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Many species establish symbiotic partnerships with different organisms to benefit energetically from living together to fit into environments, and such symbiosis is frequently found in the modern ocean as well as throughout Earth's history. For example, coral reef ecosystems represent one of the most productive and biologically diverse ecosystems in the modern ocean, which is simply explained by an assumption that many autotroph-heterotroph symbiotic species found in there increase the efficiency of trophic transfer from primary producers (i.e., algal symbionts) to primary consumers (i.e., animal hosts), and that such high efficiency may be propagated to entire food webs. However, this high efficiency has not been proved and illustrated with quantitative data in the trophic transfer of photosynthates from algal symbionts to animal hosts. In the present study, we measured the energetic balance between degradation and biomass growth, which is a major factor of the efficiency of trophic transfer, based on the analysis of stable nitrogen isotope ratios of amino acids for several species including sea anemones, stony corals, zoanthids, and soft corals, that were bred under an autotrophic condition in a laboratory aquarium. The results confirm that the symbiosis indeed provides highly effective energy transfer of algal photosynthates to animal hosts, and allow us to quantify that the energy transfer in the symbiosis increases by approximately twice of that when non-symbiotic herbivorous species feed on primary producers. These results induce a new perspective that the effective energy transfer driven by symbiosis is a critical factor controlling the development of highly productive and biologically diverse ecosystems in the modern ocean as well as throughout Earth's history. [ABSTRACT FROM AUTHOR] more...

Both natural and human-induced stressors cause reef erosion, resulting in reef rubble formation. When consolidated, the rubble can facilitate reef recovery, sparking interest in artificial rubble stabilization as a method for reef restoration. However, our understanding of the natural processes governing coral reef regeneration within rubble beds is limited. This study examines the regeneration processes within ancient rubble frameworks in a Late Triassic carbonate platform. Results show that Late Triassic rubble environments exhibit successional trajectories similar to contemporary rubble environments. Key organisms such as sponges, calcareous red algae, bryozoans, microbes and scleractinian corals, which are instrumental in the consolidation of modern reef rubble, appear to have played comparable roles during the Late Triassic. The similarities between Late Triassic and modern reef rubble consolidation highlight enduring ecological mechanisms important for reef regeneration. This study deepens our understanding of reef dynamics and offers valuable insights for improving current reef restoration strategies, grounded in time-tested natural processes. [ABSTRACT FROM AUTHOR] more...

The unprecedented mortality of stony corals on Florida's Coral Reef from stony coral tissue loss disease (SCTLD) was mitigated on some priority sites and corals through the use of a topical amoxicillin paste to halt disease lesion progression. One management concern about the use of antibiotics on these corals was the impact it may have on gametogenesis. We used histology to assess gametogenesis within Orbicella faveolata and Montastraea cavernosa samples from six sites and across three treatment groups. The sites covered the geographic regions of the Florida Keys, including both inshore and offshore habitats. The treatment groups were: healthy corals, samples adjacent to active SCTLD lesions, and samples adjacent to previous SCTLD lesions that were halted by topical amoxicillin. Across both species, colonies from all sites and treatment groups were producing normal oocytes and spermaries. For M. cavernosa , gametogenesis metrics did not differ among treatment groups. Among O. faveolata colonies, healthy corals exhibited higher fecundity and higher oocyte presence than treated corals and larger oocytes than diseased corals. However, of the treated corals, those which had been treated more frequently had higher fecundity than those that were treated less frequently, suggesting that diminished fecundity throughout the group may have been the result of disease occurring earlier in gametogenesis rather than the treatment itself. Fecundity of O. faveolata colonies in the diseased group was highly dependent on whether the corals were from nearshore or offshore environments. The relationship between disease, treatment, and habitat warrants further examination, but we show that amoxicillin treatments do not prevent gametogenesis in corals. [ABSTRACT FROM AUTHOR] more...

The species richness of major clades and functional groups among gastropods, a key element of Modern Evolutionary Fauna (MEF), underlines the dominant role of carnivorous Caenogastropoda and Heterobranchia, including small ectoparasites and micrograzers, at modern tropical latitudes. Neogastropoda are active predators that radiated in the Cretaceous, but their early Mesozoic MEF roots are poorly understood. The escalation hypothesis emphasises prey–predator interactions as gastropods' macroevolutionary drivers during the Mesozoic Marine Revolution but overlooks the significance of highly diversified smaller forms. The tropical fossil record of the Permian–Triassic mass extinction (PTME) and the Triassic rise of MEF suggests that non-carnivorous species dominated gastropod fauna immediately before and after the PTME: Permian micrograzers mainly fed on sponges and waned during the rise of MEF, while ectoparasites and micrograzing carnivores diversified starting from the Ladinian period. Patterns of gastropod species richness, size, and form, the fossil record of reef builders and other benthic invertebrates, and an analysis of stem neogastropods jointly suggest a Middle Triassic revolution of small-sized gastropods, triggered by the emergence of scleractinian corals and the diversification of echinoderms. Habitat heterogeneity and new food sources offered niches for the early radiation of modern gastropod clades. [ABSTRACT FROM AUTHOR] more...

Scleractinian corals are foundation organisms under continuous pressure from global and local stressors. Coral habitats in the Southwestern Atlantic are known for their highly endemic fauna that thrive under suboptimal conditions. Exploring the dynamics of demographic parameters offers crucial insights into the processes driving colony growth, fragmentation, mortality, and recovery, which cannot be captured by studying coral cover alone. Here, we monitored the dynamics of colony size, regeneration and mortality of two dominant coral species, Mussismilia hispida and Siderastrea stellata, in Southeastern Brazil. We visited the same sites on three occasions counting and measuring all colonies visible within haphazardly positioned transects. Also, we applied a standardised injury to marked colonies and checked for tissue regeneration regularly for the following 384 days. We found that the average colony size decreased in both M. hispida and S. stellata, but the underlying processes were likely different. Given the importance of larger colonies for both populations, the loss of larger adults despite maintenance of colony density led to a substantial decrease in total coral cover of M. hispida. On the other hand, the maintenance of larger colonies and the increment of smaller size classes increased the total cover of S. stellata over time. Their failure to recover from tissue damage and their high partial mortality suggest that both species have been under intense stress, but overall responses varied considerably between and within species. These species had different trajectories, with populations of the hermatypic M. hispida declining over the region. [ABSTRACT FROM AUTHOR] more...

Depth distribution is an important trait for scleractinian corals, reflecting their adaptability and vulnerability. However, it remains to be quantified and analyzed adequately in turbid coral communities. Here, we used underwater photogrammetry to explore the depth distribution of turbid coral communities in China's Greater Bay Area (GBA). Surveys at the five sites revealed that the depth distribution of GBA coral communities ranged from − 0.91 m to -5.70 m, with an average depth of -3.41 m. The depth distribution of coral communities at different sites varied significantly, showing an increasing trend from inside to outside of Dapeng Bay. Coral cover and generic richness generally showed a unimodal pattern with increasing depth, with peaks in the depth range of -2 to -4 m. Coral genera exhibited significant differences in their distribution depths, and there were variations in generic composition across different depth ranges, suggesting that GBA coral communities exhibited zonation despite their limited depth ranges. [ABSTRACT FROM AUTHOR] more...

Identifying upper-thermal thresholds in corals is paramount to uncovering species and reefs with high thermal resistance and resilience. Recognition of the need to improve ex situ experiments (e.g., standardization of heat-stress experiment methodology) and a shift toward more robust and repeatable in situ monitoring (e.g., large-area imaging) can serve to improve thermal tolerance assessments. Yet rarely are the results derived from lab- and field-based approaches compared, leaving the congruence of findings unclear. Here, we selected three reefs in southern Taiwan with different thermal histories and compared the performance of the common scleractinian coral Pocillopora acuta using 1) an acute heat-stress assay experiment and 2) large-area imaging before and after a marine heatwave. Chlorophyll a, algal symbiont density, and protein concentration in the acute heat-stress assay declined sharply in high temperature treatments, with only subtle differences among sites observed. Dose-response curves of photochemical efficiency (ED50) in the acute heat-stress assay revealed differences among corals across reef sites that generally matched with the bleaching trends observed in situ. Site-specific coral–Symbiodiniaceae associations mirrored lab-based ED50 patterns as well as field-based bleaching observations (i.e., higher thermal tolerance when hosting Durusdinium spp. than Cladocopium spp.). However, site-specific bleaching trends observed in the lab experiment were opposite of that observed in the field, perhaps as a result of differential nubbin vs. colony response strategies, or as a consequence of reef conditions (e.g., community composition, structural complexity). A collective effort to compare lab- and field-based thermal responses can help build confidence in thermal tolerance categorization in corals. [ABSTRACT FROM AUTHOR] more...

Mesophotic coral ecosystems (MCEs) are light-dependent communities occurring at depths of 30–150 m. They have been suggested to serve as refuge against thermal stress during heat waves for some coral species. Recent studies on MCEs have revealed a high diversity of communities, some unique, and that these ecosystems are far from being immune to anthropogenic threats. However, the depths at which these ecosystems are found make their exploration and study challenging. Consequently, most suitable environments for MCEs remain unexplored. To facilitate the detection and characterization of MCEs, we improved the methodology for mesophotic scleractinian survey by environmental DNA (eDNA) metabarcoding analysis using seawater collected by underwater mini-Remote Operated Vehicle (mini-ROV). We tested this improved approach at upper mesophotic sites in Okinawa, Japan, with different corals dominating the communities (i.e., Alveopora-dominated, Seriatopora-dominated, and Acropora-dominated communities). Despite the proximity of the different sites, our eDNA metabarcoding analyses detected the dominant coral genera specific to each site. In addition, this study detected numerous other genera present at these sites, including Acropora, Pachyseris, Galaxea, Lobophyllia, Montipora, Pocillopora, Porites, and others. Therefore, this study might support a new technical gate for comprehensive survey of MCEs using eDNA samples collected by underwater mini-ROV, although further technical improvement is required for quantitative estimation. [ABSTRACT FROM AUTHOR] more...

Coral reef declines have been documented since the 1980's from a variety of global and local stressors. Management resource tools are needed to preserve these fragile ecosystems from stressors, both known and unknown. Laboratory studies have shown microplastics (MP) to have negative effects on coral physiology, but their effects in a natural environment are not well understood. Thus, our primary objectives were to explore associations between MPs and coral reef attributes. We measured MP concentrations from sub-surface water and coral tissue samples from two Caribbean/Atlantic scleractinian coral species, Montastraea cavernosa and Orbicella faveolata, from St. John, U.S. Virgin Islands and Florida's Coral Reef in 2017 and 2018, respectively. Polymer identification yielded mostly cotton or polyester fibers for both water and coral tissue samples. This study is the first to document MPs in coral tissues from either the U.S. Virgin Islands or Florida's Coral Reef and is the first to explore how MPs relate to coral reef attributes. Significant, positive relationships were seen between MPs in coral tissue and coral density, rugosity, and percent coral cover, indicating MPs may not have immediate adverse effects on coral reef health. [ABSTRACT FROM AUTHOR] more...

Stony coral tissue loss disease (SCTLD) was first documented in Florida in 2014 and has since spread through the Caribbean causing unprecedented mortality in more than 20 species of corals. The cause of SCTLD is unknown, but bacteria are suspected based on regression of gross lesions in some corals treated with antibiotics. Limited pathology studies on SCTLD exist, but it is likely that 'SCTLD' is a general term encompassing tissue loss disease of unexplained origin. Here, we examined pathology of lesions in corals from the US Virgin Islands where SCTLD has recently emerged. The typical histologic lesion of SCTLD in Florida corals was lytic necrosis comprising vacuolation and necrosis of mucus cells with erosion of mesoglea and misshapen endosymbionts with variably sized intracytoplasmic granules and common occurrence of filamentous viral-like particles in endosymbionts visible on electron microscopy (EM). In contrast, USVI corals had mainly lytic mucus cell hypertrophy and necrosis with no involvement of mesoglea, endosymbiont pathology at the light microscopy level was less evident, and VLP were rarely seen on EM. We suspect SCTLD is likely more complex with multiple presentations and potential etiologies depending on geographic region. Further pathological studies from other regions might help refine the case definition of SCTLD. [ABSTRACT FROM AUTHOR] more...

Small volumes of water containing environmental DNA (eDNA) are increasingly combined with metabarcoding to generate biodiversity data for specific fractions of marine flora and fauna. To date, however, few studies have utilized this technique to assess how well it captures seasonal patterns in coral reef communities or how environmental and methodological factors influence eDNA detections. In our study, we used three eDNA metabarcoding assays primarily targeting bony fish and elasmobranchs, as well as cnidarians and sponges (Cnidaria/Porifera) combined with monthly seawater sampling to (1) investigate temporal variation in taxonomic detections and (2) statistically test the potential effect of season, sea surface temperature, timing of spawning (using moon phase as a proxy), and sample preservation on taxon detection across a 12-month period in a model coral reef system (Big Vicki's Reef, Lizard Island, Great Barrier Reef, Australia). Species-level fish and genus-level scleractinian coral detections from standardized visual surveys conducted at the same coral reef, in addition to a curated list of all known fishes recorded from the more expansive coral reef system across 46 years, were used to validate eDNA detections. Our eDNA dataset indicated that the number of taxa detected were consistently highest in September for fish, and in February followed by September for Cnidaria/Porifera. Conversely, detections were lowest in June and July for all taxa. Some, but not all, of the environmental and methodological variables explained the observed temporal pattern in biological communities or systematic changes in the number of taxa, and in some cases, this effect was taxon dependent. Our study also highlights the significance of timing in eDNA biodiversity surveys conducted on tropical coral reefs in the Southern Hemisphere. To obtain the most meaningful estimates of site diversity, we recommend focusing sampling efforts between early spring and early autumn. Alternatively, allocating an entire year to sampling would better capture seasonal variation and provide more comprehensive insights into coral reef biodiversity. [ABSTRACT FROM AUTHOR] more...

The effects of stony coral tissue loss disease (SCTLD) in the Dutch Caribbean, specifically in Bonaire, have not been documented since its first sighting in March 2023. By comparing the results of the 2023 surveys with data from previous surveys conducted over the past 9 years, this study quantifies the overall decline in coral cover and investigates the spatial variability of SCTLD's impact across different subregions of the reef on the leeward side of Bonaire. In the year 2023, a crucial period in the initial phase of the progression of SCTLD, significant reduction in coral coverage was observed, with six key reef-building coral species showing significant vulnerability. Importantly, this research identifies specific subregions that have been disproportionately affected. The insights gained from this study are important for the potential development of specific conservation and restoration strategies for Bonaire, underscoring the necessity for ongoing ecosystem monitoring to safeguard the future of highly sensitive coral reefs in a changing ocean. By advancing our understanding of SCTLD dynamics, this research contributes to the global effort to preserve coral reef ecosystems in the face of emerging coral diseases. [ABSTRACT FROM AUTHOR] more...

Stony corals possess major components of the circadian system, which oscillate in response to light-dark cycles in aquatic environments. However, the extent to which the circadian system influences physiological processes remains unknown. This study investigated the role of circadian genes (cry1 , cry2 , cry3 , clock , cycle , and slmb) in modulating the transcription of photoreceptor (opsin1 , opsin2 , and opsin3), calcification/metabolism-related (ca , pmca , sglt , and ppp1r), and homeostasis/stress-related (hif1α , egln , sod , and hsp70) genes in Acropora digitifera , a stony coral inhabiting shallow water. Nubbins of A. digitifera were reared under light-dark (LD) and constant darkness (DD) conditions and sampled at 4-h intervals. Quantitative PCR analysis revealed that cry1 , cry2 , cry3 , and clock expression increased during the daytime under LD conditions and attenuated during the subjective daytime under DD conditions, suggesting that these genes are light-responsive. In contrast, cycle and slmb exhibited similar expression profiles with increases during the daytime/subjective daytime under both LD and DD conditions, implying robust roles in the circadian system. The abundance of opsin1 showed minimal change under LD and DD conditions, whereas the abundances of opsin2 and opsin3 increased during daytime/subjective daytime under both conditions, indicating circadian regulation. Some genes tested by qPCR significantly fluctuated with light (pmca , sglt , ppp1r , egln , sod , and hsp70) and time (ca , pmca , sglt , ppp1r , hif1α , egln , sod , and sod). Principal component analysis revealed significant correlations of circadian genes (cycle or slmb) with calcification/metabolism-related (pmca), oxygen homeostasis (hif1α), and stress indicator (sod) genes under both LD and DD conditions. Therefore, some physiological responses in A. digitifera exhibit daily changes and are partially regulated by the circadian system. [ABSTRACT FROM AUTHOR] more...

Trait-based approaches are revolutionizing our understanding of high-diversity ecosystems by providing insights into the principles underlying key ecological processes, such as community assembly, species distribution, resilience, and the relationship between biodiversity and ecosystem functioning. In 2016, the Coral Trait Database advanced coral reef science by centralizing trait information for stony corals (i.e., Subphylum Anthozoa, Class Hexacorallia, Order Scleractinia). However, the absence of trait data for soft corals, gorgonians, and sea pens (i.e., Class Octocorallia) limits our understanding of ecosystems where these organisms are significant members and play pivotal roles. To address this gap, we introduce the Octocoral Trait Database, a global, open-source database of curated trait data for octocorals. This database houses species- and individual-level data, complemented by contextual information that provides a relevant framework for analyses. The inaugural dataset, OctocoralTraits v2.2, contains over 97,500 global trait observations across 98 traits and over 3,500 species. The database aims to evolve into a steadily growing, community-led resource that advances future marine science, with a particular emphasis on coral reef research. [ABSTRACT FROM AUTHOR] more...

Background: Evolutionary tradeoffs between life-history strategies are important in animal evolution. Because microbes can influence multiple aspects of host physiology, including growth rate and susceptibility to disease or stress, changes in animal-microbial symbioses have the potential to mediate life-history tradeoffs. Scleractinian corals provide a biodiverse, data-rich, and ecologically-relevant host system to explore this idea. Results: Using a comparative approach, we tested if coral microbiomes correlate with disease susceptibility across 425 million years of coral evolution by conducting a cross-species coral microbiome survey (the "Global Coral Microbiome Project") and combining the results with long-term global disease prevalence and coral trait data. Interpreting these data in their phylogenetic context, we show that microbial dominance predicts disease susceptibility, and traced this dominance-disease association to a single putatively beneficial symbiont genus, Endozoicomonas. Endozoicomonas relative abundance in coral tissue explained 30% of variation in disease susceptibility and 60% of variation in microbiome dominance across 40 coral genera, while also correlating strongly with high growth rates. Conclusions: These results demonstrate that the evolution of Endozoicomonas symbiosis in corals correlates with both disease prevalence and growth rate, and suggest a mediating role. Exploration of the mechanistic basis for these findings will be important for our understanding of how microbial symbioses influence animal life-history tradeoffs. [ABSTRACT FROM AUTHOR] more...

Background: Larval propagation and seeding of scleractinian corals for restoration is a rapidly expanding field, with demonstrated applications to assist the recovery of declining populations on reefs. The process typically involves collecting coral reproductive material, facilitating in vitro fertilization (IVF), and settling and outplanting the resulting coral offspring. Optimizing IVF can reduce gamete wastage and increase larval yields for propagation, therefore improving the efficiency of this intervention. Methods: In this study we tested three IVF conditions in four Caribbean broadcast-spawning coral species (i.e., Diploria labyrinthiformis, Colpophyllia natans, Pseudodiploria strigosa, Orbicella faveolata) to determine sperm concentration, gamete age, and co-incubation time resulting in the highest fertilization success. For each species, we exposed eggs from a single dam to pooled sperm samples from three sires (1) at concentrations ranging from zero to 109 cell mL−1, (2) after letting gametes age for 2 to 6 h, and (3) for a period of 15 to 120 min. Results: These experiments revealed a gamete longevity of at least 4 h and clear minimum sperm concentration thresholds (>105 to 106 cell mL−1) in all four species. Fertilization took place much faster than expected (≤15 min) in the three brain corals under study, whereas O. faveolata gametes required a co-incubation period of 60 to 120 min to achieve maximum IVF success. Discussion: We present these results in the context of IVF data available for other hermaphroditic broadcast-spawning scleractinians. We then provide recommendations for coral breeding practitioners to maximize larval production from gamete collections, and finally, we discuss our findings' potential implications on fertilization dynamics during natural coral spawning events. [ABSTRACT FROM AUTHOR] more...

Ostreobium comprises endolithic algae commonly seen in conjunction with scleractinian corals. In the past, it was solely recognized as a coral skeleton bioeroder. Their relationship with corals is critical because they give photosynthetic byproducts and help the coral when it loses its primary symbionts due to stress. The variety of these algae in coral species of the genus Porites in the Tropical Eastern Pacific and western Atlantic was investigated. Ostreobium samples from seven Porites species including two from the Tropical Eastern Pacific (TEP) (P. panamensis and P. lobata) and five from the Caribbean (P. furcata, P. porites, P. colonensis, P. branneri, and P. astreoides) were extracted. Published rbcL sequences from algae found within various coral species from other parts of the world were also compared. A biogeographic analysis and two methodologies, PTP (Poisson tree process) and GMYC (general mixed Yule‐coalescent), were used to delineate the different species. The findings revealed a significant degree of genetic diversity within Ostreobium, with more than 15 groups of not more than three individuals and 40 individual lineages. Its origins date back to the Ordovician, 500 Ma, and it does not appear to preserve host specificity. The sampled locations still have a wide variety of Ostreobium. Biogeographically patterns were also confirmed, making it impossible to pinpoint the precise origins of most clades. The ancestry analyses revealed convergent events for not only the emergence of Ostreobium in a few genera of local corals, but also the phenomenon occurred in genera from far‐off places. [ABSTRACT FROM AUTHOR] more...

Brazilian coral reefs are the largest and richest reefs in the Southwestern Atlantic Ocean. Despite their historical and tourist importance, coral reefs on the east coast of Brazil remained unknown until recently. This study evaluated the structure of the reef-building coral community in three tidal pools along a gradient of anthropogenic disturbance. The pool known as Dolphin Pool is the warmest and has a high abundance of stony coral Siderastrea spp. One endemic species is on the national list of threatened species. Despite the high frequency of water temperatures above the alert threshold for mass bleaching events, the tidal pools have high densities of adults and recruits of reef-building corals. The results highlight the importance of reef formations on the coastal zone of the Royal Charlotte Bank, given the uniqueness of this area, and reinforce the need for further research and adoption of adaptive conservation approaches. [ABSTRACT FROM AUTHOR] more...

Aim: Identifying the maximum coral cover that a coral community can sustain (i.e., its 'upper limit') is important for predicting community dynamics and improving management strategies. Here, we quantify the relationship between estimated upper limits and key environmental factors on coral reefs: hard substrate availability, temperature and water clarity. Location: Great Barrier Reef (GBR), Australia (over 1400 km). Time Period: 1990 to 2022. Major Taxa Studied: Scleractinian corals. Methods: We used 32 years of data on coral cover around reef perimeters. Each reef was divided into four wave‐exposure habitats depending on prevailing wind conditions. For each site, we determined if hard coral cover had reached a plateau or upper limit. Next, we extracted existing estimates of hard substrate availability, modelled water temperature and Secchi depth. Then, we quantified the relationship between these environmental variables and the upper limits. Results: We found varying upper limits across the GBR, with a median of 33% coral cover and only 17% of the estimated upper limits exceeded 50% coral cover. Upper limits increased towards the southern reefs. Our results show that upper limits increased with increasing hard substrate availability and decreased with temperature and, to a lesser extent, with water clarity. Main Conclusions: The upper limits estimated in this study are much lower than what is commonly assumed when modelling ecological dynamics, most likely resulting in predicted recovery rates being inappropriately high. Although hard substrate ultimately restricted upper limits, there are mechanisms constraining the proportion of hard substrate that is covered by hard corals. The negative relationship between temperature and upper limits cannot be explained by changes in macroalgal abundance but may be related to changes in species composition. The quantitative relationships between the upper limits of coral cover and environmental variables will provide critical information to prioritise sites for management interventions. [ABSTRACT FROM AUTHOR] more...

Corals have complex symbiotic associations that can be influenced by the environment. We compare symbiotic dinoflagellate (family: Symbiodiniaceae) associations and the microbiome of five scleractinian coral species from three different reef habitats in Palau, Micronesia. Although pH and temperature corresponded with specific host‐Symbiodiniaceae associations common to the nearshore and offshore habitats, bacterial community dissimilarity analyses indicated minimal influence of these factors on microbial community membership for the corals Coelastrea aspera, Psammocora digitata, and Pachyseris rugosa. However, coral colonies sampled close to human development exhibited greater differences in microbial community diversity compared to the nearshore habitat for the coral species Coelastrea aspera, Montipora foliosa, and Pocillopora acuta, and the offshore habitat for Coelastrea aspera, while also showing less consistency in Symbiodiniaceae associations. These findings indicate the influence that habitat location has on the bacterial and Symbiodiniaceae communities comprising the coral holobiont and provide important considerations for the conservation of coral reef communities, especially for island nations with increasing human populations and development. [ABSTRACT FROM AUTHOR] more...

Reproduction, embryological development, and settlement of corals are critical for survival of coral reefs through larval propagation. Yet, for many species of corals, a basic understanding of the early life‐history stages is lacking. In this study, we report our observations for ex situ reproduction in the massive reef‐building coral Porites cf. P. lobata across 2 years. Spawning occurred in April and May, on the first day after the full moon with at least 2 h of darkness between sunset and moonrise, on a rising tide. Only a small proportion of corals observed had mature gametes or spawned (14–35%). Eggs were 185–311 μm in diameter, spherical, homogenous, and provisioned with 95–155 algal cells (family Symbiodiniaceae). Males spawned before females, and ex situ fertilization rates were high for the first 2 h after egg release. Larvae were elliptical, ~300 μm long, and symbiotic. Just 2 days after fertilization, many larvae swam near the bottom of culture dishes and were competent to settle. Settlers began calcification 2 days after metamorphosis, and tentacles were developed 10 days after attachment. Our observations contrast with previous studies by suggesting an abbreviated pelagic larval period in Porites cf. P. lobata, which could lead to the isolation of some populations. The high thermal tolerance and broad geographic range of Porites cf. P. lobata suggest that this species could locally adapt to a wide range of environmental conditions, especially if larvae are locally retained. The results of this study can inform future work on reproduction, larval biology, dispersal, and recruitment in Porites cf. P. lobata, which could have an ecological advantage over less resilient coral species under future climate change. [ABSTRACT FROM AUTHOR] more...

The crown-of-thorns starfish (COTS) is known to destroy coral reefs by ingesting scleractinian corals during population outbreaks. Previous studies showed that Acanthaster planci is comprised of four species collectively called the A. planci species complex. Despite available online database sequences, the Pacific group of COTS -- known as either Acanthaster solaris or Acanthaster cf. solaris -- lacks comprehensive morphological descriptions and museum voucher specimens. Hence, this study aimed to characterize COTS specimens from two sites located in southern Negros Island using morphological features and partial CO1 mitochondrial gene. Morphological and morphometric data were obtained for size, color, rigidity, pedicellariae, adambulacral and abactinal spines, and arms. Tube feet were collected for DNA barcoding. Genetic divergence was determined between southern Negros Island and reference sequences of the A. planci species complex using the Kimura 2-parameter substitution model. Specimens from SNI have a grayish-blue aboral body color with blackish-red spots distributed throughout the central disc. The body color turns grayish-white, and the spots become redder when the animals are exposed to air. They have six types of spines and minute pedicellariae all over the body. All the COTS individuals collected from southern Negros Island claded with the Pacific group of the species complex, labeled as Acanthaster cf. solaris. The intra-specific genetic divergence between southern Negros Island sequences and the Pacific clade was 0.192 and 0.38%, respectively. Our results validate the presence of A. cf. solaris in the Philippines and provide a more comprehensive morphological description of the species from the Indo-Pacific region. Voucher specimens of the species were deposited at the Silliman University Rodolfo B. Gonzales Museum of Natural History. [ABSTRACT FROM AUTHOR] more...

Global climate change is profoundly impacting coral ecosystems. Rising sea surface temperatures, in particular, disrupt coral reproductive synchrony, cause bleaching, and mortality. Oculina patagonica, a temperate scleractinian coral abundant across the Mediterranean Sea, can grow at a temperature range of 10–31 °C. Studies conducted three decades ago documented this species bleaching during the summer months, the same time as its gonads mature. However, the Eastern Mediterranean Sea is experiencing some of the fastest-warming sea surface temperatures worldwide. This study repeated the year-round in situ assessment of the reproductive cycle and gonad development and correlation to summer bleaching. In addition, thermal performance of the holobiont was assessed in an ex situ thermal stress experiment. In situ monitoring revealed no temporal changes in gonad development compared to previous studies, despite sea surface warming and concurrent bleaching. Experimental thermal performance curves indicated that photosynthetic rate peaked at 23 °C, bleached coral area was significant at 29 °C, and peaked at 34 °C. With local sea surface temperature reaching 31 °C, O. patagonica is exposed beyond its bleaching threshold during the summer months in situ. Despite this, O. patagonica maintains gonad development and physiologically recovers at the end of summer demonstrating resilience to current warming trends. [ABSTRACT FROM AUTHOR] more...

In the face of global warming and ocean acidification, understanding the cellular mechanisms underlying coral metamorphosis and early calcification is essential, as both processes are likely to be affected by a changing environment. In this study, we used cDNA microarray expression analysis to compare transcription profiles between four distinct life stages in the 'complexa' coral Acropora millepora: 1) aposymbiotic non-calcifying planula, 2) aposymbiotic calcifying flat polyp, 3) aposymbiotic calcifying primary polyp and 4) symbiotic adult tip. Highly up-regulated genes in planulae were molecules involved in calcium signalling, lipid metabolism and development. Transcripts up-regulated in post-settlement juvenile stages regulate tissue morphogenesis, cell division and responses to oxidative stress. Transcripts with the highest expression in adult polyps are involved in responses to abiotic stimuli and asexual reproduction. Transcripts up-regulated in calcifying stages included carbonic anhydrases and organic matrix components. Additionally, our results suggest an overlap between intracellular secondary messengers following settlement and metamorphosis. A subset of fluorescent proteins were up-regulated at the planula stage but down-regulated after settlement, supporting the idea that these molecules might have a role in quenching reactive oxygen species. Altogether, our results suggest that Acropora developmental stages are transcriptionally distinct units in which transcription profiles reflect responses to different physiological and ecological conditions. [ABSTRACT FROM AUTHOR] more...

Drastic declines observed in coral reefs in response to changes in climate and other anthropogenic stressors have hinged the survival of these ecosystems largely on the overall health and reproductive success of stony corals. One specific threat, Karenia brevis blooms, has drawn increased public attention in recent decades and has been documented to reach the Florida Keys, a vulnerable coral ecosystem. The purpose of this study was to investigate the sublethal impact of K. brevis exposure on three South Florida "restoration" coral species. Fragments of Porites astreoides, Acropora cervicornis, and Siderastrea radians were exposed to three environmentally relevant concentrations of K. brevis for 2 weeks in a controlled aquaria setting. At the end of exposure, ultra-high-performance liquid chromatography coupled to high-resolution tandem mass spectrometry (UHPLC-HRMS/MS) was used to perform nontargeted lipidomics and metabolomics analyses to assess physiological changes in the corals in response to red tide exposure, as well as highlight possible biological processes and pathways altered. Significant changes to the lipidome and metabolome were observed in all three species following exposure. Furthermore, the multi-omics analysis highlighted important pathways for further study including impacts on oxidative stress, energy metabolism, the immune system, and nitrogen fixation/photosynthesis of symbionts. Due to the use of environmentally relevant exposure levels and duration, these results are invaluable to understand possible future impacts of red tide on coral reef areas as well as to inform future coral reef restoration and management decisions. [ABSTRACT FROM AUTHOR] more...

Coral reefs are known to be one of the most diverse marine ecosystems on earth. However, these important ecosystems are heavily stressed by natural and anthropogenic activities. Environmental DNA (eDNA) metabarcoding is an innovative approach that can provide a greater diversity of taxonomic detections, non-invasive sampling, and a lower field component cost than traditional biomonitoring methods. Taiping Island (Itu Aba Island) is one of the major coral reef islands situated in the South China Sea where underwater visual surveys documented an outbreak of Crown-of-Thorns starfish (COTS) in 2021. In our study, we used eDNA metabarcoding to investigate whether there were shifts in coral communities by comparing pre- and post-COTS outbreak communities. One metabarcoding assay targeting the 18S gene and two assays targeting the ITS2 region (one of these assays specifically targeting Acroporid corals) were applied to 42 seawater samples collected in 2019 and 2021 from 12 sites around Taiping Island. Based on these three metabarcoding assays, 52 unique hard coral species were identified, corresponding to a total of 51 species in 2019 and 26 species in 2021. Our results indicated a significant decline in coral diversity but an increase in sponge diversity from the phylum porifera at Taiping Island in 2021. We suggest that these faunal shifts may be due to active feeding and disturbance of COTS at outbreak proportions that result in habitat changes. Our findings also suggest that eDNA can continue to serve as a promising tool to monitor the change in coral as well as reef-associated taxa during devastating outbreak events. [ABSTRACT FROM AUTHOR] more...

Climate-driven species range expansions are underway with more tropically affiliated species, including Scleractinian corals, becoming increasingly abundant at higher latitudes. However, uncertainty remains on how these range shifts will affect reef-scale ecosystem processes, which will ultimately depend on the traits of the taxa that dominate these assemblages. Here, we quantified spatiotemporal patterns in the taxonomic and trait structure of coral assemblages along the subtropical-temperate coast of Western Australia (27°–34°S). Coral abundance was generally low and coral cover < 5% across our study sites. Coral assemblages shared similarities in morphological trait structures across the latitudinal gradient, mostly characterised by taxa with simple morphologies; yet subtle differences were also observed across latitudes, with high-latitude corals characterised by slower growth rates and reduced maximum colony sizes. We found a 3.4-fold increase (from 1 to 3.4 individuals m−2) in coral abundance at one heavily disturbed location, where canopy-forming seaweeds were replaced by turfing algae, a pattern that was partly driven by an increase in the relative contribution of warm affinity taxa, such as Acropora spp. We predicted these changes would be reflected in different components of functional diversity; yet, despite a localised signal of tropicalisation, we only observed subtle changes in the functional identity, richness, evenness, and divergence. The spatially invariant trait structure of coral assemblages suggests that the nature of ecosystem functions will likely remain unchanged during early stages of tropicalisation, and hence their contribution to temperate reef-scale ecological processes will depend on dominance over other benthic foundational species. [ABSTRACT FROM AUTHOR] more...

Scleractinian corals, the principal architects of coral reefs, face substantial threats from ongoing and anticipated climate change and other anthropogenic disturbances. This underscores the significance of investigating alternative reef-building organisms and their contribution to reefs' resilience. Among these alternatives, colonial hydrozoans of the genus Millepora, commonly called 'fire corals', play substantial roles in contributing to coral reef structure and functionality by depositing calcareous exoskeletons. Despite the ecological importance of fire corals, fundamental knowledge gaps remain regarding their biology and reproductive ecology. Here, we present a comprehensive study on the population dynamics, reproductive ecology, phenology, and sex ratio of the three Red Sea fire corals—Millepora dichotoma, M. exaesa, and M. platyphylla—in the Gulf of Aqaba and Eilat. The abundance of M. dichotoma and M. exaesa seems to have remained consistent over the last 50 years across two of the three depth zones surveyed, indicating their potential resistance or resilience. However, at the third depth surveyed, their abundance appears to have decreased. Our extensive in-situ monitoring of breeding events over six consecutive years has revealed a previously undetected relationship between Millepora species breeding events and the lunar cycle. Histological analyses indicated remarkably short reproductive cycles of only 2–3 weeks, recurring multiple times within a single season, in both M. dichotoma and M. exaesa, which is a unique reproductive aspect compared to other reef-building corals. These results highlight the high reproductive and resilience potential of Millepora species. Consequently, fire corals could assume a more substantial role as keystone species in changing environments and future reefs, emphasizing their importance in reef conservation and management. [ABSTRACT FROM AUTHOR] more...

Thermal anomalies caused by climate change have emerged as a major threat to reef ecosystems globally. While the effects of warming oceans have been extensively investigated in tropical reefs, its effects on subtropical reefs, where coral diversity is lower, remain largely unstudied. We analysed the spatial distribution, mean cover and health status of scleractinian corals in the subtropical rocky reefs of the Alcatrazes Archipelago, a no‐take marine protected area located 30 km off the coast of São Paulo state, Brazil (24° S). Data were collected before (2018) and after (2022) the most intense marine heatwave ever recorded in the region, in 2019, using either fixed or random photoquadrats. Five scleractinian corals were recorded as follows: The zooxanthellate massive species Mussismilia hispida and Madracis decactis, the azooxanthellate solitary corals Astrangia spp. and Coenocyathus sebroecki and the invasive sun coral Tubastraea spp. M. hispida and M. decactis were the most abundant species, particularly in the sheltered sites, while Astrangia spp. and C. sebroecki were less abundant and only recorded in the exposed side of the island. In the single site where Tubastraea spp. colonies prevailed, other coral species were nearly absent. Both M. hispida and M. decactis exhibited resilience to the 2019's bleaching event, with their abundance remaining almost the same in 2022. Our findings add evidences to the emerging idea that subtropical reefs in the southwestern Atlantic may serve as refuges during future thermal anomalies, highlighting the importance of monitoring these reefs in the context of changing habitats driven by warming oceans. [ABSTRACT FROM AUTHOR] more...

Sexually propagated scleractinian corals are in high demand for coral reef restoration. However, for threatened reef-building corals, many of the molecular mechanisms related to their reproduction remain largely unknown, which forms a major bottleneck in the large-scale cultivation of sexually reproducing corals. In this study, we analyzed the proteomic signatures of red eggs and spermatozoa from the ecologically significant coral Galaxea fascicularis, using a data-independent acquisition mass spectrometry (DIA-MS) method. A total of 7741 and 7279 proteins from mature red eggs and spermatozoa were identified, respectively. Among these proteins, 596 proteins were spermatozoa-specific and 1056 were egg-specific. Additionally, a total of 4413 differentially abundant proteins (DAPs) were identified, among which 3121 proteins were up-regulated in red eggs and 1292 proteins were up-regulated in spermatozoa. Furthermore, anenrichment analyses showed that DAPs identified in red eggs were mainly involved in the progesterone-mediated oocyte maturation pathway and lectin pathway; and DAPs detected in spermatozoa were mainly involved in the insulin secretion pathway and metabolic pathways for the generation of energy. This result will contribute to the discovery of the intrinsic regulation pathway of gamete maturation and fertilization. Furthermore, at least 57 proteins associated with gamete maturation and reproduction were identified, including the red fluorescent protein (RFP), vitellogenin proteins (VG), the egg protein (EP), the testis-specific serine/threonine-protein kinase family (TSSKs), and the EF-hand Ca2+-binding protein family (EFHC1 and EFHC2). Particularly, the third yolk protein EUPHY was reported for the first time in G. fascicularis. In conclusion, this study unveiled groundbreaking molecular insights into coral sexual reproduction, paving the way for more effective conservation and sustainable development of coral reef ecosystems [ABSTRACT FROM AUTHOR] more...

Models of the future of coral reefs are potentially sensitive to theoretical assumptions, variable selectivity, interactions, and scales. A number of these aspects were evaluated using boosted regression tree models of numbers of coral taxa trained on ~1000 field surveys and 35 spatially complete influential environmental proxies at moderate scales (~6.25 km2). Models explored influences of climate change, water quality, direct human‐resource extraction, and variable selection processes. We examined the predictions for numbers of coral taxa using all variables and compared them to models based on variables commonly used to predict climate change and human influences (eight and nine variables). Results indicated individual temperature variables alone had lower predictive ability (R2 < 2%–7%) compared to human influence variables (6%–18%) but overall climate had a higher training–testing fit (70%) than the human influence (63%) model. The full variable model had the highest fit to the full data (27 variables; R2 = 85%) and indicated the strongly interactive and complex role of environmental and human influence variables when making moderate‐scale biodiversity predictions. Projecting changes using Coupled Model Intercomparison Project (CMIP) 2050 Representative Concentration Pathways (RCP2.6 and 8.5) water temperature predictions indicated high local variability and fewer negative effects than predictions made by coarse scale threshold and niche models. The persistence of coral reefs over periods of rapid climate change is likely to be caused by smaller scale variability that is poorly simulated with coarse scale modeled predictions. [ABSTRACT FROM AUTHOR] more...

Stony coral tissue loss disease (SCTLD) causes severe mortality in many hard corals and is now present in most of the Caribbean. The application of amoxicillin paste is currently the most successful local intervention to treat SCTLD lesions in nature, but the potential development of antibiotic resistance makes alternatives valuable. In a preliminary field trial (n = 84 corals), we compared two treatments against SCTLD, (1) amoxicillin paste and (2) chlorine mixed with cocoa butter paste and covered with a clay band. We found that amoxicillin and chlorine treatments both significantly reduced the rate of tissue loss in SCLTD-affected corals as compared to controls. Amoxicillin treatment was the most effective and effectively halted tissue loss in 78% of colonies. Even so, chlorine treated colonies lost tissue at approximately half the rate of untreated controls. The non-specific antiseptic nature of chlorine treatments may also be useful for other tissue loss diseases of unknown etiologies. Although, not perfect, the chlorinated cocoa butter treatment can be added to the growing list of methods to reduce mortality from disease in the field. [ABSTRACT FROM AUTHOR] more...

Marine actinomycetes exhibit a high level of biodiversity and possess significant potential for the production of high-value secondary metabolites. During the course of investigation of marine actinobacteria from corals, two Saccharopolyspora strains, namely, HNM0983T and HNM0986T, were isolated from stony corals collected from the coastal area of Hainan Island. The 16S ribosomal RNA (rRNA) gene sequence analysis revealed that these two strains are putative novel taxa of the genus Saccharopolyspora. Whole-genome sequencing comparisons further confirmed the two strains as belonging to two novel Saccharopolyspora species, which can be distinguished phenotypically and chemically from their current closest phylogenetic relatives. Some genomic information of the genus Saccharopolyspora was compared for evaluating the production capacity of secondary metabolites. A total of 519 biosynthetic gene clusters (BGCs) from the genus Saccharopolyspora were used for analysis, and terpene BGCs were found to be widespread and most abundant in this genus. In addition, abundant novel BGCs in the genus Saccharopolyspora are not clustered with the known BGCs in the database, indicating that the metabolites of the genus Saccharopolyspora deserve further exploration. On the basis of these presented results, Saccharopolyspora montiporae sp. nov. (type strain = HNM0983T = CCTCC AA 2020014T = KCTC 49526T) and Saccharopolyspora galaxeae sp. nov. (type strain = HNM0986T = CCTCC AA 2020011T = KCTC 49524T) are proposed as the names for the new strains, respectively. [ABSTRACT FROM AUTHOR] more...

Metrics of coral physiology can be used to identify changes in coral health due to environmental stressors or management actions. One of the most unprecedented stressors to Caribbean corals is the spread of stony coral tissue loss disease (SCTLD), which also resulted in the novel management action of in-water amoxicillin treatments on active disease lesions. Though highly effective at halting lesions and preventing coral mortality, possible unintended consequences of topical application of amoxicillin to coral tissue were unknown. We used in-water instrumentation to measure and compare photosynthesis (P), respiration (R), P/R ratios, and calcification of corals that were visually healthy, actively diseased, and diseased but treated with amoxicillin paste. Measurements occurred across three time points and two species – Orbicella faveolata and Montastraea cavernosa. Across all metrics, treatment type did not cause significant differences, indicating that neither SCTLD lesions nor amoxicillin treatments impacted the physiology of adjacent tissues. There were significant variations among time points, which may have resulted from changes to coral health across the reef, variations due to environmental variables, or other unknown factors. We suggest that physiological metrics could be an interesting way to fate track coral health across short- and long-term timeframes. We also conclude that amoxicillin treatments as a tool to halt SCTLD are not detrimental to respiration, photosynthesis, or calcification rates of adult corals. [ABSTRACT FROM AUTHOR] more...

The article discusses the spread of a sea urchin disease to the Indian Ocean, causing widespread mortalities, with evidence from Réunion Island. The disease has led to significant declines in sea urchin populations, impacting marine ecosystems. The study highlights the importance of sea urchins in maintaining ecological balance and the potential ecological consequences of large-scale sea urchin die-offs. The pathogen responsible for the disease has been identified, and its spread to other regions in the Western Indian Ocean is noted. [Extracted from the article] more...

Atlantic reef-building corals and coral reefs continue to experience extensive decline due to increased stressors related to climate change, disease, pollution, and numerous anthropogenic threats. To understand the impact of ocean warming and reef loss on the estimated extinction risk of shallow water Atlantic reef-building scleractinians and milleporids, all 85 valid species were reassessed under the IUCN Red List Categories and Criteria, updating the previous Red List assessment of Atlantic corals published in 2008. For the present assessment, individual species declines were estimated based on the modeled coral cover loss (1989–2019) and projected onset of annual severe bleaching events (2020–2050) across the Atlantic. Species traits were used to scale species' relative vulnerability to the modeled cover declines and forecasted bleaching events. The updated assessments place 45.88%–54.12% of Atlantic shallow water corals at an elevated extinction risk compared to the previous assessments conducted in 2008 (15.19%–40.51%). However, coral cover loss estimates indicate an improvement in reef coverage compared to the historic time-series used for the 2008 assessments. Based on this, we infer that, although remaining dangerously high, the rate of Atlantic reef coral cover decline has surprisingly slowed in recent decades. However, based on modeled projections of sea-surface temperature that predict the onset of annual severe bleaching events within the next 30 years, we listed 26 (out of 85) species as Critically Endangered in the IUCN Red List. Each of these species had previously been listed under a lower threatened category and this result alone highlights the severe threat future bleaching events pose to coral survival and the reef ecosystems they support. [ABSTRACT FROM AUTHOR] more...

Organismal communities associated with coral reefs, particularly invertebrates and microbes, play crucial roles in ecosystem maintenance and coral health. Here, we characterized the organismal composition of a healthy, non-urbanized reef (Site A) and a degraded, urbanized reef (Site B) in the Gulf of Eilat/Aqaba, Red Sea to assess its impact on coral health and physiology. Biomimetically designed terracotta tiles were conditioned for 6 months at both sites, then reciprocally transplanted, and scleractinian coral species, Acropora eurystoma and Stylophora pistillata, were attached for an additional 6 months. After 12 months, tiles from Site A transplanted to Site B exhibited greater invertebrate richness and diversity than Site B's original tiles (via Cytochrome c. Oxidase subunit I metabarcoding). Key bacteria from the healthy reef were more prevalent on Site A tiles and on the tiles transplanted to Site B (via 16S rRNA gene sequencing). Corals originally from Site B attached to transplanted healthy tiles (Site A) showed higher photochemical capacity, increased endosymbionts, and reduced physiological stress, measured by total antioxidant capacity and an integrated biomarker response. Our findings demonstrate the successful transfer of organismal communities between reefs, highlighting the potential benefits of healthy reef-associated invertebrates and microbes on coral physiology and their implications for reef restoration strategies. Invertebrate and microbe communities support reef ecosystems and coral health. Here, the authors characterize these communities from degraded and healthy reefs, showing that transplanting these healthy communities improved coral health at degraded reefs. [ABSTRACT FROM AUTHOR] more...

Background: Alzheimer's disease is a neurodegenerative disease that has no cure. The drugs used to treat Alzheimer's disease are based on the inhibition of the enzyme acetylcholinesterase (AChE). In this sense, marine fungal metabolites represent an alternative source for the discovery of drugs based on AChE inhibition (IAChE). The present research carried out a bioprospecting study of marine fungi with acetylcholinesterase inhibition potential. Results: A total of 17 marine fungi were isolated from three stony corals from the Veracruz Reef System. The fungal genera identified were Geotrichum, Curvularia, Penicillium, Aspergillus, and Daldinia. The IAChE was evaluated from the broth and biomass extracts of each fungal strain. As a result, Daldinia eschscholtzii was one of the three fungi with the greatest IAChE effect (32.7%). Subsequently, a bio-directed chromatographic purification of the methanolic extract of the biomass of D. eschscholtzii was carried out. The FRL8.1 fraction was the most active with an IAChE of 41.0%, a value close to Galantamine positive control (44.0%). Furthermore, compound analysis was carried out by GC-MS. Finally, it was determined that the metabolites responsible for the inhibitory effect are probably 4,7-dihydroxycoumarin and 5-nitro-2-naphthalenamine, which was demonstrated by their interactions with the AChE enzyme receptor through molecular docking studies. Conclusions: Coral-associated marine fungi produce secondary metabolites that inhibit acetylcholinesterase. This is the first report of D. eschscholtzii isolated from the stony coral Siderastrea siderea. Finally, we consider that more studies are needed to demonstrate the IAChE potential of marine fungi associated with corals or other marine organisms. [ABSTRACT FROM AUTHOR] more...

Stony coral tissue loss disease (SCTLD) has swept through Florida reefs and caused mass mortality of numerous coral species. In the wake of these losses, efforts are underway to propagate coral species impacted by SCTLD and promote population recovery. However, numerous knowledge gaps must be addressed to effectively grow, outplant, and restore populations of the slower growing, massive species that were lost. Here, we used sexual recruits of Diploria labyrinthiformis spawned in captivity to understand how conditioning, coral size, and nutritional status at outplanting affect coral survivorship, growth, and susceptibility to predation. We found that ex situ conditioning with supplemental feeding increased coral growth rates, resulting in larger sized corals at the time of outplanting. In turn, these corals had higher growth rates in the field and a lower probability of being removed by predators than outplants that were conditioned in in situ nurseries. Additionally, we found that coral size was an important predictor of survivorship, suggesting that hastening the speed at which young corals grow and outplanting larger juveniles can improve restoration outcomes. Taken together, our results suggest that providing supplemental food to corals at ex situ facilities confers benefits that could help restore populations of massive coral species impacted by SCTLD. [ABSTRACT FROM AUTHOR] more...

Melanin is an essential product that plays an important role in innate immunity in a variety of organisms across the animal kingdom. Melanin synthesis is performed by many organisms using the tyrosine metabolism pathway, a general pathway that utilizes a type-three copper oxidase protein, called PO-candidates (phenoloxidase candidates). While melanin synthesis is well-characterized in organisms like arthropods and humans, it is not as well-understood in non-model organisms such as cnidarians. With the rising anthropomorphic climate change influence on marine ecosystems, cnidarians, specifically corals, are under an increased threat of bleaching and disease. Understanding innate immune pathways, such as melanin synthesis, is vital for gaining insights into how corals may be able to fight these threats. In this study, we use comparative bioinformatic approaches to provide a comprehensive analysis of genes involved in tyrosine-mediated melanin synthesis in cnidarians. Eighteen PO-candidates representing five phyla were studied to identify their evolutionary relationship. Cnidarian species were most similar to chordates due to domain presents in the amino acid sequences. From there, functionally conserved domains in coral proteins were identified in a coral disease dataset. Five stony corals exposed to stony coral tissue loss disease were leveraged to identify 18 putative tyrosine metabolism genes, genes with functionally conserved domains to their Homo sapiens counterpart. To put this pathway in the context of coral health, putative genes were correlated to melanin concentration from tissues of stony coral species in the disease exposure dataset. In this study, tyrosinase was identified in stony corals as correlated to melanin concentrations and likely plays a key role in immunity as a resistance trait. In addition, stony coral genes were assigned to all modules within the tyrosine metabolism pathway, indicating an evolutionary conservation of this pathway across phyla. Overall, this study provides a comprehensive analysis of the genes involved in tyrosine-mediated melanin synthesis in cnidarians. [ABSTRACT FROM AUTHOR] more...

Scleractinian corals, essential ecosystem engineers that form the base of coral reef ecosystems, have faced unprecedented mortality in recent decades due to climate change-related stressors, including disease outbreaks. Despite this emergent threat to corals, many questions still remain regarding mechanisms underlying observed variation in disease susceptibility. Recent data suggest at least some degree of variation in disease response may be linked to variability in the relationship between host corals and their algal photosymbionts (Family Symbiodiniaceae). Still, the nuances of connections between symbiosis and immunity in cnidarians, including scleractinian corals, remain poorly understood. Here, we leveraged an emergent model species, the facultatively symbiotic, temperate, scleractinian coral Astrangia poculata , to investigate associations between symbiont density and both constitutive and induced immunity. We used a combination of controlled immune challenges with heat-inactivated pathogens and transcriptomic analyses. Our results demonstrate that A. poculata mounts a robust initial response to pathogenic stimuli that is highly similar to responses documented in tropical corals. We document positive associations between symbiont density and both constitutive and induced immune responses, in agreement with recent preliminary studies in A. poculata. A suite of immune genes, including those coding for antioxidant peroxiredoxin biosynthesis, are positively associated with symbiont density in A. poculata under constitutive conditions. Furthermore, variation in symbiont density is associated with distinct patterns of immune response; low symbiont density corals induce preventative immune mechanisms, whereas high symbiont density corals mobilize energetic resources to fuel humoral immune responses. In summary, our study reveals the need for more nuanced study of symbiosis-immune interplay across diverse scleractinian corals, preferably including quantitative energy budget analysis for full disentanglement of these complex associations and their effects on host pathogen susceptibility. [ABSTRACT FROM AUTHOR] more...

The distributions of anthozoan corals are undercharacterized due to their wide bathymetric ranges, occurrences in remote locales, and difficulties of identification from morphology alone. Environmental DNA (eDNA) sequencing promises to be a noninvasive strategy to complement conventional approaches for mapping and monitoring the distribution and biodiversity of coral communities. Primers for eDNA metabarcoding have been designed to amplify nuclear and mitochondrial DNA barcodes in shallow scleractinians and mitochondrial MutS in deep-sea octocorals. However, a comprehensive method for eDNA metabarcoding of all anthozoan corals, including black corals, has not been developed. We leveraged a sequence database of global coral collections, from shallow water to the deep sea, to design new PCR primers for coral eDNA sequencing that target the 28S rRNA gene (28S rDNA). We tested the performance of these primers by amplifying and sequencing eDNA from water samples collected in the Gulf of Mexico near mesophotic and deep-sea corals that were also imaged, sampled, and sequenced. Sequencing libraries produced using the primers were highly enriched in eDNA from octocorals, black corals and scleractinians, with up to 99.9% of the reads originating from these corals. Further, the 28S barcode amplified using the primers distinguished coral genera and species in many cases, like previously developed methods that target eDNA in only octocorals or scleractinians. We recovered amplicon sequencing variants (ASVs) identical to DNA barcodes derived from Sanger sequencing and genome skimming of corals sampled at the same field sites. This new eDNA metabarcoding strategy permits targeted eDNA sequencing of black corals, octocorals, and scleractinians at sites where they co-occur and expands our current toolkit for mapping and monitoring coral communities in shallow coral reefs and the deep sea. [ABSTRACT FROM AUTHOR] more...

Florida's coral reefs are facing a multi-year outbreak of stony coral tissue loss disease (SCTLD) with dramatic consequences for coral communities. However, potential anthropogenic and environmental drivers of SCTLD progression and severity remain poorly understood. This study was designed to determine the potential impacts of nutrient amendments on the progression and spread of SCTLD on reefs in Southeast Florida. In situ fertilizer amendments with 30 g of Osmocote™ slow-release fertilizer were used to mimic the effects of agricultural and urban runoff. Fifteen healthy and thirty SCTLD-affected Montastraea cavernosa coral colonies were tagged and divided into three experimental groups: apparently healthy colonies, SCTLD-affected nutrient-amended colonies, and SCTLD-affected control colonies. SCTLD lesion progression, coral tissue loss, and disease prevalence were tracked over a 30-day nutrient amendment period and for an additional 40 days after nutrient amendment removal to determine if there were any latent or recovery effects. Coral tissue loss was tracked over time using Structure-from-Motion photogrammetry and disease prevalence was recorded from diver surveys within a 3-m radius surrounding five centroid colonies from each experimental group. Throughout the experiment, temperature, nutrient concentrations, and SCTLD status of the coral colonies were also monitored. Ultimately, we observed no significant differences in SCTLD progression or surrounding SCTLD prevalence between the nutrient-amended and control groups, suggesting that nutrient amendment had no effect on SCTLD severity during this experiment in Southeast Florida. [ABSTRACT FROM AUTHOR] more...

As a part of the important species that form coral reef ecosystems, stony corals have become a potential source of pharmacologically active lead compounds for an increasing number of compounds with novel chemical structures and strong biological activity. In this study, the secondary metabolites and biological activities are reported for Aspergillus terreus C21-1, an epiphytic fungus acquired from Porites pukoensis collected from Xuwen Coral Reef Nature Reserve, China. This strain was cultured in potato dextrose broth (PDB) media and rice media with different salinities based on the OSMAC strategy. The mycelial morphology and high-performance thin layer chromatographic (HPTLC) fingerprints of the fermentation extracts together with bioautography were recorded. Furthermore, an untargeted metabolomics study was performed using principal component analysis (PCA), orthogonal projection to latent structure discriminant analysis (O-PLSDA), and feature-based molecular networking (FBMN) to analyze their secondary metabolite variations. The comprehensive results revealed that the metabolite expression in A. terreus C21-1 differed significantly between liquid and solid media. The metabolites produced in liquid medium were more diverse but less numerous compared to those in solid medium. Meanwhile, the mycelial morphology underwent significant changes with increasing salinity under PDB cultivation conditions, especially in PDB with 10% salinity. Untargeted metabolomics revealed significant differences between PDB with 10% salinity and other media, as well as between liquid and solid media. FBMN analysis indicated that alkaloids, which might be produced under high salt stress, contributed largely to the differences. The biological activities results showed that six groups of crude extracts exhibited acetylcholinesterase (AChE) inhibitory activities, along with 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and antibacterial activities. The results of this study showed that the increase in salinity favored the production of unique alkaloid compounds by A. terreus C21-1. [ABSTRACT FROM AUTHOR] more...

Mesophotic coral ecosystems are characterised by the presence of photosynthetic scleractinian corals despite the decreasing amounts of light available with depth. To better understand physiological strategies across a broad depth gradient, we studied the biological trait responses of Pocillopora cf. verrucosa from 6 to 60 m depth and Pachyseris "speciosa" spp. from 20 to 90 m depth at four islands of French Polynesia. Specifically, we characterised associated Symbiodiniaceae communities, photophysiological traits (Symbiodiniaceae density and chlorophyll concentrations), micro-morphology and trophic plasticity (autotrophy vs heterotrophy inferred from stable isotopes). Our results showed that both taxa can live at mesophotic depths without significant genetic structuring in their generic Symbiodiniaceae communities, mainly composed of Cladocopium and Durusdinium. Yet, the prevalence of Symbiodiniaceae ITS2 profiles revealed location-based variations that sometimes interact with depth and highlight putative shallow- or depth-tolerant taxa. For both taxa, symbiont density and chlorophyll pigment concentrations increased with increasing depth. We also found a change in their skeletal micro-morphology with an increase in the inter-corallite distance for Pocillopora cf. verrucosa and a decrease in the height of septa for Pachyseris "speciosa" spp. with depth. Finally, we found no isotopic evidence of switching to a more heterotrophic diet as their primary energy source, although host–tissue δ13C ratios became more negative with depth in both corals. Overall, our findings show similarity (across the two species) and species-specific strategies (biological trait patterns with increasing depth) underlying the capacity of symbiotic scleractinian corals to live in low-light environments. [ABSTRACT FROM AUTHOR] more...

Photoreception is essential to coral growth, reproduction, and stress responses. Thus far, opsin-based photoreception and potential photoadaptation in Scleractinian corals remains unclear. This study used natural and light-emitting diode (LED) lighting to investigate how Acropora digitifera, which is adapted to shallow-water environments, responds to day–night conditions. We successfully cloned three opsin genes (Adopsin1, Adopsin2, and Adopsin3). Adopsin1 and Adopsin2 clustered with the Cnidopsins, whereas Adopsin3 clustered with the anthozoan-specific opsin I group. In situ hybridization showed positive signals of these genes in coral endodermal and ectodermal layers. When A. digitifera branches were reared under a day–night cycle with natural light, a day-high and night-low pattern was observed in the transcript levels of Adopsin1 and Adopsin3. Genes related to calcification [plasma membrane calcium transporting ATPase 2 (PMCA)] and oxygen homeostasis regulation [hypoxia-inducible factor 1 alpha (HIF1α)] showed similar patterns. Rearing of branches under a day–night cycle (photoperiod = 12:12, 26.5–29.3 μmol s−1 m−2) with red (λmax = 628 nm), but not blue (464 nm) or green (519 nm) LED lighting led to increases in transcript levels of Adopsin1 and Adopsin3 during photophase. The transcript levels of carbonic anhydrase, PMCA, HIFα, and sodium-glucose cotransporter were significantly higher during photophase than during scotophase. Furthermore, Adopsin3 upregulation occurred within 4 h of exposure to a red LED light at night. These results suggest that A. digitifera can responding to long wavelengths of light, which play a crucial role in the photophysiology of the coral host. The capacity to perceive red light provides advantages in physiological adaptation and ecological niche occupation by A. digitifera in shallow waters. [ABSTRACT FROM AUTHOR] more...

The capacity for natural coral reef recovery and the effectiveness of active restoration efforts are often contingent upon uncertain and understudied background variables, such as chronic predation for example. In the Maldives, small coral colonies (< 10 cm), primarily from the genera Pocillopora and Acropora (often found recolonising degraded reefs) are frequently predated on by the spiny cushion sea-star (Culcita schmideliana). Incidentally, these same corals (especially Acroporids) are often prioritised in active reef restoration practices. However, the level of risk these corallivores pose on restoration success has not yet been assessed. Here, we aimed to initially document the population densities of C. schmideliana on a degraded reef system in the Maldives (Kunfunadhoo, Baa Atoll). We then assessed their associated predatory effects on coral recruits and transplants, and explored the benefits of C. schmideliana removal on the survival of these corals. Population densities ranged between 1.2 and 3.3 individuals per 100 m2, which resulted in high predation rates on coral recruits (4 – 20%) and transplants (11 – 43%). Culcita schmideliana predation accounted for the majority of the documented mortality (85%). Where C. schmideliana were removed, a significant increase in survival for recruits (9% higher) and transplants (24% higher) was shown. Further observations linked a cessation of C. schmideliana removal to a significant rise in predation instances for previously protected corals (up to 52%). Our study therefore highlights the severe impacts of C. schmideliana predation and shows Culcita spp. population management as a viable passive solution for effective reef restoration. [ABSTRACT FROM AUTHOR] more...

In the face of rising global temperatures, coral reefs experience coral mass bleaching and mortality. Subtropical and mesophotic environments may represent refugia for reef corals under climate change, where they can survive and eventually recolonize degraded areas. Using a comprehensive database of fossil reefs, we empirically assess the efficacy of subtropical, deeper, and turbid mesophotic environments to restore coral reefs after past global warming events. We focus on tropical coral reefs over the last 275 million years and four rapid climate warming events, which coincided with global reef crises in the geological record. In the aftermath of such hyperthermal events, we observed an increase in the proportions of reefs occurring in deeper (blue) mesophotic environments. Additionally, we found a trend of reef distributions and coral shifting towards higher latitudes. The number of coral occurrences in turbid (brown mesophotic) environments also increased after hyperthermal events. Our results suggest that subtropical, blue, and brown mesophotic environments may have served as immediate refugia for shallow-water coral species escaping warming seawater. While the patterns of reef range shifts and the establishment of blue and brown mesophotic refugia following ancient hyperthermal events provide some hope for coral reefs under current climate change, re-establishement of background reef conditions took most times millions of years. Ante el incremento de temperatura global, los arrecifes coralinos están experimentando eventos masivos de blanqueamiento y mortalidad. Los ambientes subtropicales y mesofóticos pueden representar refugios para los corales arrecifales, en los cuales pueden escapar de los efectos del cambio climático, sobrevivir y desde allí recolonizar áreas previamente degradadas. Mediante el uso de una exhaustiva base de datos en arrecifes coralinos, en este estudio se evaluó empíricamente la eficacia de los ambientes subtropicales y mesofóticos, tanto de aguas turbias someras (marrones) como de aguas claras profundas (azules), en la recuperación de arrecifes coralinos después de eventos hipertermales en el pasado. Nuestro enfoque estuvo en los arrecifes coralinos tropicales durante los últimos 275 millones de años y cuatro eventos de calentamiento climático rápido, los cuales coinciden con crisis globales en la ocurrencia de arrecifes en el registro fósil. Como consecuencia de dichos eventos hipertermales, observamos un aumento del número de arrecifes en ambientes mesofóticos de aguas profundas (azules). Además, encontramos una tendencia en la distribución de arrecifes y corales que se desplazan hacia latitudes más altas. También se observó un aumento en el número de corales que estuvieron presentes en ambientes de aguas turbias (marrones) después de dichos eventos hipertermales. Nuestros resultados sugieren que, en el pasado, los ambientes subtropicales, mesofóticos azules y mesofóticos marrones pudieron haber servido como refugios inmediatos para las especies de coral de aguas someras, en los cuales encuentran condiciones atenuantes ante el calentamiento oceánico. Si bien los patrones de desplazamiento de los arrecifes en el rango latitudinal y el establecimiento de refugios mesofóticos de aguas marrones y azules posteriores a eventos hipertermales brindan una luz de esperanza para el futuro de los arrecifes coralinos de cara al cambio climático actual, nuestros resultados evidencian que el restablecimiento de los arrecifes puede tomar millones de años. [ABSTRACT FROM AUTHOR] more...