape Peninsula University of Technology, 2010
Coral reefs are in a worldwide state of crisis due to overexploitation. One of the factors contributing to the over exploitation is the marine ornamental industry. This industry utilises a diversity of organisms, comprising approximately 1470 species of fish and more than 300 species of invertebrates. Between April and December 2007, five of the 18 companies who had import permits for South Africa, imported a total of 359 different ornamental species, 252 of these were fish species while the remaining 107 species were invertebrates. During these nine months a total of 32 005 individual organisms were imported into South Africa by the five companies. There were two groups of fish that represented the highest import volumes. These were Amphiprion spp. and Pomacentradae spp., as well as the Gobidae spp. These groups represented 38% and 19% respectively of the total number of fish imported" Aquaculture has the potential to substantially reduce the harvesting pressure on coral reef organisms globally. A small-scale multi-species mariculture system was designed and constructed for benthic egg-laying species of fish (brood stock), corals, and ornamental algae. The system was designed to be low cost and easy to operate. The total capital costs for the system was R15 680.70. In order to estimate the potential yield of an aquaculture facility it is important to know the growth rate of the proposed species under pilot conditions. The use of artificial lighting regimes in aquaculture comes at a financial cost. It is for this reason that it is important to know what lighting scenario yields the highest growth rate of corals. The effects of photoperiod were tested on Sinularia sp. of coral. Two photoperiods were tested, namely: Groups (8:16 h Iight:dark cycle) and Group12 (12:12 h light:dark cycle). No significant difference in weight was found between Group8 and Group12 (p = 0.975). There was however a significant increase (p = 0.002) in Surface-area Pixel Value (SPV) for Groups (1996.73 millipixels pixel-1 day -1) compared to Group12 (983.73 millipixels pixel-1 day -1). The use of a 8:16 h lightdark cycle can thus yield coral of a larger size but not necessarily a higher mass.

Since the 1980’s, there has been an unprecedented decline in the reef-building Caribbean corals, Acropora cervicornis and A. palmata, which has led to their listing as “threatened” under the U.S Endangered Species Act. Despite this protective status, these Acropora species continue to experience declines primarily attributed to disease, global climate change, and storm damage. Recent evidence suggests the hybrid of these threatened species (A. prolifera) is found at abundances similar to or higher than the parental species at many sites throughout the Caribbean. However, there is still much that is unknown as to how and why hybrids may be increasing in abundance at select sites. In 2007, scientists from NOAA NMFS established 9 permanent transects at three sites in the USVI to quantify fish diversity and coral tissue condition in A. cervicornis thickets. Over the years, they observed that A. prolifera seemed to be increasing in abundance on transects that were once dominated by A. cervicornis. This dataset provided a unique opportunity to investigate whether a shift from a threatened parental species to its hybrid may have occurred. This study has two objectives, (1) to quantify the change in A. cervicornis and A. prolifera percent cover and colony health over a 9-year period, and (2) to compare the genotypic diversity among the three Caribbean acroporids on and near the transects to determine the primary method of propagation, i.e., sexual versus asexual. For this study, I used transect photographs taken in March, July and November 2009, April 2012, and August 2017 to compare intra- and interannual variation in acroporid cover and colony health. Striking losses were observed in A. cervicornis cover between March 2009 and August 2017. At Thatch Cay, A. cervicornis declined from 25.7% to 8.9% between March 2009 and November 2009, but remained stable (10.2%) up to August 2017. Acropora cervicornis cover declined from 13.2% to 0% at Lovango Cay, and from 8.2% to 0% at No-Name Bay. At the one site (No-Name Bay) that A. prolifera was present during the original surveys of the transects, the percent cover remained relatively high and stable over the sample period. At No-Name Bay, A. prolifera percent cover (18.2%) was significantly higher than A. cervicornis (5.4%) by November 2009. It appears that A. prolifera expanded in the habitat left void by the decline in A. cervicornis. The general health of A. cervicornis based on the amount of healthy versus white and pale tissue appeared to decline at all sites between March 2009 and November 2009. To determine if the high percent cover on some transects was derived from asexual propagation or sexual recruitment, 139 tissue samples were collected in 2017 and genotyped using five microsatellite markers. No significant difference in genotypic richness (number of unique genotypes divided by the sample size) was observed among A. cervicornis (0.62), A. prolifera (0.64), and A. palmata (0.68). This suggests that the hybrid colonization is from multiple sexually derived individuals, not just asexual propagation from a rare hybridization event. High genotypic diversity, stable population abundance, and healthier colonies, suggest acroporid hybrids may become the primary habitat building coral of shallow reefs in the U.S. Virgin Islands. Due to considerable differences in morphologies between A. cervicornis and A. prolifera, it is unclear how a shift to the hybrid may affect the organisms that occupy acroporid structure and if the same ecological functions can be fulfilled.

This creative project concerned the planning of an underwater park off the western coast of Negril, Jamaica. Negril is the westernmost point in Jamaica. Negril was traditionally a small fishing village before the development of tourism in the late 1960's. The rapid growth of tourism and haphazard development that followed has had detrimental effects on the marine environment and local community. Much of the local economy still depends on fishing for its subsistence. The underwater park is an attempt to preserve and protect the reefs and linked habitats in Negril.Protecting the reef will ultimately benefit the local fishing economy. The reef, with its warm, shallow waters is a breeding ground for fish. The fish rely on natural protection in the reef until they are large enough to move out into open waters. The park will prohibit collecting of any fish or plant species within the park area or any other activity with negative impacts to the reef ecology.The intent of the study was to locate and identify the underwater interpretive resources (coral communities), closely linked marine habitats and to recommend park boundaries and designate levels of use and protection. Further intent was to identify current and potential impacts, determine the proper status for the park, outline management objectives, regulations, and specify management plans for the park.The Negril Underwater Park will exist for the purpose of encouraging maximum compatible development of the coral reef system, as a visitor attraction and recreation area, while preserving the resources from degradation through a program of controlled use. The park is also intended to protect habitats linked to the coral reef especially the Great Negril Morass, Sea-grass, beach, and Mangrove areas.
Department of Landscape Architecture

Dimethylsulphoniopropionate (DMSP) and dimethylsulphoxide (DMSO) (collectively DMSP/O) are produced by marine algae, including symbiotic algae within corals. These sulphur compounds are important not only in sulphur cycle dynamics but also in potentially mediating atmospheric conditions, alleviating the effects of climate change and contributing to reef health. Most research has focused on the production of DMSP and its major degradation product, the climatically active gas, dimethylsulphide (DMS) by Acropora corals in the Great Barrier Reef. However, mechanisms for the production and release of DMSP/O by different reef taxa is poorly understood. Recently the importance of mesophotic reefs as refugia for shallow water corals has been postulated, however their role in the marine sulphur cycle is unknown. This research aimed to improve our understanding of the contemporary and climate change induced seawater and tissue production of DMSP/O in a range of reef environments and taxa. This was achieved through a combination of laboratory and field - based studies, using modern and established techniques. An effect of both elevated temperature and OA on increased tissue and seawater concentrations of DMSP/O production is reported in field and laboratory studies. Contrasting effects of benthic cover on tissue DMSP/O distributions and seawater DMSP are also noted. The importance of the physical and hydrodynamic environment on biogeochemical connectivity both within a reef and between neighbouring reefs is also focussed on. Crucially, however, the novel tissue and seawater data from mesophotic sites suggests that deeper reefs could affect the biogeochemistry of their shallow water counterparts. The key finding from this work is that climate change will result in increased seawater DMSP concentrations via two mechanisms; through the increase of cellular production of DMSP/O in all reef taxa, and by increasing the biomass of prolific DMSP producers as reefs transition to a fleshy/macroalgal assemblage. Whilst this could potentially mediate the effects of climate change, it will probably also worsen overall reef health, lead to a restructuring of reef communities from the microbial level upwards and will have possibly permanent and deleterious effects on overall ecosystem function.

The need for a broader geographical and functional perspective in managing natural resources of the Belize barrier reef system was examined. The small country of Belize in Central America is struggling to increase its economic development and growth. It has an excellent natural resource base, the most dramatic component being the extensive barrier reef system just offshore. The research identified key economic and environmental issues relative to Belize’s reef complex, and analyzed resource management policies and actions taken to date. Development and conservation needs suggest a multiple use strategy aimed at economic and environmental sustainability. Due to areal extent and ecological complexity, the present reactive, small-scale and piecemeal approach is not adequate to realize sustainable utilization of the area’s resources. This research shows the need for a broad spatial and interdisciplinary “coastal zone" perspective, leading to a comprehensive and integrated strategy upon which to base resource planning and management. A strategy for the reef system must be accomplished within the broader context of a national resource management strategy, integrating concerns of economic development and environmental protection. As a component of this national policy, the proposed strategy for the barrier reef system is based on principles of multiple use of resources, coastal zone scope, and sustainability. The research supports a reef system-wide protected area, using a biosphere reserve framework and a customized model planning process to implement the strategy.
Master of Science

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Civil and Environmental Engineering; and the Woods Hole Oceanographic Institution), 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references.
To understand how waves and sea level shape sandy shoreline profiles, I use existing energetics-based equations of cross-shore sediment flux to describe shoreface evolution and equilibrium profiles, utilizing linear Airy wave theory instead of shallow-water wave assumptions. By calculating a depth-dependent characteristic diffusivity timescale, I develop a morphodynamic depth of shoreface closure for a given time envelope, with depth increasing as temporal scale increases. To assess which wave events are most important in shaping the shoreface in terms of occurrence and severity, I calculate the characteristic effective wave conditions for both cross-shore and alongshore shoreline evolution. Extreme events are formative in the cross-shore shoreface evolution, while alongshore shoreline evolution scales linearly with the mean wave climate. Bimodal distributions of weighted wave heights are indicative of a site impacted more frequently by tropical storms rather than extra-tropical storms. To understand how offshore wave climate and underlying geometry of a carbonate reef platform shapes evolution of atolls, I simulate the hydrodynamics of a simplified reef flat, using XBeach, a two-dimensional model of infragravity wave propagation. The reef flat self-organizes to a specific width and water depth depending on the offshore wave climate and characteristics of the available sediment. Formation of a sub-aerial landmass, like a motu, can be initiated by a change in offshore wave climate (like a storm), which can create a nucleation site from mobilization and deposition of coarse sediment on the reef flat. Once a motu is present, the shoreline should prograde until reaching a critical reef-flat width. Our conceptual model of reef-flat evolution and motu formation is governed by understanding the hydrodynamics of the system and subsequent response of sediment transport.
by Alejandra C. Ortiz.
Ph. D.

Parrotfish are a critical component of the herbivore functional group on tropical coral reefs around the world because they mediate competition that occurs between algae and scleractinian corals. Also, because of their feeding technique, which consists of rasping at the substratum with their beak-like teeth, they play an important role in carbonate turnover and the clearing of reef surface area for the settlement of new sessile organisms. Because of these roles, parrotfishes are an important structuring component of coral reef communities. However, individual species can play different roles depending on their physiology, behaviour and ecology. Despite the possible ecological differences that may exist amongst species, specific roles of the fishes remain unclear as the group is most often studied at higher community levels. This thesis applied stable isotope analysis to differing levels of organisation within a parrotfish community to help elucidate their trophic ecology on coral reefs in Zanzibar. Firstly, blood and muscle tissues were compared to identify differences in their isotope signatures. In other organisms, blood turns over faster than muscle tissue so that muscle tissue represents the diet as integrated over a longer period of time. In most species of parrotfish the blood and muscle δ¹³C signatures were not found to be significantly different, but the δ¹⁵N signatures were significantly different between tissues. This indicated that the δ¹³C signature of both tissues would reveal similar dietary information. Conversely, differences in the δ¹⁵N signature indicated that the nitrogen relationship between tissues was more complicated. Secondly, spatial variability in parrotfish, coral, detritus and macroalgae isotope signatures was assessed at different scales. In macroalgae and coral tissues (zooxanthellae and polyp treated separately), the δ¹³C signatures were shown to differ with depth, presumably because of changes in photosynthetic processes related to depth-associated changes in light. While δ¹⁵N signatures were not affected by depth, all organisms showed enrichment at the Nyange reef, the closest reef to the capital of Zanzibar, Stone Town, presumably reflecting the effects of sewage outfall. These results show that processes that impact the δ¹⁵N signatures of primary producers (macroalgae and zooxanthellae) can be traced to higher trophic levels (coral polyps and fish). Lastly, δ¹³C and δ¹⁵N signatures were used to identify ontogenetic dietary changes in multiple species of parrotfish. Four of the species showed stages that varied from the diets that are normally assumed on the basis of their dentition and feeding technique. This indicates that functional roles based on taxonomy or morphology may fail to include possible ontogenetic dietary changes, and may also fail to elucidate the full impact a species could have on coral reef communities. The conclusions from these studies indicate that the species-specific ecological role of parrotfish in coral reef communities can be complex within and between species, and may differ amongst reefs. In light of the natural and anthropogenic pressures that affect coral reef systems, management decisions based on a more complete understanding of the role of these fish in coral reef communities will help decisions that maintain resilience in these fragile systems.

Depuis le début de la période industrielle, les activités humaines ont généré une augmentation importante de la concentration atmosphérique en CO2. Une partie de ce CO2 s’accumule dans l’atmosphère, entraînant une augmentation de l’effet de serre naturel et de la température à la surface du globe. Ce processus est plus connu sous le terme réchauffement climatique ou global. De plus, environ 25 % du CO2 produit sont absorbés par les océans. La dissolution du CO2 dans l’eau de mer, entraîne une augmentation de la concentration en protons et en ions bicarbonates (HCO3-) et une diminution de la concentration en ions carbonates (CO32-). Il en résulte une diminution du pH et du taux de saturation de l’eau de mer vis-à-vis du carbonate de calcium. L’ensemble de ces processus est appelé acidification des océans (AO). Le pH des eaux de surface océaniques a déjà diminué de 0,1 unité depuis le début de l’ère industrielle. Ce phénomène devrait s’intensifier au cours du siècle. Selon les prévisions moyennes d’émissions futures de gaz à effet de serre de l’IPCC, la température moyenne des eaux de surface devrait augmenter de 2 à 4 °C et son pH devrait diminuer de 0,3 à 0,4 unité d’ici 2100.

Au cours des deux dernières décennies, de nombreuses études ont mis en évidence l’impact négatif de l’AO sur les organismes marins. Les premières études ont été menées principalement en milieu artificiel et ont mis en évidence des conséquences majeures sur la physiologie des organismes, principalement au niveau individuel. Cependant, les dernières études menées dans le domaine ont souligné l'importance de mettre en place des expériences à long terme, à l'échelle de l'écosystème, et dans des conditions plus proches du milieu naturel. Ce type d’étude permet de prendre en compte les interactions écosystémiques et les processus d’acclimatation afin de mieux prévoir les effets directs mais aussi indirects de la diminution du pH dans les océans.

L’existence des récifs coralliens tropicaux dépend de la vitesse de formation du socle récifal qui les façonnent (principalement via la calcification des coraux hermatypiques) qui doit rester supérieure à sa (bio)érosion. D’une part, plusieurs études ont montré que le taux de calcification des coraux hermatypiques diminue lorsque la pCO2 augmente. D’autre part, les oursins sont d’importants bioérodeurs des récifs et contribuent donc à la perte de masse calcaire récifale. Cependant, les oursins empêchent également, par leur broutage, le recouvrement des coraux par les algues favorisées par l’AO. Dès lors l’effet de l’élévation de la pCO2 sur les oursins et leur capacité bioérosive peut être déterminant pour l'avenir des récifs coralliens tropicaux au cours du siècle, particulièrement ceux où la densité de ces bioérodeurs est importante. Une telle prédiction est d’autant plus complexe si l’on prend en compte la possible acclimatation des différents acteurs à long terme.

Dès lors, le but du présent travail fut d'évaluer l'effet à long terme de l’élévation de la pCO2 prévue en 2100 sur la physiologie et l’activité érosive d’un oursin clé de certains récifs coralliens, Echinometra mathaei, dans un dispositif artificiel reproduisant l’écosystème corallien.

La première étape a été la mise en place un outil expérimental permettant de maintenir à long terme un écosystème de récifs coralliens simplifié en condition contrôle et au pH prévu en 2100 tout en maintenant les autres paramètres physico-chimiques identiques et proches du milieu naturel (y compris dans leurs variations journalières). Le système mis en place est composé de scléractiniaires hermatypiques comme constructeurs de récif, d’oursins (E. mathaei) comme bioérodeurs et brouteurs et un substrat calcaire de récif avec ses communautés d’algues, bactéries, archae, champignons et méiofaune. Les variations journalières de pH et de température reproduisent celles mesurées in situ dans le site de La Saline, Ile de La Réunion, d’où proviennent une partie des organismes. Le pH moyen des aquariums contrôles a été maintenu avec succès à une moyenne de 8,09 ± 0,04, celui des aquariums à pCO2 élevée à 7,63 ± 0,02. L’alcalinité totale du système a pu être maintenue entre 2350 et 2450 µmol.kg-1.

L’impact de l’AO prévue en 2100 (pH 7,7) sur la physiologie d’E. mathaei été étudié à court terme (sept semaines). La principale source de nourriture des oursins fut la communauté algale se développant sur le substrat, comme en conditions naturelles. Cette étude a permis de mettre en évidence, à court terme, la capacité de résistance de cet oursin à une AO modérée. En effet, la croissance et le métabolisme ne furent pas affectés significativement. Ces observations ont été associées au maintien de la balance acide-base du fluide extracellulaire, le liquide cœlomique, par accumulation de bicarbonates dans celui-ci.

Une même expérience a ensuite été réalisée à long terme. La diminution du pH a été induite progressivement durant six mois jusqu'à atteindre un pH moyen de 7,65 qui fut ensuite maintenu à cette valeur pendant sept mois supplémentaires. La capacité de régulation de la balance acide-base du liquide cœlomique et la résistance d’E. mathaei à l’AO a été confirmée à long terme. Tant la croissance que le métabolisme et les propriétés mécaniques du squelette ne furent pas affectés. Cette résistance apparaît liée aux capacités de régulation acide-base d’E. mathaei, un trait apparemment d’origine génétique. Cette résistance pourrait également dépendre de la quantité et de la qualité de la nourriture disponible (calcaire ou non). Il est suggéré que les ions bicarbonates impliqués dans la régulation acide-base proviendraient en partie de la nourriture.

Parallèlement à ces mesures physiologiques, l’activité érosive d’E. mathaei a été mesurée. Les résultats indiquent que le taux de bioérosion triple en conditions acidifiées (pH 7,65). Cette augmentation serait liée à l’augmentation de l'activité de broutage des oursins et à la dissolution biologique du substrat, les propriétés mécaniques des dents des oursins et du squelette des coraux ne semblant pas affectés significativement. Nous suggérons que cette activité érosive accrue pourrait avoir un impact sur l'équilibre dynamique entre bioerosion et bioaccrétion des coraux et pourrait déterminer l'avenir des récifs coralliens où E. mathaei est le principal bioérodeur. Il faut toutefois noter que l’activité érosive de cet oursin est liée à une consommation accrue des macro-algues en compétition avec les coraux et algues corallines, favorisant ainsi ces derniers.

Les résultats obtenus, associés à ceux provenant de la littérature, indiquent que les changements globaux pourraient provoquer un changement profond des écosystèmes coralliens tropicaux. En effet, l’ensemble des bioérodeurs principaux étudiés jusqu’à présent semblent résistants aux changements climatiques globaux et montrent une augmentation de leur activité érosive. Dans le cas des récifs ayant déjà à l’heure actuelle une faible calcification nette, l’augmentation de la bioérosion pourrait mener à l’érosion nette et à la réduction puis à la disparition du récif. La prédiction du devenir des récifs coralliens tropicaux à l’échelle planétaire doit toutefois prendre en compte de nombreux paramètres :acclimatation, résistance/sensibilité et interactions des différents acteurs des récifs. D’autres études comparables à celles menées dans le présent travail devraient être mises en place afin de tester ces différents facteurs. Les données obtenues pourraient dès lors être utilisées dans la construction d’un modèle mécanistique permettant de mettre en place localement des mesures de conservation du récif, en complément de l’indispensable réduction massive de l’émission de CO2 atmosphérique à l’échelle mondiale.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

To understand and predict community dynamics in habitats where physical disturbance is a major cause of mortality, we must understand the frequency and intensity of these events, as well as their differential effects on the community’s structural species. Using a tropical coral reef as a study system, the aim of this thesis was to quantify the mechanical vulnerability of the habitat-forming structural species, scleractinian corals, and build a framework to estimate size- and species-specific mortality rates based on the return time and magnitude of hydrodynamic disturbances. To accomplish this aim, a geometric model and classical engineering theory were used to identify the factors upon which colony strength depends. These factors were 1) the tensile strength of the limiting material at the colony/substrate interface, 2) the projected shape of the colony perpendicular to water motion and 3) the maximum water velocity per wave cycle. To investigate the first of these factors, the strength of coral skeleton from three morphologically disparate species (submassive Acropora palifera [Subgenus Isopora], corymbose Acropora gemmifera and tabular Acropora hyacinthus) and the strength of the reef substrate were investigated spatially at a hydrodynamicallyexposed shallow reef platform (Lizard Island, Australia) to determine whether overall colony strength (i.e., a colony’s ability to withstand physical stress) is limited by skeletal strength or the reef substrate to which it is attached. To investigate the second factor, colonies of the three study species were photographed from the exposed reef crest along belt transects shoreward towards the relatively sheltered reef back and mechanically quantified using a novel technique for calculating the maximum predicted stress (MPS) at the base of a colony as a function of its projected shape for a given water velocity (MPS can be thought of as an objective quantification of mechanical vulnerability). Finally, to examine the third factor, a 37-year meteorological record of hourly wind conditions, in conjunction with a field-calibrated oceanographic modelling procedure, was used to comprehensively quantify maximum water motion (i.e., displacement, velocity and acceleration per wave cycle) on the study reef platform at scales ranging from seconds to decades and from metres to the entire reef. Using the measurements of each colony’s limiting strength (factor 1) and MPS (factor 2), the maximum water velocity that each colony is predicted to be able to withstand was calculated. The expected mortality rates of colonies from physical disturbances were calculated by fitting the exponential probability density function to the frequency distribution of times between wave events which produced maximum water velocity (per wave cycle; factor 3) greater than that which the colony is predicted to be able to withstand at a given location on the reef. The carbonate substrate of coral reefs served as the limiting factor to the strength of mechanically threatened coral reef colonies and raises the question of why corals invest resources into building skeletons that are stronger than mechanically necessary. The robust, submassive Acropora palifera has a significantly lower MPS than the corymbose Acropora gemmifera, which in turn has a significantly lower MPS than the competitively superior, yet more mechanically vulnerable, tabular Acropora hyacinthus. In addition to these inter-specific differences, these three species display distinctly different intra-specific patterns of MPS when examined with relation to colony size. Acropora palifera demonstrates approximately equal MPS values regardless of size, whereas Acropora gemmifera and Acropora hyacinthus become significantly more mechanically vulnerable with increased size. In addition, the lognormal distribution of MPS values of the mechanically inferior species, Acropora hyacinthus, was truncated at the reef crest, suggesting the imposition of a mechanical threshold by a recent hydrodynamic disturbance which caused colonies with an MPS above the threshold to have been dislodged from their position on the reef. Superimposition of the disturbance thresholds modelled from the meteorological record onto the three study populations illustrated that larger colonies of Acropora hyacinthus are indeed predicted to be mechanically removed at regular intervals from the reef at Lizard Island, and such removal regimes are predicted to occur in a manner consistent with present distributions of this species on the reef. Finally, estimated mortality rates for coral colonies in general (i.e., based on their MPS) vary significantly over the reef’s hydrodynamic gradient and suggest that a mechanical refuge exists approximately 40-60m back from the reef crest. This refuge is in addition to the expected refuges found at the reef base and reef back, each of which should theoretically promote mechanical, and therefore morphological, diversity. This study has developed a framework for which the change in community structure of scleractinian corals caused by recurrent physical disturbance can be estimated. Building on this framework will significantly enhance ecological understanding of the relationship between physical disturbance and biodiversity on coral reefs, and will facilitate the estimation of general future community changes resulting from changes in the intensity and frequency of physical disturbance that may be associated with global climate change.

Missing leaves: 170.
Mode of access: World Wide Web.
Thesis (Ph. D.)--University of Hawaii at Manoa, 2005.
Includes bibliographical references (leaves 190-203).
Electronic reproduction.
Also available by subscription via World Wide Web
xvi, 203 leaves, bound ill. (chiefly col.), col. maps 29 cm

Fung, Ho Lam.
Thesis submitted in: November 2006.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2007.
Includes bibliographical references (leaves 343-360).
Abstracts in English and Chinese.
Acknowledgements --- p.i
Abstract --- p.iii
Contents --- p.xii
List of Tables --- p.xix
List of Figures --- p.xxxi
Chapter Chapter 1: --- General Introduction
Chapter 1.1 --- Introduction --- p.1
Chapter 1.2 --- Objectives --- p.17
Chapter 1.3 --- Monitoring methods investigated in this research --- p.18
Chapter 1.4 --- The distribution of corals in Hong Kong --- p.21
Chapter 1.5 --- Study sites --- p.23
Chapter 1.6 --- Thesis Outline --- p.25
Chapter Chapter 2: --- "Coral Mapping in Cheung Sha Wan, A Ye Wan and A Ma Wan, Tung Ping Chau"
Chapter 2.1 --- Introduction --- p.31
Chapter 2.2 --- Study sites --- p.37
Chapter 2.3 --- Methods and Materials --- p.38
Chapter 2.3.1 --- Fieldwork procedure --- p.38
Chapter 2.3.2 --- Laboratory work procedure --- p.40
Chapter 2.3.3 --- Data analysis --- p.40
Chapter 2.4 --- Results and Discussion --- p.42
Chapter 2.4.1 --- Species count --- p.42
Chapter 2.4.2 --- Coral coverage --- p.42
Chapter 2.4.3 --- Species composition --- p.43
Chapter 2.4.4 --- Diversity index --- p.43
Chapter Chapter 3 --- "Evaluation of Monitoring Methods in Cheung Sha Wan, Tung Ping Chau, a Coral Community with Low (< 10%) Coral Cover"
Chapter 3.1 --- Introduction --- p.52
Chapter 3.2 --- Materials and methods --- p.61
Chapter 3.2.1 --- Line Intercept Transect (LIT) Method --- p.62
Chapter 3.2.2 --- Point Intercept Transect (PIT) Method --- p.62
Chapter 3.2.3 --- Random Point Video Transect (RPVT) Method --- p.63
Chapter 3.2.4 --- Quadrat (QUAD) Method --- p.64
Chapter 3.2.6 --- Sampling effort in each monitoring method --- p.65
Chapter 3.2.7 --- Sample size determination --- p.66
Chapter 3.2.7.1 --- Optimal sample size --- p.66
Chapter 3.2.7.2 --- Unit effort sample size --- p.67
Chapter 3.2.8 --- Statistical analysis --- p.68
Chapter 3.2.8.1 --- Univariate analysis --- p.68
Chapter 3.2.8.2 --- Multivariate analysis --- p.69
Chapter 3.4 --- Results --- p.70
Chapter 3.4.1 --- Optimal sample size --- p.70
Chapter 3.4.1.1 --- Percent coral cover --- p.71
Chapter 3.4.1.2 --- Species count --- p.72
Chapter 3.4.1.3 --- Diversity indices --- p.72
Chapter 3.4.1.4 --- Community structure --- p.73
Chapter 3.4.2 --- Sampling efforts in different monitoring methods --- p.75
Chapter 3.4.3 --- Sample size under fixed effort --- p.76
Chapter 3.4.3.1 --- Percent coral cover --- p.77
Chapter 3.4.3.2 --- Species count --- p.78
Chapter 3.4.3.3 --- Diversity indices --- p.78
Chapter 3.4.3.4 --- Community structure --- p.80
Chapter 3.5 --- Discussion --- p.84
Chapter 3.5.1 --- Optimal sample size --- p.84
Chapter 3.5.2 --- Coral cover --- p.86
Chapter 3.5.3 --- Species count --- p.90
Chapter 3.5.4 --- Diversity Indices --- p.93
Chapter 3.5.5 --- Community structure --- p.96
Chapter Chapter 4 --- "Evaluation of Monitoring Methods in A Ye Wan and A Ma Wan, Tung Ping Chau: Coral Communities with Mid to High Percent Coral Cover (25% to 50%)"
Chapter 4.1 --- Introduction --- p.146
Chapter 4.2 --- Methods and material --- p.149
Chapter 4.2.1 --- Field monitoring --- p.149
Chapter 4.2.2 --- Laboratory work --- p.149
Chapter 4.2.3 --- Sampling effort in each monitoring method --- p.150
Chapter 4.2.4 --- Sample size determination --- p.150
Chapter 4.2.5 --- Statistical analysis --- p.151
Chapter 4.2.5.1 --- Univariate analysis --- p.151
Chapter 4.2.5.2 --- Multivariate analysis --- p.152
Chapter 4.3 --- Results --- p.152
Chapter 4.3.1 --- A Ye Wan --- p.152
Chapter 4.3.1.1 --- Optimal sample size --- p.152
Chapter 4.3.1.1.1 --- Percent coral cover --- p.154
Chapter 4.3.1.1.2 --- Species count --- p.154
Chapter 4.3.1.1.3 --- Diversity indices --- p.155
Chapter 4.3.1.1.4 --- Community structure --- p.155
Chapter 4.3.1.2 --- Sampling efforts in different monitoring methods --- p.157
Chapter 4.3.1.3 --- Sample size under fixed effort --- p.158
Chapter 4.3.1.3.1 --- Percent coral cover --- p.158
Chapter 4.3.1.3.2 --- Species Count --- p.159
Chapter 4.3.1.3.3 --- Diversity indices --- p.160
Chapter 4.3.1.3.4 --- Community structure --- p.162
Chapter 4.3.2 --- A Ma Wan --- p.165
Chapter 4.3.2.1 --- Optimal sample size --- p.165
Chapter 4.3.2.1.1 --- Percent coral cover --- p.167
Chapter 4.3.2.1.2 --- Species count --- p.167
Chapter 4.3.2.1.3 --- Diversity indices --- p.168
Chapter 4.3.2.1.4 --- Community structure --- p.169
Chapter 4.3.2.2 --- Sampling efforts in different monitoring methods --- p.171
Chapter 4.3.2.3 --- Sample size under fixed effort --- p.172
Chapter 4.3.2.3.1 --- Percent coral cover --- p.172
Chapter 4.3.2.3.2 --- Species Count --- p.173
Chapter 4.3.2.3.3 --- Diversity indices --- p.174
Chapter 4.3.2.3.4 --- Community structure --- p.175
Chapter 4.4 --- Discussion --- p.178
Chapter 4.4.1 --- Optimal sample size --- p.178
Chapter 4.4.2 --- Coral Cover --- p.178
Chapter 4.4.3 --- Species Count --- p.181
Chapter 4.4.4 --- Diversity Indices --- p.182
Chapter 4.4.5 --- Community Structure --- p.184
Chapter Chapter 5 --- Role of Community Characteristic on the Performance of Monitoring Methods
Chapter 5.1 --- Introduction --- p.281
Chapter 5.2 --- Methods and materials --- p.284
Chapter 5.2.1 --- Coral Mapping --- p.284
Chapter 5.2.2 --- Monitoring Methods --- p.285
Chapter 5.2.3 --- Statistical analysis --- p.286
Chapter 5.3 --- Results --- p.286
Chapter 5.3.1 --- Sample size as a function of different reef characteristics --- p.286
Chapter 5.3.2 --- Performance of reef monitoring methods in sites with different reef characteristics --- p.287
Chapter 5.3.2.1 --- Coral cover --- p.287
Chapter 5.3.2.2 --- Species count and Margalef's Index --- p.288
Chapter 5.3.2.3 --- Other diversity indices --- p.289
Chapter 5.3.2.4 --- Community structure --- p.290
Chapter 5.4 --- Discussion --- p.291
Chapter 5.4.1 --- Effect of reef characteristics on sampling time --- p.291
Chapter 5.4.2 --- Effect of reef characteristics on the performance of monitoring methods --- p.293
Chapter 5.4.3 --- Recommendation on the choice of monitoring method --- p.301
Chapter Chapter 6 --- Summary and Prospectives --- p.337
References --- p.343

Coral reefs are being destroyed and degraded by natural and anthropogenic processes. Live corals are becoming increasingly popular as marine aquarium specimens, in both the commercial and private sectors, leading to the degradation of coral reefs. This often has serious economic implications for the fishing, aquarium and tourist industries. It is clear that there is a need for the management and protection of these fragile ecosystems. The artificial propagation of coral is desirable as it will alleviate the demand for wild coral specimens, and will also provide a stock for the rehabilitation of damaged reefs. Although corals are being propagated worldwide by hobbyists, reports on their work are mainly anecdotal and there is little in the scientific literature on the specific requirements for optimal growth rates and survival in suitable coral species. This study thus focused on developing techniques to propagate a range of appropriate coral species and to promote their optimal growth. The results revealed that different morphological groups of scleractinian corals require specialised techniques of fragmentation and attachment to ensure survival. The corals were broken using a hammer and chisel. Attachment techniques varied from the use of superglue (which is widely used in the United States), to thermoplastic glue. The mean mortality using superglue was 73% (n=120, ±0.167), using epoxy, 62% (n=120, ±0.127) and with thermoplastic glue it was 11% (n=120, ±0.108) Superglue was extremely difficult to work with and proved ineffective, especially when attempting to glue uneven surfaces. Certain species did not survive using this adhesive due to exposure of the coral to air. The most effective method of rapid attachment was the use of thermoplastic glue that set rapidly underwater. The use of electrolysis to promote the attachment of coral nubbins was tested as an alternative to the various adhesives. This method increased the survival of the nubbins and eliminated exposure to air. It has proven suitable for both coral propagation and in situ reef rehabilitation. Growth experiments revealed that the manipulation of current flow, light and the addition of different feeds had different effects on the growth rates of selected candidate species. A suite of optima was thus developed for each species. The majority of species grew best in a bi-directional current flow, with yeast as feed, under actinic blue light. An experiment that combined the optimal current flow, feed and light conditions, revealed that the majority of species grew best under mixed light with yeast as feed. The trade in corals is sensitive in terms of their handling, transportation and CITES (Convention on International Trade in Endangered Species) status. Having established the viability of their propagation, consideration was given to appropriate regulatory and marketing procedures to accommodate this sensitivity of the cultivated material.
Thesis (M.Sc.)-University of Natal, Durban, 2001.

碩士
國立中山大學
海下科技研究所
103
This study was conducted to understand the relationship of coral reefs coverage rates to the hydrographic environments and benthic habitats at Penghu Southern Four Islands. Field observations were conducted in 2012 using hydrographic instruments and a tow camera at 13 selected sites. Analysis of observed data revealed that the currents were dominated by tides, southward in ebb and northward in flood. The surface water temperature was 24℃ in May and 27℃ in September, and is about 20℃ in both season near the bottom. Salinity ranged 32.7~34.6‰, which mostly originated from SCS. The geology background of southern Penghu was volcanic basalt. The observed benthic types were dominated by rock in the shallow water around the islands. Sandy bottom and gravel/pebbles were observed in the deeper water. The bottom habitats were mainly hard corals in the rocky substrate. A few soft corals can be found in the deeper gravel bottom. Statistics suggest that the bottom coverage rate of corals is related to water depth (light). It appears that the coral reef grows very well in the rocky bottom at less than 30 m. EOF analysis using parameters including coral reefs coverage rate, hydrographic data, and benthic habitats. The resulting first EOF mode shows that the hard corals and soft corals are negatively correlated with current speed. PCA analysis shows that the second mode is highly correlated with the occupation of hard corals. The water depth and rocky bottom are major factors controlling the coverage rates of hard corals.

Generations of hard corals have built the complex reef ecosystems that harbour a huge diversity of sea-life in the world’s shallow tropical oceans. These undergo both sexual and clonal reproduction, and may contain signatures in their genomes which help to decipher the riddles of past population dynamics and evolutionary history. Two species of coral, Acropora austera and Platygyra daedalea, were collected from sites along the east African coastline from Kenya in the north to Maputaland, South Africa in the south, and from the Chagos Archipelago. Sequences of two different DNA regions were tested, in a preliminary study, for their potential ability to elucidate connectivity and differentiation among these coral populations. These were the nuclear ribosomal ITS region of P. daedalea populations, and a previously-unused marker, the carbonic anhydrase 3/550 nuclear intron of A. austera. These molecular markers indicated high levels of connectivity amongst populations in a preliminary study based on limited sample sizes and a subset of populations. It was decided to further explore the variability of the carbonic anhydrase 3/550 intron, which showed evidence of subdivision and structuring within Mozambique populations relative to South African populations, in a study in which both the sample size per site and the number and range of sampled sites were increased. ITS sequences, although highly variable, revealed no population differentiation in P. daedalea; STR markers were used in subsequent studies of population differentiation in this species. Populations of both A. austera and P. daedalea showed signs of high connectivity along the region of the coastline sampled in this study. However, there appeared to be a disjunction in ecological connectivity between reefs in Maputaland, South Africa and those in southern Mozambique, between Durban and Maputo where the Agulhas Current originates. This was reinforced in A. austera populations which displayed a region of genetic discontinuity between Inhaca Island and Maputaland reefs of the central reef complex, in the region of Rabbit Rock. Northern reef complexes also harboured unique haplotypes in contrast to southern reefs which shared all haplotypes with those in the north, an indication that northern reefs have seeded the southern (Maputaland) reefs. P. daedalea populations appeared evolutionarily panmictic over scales relevant to this study. Evidence for fine-scale structure indicated that populations were separated from one another over ecologically relevant time-scales. These populations were defined by both their habitats and their sampling location. There was a possibility that the Platygyra species complex included cryptic species that were not distinguishable from P. daedalea. However, the disjunction in the connectivity between northern and southern population groups was also evident in the population structure of P. daedalea. There was a net immigration of propagules of both P. daedalea and A. austera into populations north of the disjunction between groups, where the prevailing current regime is dictated by the Mozambique Channel eddies. In contrast populations to the south of the disjunction (the southern population group) which are subject to the swiftly flowing Agulhas Current, showed a net emigration of propagules from Maputaland reefs. These emigrants were likely to be lost to inhospitable habitat south of the marginal Maputaland region. Although there was evidence for migration of both Platygyra and Acropora propagules between the Bazaruto Archipelago reefs and certain Maputaland reefs, genetic exchange between Mozambique and Maputaland reefs appeared to be limited and may have occurred primarily at evolutionary rather than demographic levels. Managers may need to treat the regional Maputaland reefs as separate stocks and manage them accordingly, as the relative isolation of these corals in the central and southern reef complexes in Maputaland, South Africa, means that they are at risk to losing species to evolutionary extinction. It is also important that reef health in northern Mozambique and Tanzania is maintained as, despite evidence of a break in demographic connectivity, between reefs in these regions and those in Maputaland, there was evidence to suggest that reefs were connected at evolutionary scales, thus maintaining levels of genetic diversity on southern African reefs.
Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2010.

Allochthonous, seaward-dipping deposits that flank reef-rimmed carbonate platforms (reef-rimmed carbonate foreslopes) display a spectrum of deposit types, seismic-scale stratal architecture, and bed-scale heterogeneity due to diverse sediment sources and resedimentation processes. This variability has resulted in a lack of consistent characterization approaches, and has made the development of predictive models that link carbonate foreslope deposit types to stratal architecture challenging. This study uses data from outcrops, including the Upper Devonian of the Canning Basin, Western Australia and the Upper Permian of the Delaware Basin, West Texas, and examples from literature to provide 1) an approach for characterizing reef-rimmed carbonate foreslopes in terms of deposit types and architecture, 2) conceptual models that outline the variations that exist, and 3) discussion of the intrinsic and extrinsic factors that control the observed variations. The primary depositional elements that construct reef-rimmed carbonate foreslopes can be categorized as 1) debris elements (breccias and blocks) from brittle reef failure, 2) grain-dominated elements (grainstones and rudstones) from offbank transport of sand and gravel, and 3) mud-dominated elements (mud-dominated fabrics) that record relative foreslope quiescence and fine-grained periplatform shedding. The fundamental stratal geometries observed are 1) accretionary margins, characterized by margin-toforeslope interfingering and clinoforms, and 2) escarpment margins, characterized by aggrading-retrograding margin architecture and foreslope onlap. The combinations of element proportions, element distribution, stratal geometry, bed- to bedset-scale architecture, and depositional profile scale that exist in carbonate foreslopes range widely, warranting multiple depositional models. The deposit type and architectural variations observed in detail from Upper Devonian and Upper Permian outcrops of the Canning Basin, Western Australia, and the Delaware Basin, West Texas, respectively, are linked to differing scales of superimposed accommodation change and reef faunal assemblage. Observations from other outcrops and extensive literature review display further controlling factors that affect carbonate foreslope development, such as platform morphology, oceanographic conditions, slope height, tectonic setting, and siliciclastic input, suggesting a multi-variable interplay of controls. These controls dictate the productivity and resedimentation of the contributing sediment factories, and/or influence the development of the carbonate platform system as a whole. Knowledge and classification of carbonate foreslope deposit types, architecture, and controls not only improve understanding of these complex systems, but also allow for the development of predictive relationships for economic purposes.
text

The development of coral reefs is largely restricted to areas within the tropics where favourable conditions for both coral and reef growth prevail. There is, however, a continuum from these typical, accretive reefs in the tropics to marginal, non-accretive, coral-dominated reef communities which occur at higher latitudes. High-latitude reefs function similarly in many regards to their tropical counterparts and are regulated by similar processes to a varying degree. In this study, the major biological and physico-chemical processes were assessed which directly or indirectly prevent the continued persistence of reefal frameworks and thus hinder reef accretion on high-latitude reefs in the iSimangaliso Wetland Park. These reefs have a high diversity of hard and soft corals with significant reef coverage, yet little evidence of any biogenic accretion has been observed. The scleractinian coral, Acropora austera, is one of the few corals which may be responsible for reef framework production. It exhibits a gregarious growth pattern, forming large, monospecific stands with an interlocking framework characteristic of the early stages of reef accretion. The framebuilding potential of A. austera and the continued persistence of such frameworks were thus determined by in situ monitoring of coral growth, mortality, bioerosion and several physico-chemical parameters. Growth rate and mortality of A. austera branches were measured at three sites of differing stand size and apparent age. This was achieved by repeated image analysis and by staining branches with the vital stain, Alizarin Red S. Both measures of growth yielded a similar linear extension rate of 24.5 mm/yr (n = 467), comparable to related species at similar latitudes. Mean branch mortality was as high as 50%, with clear differences manifested between each A. austera stand. Branch extension rates and branch mortality were inversely related between sites. Small, young stands exhibited significantly faster coral growth rates, lower mortality and a net increase in overall branch length over the study period, whilst the opposite was true of larger, more developed stands. In addition, bioerosion was determined at each site to assess its potential for carbonate removal and its destabilizing effect on reef frameworks. Bioerosion intensity was recorded as “percentage area damage” within cross-sections and “frequency of occurrence” of bioeroding organisms in coral rubble fragments (n = 120). The level of bioerosion was found to be substantial (up to 11.5% loss in weight of coral fragments over the 12-month study period) and was found to decrease significantly with a reduction in size of each A. austera stand. Aragonite saturation state is considered a major factor that limits the geographical range of coral reefs globally. Although previously thought to be limiting in Maputaland, mean ΩArag values of 4.40±0.29 were measured on the reefs in summer and 4.33±0.21 in winter and thus would not have limited reef development. Past studies have noted the turbulence on South African east coast reefs and its adverse effect on reef development. This was corroborated in this study with the measurement of considerable sediment re-suspension (0.17 g cm⁻² day⁻¹) and regular damage to both living coral and the reef framework caused by large swells. These results lead to the theory that Acropora austera stands senesce with increasing size and age. Although large coral frameworks are found on the Maputaland reefs, they do not persist in the long term. High rates of sediment re-suspension prevent infilling of the interstitial spaces and eventual cementation, while high levels of bioerosion lead to framework instability over time. Rough seas further hamper accretion by physical removal of both living coral and the coral-derived framework, thus removing recent growth. This process is suspected to cause an imbalance in the carbonate budget of these marginal reefs, ultimately favoring carbonate removal over carbonate deposition.
Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

Thesis (M.A.)--University of Alberta, 2010.
Title from pdf file main screen (viewed July 27, 2010). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Arts, Dept. of Anthropology". Includes bibliographical references.

Coral recruitment is a key process that contributes to the community structure and resilience of coral reefs. As such, quantification of this process is important to assist with the management of these threatened ecosystems. While coral recruitment has been the focus of numerous studies over the past 30 years, an understanding of this process on the high-latitude reefs of South Africa is limited. In addition, variations in methods used in recruitment studies make the results difficult to compare. A rapid in-situ method for universal application in the detection of early post-settled recruits would thus be useful. In this study, scleractinian coral recruitment was investigated at three study sites on Two-mile Reef, over two six-month sampling periods, covering summer and winter. Two components were investigated by attaching settlement tiles consisting of ceramic and marble tiles, and ceramic tiles conditioned with crustose coralline algae (CCA) onto the reef in a spatially structured experimental design. Firstly, coral recruitment was compared on the three different tile surfaces and fluorescence photography was investigated as a rapid in situ technique to detect early post-settled recruits. Fluorescence photography was then used to compare recruitment on tiles with the surrounding natural substrata. Secondly, the spatial and temporal variation in the abundance, composition and size of recruits was investigated. Additionally, the percentage cover of biota surrounding each recruit within three millimeters of its corallum was visually estimated to quantify the microhabitat surroundings of coral recruits. Overall recruitment on the three tile types differed, yet spatial variation in coral recruitment, regardless of tile surface, accounted for most of the variance in recruitment. While the highest recruitment occurred on CCA tiles, this was not significantly greater than ceramic tiles, indicating that the conditioning of ceramic tiles with Mesophyllum funafutiense CCA did not enhance coral settlement in this study. Although many recruits were not detected with fluorescent photography (73%), it proved useful to reveal recruits as small as 0.75 mm in corallum diameter, and indicated that recruitment on the tiles and natural substratum differ significantly. Spatially, the abundance and composition of coral recruits differed between study sites, within sites, and predominantly occurred on tile edges. Coral recruitment was lowest at shallower sites, and was dominated by pocilloporids regardless of study site. Additionally, the abundance and composition of recruits differed between the two sampling periods, with a 6.6-fold decrease in the mean abundance of recruits from summer to winter, with only pocilloporid settlement occurring in the latter season. The majority of recruits were <3 mm, and their microhabitat was dominated by bare substrata and crustose coralline algae. The results suggest that, while the choice of artificial settlement surface used in such studies can have a profound influence on the results, spatial variation in recruitment can be greater. The recovery of scleractinian coral taxa on Two-mile Reef in the event of a severe disturbance is expected to differ, with greatest recovery in areas of high levels of recruitment. The microhabitat surrounding recruits is described here for the first time, suggesting that further research into coral-crustose coralline algae interactions is warranted. Finally, while fluorescence photography has its limitations, it shows promise as a useful tool for rapid qualitative, but not quantitative, assessment of recruitment.
Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

This geostrophic current-controlled Zululand/Natal shelf displays a unique assemblage of interesting physical, sedimentological and biological phenomena. The shelf in this area is extremely narrow compared to the global average of 75km, and is characterised by submarine canyons, coral reefs, and steep gradients on the continental slope. A shelf break occurs 2.1km to 4.1km offshore and the shelf can be divided into a northern region and a southern region based on the presence or absence of a defined shelf break. The southern shelf has a poorly-defined shelf break whilst the northern shelf has a well-defined break at -65m. The poor definition of the shelf break on the southern shelf can possibly be attributed to the presence of giant, climbing sand dunes offshore of Jesser Point at depths of -37m to -60m. The northern shelf has a series of coast-parallel oriented patch coral reefs which have colonised carbonate-cemented, coastal-facies sequences. The northern shelf can be divided into three distinct zones: inner-, mid-, and outer-shelf zones. The inner-shelf is defined as the area landward of the general coral reef trend, with depths varying from 0m to -I5m and having an average gradient of 1.1. The mid-shelf is defined by the general coral reef trend, varying from -9m over the shallow central axis of the reefs to -35m along the deep reef-front environments. The outer-shelf is seaward of the coral reefs and occurs at a depth range of -35m to - 65m. Gradients vary from 1° in the south to 2.5° in the northern part of the study area, and are steep compared to world average shelf gradient of 0.116°. Four submarine canyons occur in the study area and are classified as mature- or youthful-phase canyons depending on the degree to which they breach the shelf. The origin of these canyons is not related to the position of modern river mouths but can probably be linked to palaeo-outlets of the Pongola and Mkuze River systems. It is suggested that the canyons are mass-wasting features which were exploited by palaeo-drainage during regressions. The youthful-phase canyons appear to be mass-wasting features associated with an unstable, rapidly-deposited, progradational late Pliocene sequence and a steep upper continental slope. The mature-phase canyons were probably initiated by mass-wasting but have advanced shoreward, breaching the shelf, due to their link with the palaeo-outlets of the Pongola and Mkuze Rivers during late Pleistocene regressions. Evidence of modem canyon growth has been noted on numerous SCUBA diving surveys carried out on the canyon heads. These take the form of minor wall slumps and small-scale debris flows. The canyons are also supplied with large quantities of sand in the form of large-scale shelf subaqueous dunes generated and transported by the Agulhas Current. As these bedforms meet the canyons the sediment cascades down the canyon thalweg and causes erosion and downcutting of the canyon walls and floor thereby increasing the canyon dimensions. Late Pleistocene beachrock and aeolianite outcrops with or without an Indo-Pacific coral reef veneer are the dominant consolidated lithology on the shelf. These submerged, coast-parallel, carbonate cemented, coastal facies extend semi-continuously from -5m to -95m, and delineate late Pleistocene palaeocoastline events. The rock fabric of these high primary porosity lithologies shows grains floating in a carbonate cement with occasional point-contacts. Grains are mostly quartz (80-90%), minor K-feldspar and plagioclase (5-10%), and various lithic fragments. The rocks contain conspicuous organic grains including foraminifera, bivalve, echinoid, bryozoan, red algal, and occasional sponge spicule fragments; these commonly display replacement fabrics or iron-stained rims. The dominant sedimentary structures found in these sandstone outcrops include high-angle planar cross-bedding and primary depositional dip bedding. Palaeocurrent directions sngest a palaeoenvironment dominated by a combination of longitudinal and transverse dunes with wind directions similar to those observed forming the modem dune systems. Erosional features evident on the submerged beachrocks and aeolianites include gullies trending in two different directions and sea-level planation surfaces with or without the presence of potholes. The unconsolidated sediment on the shelf is either shelf sand, composed mainly of terrigenous quartz grains; or bioclastic sediment which is partially derived from biogenic sources. The quartzose sand from the inner-shelf is generally fine-grained, moderately- to well-sorted, and coarsely- to near symmetrically-skewed. Carbonate content is low, and varies between 4-13%. Quartzose sand from the outer-shelf is fine-grained, moderately- to well-sorted, and coarsely- to very coarsely-skewed. The inner-shelf quartzose sand is better sorted than the outer-shelf sand due to increased reworking of this sediment by the high-energy swell regime. Sediment from the shallower areas of the outer-shelf (< -50m) is better sorted than sediment from depths of greater than -50m. Generally wave-reworking of quartzose shelf sand from the Sodwana Bay shelf results in greater sediment maturity than that observed from geostrophic current effects or a combination of geostrophic and wave-reworking. This sediment was derived by reworking of aeolian and beach sediments, deposited on the shelf during the period leading up to the Last Glacial Maximum (15 000 - 18 000 years B.P.) when sea-level was -130m, during the Holocene (Flandrian) transgression. Bioclastic sediment on the Sodwana Bay shelf is defined as having a CaC03 content of greater than 20% and is a mixture of biogeoically-derived debris and quartzose sand. The distribution of bioclastic sediment in the study area is widespread, with reef-derived and outer-shelf-derived populations being evident. This sediment consists of skeletal detritus originating from the mechanical and biological destruction of carbonate-secreting organisms such as molluscs, foraminifera, alcyonaria, scleractinia, cirripedia, echinodermata, bryozoa, porifera. The reef-derived bioclastic population is confined to depths less than -40m in close proximity to reef areas, whereas the shelf-derived bioclastic population occurs at depths greater than -40m and is derived from carbonate-producing organisms on deep water reefs and soft-substrate environments on the shelf. Large-scale subaqueous dunes form in the unconsolidated sediment on the outer-shelf due to the Agulhas flow acting as a sediment conveyor. These dunes are a common feature on the Sodwana Bay shelf occurring as two distinct fields at depths of -35m to -70m, the major sediment transport direction being towards the south. The two dune fields, the inner- and outer subaqueous dune fields, are physically divided by Late Pleistocene beachrock and aeolianites ledges. A bedform hierarchy has been recognised. The larger, outer dune field appears to have originated as a system of climbing bedforms with three generations of bedforms being superimposed to form a giant bedform, while the inner dune field has a less complex construction. The largest bedforms are those of the outer dune field off Jesser Point, being up to 12 m high, 4 km long and 1.2 km wide. A major slip face, with a slope of 8° is present. Bedload parting zones exist where the bedform migration direction changes from south to north. Three bedload parting zones occur in the study area at depths of -60m, -47m and -45m; two in the inner dune field and one in the outer dune field. These zones are invariably located at the southern limits of large clockwise eddy systems. Such eddies appear to be the result of topographically induced vorticity changes in the geostrophic flow and/or the response to atmospheric forcing caused by coastal low-pressure system moving up the coastline. It has been demonstrated that the inner subaqueous dune sediment conveyor is not active all the time but only during periods . of increased current strength when the Agulhas Current meanders inshore. The smaller bedforms in the outer dune field undergo continuous transport due to the current velocity on the shelf edge outer dune field being higher than the velocity experienced on the inner dune field. The very large 2·D dune which forms the outer dune field is probably not active at present: this is inferred due to the shallow angle of the mega-crest lee slope (8°). The very large Sodwana Bay subaqueous dune fields may be compared with the very large, reconstructed, subaqueous dunes which occur in Lower Permian sediments of the Vryheid Formation, northern Natal. These Permian dunes are represented, in section, as a fine- to medium-grained distal facies sandstone with giant crossbeds. These large-scale bedforms are unidirectional, but rare directionally-reversed, climbing bedforms do occur, this directional reversal may be related to bedload parting zones. On the evidence presented in this thesis, it is proposed that these Permian subaqueous dunes may be ancient analogues of the modem subaqueous dune field on the Sodwana Bay shelf. Positive-relief hummocks and negative-relief swale structures are fairly common in the fine-grained, quartzose shelf sand at depths of -30m to -60m. These appear to be transitional bedforms related to the reworking by storms of medium 2-D subaqueous dunes. These hummocky structures may be the modem equivalent of hummocky cross-stratification noted in the geological record, and if so, they are probably the first to have ever been observed underwater. The occurrences of ladderback ripples on the Sodwana Bay shelf at depths of -4m to -17m, suggest that subtidal ladderback ripples may be more common than previously thought. Ladderback ripples are common features of tidal flats and beaches where they form by late-stage emergence run-off during the ebb tide. They are generally considered diagnostic of clastic intertidal environments. The mode of formation on the Sodwana Bay shelf is different from the classic late-stage emergence run-off model of intertidal occurrences, being a subtidal setting. Subaqueous observations indicate that ladderback ripples are not environment-specific, and that additional evidence of emergence is therefore necessary to support an intertidal setting in the rock record: ladderback ripples alone are insufficient to prove an intertidal environment. The coral patch reefs of the northern Natal coast are unique, being the most southerly reefs in Africa, and totally unspoilt. The Zululand reefs are formed by a thin veneer of Indo-Pacific type corals which have colonised submerged, late Pleistocene beachrocks and aeolianites. Two-Mile Reef at Sodwana Bay has been used to develop a physiograpbic and biological zoning model for Zululand coral reefs, which has been applied to other reefs in the region. Eight distinct zones can be recognised and differentiated on the basis of physiographic and biological characteristics. The reef fauna is dominated by an abundance of alcyonarian (soft) corals, which constitute 60-70% of the total coral fauna. The Two-Mile Reef zoning model has been successfully applied to larger reefs such as Red Sands Reef, and smaller patch reefs (Four-Mile and Seven-Mile Reefs) in the same general area. In this thesis extensive use has been made of Hutton's uniformitarian principles. Hutton's doctrine is particularly relevant to the study of depositional processes and relict shorelines. Coastal processes and weather patterns during the late Pleistocene were broadly similar to modem conditions enabling direct comparisons to be made. A computer-aided facies analysis model has been developed based on textural statistics and compositional features of carbonate-cemented coastal sandstones. Many attempts have been made to distinguish different ancient sedimentary depositional environments, most workers in this field having little success. The new method of facies reconstruction is based on: (1) underwater observations of sedimentary structures and general reef morphology; (2) a petrographic study of the reef-base enabling flve facies: aeolianite, backbeach, forebeach, swash, and welded bar facies to be recognised, which control the geomorphology of Two-Mile Reef; (3) cluster and discriminant analysis comparing graphic settling statistics of acid-leached reef-base samples with those of modem unconsolidated dune/beach environments. The results of this analysis demonstrated that the beachrocks and aeolianites on the shelf formed during a regression and that late Pleistocene coastal facies are similar to modem northern Zululand coastal environments, which have been differentiated into aeolian, backbeach, forebeach, swash, & welded bar. A late Pleistocene and Holocene history of the shelf shows that during the late Pleistocene, post Eemian regressions resulted in deposition and cementation of coast-parallel beachrocks and aeolianites, which define a series of four distinct palaeocoastline episodes with possible ages between 117 000 and 22 000 years B.P. The beachrock/aeolianites formed on the shelf during stillstands and slow regressions, and the gaps between these strandline episodes represent periods of accelerated sealevel regression or a minor transgressive phase which hindered deposition and cementation. The formation of these lithologies generated a considerable sediment sink in the nearshore zone. This reduced sediment supply and grain transport in the littoral zone during the Holocene, and probably enhanced landward movement of the shoreline during the Flandrian transgression. Prior to the Last Glacial Maximum, the beachrock/aeolianite sedimentary sequence was emergent and blanketed by shifting aeolian sands. The Pongola River, which flowed into Lake Sibaya, reworked the unconsolidated sediments on the shelf, and exploited the route of least resistance: along White Sands and Wright Canyon axes. The erosion resulting from fluvial denudation in Wright Canyon has caused this canyon to erode some of the beachrock/aeolianite outcrops which form palaeocoastline episode 2 and entrench the canyon to a deeper level; this eroded the shelf to a distance of 2km offshore. During the Flandrian transgression the unconsolidated sediment cover was eroded, exposing and submerging the beachrock/aeolianite sequence. Flandrian stillstands caused erosional features such as wave-planed terraces, potholes, and gullies to be incised into beachrock and aeolianite outcrops; these are seen at present depths of -47m, -32m, .26m, -22m, -17m to -15m, and -12m. High energy sediment transfers, in an onshore direction, resulted in the deposition of sand bars across the outlet of Lake Slbaya's estuary and the development of a 130m + coastal dune barrier on a pre-existlng, remnant Plelstocene dune stub. Sea-level stabilised at its present level 7 000-6 000 years B.P. and coral reef growth on the beachrock/aeolianite outcrops probably started at 5 000 years B.P. A minimum age for the formation of the northern Zululand coral reefs has been established at 3780 ± 60 years B.P. A mid Holocene transgression relating to the Climatic Optimum deposited a + 2m raised beach rock sequence. This transgression eroded the coastal dune barrier and caused a landward shoreline translation of approximately 40m. A minor transgression such as this can be used as a model for coastal erosion which will result from the predicted 1.5m rise in sea-level over the next century. This rise in sea-level could result in a 30m landward coastline translation of the present coastline, ignoring the influence that storms and cyclones will have on the coastline configuration.
Thesis (Ph.D.)-University of Natal, Durban, 1991.

Coral reef ecosystems are the most diverse on earth, and their subsistence is being threatened by natural and adverse anthropogenic patterns and processes. In an effort to understand and protect these marine environments, several programs have outlined strategies and initiatives. For example, the United States Coral Reef Task Force���s Mapping and Information Working Group has outlined a specific goal to map all coral reefs below 30 m depth by 2009. This study contributes to achieving that goal for three sites around the island of Tutuila, American Samoa, lying in the heart of the South Pacific. American Samoa, a U.S. territory, is home to the Fagatele Bay National Marine Sanctuary, the smallest and most remote in the United States, and to the National Park of American Samoa. Extensive modern scientific surveys were implemented around the territory in 2001 and have since continued and increased. The presence of protected areas and the existence of scientific data collected with state of the art technology have made the site a priority for the Coral Reef Task Force. In this study, methods for classifying surficial seafloor characteristics as bathymetric position index (BPI) zones and structures were developed and applied to the study sites. BPI zones and structures were classified by using algorithms that combine high-resolution (1 m) multibeam bathymetry and its derivatives: bathymetric position index at multiple scales and slope. The development of algorithms and the classification scheme involved the use of historical and current classification studies and three-dimensional visualization. In addition, the BPI zones and structures were compared to limited biological, geological, and physical attributes recorded during accuracy assessment surveys (photos) and towed diver surveys (video). A rugosity (surface ratio) analysis was added to the study to give a picture of the seafloor roughness. The BPI zone and structure classifications overlap and extend existing classifications from Ikonos satellite imagery for water depths shallower than 30 m. Methods, data and classifications developed and applied in this study will be available to the public as a benthic habitat mapping tool (ArcGIS extension), in an online GIS data archive, and on a compact disc attached to this thesis. They contribute to a broader understanding of the marine and coastal environment and will serve as a baseline of information for benthic habitat mapping and future biological, ecological, and geological surveys. The baseline gives a good indication of characteristics that may indicate areas of high biodiversity. The final maps presented here are especially useful to managers, researchers and scientists that seek to establish and monitor a wider and more effective network of marine and coastal protection.
Graduation date: 2005