Search Results (178)

Coral reefs are increasingly threatened by elevated seawater temperatures associated with heatwaves and El Niño events. These phenomena challenge conventional management practices, highlighting an urgent need for innovative interventions to enhance reef resilience. Investigating the role of oxidative stress—one of the main explanations for coral bleaching—is central to these efforts, as excessive production of reactive oxygen species can impair coral physiology, disrupt the coral–algal symbiosis, and ultimately lead to mortality. Here, we investigated an antioxidant-rich food web approach by feeding the reef-building coral Stylophora pistillata with Artemia that had been pre-fed with (i) low-cost and in-house-produced pellets containing curcumin, fucoxanthin, astaxanthin, vitamins C or E, or (ii) the phytoplankton species Pavlova lutheri, Symbiodinium sp., Nannochloropsis sp., Dunaliella salina or Synechococcus sp. Curcumin and the microalga P. lutheri offered the best protection to corals against oxidative stress, and represent the best candidates for potential scalable coral conservation interventions involving targeted feeding of antioxidants. Curcumin pellets offer a streamlined alternative to P. lutheri by eliminating the need for multi-stage microalgal culturing. Direct enrichment of Artemia with antioxidant-rich pellets simplifies production and may provide a cost-effective, scalable strategy to enhance coral resilience to oxidative stress, bleaching and potential mortality. Full article

Coral reef ecosystems of the Egyptian Red Sea face escalating pressure from compounding climate-driven warming and intensifying coastal development, dual stressors whose spatial expression and governance implications remained insufficiently characterized prior to the designation of the Great Fringing Reef Marine Protected Area under Prime Ministerial Decree No. 4419/2025. This study develops an integrated multi-decadal framework combining 32 years of sea surface temperature and surface current velocity records, two decades of satellite-derived chlorophyll-a observations, and four decades of satellite-derived coral reef extent mapping across five monitored coastal sites. Basin-wide SST warming of ≈1.15 °C is spatially heterogeneous, with the northern coastal sector warming nearly 25% above the southern sector rate. Surface circulation diverges structurally at Ras Banas: acceleration in the north is consistent with enhanced advective dilution of anthropogenic inputs, whereas consistent deceleration in the south (mean −0.03 m/s) is associated with an increased ecological footprint of wadi-derived sediment and nutrient discharge. Sharply localized chlorophyll-a anomalies, reaching 0.97 mg/m³ at Hurghada and spatially congruent with documented development chronologies, are consistent with anthropogenic disruption of oligotrophic water quality as an important contributor to reef degradation at northern sites. Field evidence from 2026 repeat surveys, interpreted alongside documented severe regional bleaching affecting southern Egyptian reefs during 2024, suggests that climate-driven thermal stress constitutes a parallel and active pressure, particularly in the southern sector where thermal and anthropogenic stressors appear to have converged during the period of most acute reef contraction. Landsat-derived losses of 24.1–50.2% across all monitored sites since 1985, including a 33.3% contraction at Halaib–Shalateen between 2022 and 2025 alone, reflect the cumulative outcome of these interacting pressures. These findings support the ecological necessity of the 2025 MPA while identifying spatially differentiated, dual-stressor governance priorities essential to translating its policy commitment into measurable conservation outcomes. Full article

Hyperspectral imagers (HSIs) enable the non-invasive, spectrally resolved quantification of pigments. HSIs have many environmental research applications, including the monitoring of threatened ecosystems like coral reefs and evaluating the success of coral restoration efforts. However, the high cost of commercial HSIs has restricted wider uptake of the technology. Here, we tested the efficacy of a low-cost (~USD 200) and open-source HSI device (400–1000 nm, spectral resolution of ~2 nm Full width at half maximum (FWHM)) in coral bleaching research. Specifically, we evaluated its ability to quantify the concentration of key photosynthetic pigments (chlorophyll a, chlorophyll c2, diadinoxanthin, peridinin, and total pigment content) by comparing it against a research-grade (~USD 70,000) commercial hyperspectral camera using coral fragments subjected to varying levels of thermal stress. The low-cost HSI acquired coral reflectance spectra that were similar to those acquired by the commercial hyperspectral camera, with a mean spectral angle of 11.38 ± 3.82°. However, the low-cost device was unable to resolve differences in spectral magnitude to the same accuracy as the commercial HSI and did not detect differences among coral fragments at different levels of thermal stress. Thus, the current HSI device prototype is better suited for classification and diagnostic applications in which spectral shape is of greater importance than spectral magnitude. Partial least squares regression models built from the reflectance spectra of each HSI instrument showed very similar yet moderate performance when predicting key coral pigments (commercial HSI mean Root Mean Square Error of Prediction (%RMSEP) = 22.8%, low-cost HSI = 22.12%). While the current design of the low-cost HSI device has limitations, it shows potential for coral research at a fraction of the cost of commercial alternatives. The continued development of low-cost HSI platforms is accelerating rapidly across a variety of fields in environmental research, and improved designs have the potential to enhance coral reef monitoring and restoration efforts globally. Full article

Coral reefs support marine biodiversity, fisheries, tourism, and coastal protection, but they are increasingly threatened by environmental stress and bleaching. Satellite-based reef monitoring has mainly relied on thermal metrics, especially Degree Heating Weeks (DHW), to represent bleaching risk. However, thermal exposure alone may not fully describe reef stress in optically complex coastal waters, where light availability, water clarity, and water-quality conditions can modify coral response. This limitation is important in Indonesia, where reefs span diverse coastal environments and many bleaching observations occur under relatively low DHW. In this study, we develop the Coral Reef Environmental Stress Index (CRESI), implemented as CRESI-Mamba, to estimate coral reef stress in Indonesia as a continuous and interpretable satellite-based stress index. CRESI-Mamba uses 26-week sequences of thermal variables from NOAA Coral Reef Watch and ocean-color variables from NASA Visible Infrared Imaging Radiometer Suite (VIIRS). The model decomposes the inferred stress into thermal, optical, and water-quality pathways, and maps the resulting stress index to bleaching probability for event-based evaluation. CRESI-Mamba was trained and evaluated using 8424 reef observations from eight Indonesian regions. In Leave-One-Region-Out cross-validation (LORO-CV), the model achieved a mean area under the receiver operating characteristic curve (AUC) of $0.795\pm 0.087$. In grouped 5-fold cross-validation, it achieved an AUC of $0.802\pm 0.024$, exceeding the DHW-only baseline ($0.627\pm 0.021$) and performing comparably to stronger thermal-only models, while providing a pathway-decomposed stress index. The estimated stress index separated bleached and not-bleached observations, with paired stress differences of $0.299\pm 0.098$ in LORO-CV and $0.281\pm 0.032$ in grouped 5-fold CV. Pathway analysis showed that the dominant stress pathway differed among regions, with optical stress dominant in several low-DHW bleaching cases. These results show that reef stress in Indonesia is better represented as a multi-pathway environmental condition than as thermal exposure alone. CRESI-Mamba provides a framework for interpreting satellite environmental histories as reef stress, while retaining bleaching probability as an evaluation output. Full article

Coastal small-scale fishers in the Asia-Pacific region (APR) face mounting challenges from climate change (CC), with vulnerability shaped by ecological exposure, socio-economic dependence, and limited adaptive capacity. This study reflects on two contrasting cases, Taiwan and Papua New Guinea (PNG), to explore fishers’ perceptions and perspectives on CC and practical adaptation strategies. In PNG, 209 respondents from Momase, the Islands, and Southern regions participated. In Taiwan, 45 respondents from the Yunlin and Chiayi coastal regions participated. Significant correlations in coastal communities’ vulnerabilities and perceptions towards CC were revealed. Small-scale fishers perceive rising sea temperatures, shifting fish stocks, and intensifying typhoons as disruptive shocks to livelihoods and eroding traditional fishing practices. In Taiwan, despite relatively stronger infrastructure, household income, and access to technology, adaptation remains constrained by market pressures, declining youth participation, and regulatory complexities. In PNG, fishers deeply rely on natural resources and coastal ecosystems for subsistence and income, yet face acute risks from sea-level rise, coral bleaching, and unpredictable weather. With limited financial resources, weak institutional support, and geographic isolation, fishers perceive CC as an amplifying factor to existing vulnerabilities, leaving communities dependent on traditional knowledge and communal coping strategies. Fishers’ perceptions of CC are shaped by lived experiences rather than scientific discourse, influencing adaptation choices ranging from livelihood diversification to migration. Perceptions of CC drivers, their distal and proximal impacts on coastal fishing community livelihoods are viewed as siloed; yet, remote sensing data revealed that the impacts are transboundary. The findings underscore the urgent need for context-sensitive policies that integrate local knowledge, science-based data (such as remote sensing CC maps) to strengthen institutional support, and enhance resilience among vulnerable and underserved coastal small-scale fishers. Full article

Zinc oxide (ZnO) is widely utilized as a mineral UV filter in sunscreen formulations due to its broad-spectrum efficacy, photostability, and acceptance by natural cosmetic certification bodies. Despite its growing use, the environmental impact of ZnO on marine ecosystems remains under debate. While zinc is an essential micronutrient for aquatic organisms, excessive concentrations of Zn compounds, particularly in nanoparticulate form, have been thought to have detrimental effects, including coral bleaching, oxidative stress, and disruptions in metabolic and reproductive functions in marine species. This review synthesizes the current peer-reviewed literature on the ecotoxicological effects of ZnO, with particular emphasis on coral reef health, bioaccumulation, and trophic transfer pathways. Furthermore, real-world exposure scenarios are evaluated, incorporating field data from densely visited coastal regions and modeled environmental concentrations under worst-case use conditions. The aim of this study is to provide a comprehensive risk assessment of ZnO in sunscreen applications, balancing its recognized safety in human use with potential long-term impacts on aquatic ecosystems, thereby informing future regulatory decisions and sustainable product development. Full article

Coral reefs are among the most biodiverse marine ecosystems, playing irreplaceable roles in maintaining marine ecological balance and coastal services. Under dual pressures of global climate change and human activities, coral bleaching and degradation have become increasingly frequent, creating an urgent need for large-scale, long-term, and highly automated monitoring technologies. In recent years, advances in underwater imaging and deep learning have made visual recognition a core approach for coral classification and health assessment. However, most studies only focus on isolated model accuracy optimization, lacking systematic full-chain analysis integrating datasets, model evolution, cross-domain generalization, engineering constraints, and ecological adaptation, which severely hinders large-scale cross-regional and long-term application. This paper systematically reviews coral visual recognition technologies. It summarizes underwater image acquisition, public dataset characteristics, and annotation system evolution, then compares traditional feature engineering and deep learning in key tasks, highlighting their differences in feature representation and generalization. Four core challenges are identified: class imbalance, poor underwater image quality, weak cross-device/region generalization, and mismatched algorithm metrics with ecological needs. Finally, feasible solutions based on self-supervised pre-training, domain adaptation, and multimodal fusion are discussed to enhance model robustness and ecological interpretability, providing methodological support for intelligent coral reef monitoring systems. Full article

Coral reefs are biodiversity hotspots increasingly threatened by climate-induced bleaching, yet profiling the coral holobiont—the host and its associated microbiota—remains technically challenging due to high host-DNA contamination (often >95%) and the lack of comprehensive reference databases. Here, we present holo-2bRAD, a type IIB restriction site-associated DNA sequencing approach. This method, strategically integrated with a meticulously curated hologenome database (comprising 404,946 microbial genomes and 56 coral-derived metagenome-assembled genomes), effectively overcomes overwhelming host contamination (~99%). We demonstrate its exceptional species specificity (99.92%) in profiling Galaxea fascicularis (Linnaeus, 1767; Order Scleractinia, Family Euphylliidae) holobionts across bleaching severities, thereby validating its technical feasibility. Leveraging this high-resolution tool, our hologenome analysis revealed significant restructuring of coral-associated microbiota during bleaching, where microbial shifts (e.g., depletion of beneficial Thermoanaerobacterium thermosaccharolyticum and enrichment of stress-responsive bacteria) correlated more strongly with bleaching phenotypes than host genetic variation. By providing cost-effective, multi-domain hologenome profiling at unprecedented resolution, holo-2bRAD offers a practical tool for investigating holobiont dynamics and developing microbiome-informed coral conservation strategies. Full article

Although coral bleaching–associated microbial changes have been widely studied, bacterial succession during bleaching, particularly in partly bleached corals, remains poorly understood. Here, we investigated bacterial community dynamics in healthy, partly bleached, and bleached Goniopora sp. collected from the Sanya Coral Reef Conservation District, South China Sea. A total of 599,003 valid sequences were obtained and clustered into 5094 operational taxonomic units (OTUs). These OTUs spanned 45 bacterial phyla and were identified by 16S rRNA gene sequencing, revealing a highly diverse bacterial community associated with Goniopora sp. Alpha diversity differed significantly among health statuses, with partly bleached Goniopora sp. (PBG) exhibiting the highest bacterial diversity (Shannon index: 6.25 ± 0.11), followed by bleached Goniopora sp. (BG) (5.49 ± 0.18) and healthy Goniopora sp. (HG) (3.04 ± 0.17). Beta diversity analyses showed clear separation of microbial community structures among HG, PBG, and BG. Successional analyses revealed a progressive decline in putatively beneficial bacterial taxa, including the phylum Pseudomonadota and the genus Cohaesibacter with increasing bleaching severity, whereas the relative abundance of opportunistic or stress-associated bacteria, such as Blastopirellula, Mycobacterium, and some unclassified taxa, increased. Notably, many bacterial taxa, including Acidobacteriota, Woeseia and Ruegeria, displayed non-linear abundance patterns, with pronounced shifts during the partly bleached stage. These findings highlight substantial microbial restructuring during coral bleaching and underscore the importance of the partly bleached status as a transitional phase in coral-associated bacterial succession. Full article

Long-term monitoring is essential for understanding how recurring disturbances, such as hurricanes and coral bleaching, affect reef fish communities and ecosystem processes. This study evaluates temporal trends (2013–2025) in fish assemblage composition, functional diversity, and nutrient excretion proxies (C, N, and P) across three reef sites on San Andrés Island in the Colombian Caribbean. Our results reveal significant shifts in community structure following major disturbances in 2020 (Hurricanes Eta, Iota) and 2023 (mass bleaching event). Taxonomic and functional richness (TRich, FRich) fluctuated throughout the study period, whereas functional divergence (FDiv) declined earlier (2016), highlighting site-specific differences. A trait-based nutrient-excretion proxy (NPC composite score) identified key species that maintain nutrient cycling. Despite recent coral bleaching, certain sites exhibited functional resilience, sustained by the persistence of high-performing nutrient providing species. However, the overall disconnect between taxonomic recovery and functional stability suggests that ecosystem-level processes remain vulnerable, even when species richness appears to recover. This highlights the importance of integrating functional traits and nutrient recycling proxies into monitoring programs to better predict long-term variability in San Andrés Island reefs under a changing climate. Our findings provide a framework for prioritizing management efforts in the Seaflower Biosphere Reserve with emphasis on maintaining ecosystem services. Full article

Coral reefs in Djibouti, located at the biogeographic junction of the Red Sea and the Indian Ocean, remain among the least studied in the region despite increasing climate-driven pressures. This study provides the first scientific documentation of a large-scale bleaching event in Djibouti following the extreme thermal anomaly of 2023. Benthic surveys conducted across 16 sites in Moucha–Maskali Islands, Arta, Tadjourah, and Obock revealed bleaching at all sites, with the highest levels recorded at Ras Bir (23.4%) and Sable Blanc (24.1%), predominantly affecting thermally susceptible such as Acropora and Pocillopora. More thermally tolerant massive corals, particularly Porites, Favia, and Platygyra, exhibited limited bleaching and dominated healthier sites such as Arta. Satellite-derived sea surface temperature (SST) and Degree Heating Week (DHW) data confirmed record-breaking heat stress in 2023, with SST peaking at 35.2 °C and DHW reaching 13.87 °C·week⁻¹—the highest recorded. The pronounced spatial variability in bleaching reflects the combined influence of thermal stress, sedimentation, water quality, and reef geomorphology. Although mortality remained moderate, the findings indicate rising vulnerability of Djibouti’s reefs and underscore the urgent need for continuous monitoring, targeted management interventions, and mitigation of local stressors to enhance resilience in the region. Full article

In underwater detection tasks involving bleached corals, band disease corals, and white pox disease corals, several challenges persist, including high morphological variability, difficulty in identifying small pathological regions, interference from complex underwater environments, and constraints imposed by underwater hardware. To address these issues, a lightweight underwater diseased coral target detection method, termed CD-YOLO, is proposed. Specifically, (1) a lightweight network named CDShuffleNet is constructed to replace the YOLO11 backbone, aiming to reduce model complexity while preserving detection performance; (2) a SPDConv downsampling convolution module is introduced to reduce the loss of fine-grained coral detail information during the downsampling process; and (3) attention mechanisms are incorporated through an engineering-oriented integration of EMA into the C2PSA module and the adoption of SENetV2, in order to enhance the representation of color and shape features of pathological regions and suppress interference from complex underwater environments. Experimental results demonstrate that the proposed improvements yield consistent gains in both model lightweighting and detection performance under the adopted evaluation settings. Specifically, the number of parameters, computational cost, and model size are reduced by 20.6%, 21.9%, and 18.9%, respectively, while mAP increases by 4.3 percentage points. Comparative experiments further show that the proposed method achieves a markedly higher mAP than several other state-of-the-art models. In addition, experiments conducted on the BHD Coral dataset provide preliminary evidence of cross-dataset adaptability of the proposed model. Overall, this study presents a task-oriented and application-driven improvement, demonstrating that the effective integration of lightweight components can achieve a favorable balance between model efficiency and detection performance in underwater diseased coral detection tasks. Full article

Coral reef ecosystems represent one of the most biodiverse and productive marine habitats, yet they are increasingly threatened by a range of anthropogenic stressors. Among these, emerging contaminants including pharmaceutical and personal care products (PPCPs) have started to feature as contaminants of concern due to their persistence, bioaccumulation potential, and complex interactions within reef environments. This review synthesizes current research on the occurrence, transport pathways, and ecological impacts of emerging contaminants, specifically focusing on PPCPs on coral reef systems. Evidence indicates that compounds such as UV filters, antibiotics, and endocrine-disrupting chemicals can impair coral physiology, disrupt symbiotic relationships with zooxanthellae, and contribute to bleaching events. The review further highlights the variability in coral species’ sensitivity to these contaminants, with documented effects ranging from oxidative stress to reduced growth and reproductive capacity. Despite advances in detection and risk assessment, significant knowledge gaps remain regarding long-term exposure, mixture effects, and the influence of local environmental conditions on contaminant toxicity. By consolidating recent findings, this review underscores the urgent need for targeted research and policy action to mitigate the threat of emerging contaminants to coral reef ecosystems. Full article

A rapid decline of coral reefs is taking place around the world, with climate warming being the biggest driver behind this deterioration. Efforts to increase coral climate resilience via bioengineering methods have thus become urgent, and there is hope that such interventions can help corals and coral reefs survive until a time when no further climate warming occurs and perhaps a future of climate cooling is imaginable. The manipulation of coral-associated bacterial communities is among the less advanced interventions currently being explored. Nevertheless, early findings provide confidence that some level of thermal enhancement can be achieved via the inoculation of corals with beneficial bacteria. The small number of studies available, however, is limited in terms of the traits used to select candidate bacteria and their ability to ascribe host enhancement to specific bacterial taxa and functions. Further, findings to date are unable to decipher whether candidate bacteria integrate stably within the coral microbiome. These shortcomings prevent assessment of the efficacy of bacterial manipulation to enhance the long-term thermal resilience of corals on the reef. Here we summarise the state-of-play of the field and provide recommendations to fast-track this approach via fine-tuning experimental designs and methods. Full article

Citizen science approaches for monitoring, and even restoring, coral reefs have grown in popularity though tend to be restricted to those who have taken courses that expose them to the relevant methodologies. Now that cheap (~10 USD), waterproof pouches for smart phones are widely available, there is the potential for mass acquisition of coral reef images by non-scientists. Furthermore, with the emergence of better machine-learning-based image classification approaches, high-quality data can be extracted from low-resolution images (provided that key benthic organisms, namely corals, other invertebrates, & algae, can be distinguished). To determine whether informally captured images could yield comparable ecological data to point-intercept + photo-quadrat surveys conducted by highly proficient research divers, we trained an artificial intelligence (AI), CoralNet, with images taken before and during a bleaching event in 2015 in Chagos (Indian Ocean). The overall percent coral covers of the formal, “gold standard” method and the informal, “tourist diver” approach of 38.7 and 35.1%, respectively, were within ~10% of one another; coral bleaching percentages of 30.5 and 31.8%, respectively, were statistically comparable. Although the AI was prone to classifying bleached corals as healthy in ~one-third of cases, the fact that these data could be collected by someone with no knowledge of coral reef ecology might justify this approach in areas where divers or snorkelers have access to waterproof cameras and are keen to document coral reef condition. Full article