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 Symbioses and Stress written by Joseph Seckbach and published by Springer Science & Business Media. This book was released on 2010-09-21 with total page 622 pages. Available in PDF, EPUB and Kindle. Book excerpt: Symbioses and Stress examines how organisms in tight symbiotic associations cope with abiotic and biotic stress. Presenting new findings on symbioses by experts and leading scholars in the field, this volume complements courses and lectures in biology and genetics.

Download or read book Coral Reef Science written by Hajime Kayanne and published by Springer. This book was released on 2016-07-19 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book aims to illuminate coral reefs which comprise a symbiotic system coexisting among ecosystems, landforms, and humans at various levels and to provide a scientific basis for its reconstruction. The authors conducted an interdisciplinary project called “Coral Reef Science” from 2008 to 2012 and obtained novel results and clues to unite different disciplines for a coral reef as a key ecosystem.

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.

Download or read book Stress Responses of Corals and Their Symbiotic Partners written by Contessa A. Ricci and published by . This book was released on 2019 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: Disease and temperature are primary threats to coral persistence, and these stresses can work synergistically to accelerate coral declines. In the face of climate change, understanding the effects of these stresses is key to understanding ecosystem services of future reefs. Corals are anamalgam of the coral animal, an intracellular dinoflagellate symbiont (family Symbiodiniaceae), and a consortium of other symbiotic microbes that exist in the coral surface mucus layer. As such, it is important to consider the role of each component. It is also important to view any coral study through the lens of immunity, as the existence of these symbionts ultimately occurs through the allowance of the coral host immune system. These works examine stress responses through this lens at three levels: 1) the intracellular symbiont; 2) the coral animal; and 3) the coral reef population. I use proteogenomic and biochemical techniques to assess the molecular processes at play during temperature and disease stresses. I show that responses to temperature overlap with, but are not the same as, disease responses, providing support for the specificity that can be achieved by the innate invertebrate immune system. These works provide the first cell surface proteome for a Symbiodiniaceae species and the first analysis of a coral immune response to consecutive bleaching seasons. Finally, they further the use of proteomics in the coral field, as the use of these techniques are still in its infancy. As such, they provide a framework for proteomic analysis within a non-model system.

Download or read book The Future of Coral Reefs Subject to Rapid Climate Change Lessons from Natural Extreme Environments written by Emma F. Camp and published by Frontiers Media SA. This book was released on 2019-01-22 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: Examination of corals and reef-associated organisms which endure in extreme coral reef environments is challenging our understanding of the conditions that organisms can survive under. By studying individuals naturally adapted to unfavorable conditions, we begin to better understand the important traits required to survive rapid environmental and climate change. This Research Topic, comprising reviews, and original research articles, demonstrates the current state of knowledge regarding the diversity of extreme coral habitats, the species that have been studied, and the knowledge to-date on the mechanisms, traits and trade-offs that have facilitated survival.

Download or read book Coral Health and Disease written by Eugene Rosenberg and published by Springer Science & Business Media. This book was released on 2004-04-27 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book opens with case studies of reefs in the Red Sea, Caribbean, Japan, Indian Ocean and the Great Barrier Reef. A section on microbial ecology and physiology describes the symbiotic relations of corals and microbes, and the microbial role in nutrition or bleaching resistance of corals. Coral diseases are covered in the third part. The volume includes 50 color photos of corals and their environments

Download or read book Coral Bleaching written by Madeleine J. H. van Oppen and published by Springer. This book was released on 2018-07-05 with total page 357 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the most serious consequences of global climate change for coral reefs is the increased frequency and severity of mass coral bleaching events and, since the first edition of this volume was published in 2009, there have been additional mass coral bleaching events. This book provides comprehensive information on the causes and consequences of coral bleaching for coral reef ecosystems, from the genes and microbes involved in the bleaching response, to individual coral colonies and whole reef systems. It presents detailed analyses of how coral bleaching can be detected and quantified and reviews future scenarios based on modeling efforts and the potential mechanisms of acclimatisation and adaptation. It also briefly discusses emerging research areas that focus on the development of innovative interventions aiming to increase coral climate resilience and restore reefs.

Download or read book Tolerance to Thermal Stress and Dominant Symbiont Community written by Ruben van Hooidonk and published by . This book was released on 2012 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Reef building corals are in a mutualistic symbiosis with single-celled dinoflaggelates of the genus Symbiodinium. Several different clades of Symbiodinium associate with coral,...with each clade having unique physiological characteristics that enable the coral symbiosis to be successful in a wide range of environmental conditions...But this successful symbiosis is threatened by climate change. Elevated seawater temperatures can disrupt the symbiosis and cause coral bleaching this has led to mass coral mortality on reefs worldwide...By changing the symbionts corals might be able to increase their thermal threshold...or might be able to recover after a bleaching event with an increased tolerance...To establish tolerance and relate it to the ability to change symbiont community the dominant clade of symbionts in 9 species of coral prior, and post experimental bleaching was established. To quantify tolerance, thermal stress was increased weekly and the photosynthetic efficiency of the symbionts in the corals was quantified using Pulse amplitude modulated (PAM) fluorometry...We found that corals prior to bleaching contain an uniform symbiont community, dominated by one Symbiodinium type. After being severely bleached residual symbionts remaining were not the same as those that originally dominated the colony; and the residual symbionts that were left in bleached tissue were not always the same type, BOTh within and between species"--Introduction.

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 Climate Change Effects on Coral Symbioses written by Andrea Chan and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Coral reefs are already suffering the impacts of global climate change, including mass coral bleaching, unprecedented disease outbreaks, and increased damage from more intense tropical storms. The loss of reefs would be devastating because these ecosystems support a diversity of fishes and invertebrates, as well as ecosystem services like commercially important fisheries, tourism revenue, and coastal protection. The framework of coral reefs is built by scleractinian corals, which form a symbiotic relationship with intracellular dinoflagellates in the family Symbiodiniaceae. Understanding how a multi-faceted stressor like climate change will impact coral symbioses requires research conducted at multiple levels of organization, including gene expression and physiology, population connectivity, and interactions between species. For my thesis, I studied these impacts of climate change using three different scleractinian coral species. To increase our understanding of the cellular mechanisms resulting in coral bleaching, we conducted a chronic heat stress experiment using the facultatively symbiotic northern star coral, Astrangia poculata, which naturally occurs with (symbiotic) and without (aposymbiotic) its algal symbiont Breviolum psygmophilum sometimes on the same coral colony. With replicate symbiotic and aposymbiotic ramets of A. poculata, we could separate the heat stress response of the coral host from the coral in symbiosis with its symbiont, while also characterizing the response of the symbiont. Sustained high temperature stress resulted in photosynthetic dysfunction of the symbiont, including a drop in maximum photosynthesis rate, maximum photochemical efficiency, and the absorbance peak of chlorophyll a. Interestingly, the metabolic rates of symbiotic and aposymbiotic coral hosts were differentially impacted. RNAseq analysis revealed more differentially expressed genes between heat-stressed and control aposymbiotic colonies than heat-stressed and control symbiotic colonies. Notably, aposymbiotic colonies increased the expression of inflammation-associated genes such as nitric oxide synthases. Unexpectedly, the largest transcriptional response was observed between heat-stressed and control B. psygmophilum, including genes involved in photosynthesis, response to oxidative stress, and meiosis. Thus, in contrast with previous studies, the algal symbiont responded more strongly to high temperatures than the coral host, possibly resulting in suppressed immune function of the coral. In a separate study, I developed novel microsatellite markers to assess population and clonal structure in the threatened pillar coral, Dendrogyra cylindrus, and its specific symbiont, Breviolum dendrogyrum. Patterns of population structure differed between host and symbiont, with more restricted gene flow for the symbiont along the Florida Reef Tract. Sites with multiple colonies of D. cylindrus were found to be clonal, with the same genotype of the coral host often associating with the same strain of the algal symbiont. High clonality in Florida may have increased the vulnerability of D. cylindrus to a recent thermal stress-associated disease outbreak, resulting in a precipitous population decline. Lastly, I investigated clonal structure in the lobe coral, Porites lobata, in two regions with similar gradients of abiotic variables and bioeroding mussel densities. While genotypic diversity was lower at Galapagos sites that are more acidic, similar sites in Palau had relatively equal levels of genotypic diversity across an acidification gradient. These contrasting results are likely due to differences in biotic interactions between the two regions, such as the presence of coral-biting triggerfish in the Galapagos that prey on bioeroding mussels. This points to the importance of considering these interactions when predicting how climate change could impact asexual reproduction in foundational species like corals. Overall, the work presented in this thesis highlights the variability of biological responses at different levels of organization in coral reef environments that will continue to be impacted by climate change.

Download or read book Studies of Symbiosis Breakdown in Aiptasia a Sea anemone Model for Coral Biology written by Tamaki Bieri and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Coral reefs are one of the world's most productive ecosystems and harbor an immense diversity of organisms. The energetic basis of this ecosystem is the symbiosis between corals and unicellular dinoflagellate algae of the genus Symbiodinium. Despite the importance of corals, little is known about the molecular and cellular bases of the establishment, maintenance, and breakdown of this symbiosis. Currently, the health and abundance of coral reefs are declining rapidly due to anthropogenic activities. Stresses such as rising seawater temperatures cause the symbiosis to break down, leading to a loss of the algal symbiont from the coral host, a phenomenon known as coral bleaching. Even though it is well known that corals bleach under stress, the cellular mechanisms of this process are not well understood. The study of bleaching mechanisms has been confounded in part by the difficulty of maintaining corals under laboratory conditions and their intractability to experimental manipulation. Published studies have been performed using different species and different experimental conditions, making it difficult to compare the results. To date, four possible cellular bleaching mechanisms have been reported. However, it is unclear whether there is a quantitatively predominant mechanism of bleaching and whether the bleaching mechanisms change depending on the stress type and/or duration. To answer these questions, I used a clonal strain of the small sea anemone Aiptasia, which houses Symbiodinium types similar to those in corals but is far more amenable to experimental manipulation. I exposed animals to precisely controlled stress conditions and monitored all four potential bleaching mechanisms in parallel. I found that expulsion of algae seems to be by far the most important bleaching mechanism under all stress conditions tested, with the possible exception of acute cold shock, which also induced in situ degradation of algae and detachment of host cells containing algae. It has been hypothesized that ocean acidification might exacerbate the bleaching of corals under thermal stress. However, only a few studies have examined the effect of low-pH seawater on cnidarian bleaching, and even fewer have looked at the possible synergism of these two stressors. As with studies of the cellular mechanisms of bleaching, the reports on effects of low pH are highly variable and often conflicting, perhaps because of the different study conditions and organisms used. To examine these questions, I exposed Aiptasia either to low-pH seawater as a single stressor, or to low pH in combination with mild thermal stress. The results suggest that at least in Aiptasia, low pH alone causes either no or only moderate bleaching, and that thermal bleaching is only slightly exacerbated by low pH. Using anemone strains with different combinations of host and algal genotype, I also obtained evidence that both genotypes influence the sensitivity of a given strain to low-pH seawater. The knowledge gained in my studies should lay the foundation for future studies of the molecular pathways of symbiosis breakdown under stress and help to enable a rational approach to assessing, and potentially partially remediating, the threats of anthropogenic stresses to coral reefs.

Download or read book Photosynthesis in Algae Biochemical and Physiological Mechanisms written by Anthony W.D. Larkum and published by Springer Nature. This book was released on 2020-06-03 with total page 534 pages. Available in PDF, EPUB and Kindle. Book excerpt: Algae, including cyanobacteria, are in the spotlight today for a number of reasons; firstly it has become abundantly clear over recent years that algae have been neglected in terms of basic research and that knowledge gap is being rapidly closed with the establishment of some surprising discoveries, such as the presence of Near-Infra-Red-Absorbing cyanobacteria and a wealth of natural products; secondly molecular approaches have provided a wealth of approaches to genetically modify algae and produce value-added products; thirdly it has become clear just how important, marine phytoplankton is to global carbon capture and the production of food globally; and fourthly, it has also become clear that algae present unparalleled opportunities to generate biofuels in a sustainable and non-polluting way. This volume presents 15 chapters by world experts on their subjects, ranging from reviews of algal diversity and genetics to in-depth reviews of special algal groups such as diatoms (which account for over 30% of marine carbon capture). Other chapters chart the ways in which this carbon capture occurs or how there are a multiplicity of ways in which algae intercept sun light and deploy this energy for carbon capture. A fascinating aspect here is the way in which sun light is harvested. A special chapter is devoted to the very recent and exciting possibility that algae use coherent light energy transformation to enhance the efficiency of light capture, an aspect of quantum physics that has implications for future developments at several levels and a variety of industries. Just how and why algae use Chlorophyll a as the major light capture pigment is discussed in several chapters. However, attention is also given to those cyanobacteria, which have been found to use the special Near-Infra Red absorbing chlorophylls mentioned above. And attention is also given to those algae that employ phycobiliproteins to fill in the “green window”, i.e., the spectral region from 400 – 650 nm, which is not efficiently covered by chlorophyll and carotenoid pigments. Photoinhibition and photoprotection is the subject area of several chapters and one which it is essential to understand a we work towards greater efficiency of algal photosynthesis. A final chapter is devoted to understanding the molecular basis for coral bleaching, a much-neglected area that is essential in trying to come up with solutions to this very worrying phenomenon, caused by global warming and ocean acidification. This is a book for research scientists, environmentalists, planners in a range of areas including those of marine resources, nutrient control and pollution of water bodies and that growing body of concerned citizens interested in controlling carbon emissions and global warming. Special attention has been given to generating a set of articles that will be read by university students, informed laymen and all those whose wish to understand the rapid changes that have come about in our knowledge of algae over the past decade.

Download or read book The Cnidaria Past Present and Future written by Stefano Goffredo and published by Springer. This book was released on 2016-09-07 with total page 842 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents a broad panorama of the current status of research of invertebrate animals considered belonging to the phylum Cnidaria, such as hydra, jellyfish, sea anemone, and coral. In this book the Cnidarians are traced from the Earth’s primordial oceans, to their response to the warming and acidifying oceans. Due to the role of corals in the carbon and calcium cycles, various aspects of cnidarian calcification are discussed. The relation of the Cnidaria with Mankind is approached, in accordance with the Editors’ philosophy of bridging the artificial schism between science, arts and Humanities. Cnidarians' encounters with humans result in a broad spectrum of medical emergencies that are reviewed. The final section of the volume is devoted to the role of Hydra and Medusa in mythology and art.

Download or read book The Ecology and Functional Significance of Distinct Coral Symbionts written by Allison Michelle Lewis and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Distinct coral symbiont associations have been shown to influence the response of a coral colony to environmental stress. Genetic evidence has revealed the existence of cryptic symbiont species previously masked by similar morphological traits. Thus, there is a pressing need to study the biological and underlying functional diversity of symbionts and their effects on the physiology of the coral host. Chapter 1 introduces the application of molecular genetics to understanding the diversity, evolution, and ecology of nondescript Symbiodiniaceae and how different symbiont associations respond to environmental stresses such as anthropogenic global warming. In Chapter 2, new species of Symbiodiniaceae discovered through this research are resolved. This chapter shows that a presumed symbiont generalist is actually comprised of multiple distinct species, co-evolved with specific coral taxa. These findings support the primary role of niche specialization to particular hosts in the diversification of symbiotic dinoflagellates.Dynamic or shifting symbiont associations have been observed as an adaptive mechanism to alter coral physiology, particularly for corals under acute environmental stress. It is often presumed that shifting symbiont associations is a common phenomenon, yet, few studies have investigated whether the relationship between host colony and resident symbiont is stable or dynamic over time. In Chapter 3, coral symbionts from various Indo-Pacific corals were investigated over multiple years. All colonies harbored and maintained an association with a single dominant species of Symbiodiniaceae belonging to genusCladocopium (formerly Symbiodinium Clade C). Individual clone genotypes, or strains, of the resident symbionts were diverse across the coral population, and few clones were found in more than one colony. Individual corals consistently maintained stable symbioses dominated by one or two genotypes which likely persist for the life of a colony. Chapter 4 investigates coral species from two habitats that represent extremes in environmental conditions in the Indo-Pacific. In this chapter differences in the physiology of coral with distinct symbiont pairings is investigated and then evaluated in the context of a warming climate. Our evidence shows that an association with the symbiont Durusdinium (formerly Symbiodinium Clade D) trenchii imparts thermal resilience to corals without significant trade-off to overall colony growth and stands in contrast to previous reports for corals with thermally-tolerant symbionts in other regions of the world. Symbioses involving D. trenchii in the Pacific might be better integrated and co-adapted with Pacific corals resulting in a more stable and optimized association. Thus, shifts in host-symbiont pairings to combinations that are better adapted to increasingly stressful conditions constitute an ecological response that may allow reefs to remain viable during global ocean warming.

Download or read book The Importance of the Rare written by Rachel Silverstein and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Reef ecosystems throughout much of the tropics are predicted to decline in coral cover and diversity as a result of ongoing climate change (ocean acidification, temperature increases, sea level rise), disease, pollution, and overfishing. Corals may be able to respond to some of these stressors by associating with diverse algal symbionts (Symbiodinium spp.) which vary in their physiological traits and therefore expand corals' realized niche space. This dissertation used high-sensitivity molecular techniques to investigate the presence and functional role of "background" or "rare" Symbiodinium, which occur at low abundance, and therefore may not be detected using standard molecular methods. First, in order to determine the prevalence of mixed-clade symbiont communities (including potentially low-abundance populations), I used a highly-sensitive, real-time PCR assay to analyze archived DNA from a collection of geographically and phylogenetically diverse corals. I found that mixed-clade Symbiodinium communities were common, and that clades C and D were present in all 39 coral species examined. These findings provide strong evidence that no coral species is restricted to hosting only a single symbiont type. I then investigated the functional role of low-abundance symbionts through a series of bleaching and recovery experiments involving the Caribbean coral Montastraea cavernosa. I monitored changes in symbiont community structure using newly-designed quantitative PCR assays, and monitored symbiont community function using chlorophyll fluorometry. Corals hosted only clade C symbionts before bleaching (except for 2 of 139 cores which hosted trace amounts of clade D as well). All bleached colonies (both herbicide-bleached and heat-bleached) recovered with dominant communities of clade D symbionts at both 24oC and 29oC recovery temperatures. Therefore, low-abundance (or even undetectable) symbionts became dominant in corals after disturbance. Increased temperatures, without acute disturbance, underwent less-dramatic, slower symbiont community changes. Corals that bleached, but which were not exposed to heat either during bleaching or during recovery, recovered with fewer D1a symbionts than corals bleached by heat or acclimated to higher temperatures. During a third experiment, I used these same corals to investigate how changes in symbiont clade, past thermal history, and host genotype, affect coral thermotolerance during a second heat stress exposure. I found that, during heat stress, previously-bleached corals hosting D1a symbionts lost fewer symbionts and exhibited less photochemical damage than corals hosting C3 symbionts. Prior heat exposure, either during bleaching or during recovery, did not increase coral thermotolerance, unless it was also associated with symbiont community shifts to D1a-dominance. This demonstrates that rare (or even undetectable symbionts) can become dominant, and can eventually play a critical role in coral bleaching response. Finally, a two-part experiment investigated the effect of incremental warming and cooling on these corals. D1a symbionts in corals that were incrementally heated to 33oC had higher photochemical efficiency than cores containing C3 symbionts, and experienced less symbiont loss. During cooling, however, the photochemical efficiency of D1a was either equal to, or lower than C3. Despite this, fewer D1a symbionts were still lost compared to C3. This suggests that photochemical efficiency and symbiont loss may be decoupled from one another during stress, and that D1a symbionts may be generally more resistant to expulsion, regardless of their performance in hospite. This study also shows that M. cavernosa corals hosting D1a can expand their realized thermal niches wider corals hosting C3 symbionts, reinforcing the importance of functional redundancy in dynamic environments. Together, these studies show that mixed algal symbiont communities can increase both the resistance and resilience of corals to stress and disturbance. These findings have indicate that symbiont community shifts have the potential to allow reef corals to rapidly adapt or acclimatize to environmental change.

Download or read book Corals and Coral Reefs of the Gal pagos Islands written by Peter W. Glynn and published by Univ of California Press. This book was released on 1983-01-01 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: 00 This scientifically thorough,lucidly written work explores the nature, development, and extent of the archipelago's reef-building corals. Also included is an annotated list of the Scleractianian Corals by John W. Wells This scientifically thorough,lucidly written work explores the nature, development, and extent of the archipelago's reef-building corals. Also included is an annotated list of the Scleractianian Corals by John W. Wells