Search Results (66)

This study presents updated biological and stock assessment information for two coral groupers, Plectropomus areolatus and Plectropomus marisrubri, in the Eastern Red Sea. A large sample collected from nine landing sites provided new estimates of growth, maturity, mortality, and exploitation, derived from otolith ageing, length–weight relationships, and yield-per-recruit and spawning potential ratio analyses. The two species showed distinct life-history patterns, with P. areolatus maturing earlier and exhibiting faster growth. Both species were found to be overexploited under current fishing pressure, with spawning biomass reduced well below commonly used sustainability thresholds. These results indicate that reductions in fishing mortality are required to rebuild reproductive capacity, particularly for P. areolatus. Management actions, such as increasing hook selectivity and enforcing minimum landing sizes, are supported by the observed maturity schedules. Seasonal protection of spawning periods is consistent with the low spawning potential ratios. This study provides the first recent age-based assessment for these two species in the region, offering a biological basis for species-specific management planning in the Eastern Red Sea. Full article

Recruitment is a crucial process for the recovery of coral populations after large-scale disturbances causing mass mortality events such as coral bleaching. This study examined the juvenile coral community of the remote Huvadhoo Atoll (southern Maldives, Indian Ocean) 11 years apart (2009 and 2020). Coral recruits (≤5 cm) and juveniles (5–15 cm) were surveyed at eight reef sites located in both lagoon- and ocean-facing environments, under the hypothesis that density and survival of recruits differ with respect to exposure. The total mean number of recruits differed slightly between years, with densities of 25 individuals·m⁻² in 2009 and 30 individuals·m⁻² in 2020. However, Acropora populations, which represented 60% of juvenile corals in 2009, halved in 2020, particularly in ocean reefs. The decrease in Acropora recruits seems to have favoured other corals: Pocillopora doubled compared to 2009, and species with massive growth morphologies became dominant. In all, the juvenile coral community structure underwent substantial changes between the two surveys. The comparison between the number of recruits and that of juvenile corals suggested higher survival of the species with massive growth morphologies. Whether branching corals will also have the ability to adapt to increasingly frequent climatic disturbances deserves attention in the future. Full article

Coral reefs are crucial ecosystems for marine biodiversity but are increasingly threatened by anthropogenic pressures and climate anomalies. The 2016 global bleaching event resulted in widespread coral mortality, altering reef structure and benthic communities. Here, we examine the evolution of Maldivian reefs from 2015 to 2023 using long-term monitoring data to assess post-disturbance dynamics. Analyses of 26 benthic descriptors revealed severe impacts from thermal stress, with heterogeneous recovery patterns. Reef-building capacity, which reflects the reef’s accretion potential and is mainly sustained by primary (e.g., Acropora branching corals) and secondary constructors (e.g., Tridacna spp.), rebounded substantially, while binders (e.g., coralline algae) and bafflers (e.g., erect sponges) remained depleted. Among growth forms, fast-growing branching and digitate corals, despite substantial declines, drove rapid recovery. Massive corals were less affected and continued growing, while encrusting corals declined steadily over the period. Post-bleaching community composition shifted markedly toward increased abiotic cover and reduced coral dominance, with partial reversion by 2023. Despite the 2016 collapse in constructional capacity, most reefs exhibited notable recovery within seven years. These findings underscore the moderate yet promising resilience of Maldivian reefs, exceeding previous bleaching events, and emphasize the importance of long-term monitoring to understand ecosystem responses under accelerating climate stress. Full article

Coral reefs are increasingly impacted by marine heatwaves and global warming, with the 2023–2024 El Niño–Southern Oscillation (ENSO) event causing unprecedented thermal stress across the Eastern Tropical Pacific. This study assessed the effects of this event on coral reefs in the Gulf of Papagayo, Costa Rica. Sea surface temperatures exceeded the bleaching threshold for seven months, reaching a record 10.2 Degree Heating Weeks—twice the levels recorded during the 1997–1998 ENSO. Benthic and fish community surveys revealed severe coral mortality, particularly in Pocillopora-dominated reefs, with some sites losing over 90% of live coral cover. Resilience varied across sites, likely influenced by factors such as local water circulation, coral genetic diversity, symbiont type, and heterotrophic capacity. Reefs with higher genetic diversity and thermally tolerant Durusdinium symbionts showed partial recovery. Seasonal upwelling appeared to buffer thermal stress in some areas, potentially acting as a natural climate refuge. Bleaching also impacted reef fish communities, with a notable decline in invertebrate-feeding species on degraded reefs. These findings highlight the interplay between prolonged thermal stress, coral biology, and local oceanographic processes in shaping reef resilience. Identifying and protecting such climate refugia will be critical for coral conservation under future climate change scenarios. Full article

Climate change is increasing the frequency and intensity of Marine Heatwave (MHW) events, threatening Western Tropical Pacific Small Island Developing States (SIDSs). MHWs critically threaten the fisheries sector which vitally supports food and nutrition security in local communities and local livelihoods. Currently, MHW risk to fisheries in Western Tropical Pacific SIDSs remains underexplored. Vanuatu is a Western Tropical Pacific SIDS which requires expanded MHW risk knowledge to improve the adaptive capacity of fisheries. A fundamental method for expanding MHW risk knowledge is tailored risk assessment. This study conducts the initial steps in a tailored MHW risk assessment methodology, displaying how a tailored indicator selection and weighting process can inform effective MHW risk assessment for fisheries in Western Tropical Pacific SIDSs. Hazard, vulnerability, and exposure indicators were selected through a combined process utilising a literature review and participatory research survey. Survey results were also used to develop a user-informed indicator weighting scheme. Selected indicators included sea surface temperature (SST), coral bleaching/mortality, and chlorophyll-a concentration (hazard); terrestrial-based food and income generation, fishing skills and technology, fishery fish diversity/fishery flexibility, and primary production of commercial fisheries (vulnerability); seagrass population/C content, coral habitat health/crown-of-thorns prevalence, crab stock health, and fish mortality/fish stock health (exposure). These indicators and their assigned weights are recommended for use in a future MHW risk assessment for Vanuatu fisheries. A tailored, fisheries-specific MHW risk assessment could advise local decision-makers on where/when MHW risk is high and aid the implementation of more effective fisheries risk management. Full article

Coral reefs are essential to the cultural, ecological, and economic well-being of Hawai‘i’s communities, yet they face increasing threats from environmental changes and localized stressors, including coral disease. Detecting coral disease often relies on the visible appearance of lesions; however, in the case of black-band disease (BBD), this visual cue appears too late, as disease progression can cause an average rate of tissue loss of up to 5.7 cm² per day over two months, followed by partial or full colony mortality. Reflectance spectroscopy offers a promising tool for detecting subtle spectral changes associated with coral health before visible symptoms emerge, yet few studies have applied this method to coral disease. In situ spectroscopy was used to measure the spectral reflectance of health conditions in Montiporid corals at ‘Anini Reef, Kaua‘i, USA. Discriminant analysis revealed that visually identical tissue types—live tissue on colonies with BBD (live_D) and live tissue on colonies without BBD (live_L)—were spectrally distinct. In contrast, BBD lesions (disease) and adjacent tissue that appeared healthy (transition) exhibited similar spectral signatures. Analyses identified three spectrally distinct tissue health conditions with a misclassification rate of 12.8%. These findings highlight the potential of reflectance spectroscopy for early coral disease detection, which could improve response times and support more effective coral reef conservation efforts. Full article

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

Extreme sea surface temperature (SST) events, such as marine heatwaves (MHWs) and marine cold spells (MCSs), severely affect warm water coral reefs. However, further study is required on their historical and future spatiotemporal patterns, driving mechanisms, and impacts in coral reef regions. This study analyzed the spatiotemporal patterns in MHWs/MCSs for the periods 1982–2022 and 2023–2070 using ten indices based on OISSTv2.1 and CMIP6 data, respectively, identified key MHW drivers via four machine learning methods (Random Forest, Extreme Gradient Boosting, Light Gradient Boosting Machine, and categorical boosting) and SHAP values (Shapley Additive Explanations), and then examined their relationship with coral coverage across ten global marine regions. Our results revealed that (1) MHWs are not only increasing in their average intensity but also becoming more extreme, while MCSs have declined. More MHW days are observed in regions like the Red Sea, the Persian Gulf, and the South Pacific Islands, with increases of up to 28 days per decade. (2) Higher-latitude coral reefs are experiencing more severe MHWs than equatorial regions, with up to 1.24 times more MHW days, emphasizing the urgent need to protect coral refuges. (3) MHWs are projected to occur nearly year-round by 2070 under scenario SSP5–8.5. The area ratio of MHWs to MCSs is expected to rise sharply from 2040 onward, reaching approximately 100-fold under the SSP2–4.5 scenario and 196-fold under the SSP5–8.5 scenario, particularly in the Marshall Islands and Caribbean Sea regions. (4) The coefficient of variation (CV) of annual temperature, annual ocean heat content, and monthly temperature were the top three factors driving MHW intensity. We emphasize that future MHW predictions should focus more on the CV of forecasting indicators rather than just the climate means. (5) Coral coverage exhibited post-mortality processes following MHWs, showing a strong negative correlation (r = −0.54, p < 0.01) with MHWs while demonstrating a significant positive correlation (r = 0.6, p < 0.01) with MCSs. Our research underscores the sustained efforts to protect and restore coral reefs amid escalating climate-induced stressors. Full article

The marine habitats of the world’s oceans are being driven beyond their resilience. The ongoing biodiversity crisis is happening fast, within the lifespan of researchers trying to produce the information necessary for the conservation of habitats and marine ecosystems. Here, we report on the destruction of sciaphilic sessile communities and coralligenous concretions produced by the anchoring of a high-tonnage vessel inside a Marine Protected Area in Cyprus. The damage from the anchors and the chains consisted of the dislodgement of large boulders that were dragged or rolled over the seafloor, increasing the breakage and further dislodgement of more boulders; many were left upside-down. The biological communities that thrived in the dark environments below the boulders were directly exposed to high irradiance levels and went through a slow mortality and decaying process, most probably due to a combination of several deterioration agents, such as exposure to direct sunlight, predation, mucilage aggregates, and cyanobacterial blooms. The enforcement of regulatory measures for anchoring and transit in the MPA is necessary to prevent similar destruction. Given the extent of the irreversible damage to these sciaphilic communities, our study is, unfortunately, another environmental post-mortem contribution. Full article

Snakebite is a high-priority neglected tropical disease, and a strategic goal based on four pillars has been recommended to reduce mortality and morbidity. One is empowering rural communities through citizen science, education, and engagement. In this study, an integrative approach was used to expand our knowledge of Micrurus nigrocinctus status and characterize its venom. Using citizen science data and field visits to local communities, 99 records of M. nigrocinctus distributed in Antioquia, Chocó, and Córdoba were obtained. Children, young people, and adults recognized M. nigrocinctus as the most common coral snake species in their region, and two specimens were recovered for venomic and Phylogenetic analyses. The M. nigrocinctus venom from Colombia exhibited similar chromatographic and electrophoretic profiles and biological activities and shared nearly identical protein families with Costa Rica. Commercial coral snake antivenoms also recognized and neutralized the whole venom from both countries. However, phylogenetic relationships showed greater divergence with specimens from Costa Rica. Involving communities helps prevent coral snake bites and facilitates access to rare specimens such as M. nigrocinctus, thereby enabling venom analyses, improving antivenom evaluation, and advancing toxinology research for medically significant species. Full article

Marine heatwaves (MHWs) are increasingly affecting tropical seas, causing mass coral bleaching and mortality in the wider Caribbean (WC) and eastern tropical Pacific (ETP). This leads to significant coral loss, reduced biodiversity, and impaired ecological functions. Climate models forecast a troubling future for Latin American coral reefs, but downscaled projections for the WC and ETP remain limited. Understanding regional temperature thresholds that threaten coral reef futures and restoration efforts is critical. Our goals included analyzing historical trends in July–August–September–October (JASO) temperature anomalies and exploring future projections at subregional and country levels. From 1940 to 2023, JASO air and ocean temperature anomalies showed significant increases. Projections indicate that even under optimistic scenario 4.5, temperatures may exceed the +1.5 °C air threshold beyond pre-industrial levels by the 2040s and the +1.0 °C ocean threshold beyond historical annual maximums by the 2030s, resulting in severe coral bleaching and mortality. Business-as-usual scenario 8.5 suggests conditions will become intolerable for coral conservation and restoration by the 2030s, with decadal warming trends largely surpassing historical rates, under unbearable conditions for corals. The immediate development of regional and local adaptive coral reef conservation and restoration plans, along with climate change adaptation and mitigation strategies, is essential to provide time for optimistic scenarios to materialize. Full article

Microplastics are an increasingly common threat to the aquatic environment, and, due to their small size, it is easy for them to spread and enter the seas and oceans. Micro- and mesoplastic particles are often ingested by marine organisms, especially those that have the potential for successful settlement on artificial substrata, including plastic. In laboratory experiments, we tested the tendency of the sea anemone Exaiptasia diaphana to consume plastic fragments and fibers of various sizes and shapes; these organisms are widely distributed in coastal waters, tide pools, and coral reefs. The plastic fragments and fibers were placed either in natural food or covered with a special food in gel form, which allowed them to retain their original shape. Our studies have shown that plastic in the shape of fibers is less readily consumed than in the form of fragments. The E. diaphana anemones with oral discs of diameter 10–12 mm had difficulty consuming long fibers. A total of 67% of the studied animals were unable to consume fibers of 13 mm length, while those of 3 and 7 mm length were consumed by 100% of the sea anemones. We have also established that microplastics taken with food are harmful to these cnidarians: mechanical injury to the body column was caused by the ingested polypropylene microfragments, and we also observed significantly increased mortality. Injuries, combined with the possible toxicological effects of the polymers, may have been the cause of increased mortality of the Exaiptasia diaphana. Full article

The red spotting disease harms sea urchins to the extent of mass mortality in the ocean and echinocultures, accompanied by environmental damage and economic losses. The current study emphasizes the antimicrobial resistance of three isolated bacteria, closely related to Vibrio harveyi, Vibrio owensii, and Vibrio fortis, associated with red spotting in the cultured sea urchin Tripneustes gratilla. In vitro trials examined the susceptibility of these bacterial isolates to various antibiotics. In addition, using an in silico examination, we revealed the arsenal of antimicrobial resistance genes in available genomes of various pathogenic Vibrio associated with diseases in sea urchins, fish, shellfish, and corals. These two approaches enabled the discussion of the similarities and differences between aquatic pathogenic Vibrio and their antibiotic resistance. Among them, we revealed a core resistance to tetracyclines and penams by the in vitro examined strains. At the same time, the in silico study also supported this core resistance by the presence of the adeF and CRP genes in the bacterial genomes. Nevertheless, variability and specific resistance were evident at the species and strain levels in the Vibrio bacteria and genomes. The in vitro trials highlighted the diverse resistance of the Vibrio harveyi-like isolate to all examined antibiotics, while the other two isolates were found susceptible to nitrofurantoin and sulfamethoxazole. The resistance of the Vibrio harveyi-like isolate could not have been obtained in the genome of the proposed relative of Vibrio harveyi VHJR7 that lacks the oqxA and oqxB genes, which enables such a resistance. A unique sensitivity of the Vibrio fortis-like isolate to erythromycin is proposed when compared to other isolated Vibrio and Vibrio genomes that seem capable of resisting this drug. According to the results, we propose nitrofurantoin or sulfamethoxazole for treating two of the red-spotting-associated isolates (Vibrio fortis and Vibrio owensii-like), but not Vibrio harveyi-like. We assume that a shared resistance to some antibiotics by Vibrios is gained by a horizontal gene transfer while previous exposures of a bacterial strain to a specific drug may induce the development of a unique resistance. Finally, we discuss the novel knowledge on antibiotic resistance in Vibrio from the current research in light of the potential risks when using drugs for disease control in aquaculture. Full article

Coral bleaching is occurring more frequently as the climate changes, with multiple mass mortality events recently recorded on the Great Barrier Reef. Thermal stress coupled with high irradiance have previously been shown to be primary causes for coral bleaching. Therefore, a reduction in either of these pressures could reduce coral stress and eventual bleaching. Herein, we report the early development of a novel technology capable of reducing the amount of light entering a water body by ~20% in open ocean conditions. This mono-particle “sun shield” consists of an ultra-thin monolayer material and reflective calcium carbonate particles. The monolayer enables spreading of the particles into a thin film across the water surface, with only small amounts of material needed: 7.1 g/m². A numerical modelling case study of residence times and the build-up of reactive oxygen stress in corals showed that the successful application of a stable film over the Lizard Island reef flat could reduce the reactive oxygen stress to below bleaching levels across approximately 1.5 km² of reef area. With further development, mono-particle films such as this have the potential to be deployed over at-risk coral reefs at relatively small scales during predicted heatwave conditions, potentially reducing the severity of bleaching on coral reefs. Full article

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. Full article