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Imam Bachtiar1,2, Ario Damar1, Suharsono3, Neviaty P. Zamani4
Journal of Coastal Development , 2011,
Abstract: Ecological resilience is an important property of natural ecosystem to be understood in coral reef management. Resilience of Indonesian coral reefs was assessed using 2009 COREMAP data. The assessment used 698 data of line intercept transects collected from 15 districts and 4 marine physiographies. Resilience index used in the assessment was developed by the authors but will be published elsewhere. The results showed that coral reefs at western region had higher average resilience indices than eastern region, and Sunda Shelf reefs had higher resilience indices than coral reefs at Indian Ocean, Sulawesi-Flores, or Sahul Shelf. Four districts were found to have coral reefs with highest resilience indices, i.e. Bintan and Natuna (western region), and Wakatobi and Buton (eastern region). Raja Ampat had coral reefs with lower average resilience indices than that of Wakatobi. Uses of resilience index in coral reef management should be coupled with other information such as maximum depth of coral communities.
Ecological Processes and Contemporary Coral Reef Management  [PDF]
Angela Dikou
Diversity , 2010, DOI: 10.3390/d2050717
Abstract: Top-down controls of complex foodwebs maintain the balance among the critical groups of corals, algae, and herbivores, thus allowing the persistence of corals reefs as three-dimensional, biogenic structures with high biodiversity, heterogeneity, resistance, resilience and connectivity, and the delivery of essential goods and services to societies. On contemporary reefs world-wide, however, top-down controls have been weakened due to reduction in herbivory levels (overfishing or disease outbreak) while bottom-up controls have increased due to water quality degradation (increase in sediment and nutrient load) and climate forcing (seawater warming and acidification) leading to algal-dominated alternate benthic states of coral reefs, which are indicative of a trajectory towards ecological extinction. Management to reverse common trajectories of degradation for coral reefs necessitates a shift from optimization in marine resource use and conservation towards building socio-economic resilience into coral reef systems while attending to the most manageable human impacts (fishing and water quality) and the global-scale causes (climate change).
Ecological Consequences of Sediment on High-Energy Coral Reefs  [PDF]
Christopher H. R. Goatley, David R. Bellwood
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0077737
Abstract: Sediments are widely accepted as a threat to coral reefs but our understanding of their ecological impacts is limited. Evidence has suggested that benthic sediments bound within the epilithic algal matrix (EAM) suppress reef fish herbivory, a key ecological process maintaining reef resilience. An experimental combination of caging and sediment addition treatments were used to investigate the effects of sediment pulses on herbivory and EAMs and to determine whether sediment addition could trigger a positive-feedback loop, leading to deep, sediment-rich turfs. A 1-week pulsed sediment addition resulted in rapid increases in algal turf length with effects comparable to those seen in herbivore exclusion cages. Contrary to the hypothesised positive-feedback mechanism, benthic sediment loads returned to natural levels within 3 weeks, however, the EAM turfs remained almost 60% longer for at least 3 months. While reduced herbivore density is widely understood to be a major threat to reefs, we show that acute disturbances to reef sediments elicit similar ecological responses in the EAM. With reefs increasingly threatened by both reductions in herbivore biomass and altered sediment fluxes, the development of longer turfs may become more common on coral reefs.
Coral Reef Resilience through Biodiversity  [PDF]
Caroline S. Rogers
ISRN Oceanography , 2013, DOI: 10.5402/2013/739034
Abstract: Irrefutable evidence of coral reef degradation worldwide and increasing pressure from rising seawater temperatures and ocean acidification associated with climate change have led to a focus on reef resilience and a call to “manage” coral reefs for resilience. Ideally, global action to reduce emission of carbon dioxide and other greenhouse gases will be accompanied by local action. Effective management requires reduction of local stressors, identification of the characteristics of resilient reefs, and design of marine protected area networks that include potentially resilient reefs. Future research is needed on how stressors interact, on how climate change will affect corals, fish, and other reef organisms as well as overall biodiversity, and on basic ecological processes such as connectivity. Not all reef species and reefs will respond similarly to local and global stressors. Because reef-building corals and other organisms have some potential to adapt to environmental changes, coral reefs will likely persist in spite of the unprecedented combination of stressors currently affecting them. The biodiversity of coral reefs is the basis for their remarkable beauty and for the benefits they provide to society. The extraordinary complexity of these ecosystems makes it both more difficult to predict their future and more likely they will have a future. 1. Introduction Increasing concern over worldwide deterioration of coral reefs and the likelihood that global climate change will cause further degradation has led to a focus on the concept of reef resilience. Local, regional, and global stressors have the potential to cause irreversible losses of biodiversity in some reefs and consequently of the ecosystem services they provide [1–9]. Even the physical structure of some coral reefs may be in jeopardy. Can these reefs recover and persist? Can they be managed for resilience? The future of many reefs will depend on whether fundamental processes like photosynthesis, calcification, and recruitment can continue in the face of a multitude of local and global stressors. Reefs that previously could recover after a disturbance may not be able to survive the assaults of global climate change, especially when combined with local pressures. The limits of our current knowledge of the biodiversity of coral reefs, of the potential for corals and other reef species to adapt to climate change, and of the effects of increasing sea water temperatures, ocean acidification, and other components of climate change on reef organisms make it challenging to predict what the future holds
Coral Ecosystem Resilience, Conservation and Management on the Reefs of Jamaica in the Face of Anthropogenic Activities and Climate Change  [PDF]
M. James C. Crabbe
Diversity , 2010, DOI: 10.3390/d2060881
Abstract: Knowledge of factors that are important in reef resilience and integrity help us understand how reef ecosystems react following major anthropogenic and environmental disturbances. The North Jamaican fringing reefs have shown some recent resilience to acute disturbances from hurricanes and bleaching, in addition to the recurring chronic stressors of over-fishing and land development. Factors that can improve coral reef resilience are reviewed, and reef rugosity is shown to correlate with coral cover and growth, particularly for branching Acropora species. The biodiversity index for the Jamaican reefs was lowered after the 2005 mass bleaching event, as were the numbers of coral colonies, but both had recovered by 2009. The importance of coastal zone reef management strategies and the economic value of reefs are discussed, and a protocol is suggested for future management of Jamaican reefs.
Human Disturbance, Natural Resilience and Management Futures: The Coral Reefs of Todos Os Santos Bay, Bahia, Brazil  [cached]
Leo X.C. Dutra,Robert J. Haworth
Journal of Sustainable Development , 2009, DOI: 10.5539/jsd.v1n1p13
Abstract: Between 1962 and 2003 significant coral species changes within reef assemblages at Todos os Santos Bay (TSB), Bahia (Brazil) have taken place, following what appears to have been a 400 year contraction of coral reefs from the inner, landward reaches of the bay. The last 40 years in particular encompassed rapid and extensive urban and industrial development its surrounding lands, which contributed to coral reef changes. However, changes in this environment have influenced coral reef resilience since the arrival of the Portuguese in the XVI century, creating knock-on effects that modified and simplified coral reef ecosystems in the bay. Clues to the limits of coral resilience may be found in natural and human disturbance regimes to which the corals have been subjected in the past, and for that reason we listed and categorized what little is known about Holocene and historical conditions in TSB, proposing alternatives for a resilience management of the bay.
Grazing Effects of Fish versus Sea Urchins on Turf Algae and Coral Recruits: Possible Implications for Coral Reef Resilience and Restoration  [PDF]
Leor Korzen,Alvaro Israel,Avigdor Abelson
Journal of Marine Biology , 2011, DOI: 10.1155/2011/960207
Abstract: Herbivory is an important structuring factor in coral reefs, influencing seaweed abundance, competitive interactions between seaweeds and corals, and coral reef resilience. Despite reports of a drastic increase in the cover of benthic algae and turf dominancy in the coral reefs of Eilat, Red Sea, very little is known about the factors responsible for this phenomenon or the possible effects of herbivory on turf algae and coral recruits. Here, we examine the effects of herbivory by experimentally exposing turf algae and coral recruits to grazing activities of herbivorous fish and sea urchins. Using remote video cameras to document removal of algae and coral spats, we show that the main grazing impact is due to daily grazing by fishes, whereas the significant impact of sea urchins is mainly expressed in their adverse effect on the survival of coral recruits, with a relatively low effect on algal biomass. These findings contribute to our understanding of the factors influencing turf algae establishment and proliferation, and the survival of coral recruits on the coral reefs of Eilat. The clear differences between the impact of herbivorous fish and that of sea urchins, on the Eilat reefs, have critical implications for reef resilience and restoration measures. 1. Introduction The escalating environmental threats and the concern for the future existence of the world’s coral reefs have led to increased studies and speculations on coral reef resilience. Resilience has been defined, among others, as the ability of the reefs to absorb recurrent disturbances and subsequently rebuild coral-dominated systems [1]. Resilience is critically dependent on maintaining a balance among the different reef dwellers or functional groups (e.g., algae, corals [2]). Changes in this balance can lead to a phase shift, that is, an alternative assemblage, typically characterized by algal takeover and dominancy [3]. The takeover of coral reefs by algal turf is a process that has significant ecological implications [4]. Algal communities, dominated by highly productive, small filamentous algal turf, can hinder coral settlement and overgrow coral recruits, thus contributing to the demise of a coral population [5]. The factors determining the relative abundance of either corals or algae on coral reefs are most often an outcome of the complex interactions between environmental factors (bottom-up controls such as nutrient levels) and biological factors (top-down controls such as grazing [5–7]). Herbivory, the removal of plant biomass, is one of the most important structuring factors of
Historical Reconstruction Reveals Recovery in Hawaiian Coral Reefs  [PDF]
John N. Kittinger,John M. Pandolfi,Jonathan H. Blodgett,Terry L. Hunt,Hong Jiang,Kepā Maly,Loren E. McClenachan,Jennifer K. Schultz,Bruce A. Wilcox
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0025460
Abstract: Coral reef ecosystems are declining worldwide, yet regional differences in the trajectories, timing and extent of degradation highlight the need for in-depth regional case studies to understand the factors that contribute to either ecosystem sustainability or decline. We reconstructed social-ecological interactions in Hawaiian coral reef environments over 700 years using detailed datasets on ecological conditions, proximate anthropogenic stressor regimes and social change. Here we report previously undetected recovery periods in Hawaiian coral reefs, including a historical recovery in the MHI (~AD 1400–1820) and an ongoing recovery in the NWHI (~AD 1950–2009+). These recovery periods appear to be attributed to a complex set of changes in underlying social systems, which served to release reefs from direct anthropogenic stressor regimes. Recovery at the ecosystem level is associated with reductions in stressors over long time periods (decades+) and large spatial scales (>103 km2). Our results challenge conventional assumptions and reported findings that human impacts to ecosystems are cumulative and lead only to long-term trajectories of environmental decline. In contrast, recovery periods reveal that human societies have interacted sustainably with coral reef environments over long time periods, and that degraded ecosystems may still retain the adaptive capacity and resilience to recover from human impacts.
Heterotrophic Compensation: A Possible Mechanism for Resilience of Coral Reefs to Global Warming or a Sign of Prolonged Stress?  [PDF]
Adam D. Hughes, Andréa G. Grottoli
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0081172
Abstract: Thermally induced bleaching has caused a global decline in corals and the frequency of such bleaching events will increase. Thermal bleaching severely disrupts the trophic behaviour of the coral holobiont, reducing the photosynthetically derived energy available to the coral host. In the short term this reduction in energy transfer from endosymbiotic algae results in an energy deficit for the coral host. If the bleaching event is short-lived then the coral may survive this energy deficit by depleting its lipid reserves, or by increasing heterotrophic energy acquisition. We show for the first time that the coral animal is capable of increasing the amount of heterotrophic carbon incorporated into its tissues for almost a year following bleaching. This prolonged heterotrophic compensation could be a sign of resilience or prolonged stress. If the heterotrophic compensation is in fact an acclimatization response, then this physiological response could act as a buffer from future bleaching by providing sufficient heterotrophic energy to compensate for photoautotrophic energy losses during bleaching, and potentially minimizing the effect of subsequent elevated temperature stresses. However, if the elevated incorporation of zooplankton is a sign that the effects of bleaching continue to be stressful on the holobiont, even after 11 months of recovery, then this physiological response would indicate that complete coral recovery requires more than 11 months to achieve. If coral bleaching becomes an annual global phenomenon by mid-century, then present temporal refugia will not be sufficient to allow coral colonies to recover between bleaching events and coral reefs will become increasingly less resilient to future climate change. If, however, increasing their sequestration of zooplankton-derived nutrition into their tissues over prolonged periods of time is a compensating mechanism, the impacts of annual bleaching may be reduced. Thus, some coral species may be better equipped to face repeated bleaching stress than previously thought.
Challenges for Managing Fisheries on Diverse Coral Reefs  [PDF]
Douglas Fenner
Diversity , 2012, DOI: 10.3390/d4010105
Abstract: Widespread coral reef decline has included the decline of reef fish populations, and the subsistence and artisanal fisheries that depend on them. Overfishing and destructive fishing have been identified as the greatest local threats to coral reefs, but the greatest future threats are acidification and increases in mass coral bleaching caused by global warming. Some reefs have shifted from dominance by corals to macroalgae, in what are called “phase shifts”. Depletion of herbivores including fishes has been identified as a contributor to such phase shifts, though nutrients are also involved in complex interactions with herbivory and competition. The depletion of herbivorous fishes implies a reduction of the resilience of coral reefs to the looming threat of mass coral mortality from bleaching, since mass coral deaths are likely to be followed by mass macroalgal blooms on the newly exposed dead substrates. Conventional stock assessment of each fish species would be the preferred option for understanding the status of the reef fishes, but this is far too expensive to be practical because of the high diversity of the fishery and poverty where most reefs are located. In addition, stock assessment models and fisheries in general assume density dependent populations, but a key prediction that stocks recover from fishing is not always confirmed. Catch Per Unit Effort (CPUE) has far too many weaknesses to be a useful method. The ratio of catch to stock and the proportion of catch that is mature depend on fish catch data, and are heavily biased toward stocks that are in good condition and incapable of finding species that are in the worst condition. Near-pristine reefs give us a reality check about just how much we have lost. Common fisheries management tools that control effort or catch are often prohibitively difficult to enforce for most coral reefs except in developed countries. Ecosystem-based management requires management of impacts of fishing on the ecosystem, but also vice versa. Marine Protected Areas (MPAs) have been a favorite management tool, since they require little information. MPAs are excellent conservation and precautionary tools, but address only fishing threats, and may be modest fisheries management tools, which are often chosen because they appear to be the only feasible alternative. “Dataless management” is based on qualitative information from traditional ecological knowledge and/or science, is sufficient for successful reef fisheries management, and is very inexpensive and practical, but requires either customary marine tenure or strong
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