Search

Ocean warming and acidification caused by increases of atmospheric carbon dioxide are now thought to be major threats to coral reefs on a global scale. Here we evaluated the environmental conditions and benthic community structures in semi-closed Nikko Bay at the inner reef area in Palau, which has high pCO2 and seawater temperature conditions with high zooxanthellate coral coverage. Nikko Bay is a highly sheltered system with organisms showing low connectivity with surrounding environments, making this bay a unique site for evaluating adaptation and acclimatization responses of organisms to warmed and acidified environments. Seawater pCO2/Ωarag showed strong gradation ranging from 380 to 982 µatm (Ωarag: 1.79–3.66), and benthic coverage, including soft corals and turf algae, changed along with Ωarag while hard coral coverage did not change. In contrast to previous studies, net calcification was maintained in Nikko Bay even under very low mean Ωarag (2.44). Reciprocal transplantation of the dominant coral Porites cylindrica showed that the calcification rate of corals from Nikko Bay did not change when transplanted to a reference site, while calcification of reference site corals decreased when transplanted to Nikko Bay. Corals transplanted out of their origin sites also showed the highest interactive respiration (R) and lower gross photosynthesis (Pg) to respiration (Pg:R), indicating higher energy acquirement of corals at their origin site. The results of this study give important insights about the potential local acclimatization and adaptation capacity of corals to different environmental conditions including pCO2 and temperature. [ABSTRACT FROM AUTHOR]

The impacts of human and natural disturbances on coral reefs are typically quantified through visible damage (e.g., reduced coral coverage as a result of bleaching events), but changes in environmental conditions may also cause damage in less visible ways. Despite the current paradigm, which suggests consistent, highly synchronized spawning events, corals that reproduce by broadcast spawning are particularly vulnerable because their reproductive phenology is governed by environmental cues. Here, we quantify coral spawning intensity during four annual reproductive seasons, alongside laboratory analyses at the polyp, colony, and population levels, and we demonstrate that, compared with historical data, several species from the Red Sea have lost their reproductive synchrony. Ultimately, such a synchrony breakdown reduces the probability of successful fertilization, leading to a dearth of new recruits, which may drive aging populations to extinction. [ABSTRACT FROM AUTHOR]

Climate change and anthropogenic pressures inflict a wide range of profound damages on coral reef ecosystems, reshaping coral reef communities due to their physiological and ecological intolerance to the newly developing environmental conditions. Here, I present coral chimerism as an evolutionary rescue tool for accelerating adaptive responses to global climate change impacts. The "evolutionary rescue" power is contingent on the premise that coral chimerism counters the erosion of genetic and phenotypic diversity. Further benefits are gained when flexible chimeric entities alter their somatic constituents following changes in environmental conditions, synergistically presenting the best‐fitting combination of their genetic components to endure in a capricious environment, exhibiting always their environmentally matched physiological characteristics. Chimerism should be considered as an integral part of the ecological engineering toolbox being developed for active reef restoration. Coral chimerism can be used as an evolutionary rescue instrument for accelerating adaptive responses to global climate change assaults. Three hypothetical scenarios for such situations are illustrated: Scenario 1 exhibits a case where a chimera gains benefits by sharing different two traits; scenario 2 presents a case where the partners in the chimera perform differently on a single trait; and scenario 3 reflects a multichimerism case, where three or more genotypes share the chimeric entity. The three scenarios follow the tenet that chimerism in corals is a cell mixed state rather than sectorial. [ABSTRACT FROM AUTHOR]

Most coral reefs worldwide are threatened by natural and anthropogenic impacts. Among them, the release in seawater of sunscreen products commonly used by tourists to protect their skin against the harmful effects of UV radiations, can affect tropical corals causing extensive and rapid bleaching. The use of inorganic (mineral) filters, such as zinc and titanium dioxide (ZnO and TiO 2 ) is increasing due to their broad UV protection spectrum and their limited penetration into the skin. In the present study, we evaluated through laboratory experiments, the impact on the corals Acropora spp. of uncoated ZnO nanoparticles and two modified forms of TiO 2 (Eusolex®T2000 and Optisol™), largely utilized in commercial sunscreens together with organic filters. Our results demonstrate that uncoated ZnO induces a severe and fast coral bleaching due to the alteration of the symbiosis between coral and zooxanthellae. ZnO also directly affects symbiotic dinoflagellates and stimulates microbial enrichment in the seawater surrounding the corals. Conversely, Eusolex® T2000 and Optisol™ caused minimal alterations in the symbiotic interactions and did not cause bleaching, resulting more eco-compatible than ZnO. Due to the vulnerability of coral reefs to anthropogenic impacts and global change, our findings underline the need to accurately evaluate the effect of commercial filters on stony corals to minimize or avoid this additional source of impact to the life and resilience ability of coral reefs. [ABSTRACT FROM AUTHOR]

Coral reef ecosystems have great economic, social, and ecological value. The ecological success of coral reef ecosystems critically depends on coral-algal symbiosis and coral-prokaryotic partnership. However, seasonal changes underlying these relationships in subtropical hard corals of Hong Kong are poorly studied. Here, we compared the community changes of algal symbionts and prokaryotic partners in Platygyra carnosa and Galaxea fascicularis from Hong Kong collected at two seasonal time points of winter and summer via massively parallel sequencing of genetic markers and multivariate analysis. The results indicated that algal symbionts showed no significant changes between the two seasonal time points but prokaryotic partners changed substantially. Prokaryotic partners putatively involved in photosynthesis, nitrogen fixation, and sulfur oxidation increased significantly from winter to summer, while prokaryotic partners potentially associated with chemosynthesis, ammonia oxidation, and nitrite oxidation decreased significantly from winter to summer. Dissolved oxygen and pH served as the main contributors influencing prokaryotic partners in winter, while temperature, turbidity, and salinity played a dominant role in shaping prokaryotic partners in summer. The findings of the present study suggest that season structures prokaryotic partners but not algal symbionts in subtropical hard corals. [ABSTRACT FROM AUTHOR]

Intensive underwater surveys have been conducted to assess the extent of coral bleaching and subsequent mortality in the Gulf of Mannar between March and October 2016. The extent of bleaching was 23.92% ± 10.55% during the period between March and June 2016, and the live coral cover was drastically reduced to 22.69 ± 9.07% during October 2016 with a mortality of 16.17 ± 8.46%. Fast-growing coral forms, including the genera Acropora, Montipora and Pocillopora were most affected, not only by bleaching but also by severe mortality. Boulders, including the genera Porites, Favia and Favites were found to be resistant to bleaching. During the bleaching period, water temperature was between 31.2°C and 32.6°C. The current bleaching is in alignment with the third global coral bleaching event which occurred between 2014 and 2017. Management interventions, including protection and rehabilitation using the native resistant coral species will not only help in the recovery process, but also increase the live coral cover. [ABSTRACT FROM AUTHOR]

Understanding temporal and spatial variation of coral reef communities allows us to analyze the relative effects of local stressors, such as fishing and eutrophication, and global stressors, such as ocean warming. To test for spatial and temporal changes in coral reef communities, we combined recent benthic and fish surveys from 2016 with long-term data, dating back to the late 1990s, from four zones located at different distances from Central Havana, Cuba's largest population center. These changes may indicate the shifting importance of local vs global stressors affecting reef communities. Regardless of the distance from Havana, we found that coral cover was uniformly low (approximately 10%), whereas macroalgal abundance was often high (approximately 65%). Similarly, fish biomass was low across zones, particularly for herbivorous fishes (approximately 12 g m-2) that are critical ecological drivers of reef structure and coral resilience. Analyses of longer-term trends revealed that coral cover near Havana has been below about 10% since at least 1995, potentially because of local stressors. In contrast, reefs farther from Havana maintained relatively high coral cover (approximately 30%) until the early 2000s, but declined more recently to approximately 15%, putting them near the Caribbean-wide average. These distinct spatial and temporal trajectories of reef communities may be the result of the expansion of local stressors away from Havana as the human population increased, or as fishers ventured farther away to exploit new resources. Alternatively, the more recent decline of reefs farther from population centers may have resulted from increasingly frequent global stressors, such as bleaching events and hurricanes. [ABSTRACT FROM AUTHOR]

From long-term stratigraphic records in Pacific Island archaeological sites, researchers have documented alterations to molluskan species richness and abundance, decreases or increases in mollusk shell size and, in rare cases, human foraging may have contributed to the extirpation of mollusk taxa. Mollusks perform critical ecosystem functions in tropical intertidal environments, including improving water quality through filtration, regulating algal cover, and increasing habitat and substratum complexity through ecosystem engineering. These critical ecosystem functions can be negatively affected by human foraging, possibly contributing to decreased resilience of coral reefs to climatic alterations. We review modern ecological research on human impacts to mollusks and intertidal ecosystems that illustrates the mechanisms and effects of human foraging. We then examine centuries to millennial scale archaeological records from the Pacific Islands to understand long-term, time-averaged trends in human impacts to intertidal ecosystems. [ABSTRACT FROM AUTHOR]

Yongxing Island is a coral reef island formed by the growth and accumulation of corals and other skeletal fragments on a reef platform. The reef flat is developed around the entire island. The southeast reef flat and the north and northwest reef flat are asymmetrical in proportions, showing significant differences in reef‐flat width, patterns of sedimentary and ecological zonation, fore‐reef slope gradients, and submarine geomorphic features. Through application of an underwater survey, measurements and statistics were recorded on the extensional pattern of the Yongxing reef platform, the reef pool, and the spur–groove systems incised on the reef crests and forereefs. It is demonstrated that the Yongxing reef platform is an irregular ovoid in form with a distinct NW‐SE elongation that includes gently and steeply sloping forereefs and fore‐reef slopes. A gradual transition to the deep sea basin occurs in the southeast part of the Yongxing reef platform, whereas a steep forereef and fore‐reef slope that rapidly transition to the deep‐water basin are more characteristic of the north and northwest sectors of the Yongxing reef platform. The width of the reef platform in the southeast direction is much greater than that in the northwest direction. Correspondingly, the developmental pattern of the north and northwest reef crest and forereef is different from that of the southeast reef crests and forereefs. The southeast reef crest and forereef are characterized by reef pools with various shapes, different water depths, and discontinuous tidal channels on the outer reef flat. In contrast, the north and northwest reef crest and forereef developed a typical spur‐and‐groove system. The former is related to coral reef growth and construction, whereas the latter is shaped by wave or tide flow scouring that contributes to substrate erosion. Similar geomorphic features are known from examples of Indian‐Pacific and Caribbean‐Atlantic reef crests and forereefs, but the occurrence of such features in different parts of the same reef platform provides a new example of reef crest and forereef development. The differences in slope gradient of forereef and fore‐reef slopes (gentle vs. steep in transition), the development of contrasting submarine platform widths in different directions, as well as other submarine geomorphic features on reef crests and forereefs around the reef flats of Yongxing Island may be related to the confluence of several factors. These include the tectonic uplift of reef platform, the island's initial underwater topography, the windward and leeward positions, the direction and strength of winter and summer monsoon, the sea‐water dynamics, and the substrate characteristics related to coral reef growth. [ABSTRACT FROM AUTHOR]

Impacts of global climate change on coral reefs are being amplified by pulse heat stress events, including El Niño, the warm phase of the El Niño Southern Oscillation (ENSO). Despite reports of extensive coral bleaching and up to 97% coral mortality induced by El Niño events, a quantitative synthesis of the nature, intensity, and drivers of El Niño and La Niña impacts on corals is lacking. Herein, we first present a global meta-analysis of studies quantifying the effects of El Niño/La Niña-warming on corals, surveying studies from both the primary literature and International Coral Reef Symposium (ICRS) Proceedings. Overall, the strongest signal for El Niño/La Niña-associated coral bleaching was long-term mean temperature; bleaching decreased with decreasing long-term mean temperature (n = 20 studies). Additionally, coral cover losses during El Niño/La Niña were shaped by localized maximum heat stress and long-term mean temperature (n = 28 studies). Second, we present a method for quantifying coral heat stress which, for any coral reef location in the world, allows extraction of remotely-sensed degree heating weeks (DHW) for any date (since 1982), quantification of the maximum DHW, and the time lag since the maximum DHW. Using this method, we show that the 2015/16 El Niño event instigated unprecedented global coral heat stress across the world's oceans. With El Niño events expected to increase in frequency and severity this century, it is imperative that we gain a clear understanding of how these thermal stress anomalies impact different coral species and coral reef regions. We therefore finish with recommendations for future coral bleaching studies that will foster improved syntheses, as well as predictive and adaptive capacity to extreme warming events. [ABSTRACT FROM AUTHOR]

Coral reefs in the Caribbean Sea have progressively degraded in recent decades due to multiple stressors that include the mass mortality of a keystone invertebrate herbivore, Diadema antillarum (Philippi, 1845), in the 1980s. The population of D. antillarum in the Florida Keys has yet to recover, but recent advances in rearing captive-spawned D. antillarum have raised the possibility that D. antillarum can be produced in captivity and released into the wild as part of coral reef restoration efforts. However, organisms raised under artificial conditions could differ from their wild counterparts in ways that might reduce their fitness. Therefore, we conducted a series of experiments that compared the behavioral and morphological characteristics of hatchery-propagated and wild-collected D. antillarum. We demonstrate that hatchery-propagated D. antillarum raised in a non-rugose environment do not display the crevice shelter-seeking behavior of wild individuals. However, they did respond to the chemosensory stimulus of a potential predator, although they did not exhibit the escape behavior exhibited by wild individuals. Hatchery-propagated D. antillarum also exhibited lower spine density than wild individuals, likely the result of being maintained in conditions that did not induce spine breakage. However, this apparent habitat-induced morphological deficit was mitigated by maintaining them in rugose conditions. Our results suggest that competent hatchery-propagated D. antillarum can eventually be produced for coral reef restoration efforts, but they also underscore the need to further evaluate whether the behavioral deficiencies we identified can be effectively mitigated to ensure that ecologically competent individuals can be produced for such efforts. [ABSTRACT FROM AUTHOR]

In situnurseries have been a crucial part of coral reef restoration initiatives for the past two decades. However, the advantages over direct transplantation in sedimented waters has yet to be examined. In the present study, we showed thatPachyseris speciosaandPocillopora damicornisfragments reared inin situnurseries (NR) in Singapore’s sedimented waters grew significantly faster (by three to five times) than those which were directly transplanted (DT) onto the substrates. The increased growth rate during the nursery phase augmented the size of NR transplants, and had a flow-on effect on their performance during the post-transplantation phase. Overall, the maximum diameter of the NR transplants was 1.8–2.7 times larger than DT transplants after 11 months. The growth enhancement of the nursery-reared transplants improved the cost-effectiveness of our restoration effort: the estimated cost per centimetre growth of NR transplants was one-fifth of the DT corals despite the additional costs incurred to construct the nurseries. These results highlight that coral nurseries are beneficial to reef restoration in chronically sedimented waters. [ABSTRACT FROM AUTHOR]

Shallow water depth measurements using multispectral images are crucial for marine surveying and mapping. At present, relevant studies either depend on the use of other auxiliary data (such as field water depths or water column data) or contain too many unknown variables, thus making these studies suitable only for images that contain enough visible wavebands. To solve this problem, a Quasi-Analytical Algorithm (QAA) approach is proposed in this paper for estimating the water depths aroundWeizhou Island by developing a QAA to estimate the diffuse attenuation coefficients and simplifying the parameterization of the bathymetric model. The approach contains an initialization sub-approach and a novel global adjustment sub-approach. It is not only independent of other auxiliary data but also greatly reduces the number of unknowns. Experimental results finally demonstrated that the Root Mean Square Errors (RMSEs) were 1.01 m and 0.77 m for the ZY-3 image and the WorldView-3 (WV-3) image, respectively, so the approach is competitive to other QAA bathymetric methods. Besides, the global adjustment sub-approach was also seen to be superior to common smoothing filters: if the Signal-to-Noise Ratio (SNR) is as low as 42, i.e., ZY-3, it can smooth the water depths and improve the accuracies, otherwise can avoid the over-smoothing of water depths. [ABSTRACT FROM AUTHOR]

With the rapid rise in pollution-associated nitrogen inputs to the western Pacific, it has been suggested that even the open ocean has been affected. In a coral core from Dongsha Atoll, a remote coral reef ecosystem, we observe a decline in the 15N/14N of coral skeleton–bound organic matter, which signals increased deposition of anthropogenic atmospheric N on the open ocean and its incorporation into plankton and, in turn, the atoll corals. The first clear change occurred just before 2000 CE, decades later than predicted by other work. The amplitude of change suggests that, by 2010, anthropogenic atmospheric N deposition represented 20 ± 5% of the annual N input to the surface ocean in this region, which appears to be at the lower end of other estimates. [ABSTRACT FROM AUTHOR]

The genus Symbiodinium plays an essential role in the resistance and survival of reef-building corals during temperature anomalies. Coral colonies inhabiting the Persian Gulf ( PG) experience extended periods of different stresses. Kish Island is located in the harsh environment of the Northern PG with previously reported bleaching episodes. Samples of six coral species from Northwestern Kish Island were analysed by internal transcribed spacer 2 of ribosomal DNA to identify in hospite Symbiodinium populations. The results showed that lineage D of Symbiodinium was the most prevalent clade among different coral colonies, while clade C was only detected in symbiosis with a single coral species. However, the detected Symbiodinium subclades belonged to two host generalists. The predominance of the stress tolerant Symbiodinium trenchii and subclade C3 could suggest an acclimatization strategy to cope with the hostile environment of the PG. [ABSTRACT FROM AUTHOR]

Environmental stressors in coastal areas threaten the sustainability of marine resources and reduce their resilience to climate change impacts. Accelerated land erosion is a major stressor that leads to increased turbidity and sedimentation on downstream coral reefs and the degradation of ecosystem functions. Volunteers from a community-based initiative in Guam installed 130 tree seedlings and 54 m of sediment filter socks in eroding hillsides above Fouha Bay, to reduce erosion. A soil probing method for measuring soil depth was developed and used to evaluate the effectiveness of the watershed restoration tools. The trees and socks trapped 111.8 tons of sediment on land after 21 months. In heavily eroding portions of the restoration plot, where socks and trees were used in combination, the mean sediment trapping efficiency was 44 kg m −2 yr −1 . Previous studies indicate a 75% reduction in sedimentation rate is required to bring Fouha Bay below severe-catastrophic sedimentation stress (>50 mg cm −2 day −1 ). Based on the observed sediment trapping efficiency of restoration tools in this study, an estimated 0.05 km 2 of severely eroding hillsides must be treated with 19 km of socks and 11,000 trees to trap 2121 tons of sediment and achieve the necessary reduction. If sediment input into the bay is controlled, existing sediment will clear out with storm-driven swells. As shown in other high islands, coral reefs are resilient and can recover after sedimentation stress is reduced. Data generated on the efficiency of watershed restoration tools in this study can be used in watershed management plans to promote the sustainability and resilience of coastal areas in other tropical islands. [ABSTRACT FROM AUTHOR]

The growing coastal development, dredging and dumping activities, overfishing and expansion of marine cage culture in Nha Trang Bay ( NTB) of Central Vietnam since the beginning of the 2000s have resulted in a dramatic decrease of live coral cover. Surveys conducted in April-May 2013 and the same period in 2014 revealed that with an increase in distance from the outer part of the bay towards the mainland, the rivers' influxes and dredged areas, coral cover decreased from 75% to 0.6% and species richness from 63 to 5, while the abundance of macroalgae increased from 0% to 56%. These changes correlate with differences in the concentration of suspended sediments on the same gradient. The abundance of the crown-of-thorns starfish Acanthaster planci and of the echinoid Diadema setosum significantly increased between the first estimation in 1998 and the survey in 2014, from 0 to 1.7 individuals (ind.) per 100 m−2 and from 50.8 to 94.5 ind. per 100 m−2, respectively, contributing to coral loss and intensive bioerosion of the reef framework in the bay. The large sizes of adult colonies of tabulate Acropora on the remote stations with negligible sedimentation and eutrophication loads were inconsistent with the assumptions that temperature-induced coral bleaching or cyclones could be the major impacts in Nha Trang Bay. Analysis of the 16-year thermal history of the bay did not reveal any instances in which the coral thermal bleaching threshold had been exceeded up to the present study. Seasonal upwelling, which occurs annually in the vicinity of Central Vietnam, may contribute to mitigation of thermal anomalies within NTB and to the maintenance of healthy coral communities on the remote reefs with relatively low anthropogenic impact. [ABSTRACT FROM AUTHOR]

The article offers information about a study related to morphological plasticity of the depth generalist coral, Montastraea cavernosa, on mesophotic reefs in Bermuda. Topics discussed include importance of Scleractinian corals; ways in which reef building corals form the architectural framework for shallow water tropical reef systems, that supports the most productive and biologically diverse marine ecosystems; and corals' ability to adapt to low light conditions and protect certain species.

The Great Barrier Reef ( GBR) is an iconic coral reef system extending over 2000 km along the north-east coast of Australia. Global recognition of its Outstanding Universal Value resulted in the listing of the 348 000 km2 GBR World Heritage Area ( WHA) by UNESCO in 1981. Despite various levels of national and international protection, the condition of GBR ecosystems has deteriorated over the past decades, with land-based pollution from the adjacent catchments being a major and ongoing cause for this decline. To reduce land-based pollution, the Australian and Queensland Governments have implemented a range of policy initiatives since 2003. Here, we evaluate the effectiveness of existing initiatives to reduce discharge of land-based pollutants into the waters of the GBR. We conclude that recent efforts in the GBR catchments to reduce land-based pollution are unlikely to be sufficient to protect the GBR ecosystems from declining water quality within the aspired time frames. To support management decisions for desired ecological outcomes for the GBR WHA, we identify potential improvements to current policies and incentives, as well as potential changes to current agricultural land use, based on overseas experiences and Australia's unique potential. The experience in the GBR may provide useful guidance for the management of other marine ecosystems, as reducing land-based pollution by better managing agricultural sources is a challenge for coastal communities around the world. [ABSTRACT FROM AUTHOR]

The high importance of bathymetric character for many processes on reefs means that high-resolution bathymetric models are commonly needed by marine scientists and coastal managers. Empirical and optimisation methods provide two approaches for deriving bathymetry from multispectral satellite imagery, which have been refined and widely applied to coral reefs over the last decade. This paper compares these two approaches by means of a geographical error analysis for two sites on the Great Barrier Reef: Lizard Island (a continental island fringing reef) and Sykes Reef (a planar platform reef). The geographical distributions of model residuals (i.e., the difference between modelled and measured water depths) are mapped, and their spatial autocorrelation is calculated as a basis for comparing the performance of the bathymetric models. Comparisons reveal consistent geographical properties of errors arising from both models, including the tendency for positive residuals (i.e., an under-prediction of depth) in shallower areas and negative residuals in deeper areas (i.e., an over-prediction of depth) and the presence of spatial autocorrelation in model errors. A spatial error model is used to generate more reliable estimates of bathymetry by quantifying the spatial structure (autocorrelation) of model error and incorporating this into an improved regression model. Spatial error models improve bathymetric estimates derived from both methods. [ABSTRACT FROM AUTHOR]

As for terrestrial remote sensing, pixel-based classifiers have traditionally been used to map coral reef habitats. For pixel-based classifiers, habitat assignment is based on the spectral or textural properties of each individual pixel in the scene. More recently, however, object-based classifications, those based on information from a set of contiguous pixels with similar properties, have found favor with the reef mapping community and are starting to be extensively deployed. Object-based classifiers have an advantage over pixel-based in that they are less compromised by the inevitable inhomogeneity in per-pixel spectral response caused, primarily, by variations in water depth. One aspect of the object-based classification workflow is the assignment of each image object to a habitat class on the basis of its spectral, textural, or geometric properties. While a skilled image interpreter can achieve this task accurately through manual editing, full or partial automation is desirable for large-scale reef mapping projects of the magnitude which are useful for marine spatial planning. To this end, this paper trials the use of multinomial logistic discrete choice models to classify coral reef habitats identified through object-based segmentation of satellite imagery. Our results suggest that these models can attain assignment accuracies of about 85%, while also reducing the time needed to produce the map, as compared to manual methods. Limitations of this approach include misclassification of image objects at the interface between some habitat types due to the soft gradation in nature between habitats, the robustness of the segmentation algorithm used, and the selection of a strong training dataset. Finally, due to the probabilistic nature of multinomial logistic models, the analyst can estimate a map of uncertainty associated with the habitat classifications. Quantifying uncertainty is important to the end-user when developing marine spatial planning scenarios and populating spatial models from reef habitat maps. [ABSTRACT FROM AUTHOR]

Coral reefs are considered one of the ecosystems most vulnerable to ongoing global climate change. However, geographic and taxonomic responses to climate change are highly variable, and fundamental aspects of key research approaches remain unresolved, leaving substantial uncertainty in our ability to predict the future of coral reefs. I review the ecological and evolutionary response of coral reefs to climate change in a broad temporal context, primarily focusing on tropical reef corals. I show critical gaps in our understanding that impede accurate prediction of future responses. These gaps include the response of past reefs to global change, the interpretation of coral response to thermal stress and ocean acidification, how corals and other reef organisms might respond evolutionarily, and our approach to evaluating response to climate in the context of multiple stressors. Reducing uncertainty by filling these gaps and by incorporating variation in geographic and taxonomic response will substantially improve our ability to model coral reef futures and manage coral reefs. [ABSTRACT FROM AUTHOR]

Shallow coral reefs threatened by climate change must be spatio-temporally analyzed in terms of their protection of coastal human populations. This study combines Japanese spatio-temporal gradients of population/asset and coral buffering exposure to stress-inducing and stress-mitigating factors so that the socio-economic and ecological (SEE) resilience tied to coral reefscapes can be regionally mapped (1200 km) at a fine resolution (1 arcsec) over a decade (11 years). Fuzzy logic was employed to associated environmental factors based on the related population/asset/coral buffering responses, as found in the literature. Once the factors were weighted according to their resilience contributions, temporally static patterns were evident: (1) a negative correlation occurs between coral buffering resilience and latitude; (2) the least resilient islands are low-lying, deprived of wide reef barriers, and located on the eastern and southern boundaries of the Nansei archipelago; (3) the southwestern-most, middle and northeastern-most islands have the same SEE resilience; and (4) Sekisei Lagoon islands have a very high coral buffering resilience. To overcome uncertainty, future studies should focus on the socio-ecological adaptive capacity, fine-scale ecological processes (such as coral and fish functional groups) and the prediction of the flood risks in the coming decades. [ABSTRACT FROM AUTHOR]

Globally marine fungal diversity is poorly known, especially in Mexico. We evaluated the diversity of marine ascomycetes on five tourist beaches on Cozumel Island in September 2004, and in February 2007. Fifty sample units were collected randomly from each beach during each sampling time. Seven species were recovered, of which Lindra thalassiae and Corollospora maritima were the most dominant species. Corollospora gracilis and Lulworthia grandispora are new records for Cozumel Island. The highest diversity value was found in San Francisco beach, probably because the surrounding coral reefs are an important source of a wide variety of substrata for these fungi. [ABSTRACT FROM AUTHOR]

Small-scale experiments and theory suggest that ecological functions provided by communities become more stable with increased species richness. Whether these patterns manifest at regional spatial scales and within species-rich communities (e.g., coral reefs) is largely unknown. We quantified five biogeochemical processes, and an aggregate measure of multifunctionality, in species-rich coastal fish communities to test three questions: (1) Do previously predicted biodiversity-ecosystem-function relationships hold across large spatial scales and in highly diverse communities? (2) Can additional covariates of community structure improve these relationships? (3) What is the role of community biomass and functional group diversity in maintaining biogeochemical processes under various scenarios of species loss across ecosystem types? These questions were tested across a large regional gradient of coral reef, mangrove and seagrass ecosystems. Statistical models demonstrated that species richness and the mean maximum body size per species strongly predicted biogeochemical processes in all ecosystem types, but functional group diversity was only a weak predictor. Simulating three scenarios of species loss demonstrated that conserving community biomass alone increased the ability for communities to maintain ecosystem processes. Multifunctionality of biogeochemical processes was maintained least in simulations that conserved biomass and community structure, underscoring the relative lack of importance of community structure in maintaining multiple simultaneous ecosystem functions in this system. Findings suggest that conserving community biomass alone may be sufficient to sustain certain biogeochemical processes, but when considering conservation of multiple simultaneous biogeochemical processes, management efforts should focus first on species richness. [ABSTRACT FROM AUTHOR]

The article discusses findings of a study by Jules Jaffe and colleagues at the Scripps Institution of Oceanography at the University of California, San Diego, California, which examines the ecological behavior of free-floating single-celled ocean plankton. The study explores the use of a transmission illumination for plankton imaging to a stationary coral reefs. The study also allows researchers to examine the behavior of planktons towards coral reefs.

The article discusses the monitoring, prediction and management of Australia's Great Barrier Reef (GBR), one of the seven Natural Wonders of the World. It mentions the findings of a 2007 report by Access Economics for the Great Barrier Reef Marine Park Authority on the contributions of the GBR in the country's economy. Also discussed are several threats to the GBR including the declining water quality, climate change and tropical cyclones.

While bleaching events have received wide public attention, little attention has been given to the follow on effects on coral reefs. Bleached colonies of five species of Acropora of known age were sampled to study rates and agents of internal bioerosion at two sites on the southern Great Barrier Reef. The dominant erosion agents were worms and sponges and up to 23% of branches were eroded after 37 months. Significant differences were exhibited between species and between sites in terms of the animals responsible for internal erosion. The significance of bleaching and subsequent death of coral colonies is discussed with regard to their increased susceptibility storm damage and the loss of associated fish and invertebrates dependent on these habitat forming corals. [ABSTRACT FROM AUTHOR]

A "black water" event, as observed from satellites, occurred off southwest Florida in 2012. Satellite observations suggested that the event started in early January and ended in mid-April 2012. The black water patch formed off central west Florida and advected southward towards Florida Bay and the Florida Keys with the shelf circulation, which was confirmed by satellite-tracked surface drifter trajectories. Compared with a previous black water event in 2002, the 2012 event was weaker in terms of spatial and temporal coverage. An in situ survey indicated that the 2012 black water patch contained toxic K. brevis and had relatively low CDOM (colored dissolved organic matter) and turbidity but high chlorophyll-a concentrations, while salinity was somewhat high compared with historical values. Further analysis revealed that the 2012 black water was formed by the K. brevis bloom initiated off central west Florida in late September 2011, while river runoff, Trichodesmium and possibly submarine groundwater discharge also played important roles in its formation. Black water patches can affect benthic coral reef communities by decreasing light availability at the bottom, and enhanced nutrient concentrations from black water patches support massive macroalgae growth that can overgrow coral reefs. It is thus important to continue the integrated observations where satellites provide synoptic and repeated observations of such adverse water quality events. [ABSTRACT FROM AUTHOR]

The northern reef of Yongxing Island, the largest reef island of the Xisha Islands in the South China Sea, was in good condition with significant cover of scleractinian corals until 2002. Surveys in 2008 and 2010, however, found that coral coverage had declined rapidly and severely, implying that catastrophic coral mortality occurred during the past 8 years. A blackish mat was observed covering live and dead corals in both 2008 and 2010 that was identified as an encrusting sponge, Terpios hoshinota, by special surface morphology and spicule structure. In addition, spicule residues were found on the surface of long-dead corals, indicating a previous invasion of T. hosinota. T. hoshinota is referred to as the 'black disease' because it rapidly overgrows and kills corals. Our evidence indicates that outbreaks of black disease are at least partially responsible for the massive coral mortality at the northern reef of Yongxing Island over the past 8 years, although human activities and heat-related coral bleaching cannot be discounted as minor causes for this coral decline. [ABSTRACT FROM AUTHOR]

The thermal environment of a coral reef is moderated by complex interactions of air-sea heat and moisture fluxes, local to synoptic-scale weather and reef hydrodynamics. Measurements of air-sea energy fluxes over coral reefs are essential to understanding the reef-atmosphere processes that underpin coral reef environmental conditions such as water temperature, cloud, precipitation, and local winds (such as during coral bleaching events). Such measurements over coral reefs have been rare, however, and the spatial heterogeneity of surface-atmosphere energy exchanges due to the different geomorphic and biological zones on coral reefs has not been captured. Accordingly, the heterogeneity of coral reefs with regard to substrate, benthic communities, and hydrodynamic processes has not been considered in the characterization of the surface radiation budget and energy balance of coral reefs. Here, the first concurrent in situ eddy covariance measurements of the surface energy balance and radiation transfers over different geomorphic zones of a coral reef are presented. Results showed differences in radiation transfers and sensible and latent heat fluxes over the reef, with higher Bowen ratios over the shallow reef flat zone. The energy flux divergence between sites increased with wind speed and during unstable, southeasterly trade winds with the net flux of heat being positive and negative over different geomorphic zones. The surface drag coefficient at measurement height ranged from 1 × 10−3 to 2.5 × 10−3, with no significant difference between sites. Results confirm that spatial variation in radiation and air-reef-water surface heat and moisture fluxes occurs across a lagoonal platform reef in response to local meteorological conditions, hydrodynamics, and benthic-substrate cover. [ABSTRACT FROM AUTHOR]

The article presents a comparison of the climate change prevention strategies that have been implemented to protect the coral reefs in Australia and France as of January 2012, focusing on Australia's Great Barrier Reef, the potential impact of overfishing on coral reefs, and unsustainable coastal development. Australian and French marine management systems and the establishment of Marine Protected Areas are addressed, along with ecosystem governance and the economic aspects of climate change.

The article reports that while coral reef degradation has been extensively documented, the fate of other reef-associated metazoans such as invertebrate animals has not received sufficient attention. It mentions that coral reefs provide essential habitat niches for an estimated 93,000 global species richness grouped into 31 animal phyla, many are undiscovered because of their cryptic or sibling nature. The article also warns of a large-scale extinction following the loss of reef corals.

As the effects of climate change have become increasingly visible over the past three decades, coral reefs have suffered from a number of natural and anthropogenic disturbances that have caused a critical decline in coral populations. Among these disturbances are coral diseases, which have appeared with increasing frequency and severity, often in correlation with increases in water temperature. Although the crucial role played by Vibrio species in coral disease has been widely documented, the scientific community does not yet fully understand the infection process of Vibrio or its impact on coral physiology and immunology. Here, we investigated the physiological and transcriptomic responses of a major reef-building coral, Pocillopora damicornis, when exposed to a specific pathogen (Vibrio coralliilyticus) under virulent (increasing water temperature) and non-virulent (constant low temperature) conditions. The infection process was examined by electron microscopy and quantitative reverse-transcription PCR, and coral health was monitored by visual observations and measurements of zooxanthellar density. The results obtained suggest that coral tissue invasion occurs upon increasing water temperature only. Transcriptomic variations were investigated using a suppression-subtractive-hybridization approach, and the expression levels of six candidate immune-related genes were examined during bacterial exposure. These genes correspond to three lectin-like molecules putatively involved in the recognition of pathogens, two metal-binding proteins putatively involved in antibacterial response and one cystein protease inhibitor. The transcription patterns of these selected genes provide new insights into the responses of coral colonies to virulent versus non-virulent bacteria. [ABSTRACT FROM AUTHOR]

Coral diseases have increased in frequency over the past few decades and have important influences on the structure and composition of coral reef communities. However, there is limited information on the etiologies of many coral diseases, and pathways through which coral diseases are acquired and transmitted are still in question. Furthermore, it is difficult to assess the impacts of disease on coral populations because outbreaks often co-occur with temperature-induced bleaching and anthropogenic stressors. We developed spatially explicit population models of coral disease and bleaching dynamics to quantify the impact of six common diseases on Florida Keys corals, including aspergillosis, dark spots, white band, white plague, white patch, and Caribbean yellow band. Models were fit to an 8-year data set of coral abundance, disease prevalence, and bleaching prevalence. Model selection was used to assess alternative pathways for disease transmission, and the influence of environmental stressors, including sea temperature and human population density, on disease prevalence and coral mortality. Classic disease transmission from contagious to susceptible colonies provided the best-fit model only for aspergillosis. For other diseases, external disease forcing, such as through a vector or directly from pathogens in the environment, provided the best fit to observed data. Estimates of disease reproductive ratio values (R 0) were less than one for each disease, indicating coral colonies were below densities required for diseases to become established through contagious spread alone. Incidences of white band and white patch disease were associated with greater susceptibility or slower recovery of bleached colonies, and no disease outbreaks were associated with periods of elevated sea temperatures alone. Projections of best-fit models indicated that, at least during the period of this study, disease and bleaching did not have substantial impacts on populations and impaired rates of population growth appeared to be attributable to other stressors. By applying epidemiological models to field data, our study gives qualitative insights into the dynamics of coral diseases, relative stressor impacts, and directions for future research. [Copyright &y& Elsevier]

Reef corals are examples of metazoans that engage in mutualisms with a variety of microorganisms, including dinoflagellates, Bacteria, Archaea, and viruses. The high adaptive capacity of these microbial symbionts can be co-opted by their coral hosts, and various emergent traits of these associations, such as thermotolerance, are undergoing strong selection due to climate change. This selection may spur the rise of microbial 'disaster taxa': opportunistic, cosmopolitan generalists that can proliferate and increase host survivorship following disturbances. Coral bleaching (a stress-induced loss of dinoflagellates) constitutes one type of catastrophic disturbance for resident symbiont communities, and opens novel patches of host for colonization by microbial disaster taxa. Moreover, the compartmentalization of microbial symbionts within coral polyps reduces their effective population size and thus facilitates the spread of disaster taxa during times of environmental change. These phenomena suggest that, despite widespread loss of coral cover as a result of climate disturbances, the potential spread of resilient microbial disaster taxa in surviving colonies can have important implications for coral reef persistence over the coming decades. [ABSTRACT FROM AUTHOR]

Anthropogenic rise in the carbon dioxide concentration in the atmosphere leads to global warming and acidification of the oceans. Ocean acidification (OA) is harmful to many organisms but especially to those that build massive skeletons of calcium carbonate, such as reef corals. Here, we test the recent suggestion that OA leads not only to declining calcification of reef corals and reduced growth rates of reefs but may also have been a trigger of ancient reef crises and mass extinctions in the sea. We analyse the fossil record of biogenic reefs and marine organisms to (1) assess the timing and intensity of ancient reef crises, (2) check which reef crises were concurrent with inferred pulses of carbon dioxide concentrations and (3) evaluate the correlation between reef crises and mass extinctions and their selectivity in terms of inferred physiological buffering. We conclude that four of five global metazoan reef crises in the last 500 Myr were probably at least partially governed by OA and rapid global warming. However, only two of the big five mass extinctions show geological evidence of OA. [ABSTRACT FROM AUTHOR]

Human activities threaten reef ecosystems globally, forcing ecological change at rates and scales regarded as unprecedented in the Holocene. These changes are so profound that a cessation of reef accretion (reef 'turn-off') and net erosion of reef structures is argued by many as the ultimate and imminent trajectory. Here, we use a regional scale reef growth dataset, based on 76 core records (constrained by 211 radiometric dates) from 22 reefs along and across the inner-shelf of the Great Barrier Reef, Australia, to examine the timing of different phases of reef initiation ('turn-on'), growth and 'turn-off' during the Holocene. This dataset delineates two temporally discrete episodes of reef-building over the last 8500 years: the first associated with the Holocene transgression-early highstand period [∼8.5-5.5 k calibrated years (cal y)]; the second since ∼2.3 k cal y. During both periods, reefs accreted rapidly to sea level before entering late evolutionary states - states naturally characterized by reduced coral cover and low accretion potential - and a clear hiatus occurs between these reef-building episodes for which no records of reef initiation exist. These transitions mimic those projected under current environmental disturbance regimes, but have been driven entirely by natural forcing factors. Our results demonstrate that, even through the late Holocene, reef health and growth has fluctuated through cycles independent of anthropogenic forcing. Consequently, degraded reef states cannot de facto be considered to automatically reflect increased anthropogenic stress. Indeed, in many cases degraded or nonaccreting reef communities may reflect past reef growth histories (as dictated by reef growth-sea level interactions) as much as contemporary environmental change. Recognizing when changes in reef condition reflect these natural 'turn-on'- growth -'turn-off' cycles and how they interact with on-going human disturbance is critical for effective coral reef management and for understanding future reef ecological trajectories. [ABSTRACT FROM AUTHOR]

Coral reefs are under increasing pressure in a changing climate, one such threat being more frequent and destructive outbreaks of coral diseases. Thermal stress from rising temperatures has been implicated as a causal factor in disease outbreaks observed on the Great Barrier Reef, Australia, and elsewhere in the world. Here, we examine seasonal effects of satellite-derived temperature on the abundance of coral diseases known as white syndromes on the Great Barrier Reef, considering both warm stress during summer and deviations from mean temperatures during the preceding winter. We found a high correlation (r2 = 0.953) between summer warm thermal anomalies (Hot Snap) and disease abundance during outbreak events. Inclusion of thermal conditions during the preceding winter revealed that a significant reduction in disease outbreaks occurred following especially cold winters (Cold Snap), potentially related to a reduction in pathogen loading. Furthermore, mild winters (i.e., neither excessively cool nor warm) frequently preceded disease outbreaks. In contrast, disease outbreaks did not typically occur following warm winters, potentially because of increased disease resistance of the coral host. Understanding the balance between the effects of warm and cold winters on disease outbreak will be important in a warming climate. Combining the influence of winter and summer thermal effects resulted in an algorithm that yields both a Seasonal Outlook of disease risk at the conclusion of winter and near real-time monitoring of Outbreak Risk during summer. This satellite-derived system can provide coral reef managers with an assessment of risk three-to-six months in advance of the summer season that can then be refined using near-real-time summer observations. This system can enhance the capacity of managers to prepare for and respond to possible disease outbreaks and focus research efforts to increase understanding of environmental impacts on coral disease in this era of rapidly changing climate. [ABSTRACT FROM AUTHOR]

Background: In recent decades, large pelagic and coastal shark populations have declined dramatically with increased fishing; however, the status of sharks in other systems such as coral reefs remains largely unassessed despite a long history of exploitation. Here we explore the contemporary distribution and sighting frequency of sharks on reefs in the greater- Caribbean and assess the possible role of human pressures on observed patterns. Methodology/Principal Findings: We analyzed 76,340 underwater surveys carried out by trained volunteer divers between 1993 and 2008. Surveys were grouped within one km2 cells, which allowed us to determine the contemporary geographical distribution and sighting frequency of sharks. Sighting frequency was calculated as the ratio of surveys with sharks to the total number of surveys in each cell. We compared sighting frequency to the number of people in the cell vicinity and used population viability analyses to assess the effects of exploitation on population trends. Sharks, with the exception of nurse sharks occurred mainly in areas with very low human population or strong fishing regulations and marine conservation. Population viability analysis suggests that exploitation alone could explain the large-scale absence; however, this pattern is likely to be exacerbated by additional anthropogenic stressors, such as pollution and habitat degradation, that also correlate with human population. Conclusions/Significance: Human pressures in coastal zones have lead to the broad-scale absence of sharks on reefs in the greater-Caribbean. Preventing further loss of sharks requires urgent management measures to curb fishing mortality and to mitigate other anthropogenic stressors to protect sites where sharks still exist. The fact that sharks still occur in some densely populated areas where strong fishing regulations are in place indicates the possibility of success and encourages the implementation of conservation measures. [ABSTRACT FROM AUTHOR]

Disentangling the ecological effects of biological invasions from those of other human disturbances is crucial to understanding the mechanisms underlying ongoing biotic homogenization. We evaluated whether the exotic seaweed, Caulerpa racemosa, is the primary cause of degradation (i.e., responsible for the loss of canopy-formers and dominance by algal turfs) on Mediterranean rocky reefs, by experimentally removing the invader alone or the entire invaded assemblage. In addition, we assessed the effects of enhanced sedimentation on the survival and recovery of canopy-forming macroalgae at a relatively pristine location and how their loss affects the ability of C. raceinosa to conquer space. C. raceowsa did not invade dense canopy stands or influence their recovery in cleared plots. Competition with C. raceniosa could not explain the rarity of canopy-forming species at degraded sites. Removing the assemblages invaded by C. racemosa and preventing reinvasion did not trigger the transition from algal turfs to canopies, but it enhanced the cover of morphologically complex erect macroalgae under some circumstances. Once established, C. raceniosa, enhancing sediment accumulation, favors algal turfs over erect algal forms and enables them to monopolize space. Our results show that introduced species that rely on disturbance to establish can subsequently become the main drivers of ecological change. [ABSTRACT FROM AUTHOR]

Recent outbreaks of coral bleaching and disease have contributed to substantial declines in the abundance of reef-building coral. Significant attention has been paid to both phenomena in order to determine their effect on reef trajectories. Although each is positively correlated with high temperatures, few studies have, explored the potential links between bleaching and disease. A longitudinal study of corals in the Florida Keys was therefore conducted during the 2005 Caribbean bleaching event to quantify bleaching extent and disease incidence in corals, and to determine whether they were related or if they acted as discrete phenomena. These data indicated that overall, a positive correlation exists between bleaching extent and disease incidence. However, the specific interactions between these two phenomena varied among disease bleaching combinations. Montastraea faveolala colonies with greater bleaching intensities later developed white plague (WP) infections. Meanwhile, Siderastrea siderea colonies with dark spot disease (DS) bleached more extensively than apparently healthy colonies. Finally, bleaching and black band disease (BB) co-occurred on Colpophyllia natans throughout the bleaching event. WP, BB, and bleaching are each independently capable of changing the structure of coral populations through loss of living tissue, and DS is an important indicator of reef health. Understanding the dynamics of how these mortality sources interact is critical to understanding mortality patterns and predicting how reef. communities will respond to future events. [ABSTRACT FROM AUTHOR]

Natural and anthropogenic disturbances are leading to changes in the nature of many habitats globally, and the magnitude and frequency of these perturbations are predicted to increase under climate change. Globally coral reefs are one of the most vulnerable ecosystems to climate change. Fishes often show relatively rapid declines in abundance when corals become stressed and die, but the processes responsible are largely unknown. This study explored the mechanism by which coral bleaching may influence the levels and selective nature of mortality on a juvenile damselfish, Pomacentrus amboinensis, which associates with hard coral. Recently settled fish had a low propensity to migrate small distances (40 cm) between habitat patches, even when densities were elevated to their natural maximum. Intraspecific interactions and space use differ among three habitats: live hard coral, bleached coral and dead algal-covered coral. Large fish pushed smaller fish further from the shelter of bleached and dead coral thereby exposing smaller fish to higher mortality than experienced on healthy coral. Small recruits suffered higher mortality than large recruits on bleached and dead coral. Mortality was not size selective on live coral. Survival was 3 times as high on live coral as on either bleached or dead coral. Subtle behavioural interactions between fish and their habitats influence the fundamental link between life history stages, the distribution of phenotypic traits in the local population and potentially the evolution of life history strategies. [ABSTRACT FROM AUTHOR]

Coral reefs worldwide are becoming increasingly and detrimentally impacted upon by a variety of factors including significant climate changes, such as global warming and increased El Niño-Southern Oscillation activity. Generally, the persistence of coral reefs, especially at low-latitudes, is governed, in part, by sea surface temperatures not exceeding the critical limit (∼30°C) at which mass mortality can occur. Thus, it is thought that corals living at high-latitudes (i.e., currently cooler sea surface temperatures) will likely respond more favourably to hypothesized future temperature increases than corals living at low-latitudes (i.e., currently warmer sea surface temperatures). Consequently, high-latitude coral communities may have the potential to act as regions of refugia for many coral species in the face of potential future global warming. The Daya Bay (22°31'-22°50'N), northern South China Sea, contains several high-latitude non-reefal coral communities and represents one of the most northerly distributions of scleractinian corals within the region. Significantly, Daya Bay has experienced dramatic warming in both air and sea surface temperatures throughout the past 50 years. In this paper, we analyze 25 years of change in the Daya Bay coral communities, based both on historic surveys and our latest 2006-2008 regional ecological surveys. Our results suggest that, contrary to predictions, there have been significant declines in coral cover within the Daya Bay during the past 25 years (i.e., 76.6% coral cover in 1983/1984 to only 15.3% coral cover by 2008). Such changes also reflect a significant shift in the most abundant coral species, from Acropora pruinosa to Favites abdita. Most of the modern coral communities became established between 15 and 30 years ago, corresponding to a period of increased winter sea surface temperature. However, very few colonies have become established within the last 15 years, despite a more intense period of warming. By taking into account additional factors, we hypothesize that direct anthropogenic impacts, rather than climatic events, have both restricted the development, and drove the decline, of Daya Bay coral communities in the last 15 years. The Daya Bay has also been subjected to occasional extreme cold events during the past 50 years, with the most recent occurring in early 2008 (13 January-13 February). During the 2008 cold event, the lowest air temperature reaches only 6.6°C, and the mean sea surface temperature for February fall to <14°C, including six continuous days at 12.3°C. Significantly, the sea surface temperatures fall below the hypothesized critical lower temperature threshold (∼13°C) that commonly leads to mass mortality in scleractinian coral communities. Surprisingly, our coral community surveys, conducted both before (August 2007) and after (late February 2008) the extreme 2008 cold event, demonstrate that the Daya Bay coral ecosystems are barely impacted upon during the cold period. Those observations suggest that the Daya Bay scleractinian coral communities have developed adaptations to low sea surface temperatures. Overall, our data support the hypothesis that high-latitude coral communities, such as Daya Bay, have the potential to act as areas of refugia for scleractinian corals in the advent of potential future global warming. [ABSTRACT FROM AUTHOR]