Search Results (40)

Coral reefs are increasingly threatened by global climate change, and mass bleaching and mortality events caused by elevated seawater temperature have led to coral loss worldwide. Hainan Island hosts extensive coral reef ecosystems in China, yet seasonal variation in Symbiodiniaceae communities within this region remains insufficiently understood. We aimed to investigate the temperature-driven adaptability regulation of the symbiotic Symbiodiniaceae community in reef-building corals, focusing on the environmental adaptive changes in its community structure in coral reefs between cold (23.6–24.6 °C) and warm (28.2–30.6 °C) months. Symbiodiniaceae shuffling and rare genotype turnover were discovered in adaptability variations in the symbiotic Symbiodiniaceae community between two months. Symbiodiniaceae genetic diversity increased during warm months, primarily due to temporal turnover of rare genotypes within the Cladocopium and Durusdinium genera. Coral Favites, Galaxea, and Porites exhibited the shuffling of Symbiodiniaceae between tolerant Durusdinium and sensitive Cladocopium. Symbiodiniaceae interactions in G. fascicularis and P. lutea exhibited the highest levels of stability with the increase in temperature, whereas the interactions in A. digitifera and P. damicornis showed the lowest levels of stability. Rare genotypes functioned as central hubs and important roles within Symbiodiniaceae communities, exhibiting minimal responsiveness to temperature fluctuations while maintaining community structural stability. The temperature-driven adaptability regulation of symbiotic Symbiodiniaceae could be achieved by Symbiodiniaceae shuffling and rare genotype turnover. The process might be aggravated by concurrent adverse factors, including elevated salinity, pollution, and anthropogenic disturbance. These findings provide insights into how the Symbiodiniaceae community influences the adaptation and resilience of coral hosts to temperature fluctuations in coral reefs. Furthermore, they may contribute to assessing the reef-building coral’s capacity to withstand environmental stressors associated with global climate change. Full article

Remote reefs offer insights into natural coral dynamics, influenced by regional environmental factors and climate change fluctuations. Clipperton Atoll is the eastern tropical Pacific’s most isolated reef, where coral reef growth and life strategies have been poorly studied so far. Recognizing the coral species’ growth response might help understand ecological dynamics and the impacts of anthropogenic stressors on coastal reefs. The present study evaluates annual coral growth parameters of the most abundant coral reef-building species, Porites australiensis, Porites arnaudi, Porites lutea, and Porites lobata. The results showed that during 2015–2019, corals exhibited the lowest annual linear extension (0.65 ± 0.29 cm yr⁻¹), skeletal density (1.14 ± 0.32 g cm⁻³), and calcification rates (0.78 ± 0.44 g cm⁻² yr⁻¹) for the genera along the Pacific. Differences in growth patterns among species were observed, with Porites lutea and Porites lobata showing a higher radial extension, developing massive-hemispherical morphologies, and acting as structural stabilizers; meanwhile, P. arnaudi and P. australiensis exhibited more skeletal compaction but also with a high plasticity on their morphologies, contributing to benthic heterogeneity. These differences are particularly important as each species fulfills different ecological functions within the reef, contributing to the ecosystem balance and enhancing the relevance of the massive species in the physical structure of remote reef systems, such as Clipperton Atoll. Full article

Coral reef survival is crucial for the socio-ecological interest of many countries, particularly for the Republic of Maldives, whose reef integrity influences the country’s livelihoods and economy. These ecosystems are being severely impacted by multiple stressors, leading to declines in biodiversity. In the last few decades, researchers have focused on studying coral-associated microorganisms (CAMs) and their symbiotic role in coral health and resilience. Metabarcoding analysis has been widely utilized to study CAM diversity under various conditions but provides limited information on their functional roles. Therefore, cultivation of bacterial strains remains indispensable for validating ecological and biotechnological hypotheses. In this study, we investigated the microbial community associated with two abundant corals in Maldives, Porites lobata and Acropora gemmifera, and evaluated the antimicrobial, antioxidant, and UV-protectant properties of 10 promising isolated strains. The selected CAMs, Pseudoalteromonas piscicida 39, Streptomyces parvus 79, Microbacterium sp. 92 (a potential novel species), and Micromonospora arenicola 93, exhibited antibiotic activity against a panel of pathogenic strains (MIC from 0.01 to 500 µg/mL), antioxidant (comparable effect to that of Trolox and ascorbic acid), and UV-screen activities (protection of human keratinocytes at 200 µg/mL). Genomes revealed their dual potential in contributing to coral restoration and drug discovery strategies. These findings highlight the biotechnological relevance of CAMs, representing an important step toward the identification of novel and bioactive bacterial species beneficial for coral reef ecosystems and human health. Full article

Photogrammetry is a common tool for evaluating ecosystem-scale questions on coral reefs due to the ability to measure complex structures in situ. This technique is also increasingly being used at smaller scales to collect growth and morphometric data about individual coral fragments in manipulative experiments. However, there are substantial uncertainties in data quality and interpretation and limited reporting of the parameters useful for standardization across studies. There is a need to characterize the capabilities of photogrammetry as applied to coral fragments, to establish validation metrics for reporting, and to determine sources of variation in measurements to refine and improve methods. Here, we used fragments of two common reef-building corals (Montipora capitata and Porites compressa) and known size standards to evaluate accuracy and precision and present suggested validation metrics. We also used a tiered experimental design to evaluate sources of error in a photogrammetry workflow in a manipulative experiment using a purpose-built multi-camera workstation. We demonstrate extremely high accuracy (R² > 0.999) in determining the surface area and volume of known objects, as well as very high precision (average CV < 0.01) in coral measurements during tests of reproducibility. These outcomes show the utility of fragment photogrammetry for experimental coral reef science and present suggested validation metrics and approaches that can help standardize data evaluation and interpretation in any application of photogrammetry to coral fragments. Full article

The lower Messinian Calcare di Rosignano Formation (Tuscany, Italy, 43° N) preserves one of the youngest and northernmost examples of coral reefs in the Mediterranean. The outcropping succession of the Acquabona quarry consists of four main facies, namely, in ascending stratigraphic order: (1) coral boundstone, (2) coralline algal rudstone, (3) serpulid floatstone to packstone, and (4) peloidal packstone to grainstone. The succession displays a trend toward increasingly more shallow conditions and progressively more restricted water circulation. The coral reef displays a limited coral biodiversity and a remarkable abundance of heterotrophs, similar to modern coral reefs developed at the edges of the ecological niche of symbiont-bearing colonial corals. The widespread presence of coral colonies pervasively encrusted by coralline algae and benthic foraminifera suggests that short-term environmental perturbations caused temporary shutdowns of the coral-dominated carbonate factory. Moving upwards, there are fewer corals and more highly adaptable carbonate producers like coralline algae and serpulids. This suggests that the decline of corals had been caused by the conditions in the basin becoming more stressful, up to the collapse of the coral community. The overall succession indicates that coral-dominated ecosystems located at the edges of the coral zone are very sensitive; they can be affected even by minor perturbations and easily collapse if negative conditions persist. Full article

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. Full article

Coral reefs worldwide are under increasing levels of pressure due to global and local stressors. Long-term monitoring of coral reefs through repeated observations at fixed survey sites allows scientists to assess temporal patterns in coral-reef communities and plays important roles in informing managers of the state of the ecosystems. Here, we describe coral assemblages in Papahānaumokuākea, the largest contiguous fully protected marine conservation area in the United States, using long-term monitoring data collected from 20 permanent (fixed) sites at three islands/atolls, Lalo, Kapou and Manawai, between 2014 and 2021. Significant temporal shifts in coral colony composition were detected at some of the monitoring sites, which were attributed to the impact of a mass coral bleaching event in 2014 and Hurricane Walaka in 2018. In particular, the bleaching affected multiple sites at Kapou and one site at Manawai where coral assemblages shifted from the Montipora dilatata/flabellata/turgescens complex to M. capitata dominance; despite being the dominant species at multiple monitoring sites prior to the bleaching, the M. dilatata/flabellata/turgescens complex has not been recorded at any of our monitoring sites in recent years. Coral conditions, such as bleaching, predation, subacute tissue loss, Porites pigmentation response and trematodiasis, did not show differences in the occurrence among the three islands/atolls once the site and temporal variabilities, as well as environmental covariates for bleaching, were considered. Coral genera, however, exhibited different sensitivities to these conditions. These findings highlight the importance of continuing coral reef monitoring at the species level, covering a broad range of coral assemblage compositions and habitat types in Papahānaumokuākea. Full article

Demographic studies that quantify species’ performances for survival, growth, and reproduction are powerful means to characterize sources of demographic bottlenecks and predict community dynamics. However, they require fine-scale surveys of populations in the field, and are often too effort-intensive to be replicable at a large scale and in the long term. We developed a standardized digital approach for extracting demographic data on species’ abundances, sizes, and positions within video transects, enabling back-from-the-field data acquisition and therefore optimizing time spent in the field. The approach is based on manual species identification, size measurements, and mapping in video transects, mimicking what is traditionally performed in the field, though it can be automated in the future with the deployment of artificial intelligence. We illustrate our approach using video surveys of a reef-building coral community in New Caledonia. The results characterize the composition of the coral community and demographic performances as key ecological indicators of coral reef health, shed light on species’ life strategies and constraints to their demographics, and open paths for further quantitative investigations. Key findings include the diversity of life strategies with contrasting levels of investment in survival, growth, and reproduction found among the six taxa dominating the coral community (Acropora, Montipora, Porites, Galaxea, Favia, Millepora), indicating the diversity of demographic paths to ecological success. Our results also indicate that several species have adapted mechanisms to prevail under limiting hydrodynamic environments through the propagation of coral fragments. Our approach facilitates image-based demographic investigations, supporting endeavors in ecology and ecosystem management. Full article

Coral reefs are declining due to multiple factors including overfishing, anthropogenic pollution, and ocean acidification. Diseases affecting corals have increased in recent decades, yet the etiology of nearly all diseases remains poorly understood. Here, we investigated three-dimensionally mapped molecules and microbes from healthy and diseased coral tissue sampled across the landscape of a coral assemblage at the Wai‘ōpae tide pools, Southeast Hawai‘i Island. A 3D molecular cartographic platform was used in combination with molecular networking tools to characterize healthy coral tissue and tissue affected by the disease growth anomaly (GA). Tissues of healthy Montipora flabellata and Montipora capitata exhibited higher microbial diversity compared to Porites lobata and GA-affected M. capitata corals. Increases in relative abundance of Ulvophyceae and sterols were observed in GA lesions, while chlorophyll decreased. Conversely, healthy coral tissues were characterized by the presence of cyanobacteria in the order of Stramenopiles, in addition to higher relative chlorophyll levels. Leveraging innovative molecular cartography provides new insight into molecular characteristics of coral colonies, and helps to better understand how diseases affect the molecular landscape of corals. Full article

In this study, the bacterial microbiota associated with apparently healthy corals of Acropora palmata, Orbicella faveolata, and Porites porites and the surrounding seawater and sediment were evaluated via the MiSeq Illumina sequencing of the V4 region of 16S rRNA at three reef sites in the Mexican Caribbean. Bacterial assemblages associated with apparently healthy corals and sediments showed no significant differences between sites. The colonies of A. palmata showed a dominance of families Amoebophilaceae, Spirochaetaceae, Myxococcaceae, and Cyclobacteriaceae. Meanwhile, the colonies of O. faveolata and P. porites revealed a high prevalence of the Rhodobacteraceae and Kiloniellaceae families. The families Rhodobacteraceae, Cryomorphaceae, Cyanobiaceae, and Flavobacteriaceae were predominant in seawater samples, while Pirellulaceae, Nitrosococcaceae, and Woeseiaceae were predominant in sediments. Variations in A. palmata bacterial assemblages were correlated with salinity, sea surface temperature, and depth. These variables, along with nitrate, phosphate, and ammonium concentrations, were also correlated with changes in the bacterial composition of P. porites, seawater, and sediments. However, none of the environmental variables were related to the bacterial taxa of O. faveolata. Aerobic chemoheterotrophy and fermentation, followed by nitrate reduction and ureolysis, were the metabolic functions with the highest occurrence in the bacterial assemblages associated with all substrates. Full article

Coral reefs in Sanya Bay have been degrading in recent decades under climate change and human activities. To identify physiological changes of scleractinian corals and corresponding influencing factors, aquatic environmental factors and physiological parameters of Pocillopora damicornis, Porites pukoensis and their symbiotic zooxanthellae were examined in four Sanya Bay coral reef areas in December 2020 (winter) and July 2021 (summer). The density and chlorophyll a+c₂ content of the symbiotic zooxanthellae were significantly high in winter and low in summer. Superoxide dismutase and caspase3 activities of corals and zooxanthellae were high in summer and low in winter, whereas catalase activity showed the opposite pattern. The variations were consistent for both coral symbionts. Water temperature and salinity were the main factors affecting the physiological variations of corals. Compared with winter, the high temperature/low salinity aquatic environment in summer reduced the density and chlorophyll a+c₂ content of zooxanthellae, resulting in high superoxide dismutase and caspase3 activities in the corals and zooxanthellae. In addition, turbidity was an important factor affecting the physiological characteristics of coral–zooxanthellae symbionts among the four coral reef areas. Our results have important implications for understanding the changes in coral reef communities in Sanya Bay and coral reef protection. Full article

Coral reefs are the most diverse habitat per unit area in the world’s oceans, supporting an estimated 1–3 million species in only 0.2% of its area. These ecosystems have suffered severe declines since the 1970s, largely as a result of climate change, ocean acidification, pollution, disease, and overfishing. Porites astreoides is a shallow species that is able to thrive in a variety of environmental conditions and has been a clear ‘winner’ on Atlantic reefs in the last decades. This, coupled with its ease of identification and wide distribution, has caused P. astreoides to become a focal species in many scientific studies. Given the current and increasing significance of P. astreoides, this review sought to (i) identify the key life history traits that allowed this species to thrive under stressful conditions; (ii) compile aspects of its biology and ecology to understand its future contribution to Atlantic reefs, and (iii) identify knowledge gaps. To date, no comprehensive overview of the literature exists for P. astreoides. All articles available on Google Scholar up to the time of submission containing the terms ‘Mustard Hill Coral’, ‘Porites astreoides’, or ‘P. astreoides’ were examined for potential inclusion in this review. Papers were assessed based on whether they captured the most influential or widespread theories, represented an important trend in the research, or contained novel findings relevant to the understanding of this species. This review provides a scholarly resource and wide-ranging synthesis of P. astreoides on Atlantic reefs of today and the future. Full article

Taking the coral communities of the Xuwen coral reef in 2020 as the research object, we analyzed the species composition, diversity, and interspecific Spearman correlation of the scleractinian coral communities, investigated the features and spatial distribution of the scleractinian coral community, and discussed the correlation between the community composition and environmental factors to identify the affecting factors and their sources. These results showed that (1) compared with the survey in 2004, the coverage of corals in 2020 had significantly decreased, while the dominant genera were still Goniopora and Porites. The coral morphology was massive, and the diversity of the coral community (Shannon–Wiener index, H’) was 2.87. The distribution of coral was uneven. The competition among some dominant species of coral was intense. (2) The mass coral bleaching event in the NSCS in August 2020 did not cause severe coral death in the short term on the Xuwen coral reef. (3) The growth of the coral community in 2020 might be greatly affected by high suspended solids and nutrient levels, which were related to the current, mariculture, and coastal erosion. (4) Anthropogenic activities such as coastal aquaculture and fishing were the major factors leading to the reduction in coral coverage on Xuwen coral reef in the past 10 years. Full article

An unprecedented decline in the diversity and health of coral reefs is occurring around the world as they are threatened by multiple global and local stressors. Rising seawater temperature and low dissolved oxygen (DO) conditions are expected to intensify as a result of climate change. Understanding the responses of corals to these stressors is necessary for making predictions and devising mitigation strategies. The three coral species—Porites lutea, Montipora tuberculosa, and Pocillopora verrucosa—were sampled from Patong Bay, Phuket, Thailand, as representatives of different coral morphologies. Coral nubbins were subjected to experimental investigation under ambient conditions (29 °C, DO > 6 mgL⁻¹), heat stress (32 °C), hypoxia (DO < 2 mgL⁻¹), and heat stress + hypoxia treatments. Photosynthetic performance indicators Fv/Fm and Fv/F0 and physiological parameters Symbiodiniaceae density, pigment concentration, and growth rate were quantified. We found P. verrucosa (branching) to be the most sensitive and severely affected by heat stress or hypoxia, more so than P. lutea (massive) and M. tuberculosa (tabular). The combination of these stressors had less impact on these species, except for a decline in growth rate of M. tuberculosa. This study also suggests that the corals respond differently to high temperature and low oxygen, with their sensitivity depending on species. These responses, however, may differ according to the lighting, especially in hypoxic conditions. The results fill a research gap to help predict the vulnerability of these three coral species in shallow reef habitats under climate change scenarios. Full article

A corallivorous nudibranch from the South China Sea reproduced explosively and caused extensive damage to Porites in our aquarium. In this study, morphological and molecular analyses of the nudibranch were conducted and described. Morphologically, this nudibranch was nearly consistent with Pinufius rebus in its characteristics intermediate between arminids and aeolids. The only detected difference was that the hook-like denticles on the masticatory border of P. rebus were absent in this nudibranch. In a molecular analysis, phylogenetic results based on the cytochrome oxidase subunit-I, 16S rRNA, and histone H3 gene sequences showed that this nudibranch and P. rebus form a well-supported sister clade under the superfamily Fionoidea, with significant interspecific divergence (0.18). Thus, we presumed that this nudibranch is a new species of Pinufius. Our results extend the distribution of Pinufius to the South China Sea, support the current taxonomic status of Pinufius under the superfamily Fionoidea, and imply that the species composition of Pinufius is more complex than previous records. Moreover, as a corallivorous nudibranch, the potential threat of Pinufius to coral health cannot be neglected. Full article