Dissertations / Theses on the topic 'Coral reef bay'

The coral reefs of Kane'ohe Bay, on the windward coast of O'ahu, Hawai'i, have changed markedly over the last half century. Some of the most spectacular coral reefs in Hawai'i were reported from Kane'ohe Bay in the late 1800's and early 1900's, but with the beginning of extensive military dredge and fill operations during the World War IT era, conditions in the bay began to change dramatically. After the War, rapid urbanization of the area began and conditions in the bay continued to decline until pressure from the public and scientific community led to the diversion of the large sewage discharges in the southeast lagoon to a newly built deep ocean outfall outside the bay in 1977-1978. Although conditions temporally improved, recent surveys indicate that current conditions in the bay are not as favorable as expected. This study provides a time series analysis of changes in coral and algae cover in Kane'ohe Bay based upon a series of coral reef surveys conducted throughout the bay in 1970171, 1983, and 1990. Beginning in 1970171, conditions in the bay were highly degraded and scientists speculated that eutrophication and sedimentation, as a result of urbanization and construction, were the primary cause of an observed decline in lagoon corals communities in the southeast lagoon and an explosive growth of the green "bubble algae", Dictyosphaeria cavemosa, which was smothering corals in the middle lagoon. In . 1983, six years after major sewage discharges were diverted from the bay, surveys indicated dramatic improvements in water quality and the reefs showed signs of recovery. D. cavemosa algae levels, associated with earlier nutrient pollution, plummeted to less than twenty percent of their former abundance levels and coral cover increased by over two hundred percent. Although it was predicted that the coral reefs of Kane'ohe Bay would continue to recover, surveys in 1990 indicate that coral recovery slowed or ceased and the growth of the green "bubble algae", D. cavemosa, more than doubled compared to 1983 levels. In addition to the failure of the t~o dominant coral species Porites compressa and Montipora capitata to continue to recover, almost all of the less common coral species including Pocillopora damicomis, Fungia scutaria, Cyphastrea ocellina, and some others, showed significant declines in reef cover. Although this study was not able to detennine the exact causes of the observed changes in Kane'ohe Bay, it is suggested that high nutrient inputs provided favorable conditions for the changes in coral and algae cover. High nutrient levels are thought to have been derived from a number of sources including chronic sewage pollution, increased sedimentation from runoff, and reef kills associated with acute but large episodes of freshwater runoff. Some of these nutrient inputs may have been the result of non-point source and point source sewage pollution derived from leaky sewer lines, cesspool and septic tank discharges, commercial tour and recreational boat waste discharges, and periodic sewage bypasses from municipal wastewater treatment plants and sewage pump stations. Other nutrients may have been derived from increased sedimentation following extensive land clearance, land development, and highway construction. Additional factors may include a decrease in herbivorous fish species owing to over fishing and the ability of D. cavemosa algae to concentrate nutrients from underlying substrates and excretion from infaunal organisms. Other factors such as increased nutrient recycling from the sediments, possible increased nitrogen fixation from reefs, and natural fluctuations in relative species abundances may also be responsible for some of the observed changes in coral reef community structure. Although rare, the largest nutrient fluxes followed the catastrophic freshwater reef-kill events caused by severe rainstorms in conjunction with low tides and low wind conditions in 1965 and 1987-1988. Although the cause and effect relationship is still uncertain, the highest levels of Dictyosphaeria cavemosa algae ever recorded in Kane'ohe Bay occurred in the years following these storm events. Results of this study indicate that further research is needed to monitor ongoing conditions in the bay and determine what is preventing the reef ecosystem from returning to its former more pristine condition. Because water quality parameters generally remained the same or improved compared to previous polluted conditions, it is suggested that current measures of water quality are not reliable in forewarning against coral reef degradation in Kane'ohe Bay. Although a reduction in all future development in and around the bay would probably help maintain environmental conditions at the status quo, additional regulations and enforcement may be needed to help reduce disturbances caused by existing land and water use. It is suggested that a reduction in nutrient inputs to the bay would be beneficial to reef corals. Recommendations made by the Kane'ohe Bay Task Force outlined in the Kane'ohe Bay Master Plan should serve as a model and be implemented as soon as possible. Continuing assessment of the Kane'ohe Bay coral reef ecosystem and surrounding watershed will then need to be made on a regular basis to ensure that further degradation of the reefs is not occurring.
Thesis (M. A.)--University of Hawaii at Manoa, 1995. Includes bibliographical references (leaves 166-175).

In Hawaii, abundance of the scleractinian Fungia scutaria is thought to have been in decline in recent years due to disturbances to Kaneohe Bay, where an unusually dense population exists. This study examines factors that could limit population growth in this coral. Sexual reproduction occurred throughout the summer. Experimental data from sperm dilution studies suggested that eggs must be released within 2m of a spawning male for successful fertilization to occur. Field surveys indicated that many patch reefs exhibited high enough densities to yield successful fertilization. However, since field surveys found that only a small percentage (1 %) of juvenile corals (5 cm in length) resulted from settled larvae, post-fertilization processes may be limiting successful recruitment. Asexual reproduction appears to be dominant, with 70% of corals occurring in close aggregations, and 93% of these in aggregations made up of a single color-morph.
Thesis (M. A.)--University of Hawaii at Manoa, 2000. Includes bibliographical references (leaves 70-74).

Madagascar, a country whose extraordinary levels of endemism and biodiversity are celebrated globally by scientists and laymen alike, yet historically has received surprisingly little research attention, is the setting of the present dissertation. Here, I contribute to the need for applied research by: 1) focusing on the most intensely fished section of the Toliara Barrier Reef, the Bay of Ranobe; 2) characterizing the marine environment, the human population, and the fisheries; and 3) collecting the longest known time-series of data on fisheries of Madagascar, thereby providing a useful baseline for future analyses. In Chapter 1, the bathymetry of the Bay was characterized following a unique application of the boosted regression tree classifier to the RGB bands of IKONOS imagery. Derivation of water depths, based on DOS-corrected images, following a generic, log-transformed multiple linear regression approach produced a predictive accuracy of 1.28 m, whereas model fitting performed using the boosted regression tree classifier, allowing for interaction effects (tree complexity= 2), provided increased accuracy (RMSE= 1.01 m). Estimates of human population abundance, distribution, and dynamics were obtained following a dwelling-unit enumeration approach, using IKONOS Panchromatic and Google Earth images. Results indicated, in 2016, 31,850 people lived within 1 km of the shore, and 28,046 people lived within the 12 coastal villages of the Bay. Localized population growth rates within the villages, where birth rates and migration are combined, ranged from 2.96% - 6.83%, greatly exceeding official estimates of 2.78%. Annual pirogue counts demonstrated a shift in fishing effort from south to the north. Gear and boat (pirogue) profiles were developed, and the theoretical maximum number of fishermen predicted (n= 4,820), in 2013, from a regression model based on pirogue lengths (R2= 0.49). Spatial fishing effort distribution was mapped following a satellite-based enumeration of fishers-at-sea, resulting in a bay-wide estimate of intensity equaling 33.3 pirogue-meters km-2. Landings and CPUE were characterized, with respect to finfish, by family, species, gear, and village. Expansion of landings to bay-wide fisheries yields indicated 1,885.8 mt year-1 of mixed fisheries productivity, with an estimated wholesale value of 1.64 million USD per annum.

This thesis details the geomorphology and timing of the mid-Holocene fossil reef at Cleveland Point, Moreton Bay, Queensland. This research presents the first subsurface data from percussion cores through the reef. Results reveal that Cleveland Point reef initiated quickly after rising seas flooded their foundations 7300 years ago. The reef remained in a "catch-up" growth mode from 7300 to 5700 years ago before reef accretion ceased. Age data suggests that the termination of the reef occurred 5700 years ago and coincided with a hypothesized lowering of sea-level and a possible change in terrigenous sediment distribution in Moreton Bay.

The Oxford English Dictionary defines 'omnifarious' as 'comprising or relating to all sorts or varieties', which quite accurately captures the very nature of octocorals and this thesis. The research reported here, aims to describe undocumented communities of coral reef organisms - the octocorals - which are an emergent dominant component within their threatened ecosystem of the Caribbean. Within the last four decades, coral reefs worldwide have experienced a precipitous plunge in many ecosystem services they provide, and most notably in the Caribbean. The foundation to reef resilience is structured on the ecosystem's ability to repair and restructure itself in the face of environmental shifts. These intricately complex strategies of resilience depend on repair mechanisms provided by a source of biodiversity, much of which remains poorly understood. This work explores many facets of the functioning within this potential future coral reef ecosystem. These reports are one of the most significant contributions to documenting and describing octocoral biodiversity (e.g. species, genetic, and community diversity) of the wider ecoregion of the Mesoamerican Barrier Reef System within the last three decades.

Inshore tropical and subtropical estuaries harbor a relatively high abundance and diversity of organisms. Specifically within estuaries, mangrove and seagrass habitats provide shelter and food for a plethora of organisms, through some or all their life histories. Given the biological connection between offshore coral reefs and coastal estuaries, there is a critical need to understand the underlying processes that determine distribution and abundance patterns within mangrove-seagrass habitats. The predatory fish assemblage within the mangrove and seagrass beds of Biscayne Bay, Florida (USA), was examined over 24-hr. time periods along a distance and habitat gradient from the mangrove edge and nearshore environment (0–300 m) to farshore (301–700 m) seagrass beds. This thesis also investigated the occurrence, distribution and timing of reef fish movement between offshore coral reef habitat and inshore seagrass beds over 24-hr periods. Results indicate that fish predators differed over both the sampling period and with distance from mangrove edge. The results also demonstrated reef fishes move into Biscayne Bay at dusk and exit at dawn by utilizing Broad Creek Channel as a passageway. This work supports the idea of diel migration of selected reef fishes to inshore seagrass beds and highlights the importance of connective channels between habitats. The results suggest that the degradation or loss of seagrass habitat could differentially impact the life-history stages of reef fish species.

2012/2013
The subject of modelling flow near wall is still open in turbulent wall bounded flows, since there is no wall layer model which works perfectly. Most of the present models work well in attached flows, specially for very simple geometries like plane channel flows. Weakness of the models appears in complex geometries, and many of them do not capture flow separation accurately in detached flows, specially when the slope of wall changes gradually. In many engineering applications, we deal with complex geometries. A possible way to simulate flows influenced by complex geometry using a structured grid, is to consider the geometry as immersed boundary for the simulation. Current wall layer models for the immersed boundaries are more complex and less accurate than the body-fitted cases (cases without immersed boundaries). In this project the accuracy of wall layer model in high Reynolds number flows is targeted, using LES for attached flows as well as detached flows (flows with separation). In addition to the body fitted cases, wall layer model in the presence of immersed boundaries which is treated totally different also regarded. A single solver LES-COAST (IE-Fluids, University of Trieste) is used for the flow simulations, and the aim is to improve wall layer model in the cases with uniform coarse grid. This is in fact novelty of the thesis to introduce a wall layer model applied on the first off-wall computational node of a uniform coarse grid, and merely use LES on the whole domain. This work for the immersed boundaries is in continuation of the methodology proposed by Roman et al. (2009) in which velocities at the cells next to immersed boundaries are reconstructed analytically from law of the wall. In body-fitted cases, since smaller Smagorinsky constant is required close to the walls than the other points, wall layer model in dynamic Smagorinsky sub-grid scale model using dynamic k (instead of Von Karman constant) is applied to optimize wall function in separated flows. In the presence of immersed boundaries, the present wall layer model is calibrated, and then improved in attached and also detached flows with two different approaches. The results are also compared to experiment and resolved LES. Consequently the optimized wall layer models show an acceptable accuracy, and are more reliable. In the last part of this thesis, LES is applied to model the wave and wind driven sea water circulation in Kaneohe bay, which is a bay with a massive coral reef. This is the first time that LES-COAST is applied on a reef-lagoon system which is very challenging since the bathymetry changes very steeply. For example the water depth differs from less than 1 meter over the reef to more than 10 meters in vicinity of the reef, in lagoon. Since a static grid is implemented, the effect of wave is imposed as the velocity of current over the reef, which is used on the boundary of our computational domain. Two eddies Smagorinsky SGS model is used for this simulation.
XXVI Ciclo
1983

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.

Several fringing coral reefs in Moreton Bay, Southeast Queensland, some 300 km south of the Great Barrier Reef (GBR), are set in a relatively high latitude, estuarine environment that is considered marginal for coral growth. Previous work indicated that these marginal reefs, as with many fringing reefs of the inner GBR, ceased accreting in the mid-Holocene. This research presents for the first time data from the subsurface profile of the mid-Holocene fossil reef at Wellington Point comprising U/Th dates of in situ and framework corals, and trace element analysis from the age constrained carbonate fragments. Based on trace element proxies the palaeo-water quality during reef accretion was reconstructed. Results demonstrate that the reef initiated more than 7,000 yr BP during the post glacial transgression, and the initiation progressed to the west as sea level rose. In situ micro-atolls indicate that sea level was at least 1 m above present mean sea level by 6,680 years ago. The reef remained in "catch-up" mode, with a seaward sloping upper surface, until it stopped aggrading abruptly at ca 6,000 yr BP; no lateral progradation occurred. Changes in sediment composition encountered in the cores suggest that after the laterite substrate was covered by the reef, most of the sediment was produced by the carbonate factory with minimal terrigenous influence. Rare earth element, Y and Ba proxies indicate that water quality during reef accretion was similar to oceanic waters, considered suitable for coral growth. A slight decline in water quality on the basis of increased Ba in the later stages of growth may be related to increased riverine input and partial closing up of the bay due to either tidal delta progradation, climatic change and/or slight sea level fall. The age data suggest that termination of reef growth coincided with a slight lowering of sea level, activation of ENSO and consequent increase in seasonality, lowering of temperatures and the constrictions to oceanic flushing. At the cessation of reef accretion the environmental conditions in the western Moreton Bay were changing from open marine to estuarine. The living coral community appears to be similar to the fossil community, but without the branching Acropora spp. that were more common in the fossil reef. In this marginal setting coral growth periods do not always correspond to periods of reef accretion due to insufficient coral abundance. Due to several environmental constraints modern coral growth is insufficient for reef growth. Based on these findings Moreton Bay may be unsuitable as a long term coral refuge for most species currently living in the GBR.

The tropical seascape is herein defined as a landscape made up of five ecosystems: coastal terrestrial forests, mangrove forests, seagrass beds, coral reefs and the deep sea. Previous studies have shown that men and women use the tropical seascape in different ways. If the seascape was to change as a result of anthropogenic climate change, then men and women could potentially be affected differently by those changes. The seascape is particularly vulnerable to the predicted rise in sea-level and ocean warming, but the coastal terrestrial forests and mangrove forests are in addition vulnerable to the increased storms and hurricanes a warmer climate is predicted to lead to. While men and women utilizes these ecosystems in many different ways, this study found, based on the literature reviewed, that in a worst-case scenario all parts of the seascape could potentially be destroyed and none of the activities performed there today could be performed in the future. The deep sea would not be destroyed, but the fish living there would move to higher latitudes and deeper waters, effectively ending the fishing practices in the tropical waters. To save the tropical seascape anthropogenic climate change would have to stop on a global scale, since the problem cannot be solved on a local or regional level.

Coral reefs are a vital resource in the low-island Republic of Maldives, where the sustainable use of these resources is central to the continued economic success of the country's two largest sectors: tourism and fisheries. This recognition has led to numerous reef conservation and protection activities, including the establishment of Marine Protected Areas (MPAs). As in many MPAs of the world, those in the Maldives exist only as paper parks: areas protected on paper but not in practice. Despite general recognition of the importance of reef resources, insufficient funds are allocated by government to implement these parks. This situation is compounded by the absence of specific information and detailed understanding by policy makers of the true value and economic benefits of reef resources. This thesis examines the an economic valuation of improved management of MPAs in the Maldives using Dhigali Haa, an MPA in Baa Atoll, Maldives, as a case study. A contingent valuation survey to elicit the willingness to pay of tourists visiting Baa Atoll to see improved management at the MPA was used in estimating the potential benefits. In addition, local community consultations were conducted to understand local perceptions of MPAs and their effectiveness, and to develop a feasible improved management scenario. The local consultations confirmed that Dhigali Haa was not effectively managed, leading to continued illegal use and degradation of the reef. The results of the CV survey revealed support from tourists visiting Baa Atoll to pay for improved management of Dhigali Haa. A one-off conservation fee per visit for all tourists visiting Baa Atoll was preferred over a user fee solely for divers visiting Dhigali Haa. The estimate for the mean WTP for the conservation fee was US$35±5 compared to a mean WTP of US$15±5 for the user fee. Comparisons between the cost of implementing improved management and the benefits gained from tourist fees showed that a conservation fee would be more beneficial than a user fee. The estimated net present value for funding the improved management via a conservation fee was US$8.65 million.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ
A baía de Tamandaré, PE, Brasil, é um ambiente recifal que apresenta uma condição ambiental de baixa cobertura de corais. Entre as possíveis causas para esta situação, estão a alta pressão que o turismo exerce na cidade de Tamandaré e a entrada de águas continentais, com grande volume de sedimento e contaminada com resíduos agrícolas e domésticos. Estes fatores apresentam uma variação sazonal, de forma que o primeiro se intensifica no período seco (setembro a fevereiro) enquanto o segundo atua mais forte sobre a baía no perído chuvoso (março a agosto). Entretanto, mesmo com estas pressões antrópicas na baía de Tamandaré, suas águas são classificadas como oligotróficas. Objetivando de avaliar o sedimento recifal da baía de Tamandaré, foram estudados composição e tafonomia dos foraminíferos bentônicos presentes no sedimento de nove amostras do período seco e chuvoso. Os resultados apontaram para uma assembléia de foraminíferos sem características de ambientes recifais, com um Índice FORAM abaixo de 4 em todas as estação, com somente uma exceção no período seco, que classificaram a baía como tendo qualidade de água desfavorável para assentamento de corais. Sazonalmente, há uma diferença entre as assembleias dos períodos seco e chuvoso refletida no número total de gêneros encontrados nos dois períodos, sendo maior no período seco que no chuvoso. Entretanto, em análises estatísticas como SHE e CLUSTER, não foram detectadas variações sazonais, sobre tudo nas estações mais profundas. Entre as razões para a baixa variação das assembleias de foraminíferos nos dois períods, a pouca variação da salinidade e temperatura, influênciadas pelo baixo volume de chuva nos meses da coleta, podem ter sido o principal motivo. Foraminíferos com processos tafonomicos como quebrado ou alteração de cor, representaram 40% a 20% do total de testas analisadas, indicando a ocorrência de ressuspenção do sedimento. Três testas com alteração tafonomica da cor e um quarta sem mudança na cor foram analisadas em MEV/EDS e mostrara a ausência ou pouca distribuição de elementos como Fe e S diferente do que seria esperado e a presença de elementos comuns de argilo minerais. De forma geral, os resultados associaram a baía de Tamandaré como ambiente não usal para assentamento de corais, com assembleias de foraminíferos similares entre os períodos analisados, e tendo como principais fatores físico-químicos que influenciam na composição da assembleia a temperatura, salinidade e ressuspenção
Tamandaré bay, PE, Brazil, it’s a reef environment which shows a low coral coverage. Among the possible causes for this situation are the, high pressures which tourism exert in Tamandaré city and the flow of continental waters, with high volume of sediment and contaminated with agricultural and domestic waste. These factors shows seasonal variation, where the first intensify during the dry season (September to February) whereas the second it’s strongest in the bay during the wet season (March to August). However, even with these anthropic pressures in the Tamandaré bay, those waters are classified as oligotrophic. Aiming evaluated the reef sediment of Tamandaré bay, were studied composition and taphonomy of benthic foraminifera present in the sediment of nine samples of dry and wet season. The results point out a foraminiferal assemblage without characteristics of reef environment, where FORAM Index was below 4 in all stations, with just one exception in the dry season, classifying the bay as have water quality unfavorable for coral attach. Seasonality, there’s just one difference between the assemblage of dry and wet seasons reflected in the total number of generous found in the two seasons, where was bigger during the dry season when compared whit dry season. Otherwise, statistical analyses like SHE and CLUSTER, didn’t detected variations between seasons, manly in the deepest stations. Among the reason for the similar foraminifera assemblage between the two seasons, the few variation of salinity and temperature, influenced by the low rain during the month of collection, seems to be the main reason. Taphonomic processes in foraminifera like broke or color change, represented 40% to 20% of the total test analyzed, suggesting sediment ressuspection. Three tests with color change and one fourth without, were analyzed in MED/EDS and shows the absence or few distribution of elements like Fe and S different of what would be expected and the presence of ordinary elements in clay minerals. All in all, the results associated Tamandaré bay as a environment unusual for coral attach, with a similarity foraminifera assemblages between the season analyzed, and had been as main physic-chemistry factors influence in assemblage composition, the temperature, salinity and ressuspection

Les habitats de coraux d’eau froide formés par des scléractiniaires coloniaux, des gorgones, des antipathaires et des pennatules sont des hotspots de biodiversité et de biomasse. Ils fournissent des fonctions importantes, comme des refuges et des zones d’alimentation, pour d’autres organismes. Mais, ils sont également vulnérables aux activités humaines, parce qu’ils sont fragiles, croissent lentement et atteignent des records de longévité. Dans les canyons sous-marins, le relief tourmenté, l’hydrodynamisme et l’hétérogénéité des substrats offrent des conditions environnementales propices au développement des habitats coralliens. Dans le Golfe de Gascogne, les coraux d’eau froide sont connus depuis la fin du 19e siècle, mais leur distribution, leur densité et leur rôle fonctionnel avaient été très peu étudiés.Pour augmenter cette connaissance, 24 canyons sous-marins et 3 sites sur l’interfluve/haut de pente contiguë aux canyons adjacents ont été visités par un ROV et une caméra tractée pendant 46 plongées au cours de 7 campagnes océanographiques. Les habitats coralliens définis par le système de classification CoralFISH ont été cartographiés à partir des images prises par les engins sous-marins puis la faune associée, les types de substrat et les déchets ont été annotés.Onze habitats coralliens et 62 morphotypes de coraux ont été observés dans les canyons sous-marins du Golfe de Gascogne hébergeant 191 morphotypes de faune associée, dont 160 morphotypes uniques. Les patrons de distribution à l’échelle locale et à l’échelle régionale pourraient être liés aux régimes hydrodynamiques et sédimentaires. Le type de substrat était important pour les assemblages de coraux et leurs faunes associées, distinguant les habitats biogéniques, sur substrat dur et sur substrat meuble. Les assemblages de coraux étaient similaires entre habitats biogéniques et habitats sur substrat dur, mais la faune associées était plus abondante et diversifiée sur les habitats biogéniques. La diversité-alpha, -beta et –gamma étaient étonnement élevée sur les habitats coralliens sur substrat meuble, égalant ou dépassant la diversité des habitats biogéniques.Les déchets marins étaient abondants et principalement composés de plastiques et de matériels de pêche. Ces déchets pourraient impacter les habitats coralliens : ils ont été trouvés à des profondeurs similaires et les déchets étaient piégés par des reliefs créés par des structures biologiques et géologiques. L’ocurrence des récifs de coraux préférentiellement sur les pentes plus abruptes des canyons sous-marins tandis que les débris de coraux sont plus fréquents sur des aires plus plates de l’interfluve ou du haut de pente, pourraient indiquer un impact de la pêche.Cette étude a contribué à l’initiative en cours de création d’un réseau Natura 2000 qui protégera à terme l’habitat « récif » dont les habitats coralliens biogéniques et sur substrat dur, mais pas les habitats coralliens sur substrat meuble. Pour ces derniers, un complément d’étude et d’autres stratégies de préservation seront nécessaires
Cold-water coral (CWC) habitats formed by colonial scleractinians, gorgonians, antipatharians and sea pens are biodiversity and biomass hotspots that provide important functions, such as shelter and feeding grounds, to other organisms. But, they are also vulnerable to human activities, because they are long-lived, grow slowly and have a low resistance. Submarine canyons may offer the environmental conditions needed for CWC habitat development, due to their steep topography, complex hydrodynamics and substrate heterogeneity. In the Bay of Biscay, which margin is incised by hundreds of canyons, CWCs are known to exist since the late 19th century, but their distribution, density and functional role remained largely unknown, which impaired their preservation.To increase this knowledge, 24 canyons and three locations between adjacent canyons were visited with an ROV and a towed camera system during 46 dives on 7 cruises. Images were analysed for CWC habitats using the CoralFISH classification system. Within these habitats, corals, associated fauna were identified and substrate cover measured. Litter was identified in 15 out of 24 canyons.Eleven coral habitats constructed by 62 coral morphotypes were observed in the canyons of the Bay of Biscay hosting 191 associated megafaunal morphotypes, including 160 unique morphotypes. The distribution patterns at regional and local scales could be linked to hydrodynamics and sedimentary regimes. Substrate type was an important driver for coral and associated faunal assemblages, distinguishing biogenic, hard substrate and soft substrate habitats. Coral assemblages were similar between biogenic and hard substrate habitats, but the associated fauna was more abundant and diverse on biogenic habitats. The alpha, beta and gamma diversity was surprisingly high on soft substrate habitats, equalling or exceeding that of biogenic habitats.Marine litter was abundant and was mainly composed of plastic items and fishing gear. Litter could co-occur with CWCs and impact them: litter and most CWC habitats were observed at similar water depths and litter was more abundant in areas with a seafloor relief created by biological or geological features. Observations of coral reefs on steeper areas in the canyons and coral debris on flatter areas on the interfluve/upper slope may indicate a potential impact of the fishing industry. This study supports the ongoing effort to create a Natura 2000 network that will protect biogenic and hard substrate habitats, but also points out the need to develop a framework for the preservation of coral habitats on soft substrate

Marine protected areas (MPAs) have proliferated in the past decades to protect biodiversity and sustain fisheries. However, most of the MPA networks have been designed without taking into account a critical factor: the larval dispersal patterns of populations within and outside the reserves. The scale and predictability of larval dispersal, however, remain unknown due to the difficulty of measuring dispersal when larvae are minute (~ cm) compared to the potential scale of dispersal (~ km). Nevertheless, genetic approaches can now be used to make estimates of larval dispersal. The following thesis describes self-recruitment and connectivity patterns of a coral reef fish species (Centropyge bicolor) in Kimbe Bay, Papua New Guinea. To do this, microsatellite markers were developed to evaluate fine-scale genetics and recruit assignment via genetic parentage analysis. In this method, offspring are assigned to potential parents, so that larval dispersal distances can then be inferred for each individual larvae. From a total of 255 adults and 426 juveniles collected only 2 parentoffspring pairs were assigned, representing less than 1% self-recruitment. Previous data from the same study system showed that both Chaetodon vagagundus and Amphiprion percula have consistent high self-recuitment rates (~ 60%), despite having contrasting life history traits. Since C. bicolor and C. vagabundus have similar characteristics (e.g. reproductive mode, pelagic larval duration), comparable results were expected. On the contrary, the results of this study showed that dispersal patterns cannot be generalized across species. Hence the importance of studying different species and seascapes to better understand the patterns of larval dispersal. This, in turn, will be essential to improve the design and implementation of MPAs as conservation and management tools.

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.

Taxonomic, seismic, vibrocore stratigraphy, surficial sedimentology, turbidity and hydrodynamic data were collected from Paluma Shoals and Phillips Reef. Paluma Shoals are a series of five near-shore patch reefs located within the inner-shelf terrestrial sediment wedge of southern Halifax Bay. Phillips Reef is an isolated patch reef located approximately 15 km northeast of Paluma Shoals. These data sets were collected to compare and contrast the sedimentary, hydrodynamic and turbidity regimes at both Paluma Shoals and Phillips Reef. The taxonomic survey (Watson, 1996) of Paluma Shoals indicated that total coral cover on the leeward reef flat (53.4±3%) was almost twice that of the windward reef flat (27.9±3.3%). The presence of juveniles was also detected at both the leeward and windward reef flats. The presence of juveniles (>5 cm) suggests that coral recruitment is occurring. The taxonomic survey suggests that the corals at Paluma Shoals are a healthy diverse population. From 79 km of high resolution seismic images, eight seismic facies were identified within the study area. These facies are consistent with those identified by previous investigations. Seven vibrocores were collected to ground truth the seismic profiles. Four postglacial facies were identified on the basis of grain size, stratigraphic relationship and mineralogy. A total of 135 surficial sediment samples were collected from the study area. Based upon field and laboratory observations and high-resolution laser diffraction grain size analysis, the study area has been divided into, two marine inner-shelf and four coastal facies assemblages. Entropy analysis of grain size distributions from 58 inner-shelf and coastal sediment samples resulted in statistical clusters which were visually discrete. Seven entropy groups were defined and high resolution grain size maps compiled. High resolution grain size mapping of the inner-shelf of Halifax Bay was successful in producing a map which mirrored the distribution of the surficial sediment facies assemblage. A total of 1340 hours of continuous high resolution time-series hydrodynamic and turbidity data were recorded at Paluma Shoals (671 hours) and Phillips Reef (669 hours) between Julian days 248 and 276 (1995). Maximum turbidity values were an order of magnitude greater at Paluma Shoals (175 NTU) than Phillips Reef (15 NTU) and generally were higher. The hydrodynamic and turbidity data suggest that Paluma Shoals and Phillips Reef are influenced by the same regional hydrodynamic processes. The surficial sediment seaward of Paluma Shoals are predominantly muddy sand, sandy mud and gravelly muddy sand and on the reef top, muddy sand and sandy mud. Therefore, there is a large source of fine grained sediment available for resuspension. The surficial sediments surrounding Phillips Reef are mostly gravelly muddy sand. Therefore, there is less fine grained sediment available for mobilisation. The variations in near bed turbidity values at Paluma Shoals and Phillips Reef appear to be a function of local surficial sediment distribution, wind direction and hydrodynamics. At Paluma Shoals the complex interaction between these processes results in high turbidity values but limited sediment settling. At Phillips Reef the limited sediment resuspension and transport (low NTU values) may be attributed to the reefs depth and coarse grained nature of the surface sediments. Three main implications arose from the collection and collation of these data sets, these are: 1) The corals at Paluma Shoals exist in water conditions widely inferred within the literature as being detrimental to coral growth and distribution; 2) "turbid water reefs" such as Paluma Shoals are potentially common and are healthy diverse populations; 3) during coral reef initiation (c.a. 6.8 ky B.P.) sediment dynamic, hydrodynamic and therefore turbidity regimes may have been similar to those of today. Therefore, "turbid water reefs" may form modem analogues to coral reefs that underwent initiation 8.5-5ky B.P.

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.

碩士
國立臺灣師範大學
生命科學研究所
95
The purpose of this study is to understand potential factors impact on planktonic community respiration (CR) and organic carbon cycle in the water column of coral reef ecosystem in the Nan-Wan Bay, southern Taiwan. Results showed that CR varied between 1.7~ 213 mg C m-3 d-1 during study period. Further analysis showed that the rate was mainly determined by biomass and production of planktonic community, especially phytoplankton. This assumption can be evident by significant relationships observed between integrated values over euphotic zone of CR versus chlorophyll a (Chl-a; 1.8~67 mg Chl m-2) and primary production (PP; 43~569 mg C m-2 d-1; all p < 0.05). In addition, Results also showed that integrated bacterial biomass (BB; 11~1313 mg C m-2) and production (BP; 18~823 mg C m-2 d-1) were significantly regressed against both dissolved and particulate organic carbon (all p<0.01). It suggests that growth of heterotrophic bacteria in this coral reef system might be limited by the amount of organic substrates. The mean ratio of primary production to community respiration (i.e., P/R ratio) was 0.38 ± 0.51, and this indicates that the ecosystem of water column in the Nan-Wan Bay is heterotrophic. This result also suggests that allochthonous organic carbon is needed to support the organic carbon consumption, and organic exudates from the benthos, e.g., corals, might be the most important source in this coral reef ecosystem.

Coral reef ecosystems around the world face a number of threats, including ocean acidification, increased ocean temperatures due to anthropogenic global warming (AGW), increased disease outbreaks, crown-of-thorns starfish outbreaks, terrestrial sedimentation, eutrophication, pollution, and fishing pressure. At the same time, coral reef ecosystems provide valuable direct and indirect economic and social benefits to millions of people worldwide. However, the intensity and spatial distribution of threats are likely to change with increasing human population and economic development, and thus understanding how multiple stressors may interact and affect coral reefs – particularly in the face of incomplete knowledge about these stressors – is an issue of pressing importance. This thesis aims to explore and advance the understanding of interactions between multiple stressors and their effects as they pertain to coral reefs generally and the Great Barrier Reef specifically. I review several of the components that are integral to this issue, including: stressors and stress ecology, research to date on the issue of multiple stressors and coral reefs, the multiple threats from climate change to coral reefs, and approaches to modelling and managing multiple stressors. The overall aim of this thesis is to quantitatively evaluate the importance of multiple stressor interactions to coral reef ecosystems and to assess alternative management approaches to mitigating the effects of potentially increased prevalence and severity of these stressors. I do this through both assessing the state of existing knowledge as well as by using new approaches to model stressors and stressor effects within the context of the GBR. In addition, I seek to provide an example of how these effects can be conceptualized and managed more effectively in the face of uncertain knowledge and incomplete data. The specific research objectives of my thesis are as follows: 1. To synthesize the available knowledge of multiple stressors on coral reefs; 2. To use the occurrence of bleaching and disease in the GBR as a case study to determine the spatial and temporal overlap of these stressors; 3. To use expert knowledge to identify key uncertainties and knowledge gap(s) regarding multiple stressor interactions on coral reef systems; 4. To apply expert-elicited knowledge about stressors and stressor interactions on the GBR to map potential threats to reefs under a variety of different climate change and management scenarios. Chapter 2 addresses research objective 1 by using a formal literature search to provide the foundation for a qualitative and selected quantitative meta-analysis of multiple-stressors as they pertains to coral reef ecosystems, and by examining the evidence for the prevalence of synergistic, antagonistic, and additive interactions between stressors. Here I investigate stressor interactions in two ways: first by examining stressor interactions with other stressors, and secondly by looking at potentially synergistic effects between two or more stressors on a response variable (where stressors interact to produce an effect that is greater than purely additive). For stressor-stressor interactions, I found 176 studies that examined interactions between at least two stressors. Applying network analysis to analyse relationships between stressors, I found that pathogens were exacerbated by more co-stressors than any other stressor, while sedimentation, storms, and water temperature directly affected the largest number of other stressors. Pathogens, nutrients, and crown-of-thorns starfish were the most-influenced stressors. In terms of responses to multiple stressors, I found 187 studies that examined the effects of two or more stressors on a third dependent variable. The interaction of irradiance and temperature on corals has been the subject of more research than any other combination of stressors, with many studies reporting a synergistic effect on coral symbiont photosynthetic performance. Second, I performed a quantitative meta-analysis of existing literature on the interaction between temperature and irradiance. Although the sample size was small, I found that the mean effect size of combined treatments was statistically indistinguishable from a purely additive interaction. This chapter provides evidence that considerable gaps remain in our knowledge regarding numerous stressor interactions and effects, and that the available evidence is inconclusive on whether synergistic effects are widespread in coral reef systems. Chapter 3 addresses research objective 2 by using data from the AIMS Long-term Monitoring Program (LTMP) to examine the spatial and temporal overlap of bleaching and disease in the GBR. Coral bleaching and disease have often been hypothesized to be mutually reinforcing or co-occurring, but much of the research supporting this has only drawn an implicit connection through common environmental predictors. I examine whether an explicit relationship between white syndrome and bleaching exists using assemblage-level monitoring data from up to 112 sites on the reef slopes spread throughout the GBR over 11 years of monitoring. None of the temperature metrics commonly used to predict mass bleaching performed strongly when applied to these data, and the inclusion of bleaching as a predictor did not improve model in predicting white syndrome outbreaks. Conversely, the inclusion of white syndrome as a predictor did not improve models of bleaching. Evidence for spatial co-occurrence of bleaching and white syndrome at the assemblage level in this dataset was also very weak. These results suggest the hypothesized relationship between bleaching and disease events may be weaker than previously thought, and more likely to be driven by common responses to environmental stressors, rather than directly facilitating one another. Chapter 4 addresses research objective 3 by exploring the use of Bayesian Belief Networks (hereafter BBNs) in conjunction with expert elicitation to determine the degree of expert consensus about the greatest threats to the GBR, and assessing the degree of confidence that experts have about the effects of various stressors both alone and in combination. BBNs are finding increasing application in adaptive ecosystem management where data are limited and uncertainty is high. I used a formal expert-elicitation process to obtain estimates of outcomes associated with a variety of scenarios in the GBR that combined stressors both within and outside the control of local managers. Among consulted experts, there was much stronger consensus about certain stressor effects - such as between temperature anomalies and bleaching – than others, such as the relationship between water quality and coral health. In general, models generated from the mean responses from experts predicted that climate change effects could potentially overshadow the mitigating effects of management actions to reduce local stressors. Chapter 5 addresses research objective 4 by implementing the model developed in Chapter 4 in a spatial way through the use of several scenarios. Coral reefs are one example of an ecosystem where management of local stressors may be a way of mitigating or delaying the effects of climate change. In this chapter, I use a combination of an expert-elicited BBN and empirical, spatial environmental data to examine how hypothetical scenarios of climate change and local management would result in different outcomes for coral reefs on the GBR. I also assess whether reefs within the existing protected area network differ in their predicted probability of decline from reefs outside the protected area network. Parameterizing the BBN using the mean responses from my expert pool resulted in predictions of limited efficacy of local management in combating the effects of climate change; however, there was considerable variability in expert responses; thus, I also examine the effect that using optimistic versus pessimistic expert responses has on the model predictions of coral cover decline on the GBR. Many reefs within the central GBR appear to be at risk of further decline, but further parameterization of the model as data and knowledge become available will improve predictive power. This approach serves as a proof of concept for subsequent work that can fine-tune parameters and explore uncertainties in predictions of responses to management. My thesis thus addresses two critical elements that are often missing from studies examining the conservation implications of multiple stressors (especially on coral reefs): interactions between stressor/stressor effects and assessing the effect of different management options on these interactions.