Download or read book Effects of Heat Stress and Local Human Disturbance on the Structure of Coral Reef Ecosystems at Multiple Scales of Biological Organization written by Jennifer Magel and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The world's coral reefs are being impacted by myriad disturbances, from localized overfishing and nutrient pollution to global climate change-induced temperature increases and ocean acidification. Conservation of coral reefs in the face of increasing variability and uncertainty requires an understanding of the interacting effects of multiple stressors on the diverse components of these vital ecosystems. In this thesis, I use data from reefs around Kiritimati atoll (Republic of Kiribati) in the central equatorial Pacific Ocean to examine the effects of a severe pulse heat stress event and local human disturbance on two important components of the coral reef ecosystem - three-dimensional (3D) structural complexity and reef fish assemblages. Using 3D reef models constructed through structure-from-motion photogrammetry, I examined changes in reef structural complexity in the year following the 2015-2016 El Niño and mass coral bleaching event. I found that exposure to prolonged thermal stress and subsequent coral mortality resulted in declines in reef structural complexity, particularly reef surface rugosity and terrain ruggedness. Baseline levels of structural complexity were also negatively influenced by local human disturbance, while complexity was positively related to the densities of branching and massive coral growth forms. These findings have important implications for the maintenance of healthy reef ecosystems, as high levels of structural complexity are important for supporting diverse reef-associated fish assemblages. Next, using underwater visual censuses of reef fish assemblages, I quantified fish abundance, biomass, species richness, and assemblage structure before, during, and after the 2015-2016 El Niño. Total reef fish abundance, biomass, and species richness declined during the El Niño, suggesting that pulse heat stress events may have short-term, negative consequences for reef fish. Although these metrics did not vary substantially across the local human disturbance gradient, recovery of assemblages following the heat stress event was impeded by higher levels of local human disturbance. Reef fish assemblage structure was influenced by a more diverse array of factors, showing significant shifts in response to heat stress, human disturbance, and net primary productivity. Given the many important roles that fish play on coral reefs, declines such as those observed here may impair the ecological functioning of these ecosystems. Together, my results highlight the negative impacts of heat stress and local human disturbance on coral reefs, demonstrating ways in which these stressors may interact to limit reef resilience in the face of increasing anthropogenic pressures.

Download or read book Implications of Heat Stress and Local Human Disturbance on Early Life Stage Corals written by Kristina Tietjen and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Coral reef recovery following a disturbance relies heavily on the restoration of coral cover, via growth of existing colonies and the successful recruitment of new corals. In well-connected reef networks, recruits may be sourced from neighboring reefs. In contrast, coral recruitment on geographically isolated reefs is reliant on adult corals at that location, which may limit recovery rates following mass coral mortality events. Such mortality events are increasingly caused by climate change induced temperature anomalies, which are overlaid on the local chronic human disturbances that already affect most of the world's coral reefs. In this thesis, I exploit a natural ecosystem-scale experiment to examine how multiple anthropogenic stressors impact densities of coral recruits and small corals (e.g., juveniles; 5 cm) on Kiritimati (Christmas Island, Republic of Kiribati), an isolated atoll in the central equatorial Pacific Ocean. Specifically, I used benthic survey videos from before, during, and one year following the 2015-2016 El Niño and coral settlement tiles deployed during the three years after the event at 22 sites across the island, to quantify small corals and coral recruits, respectively. Local chronic stress negatively impacted small corals, with densities 47% lower at sites exposed to very high levels of chronic stress prior to the heat stress. The El Niño further resulted in a 56% loss of small corals, particularly for competitive coral species. Following the event, stress tolerant small corals rebounded to pre-El Niño densities within a year, whereas competitive and small corals overall had non-significant increases. I also quantified a low recruitment rate of 8.31 recruits m-2 per year (± 1.9 SE) during the three years following the El Niño compared to previous studies around the Pacific; recruits were genetically identified as primarily belonging to the stress tolerant family Agariciidae and the competitive genus Pocillopora. Local human disturbance also impacted coral recruitment with densities significantly lower at those with the greatest local chronic disturbance, together suggesting that local disturbance impedes post-settlement survival of recruits and the resilience of young corals during acute stress events. With increased net primary productivity, densities of both small corals and recruits (non-significant) also increased, which could reflect the positive influence of coral heterotrophic nutrition supplements during and after stress events, increasing survivability. Despite very low overall coral recruitment, all island regions did have some recruits, but Vaskess Bay (a bay region on the southern part of the island) had the highest densities. Overall these results indicate the negative consequences combined chronic and acute stressors can have on coral recruits, small corals, and accompanying coral resilience. When viewed together, this work suggests how the resilience is compromised by chronic stressors on Kiritimati and that the recovery trajectory may be variable across the disturbance gradient. Thus, local reef management may provide an avenue for enhancing recovery rates as acute temperature anomalies increase in frequency under our current climate trajectory.

Download or read book Coral Reefs An Ecosystem in Transition written by Zvy Dubinsky and published by Springer Science & Business Media. This book was released on 2010-12-02 with total page 541 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers in one volume materials scattered in hundreds of research articles, in most cases focusing on specialized aspects of coral biology. In addition to the latest developments in coral evolution and physiology, it presents chapters devoted to novel frontiers in coral reef research. These include the molecular biology of corals and their symbiotic algae, remote sensing of reef systems, ecology of coral disease spread, effects of various scenarios of global climate change, ocean acidification effects of increasing CO2 levels on coral calcification, and damaged coral reef remediation. Beyond extensive coverage of the above aspects, key issues regarding the coral organism and the reef ecosystem such as calcification, reproduction, modeling, algae, reef invertebrates, competition and fish are re-evaluated in the light of new research and emerging insights. In all chapters novel theories as well as challenges to established paradigms are introduced, evaluated and discussed. This volume is indispensible for all those involved in coral reef management and conservation.

Download or read book Coral Symbioses Under Stress written by Danielle C. Claar and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Coral reefs, the planet's most diverse marine ecosystems, are threatened globally by climate change and locally by overfishing and pollution. The dynamic partnership between coral and their endosymbiotic algae (Symbiodinium) is the foundation of all tropical reef ecosystems. Symbiodinium provide coral with nutrients for growth, but stress can break down this symbiosis, causing coral bleaching. There are also life-history trade-offs amongst Symbiodinium types - some provide coral with more nutrition, while others are better able to cope with environmental stressors. Although these symbioses are believed to be a critical element of reef resilience, little is known about how local and global stressors alter these partnerships. In this thesis, I combine synthetic literature reviews and a meta-analysis, with field research, molecular analyses, bioinformatics, and statistical analyses to investigate environmentally-driven mechanisms of change in coral-symbiont interactions with the aim of advancing understanding of how corals will adapt to the stressors they now face. First, I conducted a review of coral-Symbiodinium interactions, from molecules to ecosystems and summarized the current state of the field and knowledge gaps. Next, I conducted a meta-analysis of coral bleaching and mortality during El Niño events and created an open-source coral heat stress data product. I found that the 2015-2016 El Niño instigated unprecedented thermal stress on reefs globally, and that, across all El Niño events, coral bleaching and mortality were greater at locations with higher long-term mean temperatures. I provided recommendations for future bleaching surveys, and in a related perspectives piece, highlighted the importance of survey timing during prolonged coral bleaching events. The latter three empirical chapters are based on my six field expeditions to Kiritimati (Christmas Island). Taking advantage of the atoll's natural ecosystem-scale experiment, I tagged, sampled and tracked over 1,000 corals across its chronic human disturbance gradient. Since corals can uptake Symbiodinium from the surrounding environment, I first investigated the effect of local disturbance and winter storm waves on Symbiodinium communities in coral, sediment, and seawater. Greater variability in Symbiodinium communities at highly disturbed sites suggests that local disturbance destabilizes symbiont community structure. Since local disturbance influences Symbiodinium community structure and coral-associated microbial communities, I next examined the covariance of coral-associated Symbiodinium and microbial communities for six coral species across Kiritimati's disturbance gradient. Most strikingly, I found corals on Kiritimati that recovered from globally unprecedented thermal stress, experienced during the 2015-2016 El Niño, while they were still at elevated temperatures. This is notable, because no coral has previously been documented to recover from bleaching while still under heat stress. Only corals protected from local stressors exhibited this capacity. Protected corals had distinct pre-bleaching algal symbiont communities and recovered with different algal symbionts, suggesting that Symbiodinium are the mechanism of resilience and that protection governs their communities. Together, this research provides novel evidence that local protection may be more important for coral resilience than previously thought, and that variability in symbiotic and microbial communities provides a potentially flexible mechanism for corals to respond to both local and global stressors.

Download or read book Coral Reefs in the Anthropocene written by Charles Birkeland and published by Springer. This book was released on 2015-11-03 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume investigates the effects of human activities on coral reefs, which provide important life-supporting systems to surrounding natural and human communities. It examines the self-reinforcing ecological, economic and technological mechanisms that degrade coral reef ecosystems around the world. Topics include reefs and limestones in Earth history; the interactions between corals and their symbiotic algae; diseases of coral reef organisms; the complex triangle between reef fishes, seaweeds and corals; coral disturbance and recovery in a changing world. In addition, the authors take key recent advances in DNA studies into account which provides new insights into the population biology, patterns of species distributions, recent evolution and vulnerabilities to environmental stresses. These DNA analyses also provide new understandings of the limitations of coral responses and scales of management necessary to sustain coral reefs in their present states. Coral reefs have been essential sources of food, income and resources to humans for millennia. This book details the delicate balance that exists within these ecosystems at all scales, from geologic time to cellular interactions and explores how recent global and local changes influence this relationship. It will serve as an indispensable resource for all those interested in learning how human activities have affected this vital ecosystem around the world.

Download or read book The Great Barrier Reef written by Pat Hutchings and published by CSIRO PUBLISHING. This book was released on 2008-11-07 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Great Barrier Reef Marine Park is 344 400 square kilometres in size and is home to one of the most diverse ecosystems in the world. This comprehensive guide describes the organisms and ecosystems of the Great Barrier Reef, as well as the biological, chemical and physical processes that influence them. Contemporary pressing issues such as climate change, coral bleaching, coral disease and the challenges of coral reef fisheries are also discussed. In addition,the book includes a field guide that will help people to identify the common animals and plants on the reef, then to delve into the book to learn more about the roles the biota play. Beautifully illustrated and with contributions from 33 international experts, The Great Barrier Reef is a must-read for the interested reef tourist, student, researcher and environmental manager. While it has an Australian focus, it can equally be used as a baseline text for most Indo-Pacific coral reefs. Winner of a Whitley Certificate of Commendation for 2009.

Download or read book Insight Into Coral Reef Ecosystems written by Sean Dimoff and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Coral reefs around the world are threatened by a variety of sources, from localized impacts, including overfishing and coastal development, to global temperature increases and ocean acidification. Conserving these marine biodiversity havens requires both global and local action informed by scientific research. In this thesis, I use data collected from the coral reefs around Kiritimati atoll (Republic of Kiribati) in the central equatorial Pacific, first to assess the applicability of two common metrics used in passive underwater acoustic research, and second to examine the effects of a marine heatwave and local human disturbance on an assemblage of corallivorous fish. Using acoustic data recorded in 2017 and 2018 on reefs around Kiritimati, I assess how sound pressure level (SPL) and the acoustic complexity index (ACI) respond to changes in fish sounds in a low frequency band (160 Hz - 1 kHz) and snapping shrimp snaps in a high frequency band (1 kHz - 22 kHz). I found that while SPL was positively correlated with increases in fish sounds and snap density, changes in ACI were dependent upon the settings chosen for its calculation, with the density of snaps negatively correlated with ACI across all settings. These findings provide evidence that despite its quick and prolific adoption, acoustic metrics like ACI should be thoroughly field-tested and standardized before they are applied to new ecosystems like coral reefs. Next, using underwater visual censuses (UVCs) of reef fish assemblages, I quantified how two functional groups of corallivores, obligate and facultative, responded to a mass coral mortality event created by the 2015-2016 El Niño. Declines in abundance of both groups were largely driven by the response of coral-associated damselfishes, Plectroglyphidodon johnstonianus in the obligate group and Plectroglyphidodon dickii in the facultative group, to heat stress and subsequent coral mortality. I also observed a significant decline in the species richness of obligate corallivores, and a continued decline in the abundance of obligate corallivores three years after the mass coral mortality event. Additionally, facultative corallivore abundance increased with disturbance, although the effect was modulated by year, likely due to their more adaptable diets. Corallivore assemblage structure was also influenced by the heat stress event, recovery, and local human disturbance. These results detail how an entire corallivorous assemblage is impacted by a coral mortality event and incidentally provide a timeline for corallivore decline. Together, these results provide information about new ways of monitoring coral reefs, and the ways in which two components of the reef fish community, obligate and facultative corallivores, respond to a mass coral mortality event.

Download or read book Coral Reefs in the Anthropocene written by Charles Birkeland and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume investigates the effects of human activities on coral reefs, which provide important life-supporting systems to surrounding natural and human communities. It examines the self-reinforcing ecological, economic, and technological mechanisms that degrade coral reef ecosystems around the world. Topics include reefs and limestones in Earth history; the interactions between corals and their symbiotic algae; diseases of coral reef organisms; the complex triangle between reef fishes, seaweeds, and corals; coral disturbance and recovery in a changing world. In addition, the authors take key recent advances in DNA studies into account which provides new insights into the population biology, patterns of species distributions, recent evolution, and vulnerabilities to environmental stresses. These DNA analyses also provide new understandings of the limitations of coral responses and scales of management necessary to sustain coral reefs in their present states. Coral reefs have been essential sources of food, income, and resources to humans for millennia. This book details the delicate balance that exists within these ecosystems at all scales, from geologic time to cellular interactions, and explores how recent global and local changes influence this relationship. It will serve as an indispensable resource for all those interested in learning how human activities have affected this vital ecosystem around the world.

Download or read book Coral Reefs and Climate Change written by Jonathan Turnbull Phinney and published by American Geophysical Union. This book was released on 2006-01-10 with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Coastal and Estuarine Studies, Volume 61. The effects of increased atmospheric carbon dioxide and related climate change on shallow coral reefs are gaining considerable attention for scientific and economic reasons worldwide. Although increased scientific research has improved our understanding of the response of coral reefs to climate change, we still lack key information that can help guide reef management. Research and monitoring of coral reef ecosystems over the past few decades have documented two major threats related to increasing concentrations of atmospheric CO2: (1) increased sea surface temperatures and (2) increased seawater acidity (lower pH). Higher atmospheric CO2 levels have resulted in rising sea surface temperatures and proven to be an acute threat to corals and other reef-dwelling organisms. Short periods (days) of elevated sea surface temperatures by as little as 1–2°C above the normal maximum temperature has led to more frequent and more widespread episodes of coral bleaching-the expulsion of symbiotic algae. A more chronic consequence of increasing atmospheric CO2 is the lowering of pH of surface waters, which affects the rate at which corals and other reef organisms secrete and build their calcium carbonate skeletons. Average pH of the surface ocean has already decreased by an estimated 0.1 unit since preindustrial times, and will continue to decline in concert with rising atmospheric CO2. These climate-related Stressors combined with other direct anthropogenic assaults, such as overfishing and pollution, weaken reef organisms and increase their susceptibility to disease.

Download or read book A Decision Framework for Interventions to Increase the Persistence and Resilience of Coral Reefs written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2019-08-29 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coral reefs are critical to ocean and human life because they provide food, living area, storm protection, tourism income, and more. However, human-induced stressors, such as overfishing, sediment, pollution, and habitat destruction have threatened ocean ecosystems globally for decades. In the face of climate change, these ecosystems now face an array of unfamiliar challenges due to destructive rises in ocean temperature, acidity and sea level. These factors lead to an increased frequency of bleaching events, hindered growth, and a decreasing rate of calcification. Research on interventions to combat these relatively new stressors and a reevaluation of longstanding interventions is necessary to understand and protect coral reefs in this changing climate. Previous research on these methods prompts further questions regarding the decision making process for site-specific interventions. A Decision Framework for Interventions to Increase the Persistence and Resilience of Coral Reefs builds upon a previous report that reviews the state of research on methods that have been used, tested, or proposed to increase the resilience of coral reefs. This new report aims to help coral managers evaluate the specific needs of their site and navigate the 23 different interventions described in the previous report. A case study of the Caribbean, a region with low coral population plagued by disease, serves as an example for coral intervention decision making. This report provides complex coral management decision making tools, identifies gaps in coral biology and conservation research, and provides examples to help individuals and communities tailor a decision strategy to a local area.

Download or read book Human Disturbance Alters Pacific Coral Reef Fish Beta diversity at Three Spatial Scales written by Logan Douglas Wiwchar and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Coral reefs are the most diverse marine ecosystem, but are increasingly threatened by local and global anthropogenic changes. In this thesis, I examine the impact of local stressors on the spatial variability of coral reef fish community composition by modeling the !-diversity of 35 islands across the Pacific Ocean that are characterized by either low or high human disturbance. By examining !-diversity across three spatial scales (within island, within island group, and across island group), and using null models to control for differences in alpha-diversity or abundance, I reveal previously undocumented effects of human disturbance on coral reef fish assemblages. At all scales, human disturbances alter !-diversity. At the largest-scale, islands with high human disturbance have lower incidence- and abundance-based !-diversity, consistent with biotic homogenization. This pattern was driven by both species with high and low abundances that differed across islands. At the smaller two scales (within islands or island groups), the presence of low abundance species is more variable on islands with high human disturbance (manifest in greater incidence-based !-diversity), but these islands have lower abundance-based !- diversity driven by moderately abundant and widespread species. Multivariate techniques show that islands with high human disturbance have a weaker species-environment relationship, and as such, I suggest that homogenization of coral reef fish assemblages by human disturbances is resulting in greater stochasticity of species composition.

Download or read book Understanding and Predicting Disturbances on Coral Reefs at Multiple Spatial Scales written by Joseph Maina Mbuie and published by . This book was released on 2013 with total page 215 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Global Climate Change and Coral Reefs written by Clive R. Wilkinson and published by IUCN. This book was released on 1994 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: A global overview of the potential impacts of climate change and sea level rise on coral reefs, and of the implications of such impacts for ecological sustainable use of coral reefs. Includes information on the status and trends of reef conservation and use around the world, and suggestions for management of reefs in a changing world.

Download or read book Herbivorous Coral Reef Fish Responses to Local and Global Stressors written by Jenny Smith and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Given the current state of the climate and continuing local human impacts to coral reefs, conservation of these ecosystems requires active management efforts to arrest further deterioration. Some current management strategies focus on regulating local impacts such that reefs are provided the best chance at resisting further degradation from global, climate change-induced disturbances. One such strategy is to manage local herbivore populations. Herbivorous coral reef fish are considered natural drivers of reef recovery due to their prevention of algal overgrowth on coral and of further degradation of the reef to an undesirable state dominated by macroalgae. While the numerical response of herbivorous fish to disturbance is commonly investigated, the response of their key function to large-scale, global disturbance is still not well understood. In this thesis, I attempt to take a functional approach to describe herbivory on Kiritimati (Christmas Island), the largest coral atoll, located in the equatorial Pacific Ocean. First, I describe species-specific herbivory using three metrics: (i) bite rates; (ii) grazing impacts; and (iii) selectivity, to explore how these metrics vary with herbivore identity, individual size and life phase, and to determine if they are influenced by local gradients of human disturbance and whether or not they respond to a pulse heat stress and coral bleaching disturbance that resulted from the 2015-2016 El Niño. I found that herbivore functional groups and species exhibit distinct herbivory, driven, in part, by differences in fish size. Disturbance at a local level does not appear to have a significant influence on species-specific herbivory, but I detected an increase in bite rates and grazing impacts in response to a global heat stress event. These findings have implications for how herbivores respond to different levels of disturbance. I then scale up species-specific grazing impacts using site-averaged species' densities to explore how the herbivore assemblage grazing function responds to disturbance. Further, I summed average species' impacts at each site by functional group and detected distinct grazing impacts among groups and an increase following a global heat stress event. These findings suggest that the herbivory function of the assemblage is relatively robust to withstanding disturbance. Given that global scale disturbances of reef ecosystems are projected to become more frequent in the future, it is imperative to understand how this function will be influenced by disturbance at different scales. Taken together, the results in this thesis provide insight into the differing impacts of local and global scale disturbances on the herbivory function and suggest a somewhat promising outcome for the potential recovery of reefs following future disturbance.

Download or read book Climate Carbon and Coral Reefs written by and published by . This book was released on 2010 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This brochure illustrates some of the linkages among climate, carbon dioxide and coral reefs, while describing the necessary steps to appropriately assess the threats at the local and regional scales, as well as to devise suitable monitoring, conservation and mitigation strategies."--Provided by publisher.

Download or read book Ocean Acidification written by National Research Council and published by National Academies Press. This book was released on 2010-09-14 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ocean has absorbed a significant portion of all human-made carbon dioxide emissions. This benefits human society by moderating the rate of climate change, but also causes unprecedented changes to ocean chemistry. Carbon dioxide taken up by the ocean decreases the pH of the water and leads to a suite of chemical changes collectively known as ocean acidification. The long term consequences of ocean acidification are not known, but are expected to result in changes to many ecosystems and the services they provide to society. Ocean Acidification: A National Strategy to Meet the Challenges of a Changing Ocean reviews the current state of knowledge, explores gaps in understanding, and identifies several key findings. Like climate change, ocean acidification is a growing global problem that will intensify with continued CO2 emissions and has the potential to change marine ecosystems and affect benefits to society. The federal government has taken positive initial steps by developing a national ocean acidification program, but more information is needed to fully understand and address the threat that ocean acidification may pose to marine ecosystems and the services they provide. In addition, a global observation network of chemical and biological sensors is needed to monitor changes in ocean conditions attributable to acidification.

Download or read book A Research Review of Interventions to Increase the Persistence and Resilience of Coral Reefs written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2019-04-05 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coral reef declines have been recorded for all major tropical ocean basins since the 1980s, averaging approximately 30-50% reductions in reef cover globally. These losses are a result of numerous problems, including habitat destruction, pollution, overfishing, disease, and climate change. Greenhouse gas emissions and the associated increases in ocean temperature and carbon dioxide (CO2) concentrations have been implicated in increased reports of coral bleaching, disease outbreaks, and ocean acidification (OA). For the hundreds of millions of people who depend on reefs for food or livelihoods, the thousands of communities that depend on reefs for wave protection, the people whose cultural practices are tied to reef resources, and the many economies that depend on reefs for fisheries or tourism, the health and maintenance of this major global ecosystem is crucial. A growing body of research on coral physiology, ecology, molecular biology, and responses to stress has revealed potential tools to increase coral resilience. Some of this knowledge is poised to provide practical interventions in the short-term, whereas other discoveries are poised to facilitate research that may later open the doors to additional interventions. A Research Review of Interventions to Increase the Persistence and Resilience of Coral Reefs reviews the state of science on genetic, ecological, and environmental interventions meant to enhance the persistence and resilience of coral reefs. The complex nature of corals and their associated microbiome lends itself to a wide range of possible approaches. This first report provides a summary of currently available information on the range of interventions present in the scientific literature and provides a basis for the forthcoming final report.