Search

In this study, we evaluated the efficacy of sperm cryopreservation for use in larval-based propagation of Diploria labyrinthiformis and produced offspring that were maintained under controlled conditions. Gametes were collected from colonies in situ in July and August 2017 and 2018. The four largest colonies out of a total of nine appear to be senescent or produce low-quality sperm or eggs. Sperm was cryopreserved for comparison of the effects of storage time on sperm viability. We determined that cryopreserved sperm from D. labyrinthiformis is viable for at least 13 months for use in in vitro crosses, though their motility is reduced on average by 24% in comparison with fresh sperm. Using frozen sperm to fertilize freshly collected eggs led to successful fertilization, larval yields, settlement and post-settlement survival. In general, these were lower by 23%, 23%, 14% and 8%, respectively, when compared to controls fertilized with fresh sperm. Our results suggest that motility of fresh sperm is not a good indicator of the future fate of larvae because in some cases low motility led to successful settlement. We also found that not all crosses were successful, and that the direction of the cross significantly affects larval yields and settlement. Once symbionts were noticeable within the primary polyps the cryo-recruits were maintained in an ex situ nursery for observation and showed similar survival with respect to recruits produced with fresh sperm. Prior to the 2018 spawning event, Stony Coral Tissue Loss Disease (SCTLD) was detected in the studied colonies and by February 2020 seven of the nine colonies (78%) had succumbed to the disease. The sperm from these colonies was banked in a repository and since then has been used in genetic rescue projects for this species. Thus, we show that cryopreservation is a useful tool in actions designed to recover D. labyrinthiformis and can potentially be applied to other species of corals severely affected by SCTLD or in need of genetic rescue.

Stony coral tissue loss disease (SCTLD) has devastated coral populations along Florida’s Coral Reef and beyond. Although widespread infection and mortality of adult colonies have been documented, no studies have yet investigated the susceptibility of recruits to this disease. Here, we exposed eight-month-old Diploria labyrinthiformis recruits and four-month-old Colpophyllia natans recruits to two sequential doses of SCTLD in the laboratory to track infection and assess potential resilience. Both species began to develop lesions as early as 48 h after exposure began. During the first dose, 59.0% of C. natans recruits lost all tissue (died) within two to eight days of developing lesions, whereas D. labyrinthiformis recruits experienced significantly slower rates of tissue loss and minimal eventual mortality. In C. natans, larger recruits and those fused into groups of multiple genets (chimeras) exhibited the highest survivorship. In contrast, smaller and/or single (ungrouped) recruits had the lowest survivorship (9.9 - 26.5%). After 20 days, a second SCTLD dose was delivered to further test resistance in remaining recruits, and all recruits of both species succumbed within 6 days. Although no recruits showed absolute resistance to SCTLD following repeated exposures, our results provide evidence that interactions between species, size, and chimerism can impact relative resistance. This study represents the first report of SCTLD in Caribbean coral recruits and carries implications for natural species recovery and reef restoration efforts. Additional research on the susceptibility of coral juveniles to SCTLD is urgently needed, to include different species, locations, parents, and algal symbionts, with the goal of assessing relative susceptibility and identifying potential sources of resilience for this critical life history stage.

This work is the first record of the perception of fishers and artisanal fishers in the Caravela city- Bahia and its respective districts (Ponta de Areia and Barra de Caravelas) regarding the species Mussismilia braziliensis, its ethnozoological aspects and its socio-environmental importance. The main objective is to associate the knowledge of these artisanal fishers about this species with the ethnoconservation of the Abrolhos Marine National Park (PARNAM-Abrolhos). Data collection was conducted from March to August 2019 through semi-structured interviews with 14 fishers from each fishing communities (Caravelas, Ponta de Areia and Barra de Caravelas). An ethno-mapping was carried out with two focal groups in order to know if the fishing grounds have received their names due to the presence or absence of corals. Using morphological characteristics, the focus species is grouped together with other corals belonging to different families, which are all considered to be brain corals. Other studies are recommended to appreciate the knowledge of the Caravelas fishers and use it for future environmental education, management and conservation projects of the PARNAM-Abrolhos.

Reef corals in the Mexican Reef System have been severely affected by the emergence of a white syndrome that resembles both White Plague II and SCTLD descriptions. Meandroid scleractinian coral species are among the most severely affected. To gain insight into this affliction we conducted a broad study in the brain coral Pseudodiploria strigosa at a rear reef site in the NE Mexican Caribbean. We describe macro and microscopical signals of the disease, characterize the outbreak dynamics, the tissue histopathology, explore immunological responses in the individuals, and compare microbial assemblages associated with the surface mucus layer of healthy and unhealthy colonies. At the study site, the white syndrome outbreak on P. strigosa showed a high incidence rate in summer-fall and a low one in winter, as well as low survival expectation of diseased colonies at the end of the study. After 306 days of observation, out of 96 tracked colonies, eight remained apparently healthy and seven were diseased. No effective resistance to colony disease progression was observed once white syndrome signs developed. Tissue loss rate during the study varied among colonies (mean = 10.8 cm2, s.d. = 7.8 cm2) suggesting a complex relation between causal agents and colony resistance. The deterioration of tissues was evidenced from the basal to the surface body wall of polyps (up to 66% hypertrophy and liquefactive necrosis in unhealthy colonies), implying that microscopic alterations begin before macroscopic signals develop, suggesting this may be a systemic disease. We measured high levels of phenoloxidase (two orders of magnitude higher PO activity than P. strigosa affected by BBD) and antibacterial activity without significant reduction in unhealthy samples from the mucus layer, indicative of an enhanced immunological response. Results showed that opportunistic bacteria dominated damaged colonies, where six genera of the Bacteroidia class were found with significant changes in unhealthy colonies after DeSeq2 analysis. Nevertheless, histological observations did not support infection of the tissues. The opportunistic overload seems to be contained within the mucus layer but may be associated with the mortality of tissues in a yet unclear way. Future research should focus on experimental infections, the tracking of natural infections, and the immunocompetence of corals in the face of environmental pressures due to local, regional, and global impacts. If environmental deterioration is the primary cause of the continuing emergence and re-emergence of lethal coral diseases, as has been proposed by many authors, the only true option to effectively help preserve the coral reef biodiversity and services, is to restore the environmental quality of reef waters at the local scale and reduce greenhouse gases at the global scale.

Extraordinary marine inundation scattered clasts southward on the island of Anegada, 120 km south of the Puerto Rico Trench, sometime between 1200 and 1480 calibrated years (cal yr) CE. Many of these clasts were likely derived from a fringing reef and from the sandy flat that separates the reef from the island’s north shore. The scattered clasts include no fewer than 200 coral boulders, mapped herein for the first time and mainly found hundreds of meters inland. Many of these are complete colonies of the brain coral Diploria strigosa . Other coral species represented include Orbicella (formerly Montastraea ) annu­laris , Porites astreoides , and Acropora palmata . Associated bioclastic carbonate sand locally contains articulated cobble-size valves of the lucine Codakia orbicularis and entire conch shells of Strombus gigas , mollusks that still inhabit the sandy shallows between the island’s north shore and a fringing reef beyond. Imbricated limestone slabs are clustered near some of the coral boulders. In addition, fields of scattered limestone boulders and cobbles near sea level extend mainly southward from limestone sources as much as 1 km inland. Radiocarbon ages have been obtained from 27 coral clasts, 8 lucine valves, and 3 conch shells. All these additional ages predate 1500 cal yr CE, all but 2 are in the range 1000–1500 cal yr CE, and 16 of 22 brain coral ages cluster in the range 1200–1480 cal yr CE. The event marked by these coral and mollusk clasts likely occurred in the last centuries before Columbus (before 1492 CE). The pre-Columbian deposits surpass Anegada’s previously reported evidence for extreme waves in post-Columbian time. The coarsest of the modern storm deposits consist of coral rubble that lines the north shore and sandy fans on the south shore; neither of these storm deposits extends more than 50 m inland. More extensive overwash, perhaps by the 1755 Lisbon tsunami, is marked primarily by a sheet of sand and shells found mainly below sea level beneath the floors of modern salt ponds. This sheet extends more than 1 km southward from the north shore and dates to the interval 1650–1800 cal yr CE. Unlike the pre-Columbian deposits, it lacks coarse clasts from the reef or reef flat; its shell assemblage is instead dominated by cerithid gastropods that were merely stirred up from a marine pond in the island’s interior. In their inland extent and clustered pre-Columbian ages, the coral clasts and associated deposits suggest extreme waves unrivaled in recent millennia at Anegada. Bioclastic sand coats limestone 4 m above sea level in areas 0.7 and 1.3 km from the north shore. A coral boulder of nearly 1 m 3 is 3 km from the north shore by way of an unvegetated path near sea level. As currently understood, the extreme flooding evidenced by these and other clasts represents either an extraordinary storm or a tsunami of nearby origin. The storm would need to have produced tsunami-like bores similar to those of 2013 Typhoon Haiyan in the Philippines. Normal faults and a thrust fault provide nearby tsunami sources along the eastern Puerto Rico Trench.

Coral skeletal growth anomaly (GA) is a common coral disease. It has been considered as a pathological condition comparable to abnormal tissue growth in mammals, but little is known about the molecular changes underlying coral GA. To investigate the molecular pathology of GA, we compared the proteome between normal and GA-affected tissues of the brain coral Platygyra carnosa using iTRAQ-labeling and LC-MS/MS, which quantified 818 proteins and identified 117 differentially expressed proteins (DEPs). GO analyses revealed DEPs that might be related to GA included "translational elongation", "proteasome core complex", "amine metabolic processes" and "lysosome". Several proteins implicated in calcification and fluorescence were differentially expressed at both protein and mRNA level. Protein-protein interaction network suggested possible involvement of TNF receptor signaling in GA. Overall, our results provided novel insights into the molecular pathology of coral GA, which will pave the way for determination of the causative agent(s) of this coral disease.

Despite the fact that most of the severe demographic bottlenecks in coral populations occur during their earliest life stages, information on the reproductive biology and early life history traits of many coral species is limited and often inferred from adult traits only. This study reports on several atypical aspects of the reproductive biology and early life ecology of the grooved brain coral, Diploria labyrinthiformis (Linnaeus, 1758), a conspicuous reef-building species on Caribbean reefs. The timing of gamete release of D. labyrinthiformis was monitored in Curaçao over eight consecutive months, and embryogenesis, planulae behavior, and settlement rates were observed and quantified. We further studied growth and symbiont acquisition in juvenile D. labyrinthiformis for 3.5 yr and compared settler survival under ambient and nutrient-enriched conditions in situ. Notably, D. labyrinthiformis reproduced during daylight hours in six consecutive monthly spawning events between May and September 2013, with a peak in June. This is the largest number of reproductive events per year ever observed in a broadcast-spawning Caribbean coral species. In settlement experiments, D. labyrinthiformis planulae swam to the bottom of culture containers 13 h after spawning and rapidly settled when provided with settlement cues (42% within 14 h). After 5 months, the survival and growth rates of settled juveniles were 3.7 and 1.9 times higher, respectively, for settlers that acquired zooxanthellae within 1 month after settlement, compared to those that acquired symbionts later on. Nutrient enrichment increased settler survival fourfold, but only for settlers that had acquired symbionts within 1 month after settlement. With at least six reproductive events per year, a short planktonic larval phase, high settlement rates, and a positive response to nutrient enrichment, the broadcast-spawning species D. labyrinthiformis displays a range of reproductive and early life-history traits that are more often associated with brooding coral species, illustrating that classical divisions of coral species by reproductive mode alone do not always reflect the true biology and ecology of their earliest life stages.

Understanding the potential for coral adaptation to warming seas is complicated by interactions between symbiotic partners that define stress responses and the difficulties of tracking selection in natural populations. To overcome these challenges, we characterised the contribution of both animal host and symbiotic algae to thermal tolerance in corals that have already experienced considerable warming on par with end-of-century projections for most coral reefs. Thermal responses in Platygyra daedalea corals from the hot Persian Gulf where summer temperatures reach 36°C were compared with conspecifics from the milder Sea of Oman. Persian Gulf corals had higher rates of survival at elevated temperatures (33 and 36°C) in both the non-symbiotic larval stage (32-49% higher) and the symbiotic adult life-stage (51% higher). Additionally, Persian Gulf hosts had fixed greater potential to mitigate oxidative stress (31-49% higher) and their Symbiodinium partners had better retention of photosynthetic performance under elevated temperature (up to 161% higher). Superior thermal tolerance of Persian Gulf versus Sea of Oman corals was maintained after 6-months acclimatisation to a common ambient environment and was underpinned by genetic divergence in both the coral host and symbiotic algae. In P. daedalea host samples, genome-wide SNP variation clustered into two discrete groups corresponding with Persian Gulf and Sea of Oman sites. Symbiodinium within host tissues predominantly belonged to ITS2 rDNA type C3 in the Persian Gulf and type D1a in the Sea of Oman contradicting patterns of Symbiodinium thermal tolerance from other regions. Our findings provide evidence that genetic adaptation of both host and Symbiodinium has enabled corals to cope with extreme temperatures in the Persian Gulf. Thus, the persistence of coral populations under continued warming will likely be determined by evolutionary rates in both, rather than single, symbiotic partners. This article is protected by copyright. All rights reserved.

We compared the suitability of two skeletal materials of the Atlantic brain coral Diploria strigosa for 230Th/U-dating: the commonly used bulk material comprising all skeletal elements and the denser theca wall material. Eight fossil corals of presumably Last Interglacial age from Bonaire, southern Caribbean Sea, were investigated, and several sub-samples were dated from each coral. For four corals, both the ages and the activity ratios of the bulk material and theca wall agree within uncertainty. Three corals show significantly older ages for their bulk material than for their theca wall material as well as substantially elevated 232Th content and (230Th/238U) ratios. The bulk material samples of another coral show younger ages and lower (230Th/238U) ratios than the corresponding theca wall samples. This coral also contains a considerable amount of 232Th. The application of the available open-system models developed to account for post-depositional diagenetic effects in corals shows that none of the models can successfully be applied to the Bonaire corals. The most likely explanation for this observation is that the assumptions of the models are not fulfilled by our data set. Comparison of the theca wall and bulk material data enables us to obtain information about the open-system processes that affected the corals. The corals showing apparently older ages for their bulk material were probably affected by contamination with a secondary (detrital) phase. The most likely source of the detrital material is carbonate sand. The higher (230Th/232Th) ratio of this material implies that detrital contamination would have a much stronger impact on the ages than a contaminant with a bulk Earth (230Th/232Th) ratio and that the threshold for the commonly applied 232Th reliability criterion would be much lower than the generally used value of 1 ng g−1. The coral showing apparently younger ages for its bulk material was probably influenced by more than one diagenetic process. A potential scenario is a combination of detrital contamination and U addition by secondary pore infillings. Our results show that the dense theca wall material of D. strigosa is generally less affected by post-depositional open-system behaviour and better suited for 230Th/U-dating than the bulk material. This is also obvious from the fact that all ages of theca wall material reflect a Last Interglacial origin (∼125 ka), whereas the bulk material samples are either substantially older or younger. However, for some corals, the 230Th/U-ages and activity ratios of the bulk material and the theca wall samples are similar. This shows that strictly reliable 230Th/U-ages can also be obtained from bulk material samples of exceptionally well-preserved corals. However, the bulk material samples more frequently show elevated activity ratios and ages than the corresponding theca wall samples. Our findings should be generally applicable to brain corals (Mussidae) that are found in tropical oceans worldwide and may enable reliable 230Th/U-dating of fossil corals with similar skeletal architecture, even if their bulk skeleton is altered by diagenesis. The 230Th/U-ages we consider reliable (120–130 ka), along with a recently published age of 118 ka, provide the first comprehensive dating of the elevated lower reef terrace at Bonaire (118–130 ka), which is in agreement in timing and duration with other Last Interglacial records.

Scleractinian corals occur in tropical regions near their upper thermal limits, and are severely threatened by rising ocean temperatures. Ocean warming leads to loss of symbiotic algae (Symbiodinium), reduced fitness for the coral host, and degradation of the reef. However, several recent studies have shown that natural populations of corals harbor genetic variation in thermal tolerance that may support adaptive responses to warming. Here we’ve extended these approaches to study heat tolerance of corals in the Persian/Arabian Gulf, where heat-tolerant local populations have adapted to warm summer temperatures (>36°C). To evaluate whether selection has depleted genetic variation in thermal tolerance, estimate the potential for future adaptive responses, and understand the functional basis for these corals’ unusual heat tolerance, we measured thermal tolerance using controlled crosses in the Gulf coral Platygyra daedalea. We found that heat tolerance is highly heritable in this population (0.487-0.748), suggesting substantial potential for adaptive responses to selection for thermal tolerance. To identify genetic markers associated with this variation, we conducted genomewide SNP genotyping in parental corals and tested for relationships between paternal genotype and thermal tolerance of the offspring. We found that multilocus SNP genotypes explained a large fraction of variation in thermal tolerance in these crosses (69%). To investigate the functional basis of these differences in thermal tolerance, we profiled transcriptional responses in tolerant and susceptible families, revealing substantial sire effects on transcriptional responses to thermal stress. We also studied sequence variation in these expressed sequences, identifying alleles and functional groups associated with thermal tolerance. Our findings demonstrate that corals in these populations harbor extensive genetic variation in thermal tolerance, and these heat-tolerant phenotypes differ in both gene sequences and transcriptional stress responses from their susceptible counterparts.

In Brazil, where reefs occur in markedly turbid environments, the relationship between sedimentation/organic matter and corals is poorly known. Thus, the ex situ effects of sediment with and without organic matter over the ΔF/Fm and physical state of Mussismilia braziliensis were analyzed. The ΔF/Fm and coral physical state, evaluated through the susceptibility index to sedimentation (SI), were measured in seven colonies exposed to sedimentation (0-450 mg cm(-2) day(-1)) free of organic matter after 45 days of exposure, and in 12 colonies exposed to sedimentation (0-500 mg cm(-2) day(-1)) with organic matter content (10%), in which case ΔF/Fm was measured after 72 h and SI after 120 h. In both cases there were effects of increasing sedimentation on the SI with no effect on ΔF/Fm. Despite the tolerance to high sedimentation rates shown by this coral, we noted that the presence of organic matter might reduce its tolerance to sedimentation stress.

Background Research into various aspects of coral biology has greatly increased in recent years due to anthropogenic threats to coral health including pollution, ocean warming and acidification. However, knowledge of coral early development has lagged. The present paper describes the embryonic development of two previously uncharacterized robust corals, Favia lizardensis (a massive brain coral) and Ctenactis echinata (a solitary coral) and compares it to that of the previously characterized complex coral, Acropora millepora, both morphologically and in terms of the expression of a set of key developmental genes. Results Illumina sequencing of mixed age embryos was carried out, resulting in embryonic transcriptomes consisting of 40605 contigs for C.echinata (N50 = 1080 bp) and 48536 contigs for F.lizardensis (N50 = 1496 bp). The transcriptomes have been annotated against Swiss-Prot and were sufficiently complete to enable the identification of orthologs of many key genes controlling development in bilaterians. Developmental series of images of whole mounts and sections reveal that the early stages of both species contain a blastocoel, consistent with their membership of the robust clade. In situ hybridization was used to examine the expression of the developmentally important genes brachyury, chordin and forkhead. The expression of brachyury and forkhead was consistent with that previously reported for Acropora and allowed us to confirm that the pseudo-blastopore sometimes seen in robust corals such as Favia spp. is not directly associated with gastrulation. C.echinata chordin expression, however, differed from that seen in the other two corals. Conclusions Embryonic transcriptomes were assembled for the brain coral Favia lizardensis and the solitary coral Ctenactis echinata. Both species have a blastocoel in their early developmental stages, consistent with their phylogenetic position as members of the robust clade. Expression of the key developmental genes brachyury, chordin and forkhead was investigated, allowing comparison to that of their orthologs in Acropora, Nematostella and bilaterians and demonstrating that even within the Anthozoa there are significant differences in expression patterns. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0615-2) contains supplementary material, which is available to authorized users.

In the context of rising seawater temperatures associated with climate change, the issue of whether coral holobionts deal with this challenge by shuffling their associations with stress- and/or heat-tolerant Symbiodinium, by generating heat-resistant host genotypes, or both is important for coral survival. In this study, the composition of communities of the endosymbiont Symbiodinium and the population genetics of the coral host Platygyra verweyi were examined in a reef impacted by hot-water discharged from the outlet of a nuclear power plant in operation in Kenting, Southern Taiwan since 1984. The water at this site is 2.0-3.0 °C warmer than adjacent reefs in summer, which have an average seawater temperature of 29.0 °C. The data were compared with those for the same species at other sites within 12 km of the outlet site. Platygyra verwyei was associated with one or both of Symbiodinium types C3 (heat sensitive) and D1a (heat tolerant) at all sites with the latter being the dominant at the nuclear power plant outlet. The proportion of C3 in populations increased gradually with increasing distance from the hot-water discharge. Genetic analysis of the Platygyra verweyi host using mitochondrial and nuclear markers showed no genetic differentiation among sites. Changes in the composition of Symbiodinium types associated with P. verweyi among closely located sites in Kenting suggested that this coral might have acclimatized to the constant thermal stress by selective association with heat-tolerant Symbiodinium types, whereas the role of the host in adaptation was inconclusive.

The parrotfish Sparisoma viride often grazes live coral from edges undermined by the Caribbean encrusting and excavating sponge Cliona tenuis. To test whether parrotfish biting action has an effect on the dynamics of the sponge– coral interaction, we manipulated access of parrotfishes to the sponge–coral border in two species of massive corals. When parrotfish had access to the border, C. tenuis advanced significantly more slowly into the coral Siderastrea siderea than into the coral Diploria strigosa. When fish bites were prevented, sponge spread into S. siderea was further slowed down but remained the same for D. strigosa. Additionally, a thinner layer of the outer coral skeleton was removed by bioerosion when fish were excluded, a condition more pronounced in D. strigosa than in S. siderea. Thus, the speed of sponge-spread and the extent of bioerosion by parrotfish was coral species-dependent. It is hypothesized that coral skeleton architecture is the main variable associated with such dependency. Cliona tenuis spread is slow when undermining live S. siderea owing to the coral’s compact skeleton. The coral’s smooth and hard surface promotes a wide and shallow parrotfish bite morphology, which allows the sponge to overgrow the denuded area and thus advance slightly faster. On the less compact skeleton of the brain coral, D. strigosa, sponge spread is more rapid. This coral’s rather uneven surface sustains narrower and deeper parrotfish bites which do not facilitate the already fast sponge progress. Parrotfish corallivory thus acts synergistically with C. tenuis to further harm corals whose skeletal architecture slows sponge lateral spread. In addition, C. tenuis also appears to mediate the predator–prey fish–coral interaction by attracting parrotfish biting.

Black-band disease (BBD) is a temperature- and light-dependent syndrome typically found on shallow-dwelling corals. The bacterial consortium that creates BBD contains a photosynthetic cyanobacterium, which is particularly sensitive to light. High light causes the BBD cyanobacteria to self-shade, which encourages the formation of the anoxic microenvironment essential for the BBD consortium. From May to September 2009, a shallow-reef area was monitored to quantify the epizootiology of BBD on the brain coral Diploria strigosa . The prevalence and incidence of BBD were recorded approximately every two weeks. To test the hypothesis that reduced light would increase the rate of disease progression by reducing photoinhibition in the BBD cyanobacteria, shade structures, made out of plastic sheeting on a polyvinyl chloride (PVC) frame, were installed above D. strigosa colonies with BBD. The shade material reduced photosynthetically available radiation (PAR) by > 80%. The progression of BBD on shaded colonies was compared with cage control and control colonies. A pulse–amplitude–modulation fluorometer was used to measure the amount of PAR and maximum excitation pressure ( Q m ) on each colony after two weeks of treatment. Linear progression rates and the band width of BBD were measured weekly and treatments were compared through time. During the summer months, the prevalence of BBD showed a positive, exponential relationship with water temperature, whereas the incidence of BBD displayed a positive linear relationship with the rate of change of water temperature. PAR on, and the Q m of, shaded corals was significantly lower than the two control treatments; however, Q m values did not indicate excessive photochemical pressure on the coral host. The progression rates of BBD and the black-band width on shaded colonies significantly increased after one week of shading, whereas the control treatments did not change. During the second week of manipulation, however, black-band width and progression rates were similar to values prior to manipulation. These results suggest that, even under low-light conditions, a compact and dense ‘black’ band is essential for the persistence of the BBD consortium.

Geochemical tracers incorporated into the skeleton of reef-building corals are ideal proxies for reconstructing environmental parameters of ambient seawater such as temperature and salinity at subseasonal resolution. However, validation concerns of these environmental proxies due to the complex skeleton of some tropical Atlantic corals have hindered such coral-based environmental reconstructions in this region compared to the tropical Pacific. In order to identify complications associated with the complex skeletal architecture of the massive brain coral Diploria strigosa, we performed microsampling experiments along and across individual skeletal elements. We demonstrate that the mesoscale heterogeneity of Sr/Ca, δ18O and δ13C is a systematic feature of D. strigosa and is linked to different vital effects between skeletal elements. The thecal wall is significantly depleted in Sr, 18O and 13C compared to the adjacent septa and columella and differences between apparent temperature signatures of several degrees are greater for Sr/Ca suggesting that this temperature proxy is more sensitive to skeletal mixing than δ18O. Parallel subseasonal microsampling experiments performed along individual skeletal elements of a single corallite of a D. strigosa coral which grew at a rate of 0.65 cm/year allow for investigating potential biases associated with its complex skeletal mesoarchitecture. Highest correlation between Sr/Ca and δ18O from skeletal material retrieved from the centre of the thecal wall suggests that microdrilling the theca provides the best environmental signal compared to adjacent microsampling profiles. Moreover, based on monthly-mean climatology, the temperature dependence of Sr/Ca for this profile is comparable to previous calibrations published from faster growing D. strigosa. Based on these results, we conclude that accurate microsampling along the centre of the thecal wall of D. strigosa is a prerequisite for generating robust climate reconstructions from its skeleton.

Following rapid lesion progression of white syndrome in tabular Acropora spp., the white bare skeleton gradually changes to green, a result of endolithic algae blooms (primarily Ostreobium spp.). Endolithic algal biomass and chlorophyll concentration were found to be an order of magnitude higher in the green zone compared with healthy appearing parts of each colony. Chl b to Chl a ratio increased from 1:1.6 in the healthy area to 1:2 and 1:3.5 in the white exposed skeleton and green zones, respectively. These observations together with pulse amplitude modulated (PAM) fluorometry suggest photoacclimation of the endoliths in the green zone. Histopathological microscopy revealed that the endolithic algal filaments penetrate the coral tissue. This study highlights the interaction of endolithic algae with both the skeleton and host tissue. This may have a critical role in the processes that accompany the post-disease state in reef-building corals.

SUMMARY Photosynthetic endolithic algae and cyanobacteria live within the skeletons of many scleractinians. Under normal conditions, less than 5% of the photosynthetically active radiation (PAR) reaches the green endolithic algae because of the absorbance of light by the endosymbiotic dinoflagellates and the carbonate skeleton. When corals bleach (loose dinoflagellate symbionts),however, the tissue of the corals become highly transparent and photosynthetic microendoliths may be exposed to high levels of both thermal and solar stress. This study explores the consequence of these combined stresses on the phototrophic endoliths inhabiting the skeleton of Montipora monasteriata, growing at Heron Island, on the southern Great Barrier Reef. Endoliths that were exposed to sun after tissue removal were by far more susceptible to thermal photoinhibition and photo-damage than endoliths under coral tissue that contained high concentrations of brown dinoflagellate symbionts. While temperature or light alone did not result in decreased photosynthetic efficiency of the endoliths, combined thermal and solar stress caused a major decrease and delayed recovery. Endoliths protected under intact tissue recovered rapidly and photoacclimated soon after exposure to elevated sea temperatures. Endoliths under naturally occurring bleached tissue of M. monasteriata colonies (bleaching event in March 2004 at Heron Island) acclimated to increased irradiance as the brown symbionts disappeared. We suggest that two major factors determine the outcome of thermal bleaching to the endolith community. The first is the microhabitat and light levels under which a coral grows, and the second is the susceptibility of the coral-dinoflagellates symbiosis to thermal stress. More resistant corals may take longer to bleach allowing endoliths time to acclimate to a new light environment. This in turn may have implications for coral survival.

The aragonite skeleton of massive reef-building corals contains a record of the oceanic environment in which they grow. However, reading of the record requires understanding of how it is archived, a process complicated by the elaborate skeletal construction and seasonal growth patterns that characterize many species. In this study, we assess the utility of the massive brain coral Diploria labyrinthiformis as an archive of sea surface temperature (SST) variability in the western North Atlantic. In situ staining of live colonies combined with microscale analysis of skeletal chemistry indi- cate that D. labyrinthiformis grows throughout the year on Bermuda and records the full annual cycle of SST variability. However, skeleton accreted during the summer is overlain (thickened) by skeleton accreted during the subsequent fall and winter. As a result, conventional coarse sampling for δ 18 O enables seasonal δ 18 O cycles to be resolved but these do not capture the full amplitude of the annual SST cycle. Our data show that the shallow gradient of the δ 18 O-SST regression equation derived for D. labyrinthiformis (-0.113‰ oC -1 ) relative to the expected -0.22‰ oC -1 for marine skeletons results from dampening of the summertime peak in δ 18 O. In contrast, skeleton accreted during the winter is not thickened and wintertime δ 18 O captures the interannual wintertime SST variability at this site. Using SIMS ion microprobe to analyse strontium to calcium ratios (Sr/Ca), we avoided the thickening deposits and were able to resolve the full amplitude of the annual Sr/Ca cycle. The Sr/Ca-SST relationship obtained for D. labyrinthiformis (-0.0843 mmol/mol oC -1 ) corresponds to that derived from fast-growing tropical reef corals. X-ray intensity ratios, used as a proxy for skeletal density, reveal the expected seasonal changes associated with growth banding as well as variability on inter- annual and decadal timescales. These variations are well correlated with wintertime SST variability in the subtropical gyre and may be a valuable proxy thermometer for the North Atlantic.

Benthic marine organisms utilize an array of defensive and aggressive mechanisms that affect competition for space on hard marine substrata. The sweeper tentacles of stony corals are inducible aggressive organs used during competition, but they also may serve a pre-emptive defen- sive function. About half of the colonies of the brain coral Platygyra daedalea at Eilat, northern Red Sea, possess sweeper tentacles, many of which are not directed toward neighboring corals. These randomly oriented sweeper tentacles may be produced in order to detect the settlement or advance of corals occurring at >5 cm distance from the colony. Of coral colonies

Spawned gametes were collected from colonies of Acropora longicyathus at One Tree Island and Goniastrea aspera at Magnetic Island, Great Barrier Reef, Australia, for use in fertilisation trials. Mean fertilisation rates were significantly reduced compared with controls (P

The aims of this study were to sequence the transcriptome and organize the sequence data into a searchable database for the brain coral Platygyra carnosus, a structure-forming dominant species along the coast of southern China. We collected healthy and tumorous coral tissues from two locations, extracted RNA from each tissue sample, pooled the RNA from all tissue samples, generated a cDNA library from the pooled samples, and conducted paired-end sequencing of the cDNA library using the Illumina platform to produce 59.6 M clean sequences with a read length of 90 bp. De novo assembly of the sequence data resulted in 162,468 unigenes with an average length of 606 bp (range, 201 to 23,923 bp). This is the largest transcriptome dataset for a species of coral whose genome has not been sequenced. A BLASTx search against the NCBI protein database showed that 55,355 of the unigenes matched at least a sequence with an E-value of < 0.00001; 59 % of the matched sequences are from Metazoa, 13 % are from Alveolata to which the symbiont Symbiodinium belongs, and 7 % are from bacteria. A database (PcarnBase) was constructed to provide easy access to the unigenes with attributes such as NCBI protein annotation, GO annotation, and KEGG pathway. It will facilitate functional genomic studies of P. carnosus, such as biomarker discovery for bleaching, tumor formation, and disease development at the gene or protein level, involvement of coral symbiotic algae in the host coral’s stress responses, and genetic basis of stress resistance.

On Bermuda reefs the brain coral Diploria labyrinthiformis is rarely documented with black band disease (BBD), while BBD-affected colonies of Diploria strigosa are common. D. labyrinthiformis on these reefs may be more resistant to BBD or less affected by prevailing environmental conditions that potentially diminish host defenses. To determine whether light and/or temperature influence BBD differently on these two species, infection experiments were conducted under the following experimental treatments: (1) 26 °C, ambient light; (2) 30 °C, ambient light; (3) 30 °C, low light; and (4) 30 °C, high light. A digital photograph of the affected area of each coral was taken each day for 7 days and analyzed with ImageJ image processing software. The final affected area was not significantly different between species in any of the four treatments. BBD lesions were smaller on both species infected under ambient light at 26 °C versus 30 °C. Low light at 30 °C significantly reduced the lesion size on both species when compared to colonies infected at the same temperature under ambient light. Under high light at 30 °C, BBD lesions were larger on colonies of D. strigosa and smaller on colonies of D. labyrinthiformis when compared to colonies infected under ambient light at the same temperature. The responses of both species suggests that BBD progression on both D. strigosa and D. labyrinthiformis is similarly influenced by a combination of light and temperature and that other factors present before infections become established likely contribute to the difference in BBD prevalence in Bermuda.

[1] We use geochemical and isotope measurements on a 225-year old brain coral (Diploria labyrinthiformis) from the south shore of Bermuda (64°W, 32°N) to construct a record of decadal-to-centennial-scale climate variability. The coral was collected alive, and annual density bands visible in X radiographs delineate cold and warm seasons allowing for precise dating. Coral skeletons incorporate strontium (Sr) and calcium (Ca) in relative proportions inversely to the sea surface temperature (SST) in which the skeleton is secreted. Previous studies on this and other coral colonies from this region document the ability to reconstruct mean annual and wintertime SST using Sr/Ca measurements (Goodkin et al., 2007, 2005). The coral-based records of SST for the past 2 centuries show abrupt shifts at both decadal and centennial timescales and suggest that SST at the end of the Little Ice Age (between 1840 and 1860) was 1.5° ± 0.4°C colder than today (1990s). Coral-reconstructed SST has a greater magnitude change than does a gridded instrumental SST record from this region. This may result from several physical processes including high rates of mesoscale eddy propagation in this region. Oxygen isotope values (δ18O) of the coral skeleton reflect changes in both temperature and the δ18O of seawater (δOw), where δOw is proportional to sea surface salinity (SSS). We show in this study that mean annual and wintertime δ18O of the carbonate (δOc) are correlated to both SST and SSS, but a robust, quantitative measure of SSS is not found with present calibration data. In combination, however, the Sr/Ca and δOc qualitatively reconstruct lower salinities at the end of the Little Ice Age relative to modern day. Temperature changes agree with other records from the Bermuda region. Radiative and atmospheric forcing may explain some of the SST variability, but the scales of implied changes in SST and SSS indicate large-scale ocean circulation impacts as well.

The light microclimate of phototrophic endoliths growing within the scleractinian corals Porites cylindrica and Montipora monasteriata was described by scalar irradiance microprobe measurements within different layers of the coral skeleton. Characterisation of the pigments in individual layers was done by reflectance spectroscopy with fibre-optic radiance microprobes. The spectral measurements showed the presence of an endolithic community largely comprised of the green alga Ostreobium sp. within a 1 to 2 mm thick green band 2 to 6 mm below the coral surface. Additionally, spectral signatures of cyanobacteria and anoxygenic phototrophic bacteria were detected both in the coral tissue-containing top layer and within the skeleton matrix, The light microclimate within the coral skeleton was extremely poor in visible light but enriched in far-red wavelengths. Only a fraction of the incident photosynthetically available radiation (PAR, 400 to 700 nm) penetrated the coral tissue-containing layer, wherein 90 to 99 % of the incident irradiance was attenuated due to intense scattering and absorption. Near-infrared radiation (NIR, >700 to 1000 nm) was mainly scattered in the tissue-skeleton matrix and penetrated much deeper into the skeleton. Multiple scattering and light-trapping effects caused high NIR scalar irradiance levels in the topmost layers of the coral. Our data show that the endolithic community in healthy corals is strongly light-limited with respect to PAR, but not with respect to NIR in shallow waters where water absorption of NIR is not limiting. Light limitation of PAR is mainly imposed by the tissue-containing part of the coral, and could thus be alleviated during coral bleaching, resulting in blooming of the phototrophic endoliths. © Inter-Research 2007.

This study provides the first monthly resolved, 41-year record of geochemical variations (δ18O and Sr/Ca) in a fast-growing Diploria strigosa brain coral from Guadeloupe, Caribbean Sea. Linear regression yields a significant correlation of coral Sr/Ca (δ18O) with instrumental sea surface temperature (SST) on both monthly and mean annual scales (e.g., r = −0.59 for correlation between Simple Ocean Data Assimilation (SODA) SST and Sr/Ca, and r = −0.66 for δ18O; mean annual scale, p < 0.0001). The generated coral Sr/Ca (δ18O)-SST calibration equations are consistent with each other and with published equations using other coral species from different regions. Moreover, a high correlation of coral Sr/Ca and δ18O with local air temperature on a mean annual scale (r = −0.78 for Sr/Ca; r = −0.73 for δ18O; p < 0.0001) demonstrates the applicability of geochemical proxies measured from Diploria strigosa corals as reliable recorders for interannual temperature variability. Both coral proxies are highly correlated with annual and seasonal mean time series of major SST indices in the northern tropical Atlantic (e.g., r = −0.71 for correlation between the index of North Tropical Atlantic SST anomaly and Sr/Ca, and r = −0.70 for δ18O; mean annual scale, p < 0.001). Furthermore, the coral proxies capture the impact of the El Nino–Southern Oscillation on the northern tropical Atlantic during boreal spring. Thus fast-growing Diploria strigosa corals are a promising new archive for the Atlantic Ocean.

[1] Strontium to calcium ratios (Sr/Ca) are reported for a massive brain coral Diploria labyrinthiformis collected from the south shore of Bermuda and are strongly correlated with both sea surface temperature (SST) and mean annual skeletal growth rate. High Sr/Ca ratios correspond with cold SSTs and slow skeletal growth rate and vice versa. We provide a quantitative calibration of Sr/Ca to extension rate and SST along the axis of maximum growth and derive a growth-dependent Sr/Ca–SST calibration equation to reconstruct western subtropical North Atlantic SSTs for the past 223 years. When the influence of growth rate is excluded from the calibration, Sr/Ca ratios yield SSTs that are too cold during cool anomalies and too warm during warm anomalies. Toward the end of the Little Ice Age (∼1850), SST changes derived using a calibration that is not growth-dependent are exaggerated by a factor of 2 relative to those from the growth-corrected model that yields SSTs ∼1.5°C cooler than today. Our results indicate that incorporation of growth rate effects into coral Sr/Ca calibrations may improve the accuracy of SSTs derived from living and fossil corals.

A new sublethal toxicity test was developed in this study to measure the effect of copper and lead on the motility of coral larvae. Larval motility was significantly affected by copper and lead doses immediately after dosing. The copper EC50 values for motility of Goniastrea aspera brain coral larvae (12 h, 21 microg/L; 24 h, 16 microg/L; 48 h, 22 microg/L) were much lower than the copper LC50 values for G. aspera larval survival (6 h, 260 microg/L, and 24 h, 121 microg/L, for 5-day-old larvae and 6 h, 248 microg/L, and 24 h, 136.64 microg/L, for 6-day-old larvae) during the early part of the experiments. However, at later times, the LC50 values (48 h, 40 microg/L, for 5-day-old larvae and 48- h, 87 microg/L, for 6-day-old larvae) were similar to the EC50 values for larval motility. The lead 72-h EC50 value for G. aspera larval motility (2900 microg/L) was much lower than the lead 72-h LC50 value for larval survival (9890 microg/L). The results show that larval motility can be a useful parameter to measure in order to determine the sublethal effects of trace metals on coral larvae.

RNA-arbitrarily primed PCR techniques have been applied for the first time to identify differential gene expression in black band disease (BBD), a virulent coral infection that affects reef ecosystems worldwide. The gene activity for the BBD mat on infected surfaces of the brain coral Diploria strigosa was compared with that for portions of the BBD mat that were removed from the coral and suspended nearby in the seawater column. The results obtained indicate that three genes (DD 95-2, DD 95-4, and DD 99-9) were up-regulated in the BBD bacterial mat on the coral surface compared to the transcript base levels observed in the BBD mat suspended in seawater. Clone DD 95-4 has homology with known amino acid ABC transporter systems in bacteria, while clone DD 99-9 exhibits homology with chlorophyll A apoprotein A1 in cyanobacteria. This protein is essential in the final conformation of photosystem I P700. DD 95-2, the only gene that was fully repressed in the BBD mat samples suspended in seawater, exhibited homology with the AraC-type DNA binding domain-containing proteins. These transcriptional activators coordinate the expression of genes essential for virulence in many species of gram-negative bacteria.

The photoacclimation of endolithic algae (of the genus Ostreobium) inhabiting the skeleton of the Mediterranean coral Oculina patagonica during a bleaching event was examined. Pulse amplitude modulated (PAM) chlorophyll fluorescence techniques in situ were used to assess the photosynthetic efficiency of endolithic algae in the coral skeleton and the symbiotic dinoflagellates (zooxanthellae) in the coral tissue. Relative photosynthetic electron transport rates (ETRs) of the endolithic algae under bleached areas of the colony were significantly higher than those of endolithic algae from a healthy section of the colony and those of zooxanthellae isolated from the same section. Endolithic algae under healthy parts of the colony demonstrated an ETRmax of 16.5% that of zooxanthellae from tissue in the same section whereas endolithic algae under bleached sections showed ETRmax values that were 39% of those found for healthy zooxanthellae. The study demonstrates that endolithic algae undergo photoacclimation with increased irradiance reaching the skeleton. As PAM fluorometry has become a major tool for assessing levels of stress and bleaching in corals, the importance of considering the contribution of the endolithic algae to the overall chlorophyll fluorescence measured is highlighted. M F0312 Pho to io i ril M. F et al

The frequency of oil spills in tropical seas may threaten coral reef survival and some of the past research has indicated that oil alone as well as oil dispersed with chemical dispersants is toxic to corals. These experiments were probably realistic of intertidal reef zones and sheltered shallow reef areas. However, few experiments have incorporated analytical chemistry necessary to relate reported biological effects to actual oil spill concentrations and exposure times. This paper outlines some new results with emphasis on a 3 year programme carried out in Bermuda using a flow-through laboratory dosing system, comparative laboratory and field experiments, real time measurements of oil concentrations, and non-destructive bioassays to allow repetitive data collection from the same specimens. Suggestions for future research programmes are given in light of these results. In addition to research on the effects of oil and chemically dispersed oil on other coral species and associated organisms in the coral reef, the relative sensitivity of the various ecosystems comprising the tropical coastal zone (mangroves, seagrasses and reef) must also be addressed. It is hoped that such advances will ensure that overall oil spill clean-up decisions will give due consideration to the individual physical and biological characteristics of each of these tropical environments.

Extracellular suction electrode recordings from tentacles of Meandrina provide evidence for three conducting systems. One system may be the colonial nerve net. It is through-conducting and occasionally gives multiple responses to mechanical and electrical stimulation. The other two systems are also normally through-conducting but they conduct very slowly and are termed slow systems. One slow system (SSo) is in the oral disk and the other (SSc) is in the tissue covering the thecal ridges (coenosarc). SSo pulses travel throughout the interconnected oral disk regions of the colony but also enter the SSc. SSc pulses travel over the entire coenosarc but cannot enter the SSo. Both slow systems are present in the tentacles. Repetitive stimulation of the SSo evokes oral disk expansion and tentacle extension, seemingly identical to the expansion that normally occurs at night when the colony shows tentacular feeding. Repetitive stimulation of the SSc also evokes slight tentacle extension but more noticeably causes the coenosarc to become turgid. Many colonies show coenosarc expansion during the day and this may alter the exposure of symbiotic zooxanthellae to sunlight. The SSo and SSc are spontaneously active and both show a marked increase in pulse frequency when exposed to dissolved food substances. The level of activity in each system may also be modified by changes in light intensity and the SSc and SSo may thus control respectively diurnal and nocturnal expansion of different parts of the colony. The colonial nerve net appears to coordinate fast and slow contractions. Intense light can increase the level of spon­taneous activity in the nerve net.

A 200 year old brain coral, captured in Bermuda in 1976 was slabbed and x-rayed. Using the annual growth bands sequential, dated samples were taken over the entire growth period of the coral and analyzed for Δ14C, δ13C and δ18O. During the past 80 years atmospheric variations in Δ14C and δ13C due to human effects, such as release of bomb C-14 and dilution of both C-14 and C-13 by fossil fuel burning, are closely tracked by the coral. Prior to 1900 divergences between the coral and tree Δ14C and δ13C can be related to world-wide changes in plant production and possibly oceanic upwelling rates.

The Coroil project in Bermuda has been an intensive, multidisciplinary study of the effects of physically and chemically dispersed Arabian light crude oil on the main reef-building coral in Bermuda, Diploria strigosa. This paper reviews the results of this three year study. Corals were exposed to dispersed oil in a flow system, using spectrofluorimetry and gas chromatography to characterize and quantify the dose. Appropriate controls were included in all experiments. The studies included effects of dispersed oil on survival and behavior, the uptake and depuration of petroleum hydrocarbons, photosynthesis by symbiotic zoo-xanthellae, and skeletal growth. In behavioral and growth studies, corals were dosed in the laboratory or in the field. Laboratory-dosed colonies were returned to the field to determine long-term effects. Exposure to 20 ppm of chemically dispersed oil for 24 hours induced various behavioral reactions, including tentacle retraction, tissue contraction and mesenterial filament extrusion. However, effects were typically sublethal, and recovery was usually evident within four days. These symptoms were not significant in long-term transplants. Using the alizarin red staining technique, no long-term effects on skeletal growth could be detected following any of our treatments. Depuration studies using (9-I4C) -phenanthrene and gas chromatographic analysis showed that the uptake of petroleum hydrocarbons by the tissue of Diploria was rapid, but 75 percent of the hydrocarbon dose was eliminated within 14 days. Photosynthesis studies showed a short-term inhibition of photosynthesis only by chemically dispersed oil, with lipid synthesis being most severely affected. Total recovery occurred within 24 hours of exposure.

Two species of algae were living symbiotically with a hard brain coral, Fa@ia, harvested in the environs of the Flinders Island Group on the Great Barrier Reef in Australia. One of the algae has the microscopic appearance and pigment corn position of dinoflagellates (Halldal, 1968, Jeffrey and Haxo, 1968) and it contrib utes the dark brown color to the coral tissues which form a surface layer over the colony. This alga resembles Symbiodiniuni microadriaticum Freudenthal. Green algae lived inside the spherical coral forming another colored layer (Jeffrey, 1968) , and there was an intermediate pale green (nearly white) layer between these brown and green layers. The green algae seemed to be of mixed genera and species, most of them probably belonging to Ostreobiuni Reineckei Bornet within the order Siphonales. The present paper describes the in vivo absorption spectra of these algal layers as well as the spectral distribution. EXPERIMENTAL METHODS The samples of Favia pallida DaIla were harvested in the environs of the Flinders Island Group, and were kept in running sea-water aquaria on the open deck of the research vessel. The spectral data presented in this paper were observed for the sample which was 12 cm in diameter and 8.5 cm in thickness

1. The photosynthetic pigments of the green subsurface layer (Ostreobium) of The pigments found were chlorophylls a and b, α- and β-carotene, siphonein, traces the brain coral Favia were studied by two-dimensional paper chromatography. of siphonaxanthin and neoxanthin, and an unknown yellow-orange xanthophyll.2. The pigment composition of Ostreobium closely resembled that of two members of the Siphonales, Halimeda and Codium. Therefore, this alga may be appropriately grouped within the Siphonales.3. The three algae, Halimeda, Codium, and Ostreobium contained a high proportion of chlorophyll b, from two-thirds to three-quarters that of chlorophyll a.

Coral reef ecosystems are characterized by high species diversity and intense levels of biotic interaction, particularly competition for space among sessile benthic invertebrates. Using in situ pulse amplitude modulated fluorometry, we demonstrate that secondary metabolites present in the tissues of some Caribbean sponge species have rapid allelopathic effects on the symbiotic algae (zooxanthellae) that live in coral tissues and provide the energy for coral growth and reef formation. When incorporated into stable gels at natural concentrations and placed in contact with brain coral heads on shallow reefs for ~18 h, secondary metabolites of some sponge species caused a decrease in the photosynthetic potential of the symbiotic algae and bleaching of the coral tissue, whereas those of others interfered with algal photosynthesis without causing bleaching. Some sponges produce metabolites with different modes of action for competing with reef corals.