Search Results (907)

This study examines four shallow-water, reef-coral-bearing carbonate successions belonging to the Jhill Limestone Unit of the Gaj Formation, exposed in the area near Karachi (southern Pakistan). Sixty-two samples were collected for the quantitative analysis of the skeletal and foraminiferal assemblages. The analysis of large benthic foraminifera suggests a placement within the late Oligocene, characterized by the setup of the Late Oligocene Warming Event. Thanks to quantitative analyses and multivariate statistics, three biofacies were identified: (1) the reef coral biofacies (BFA), indicative of a sheltered, shallow-water environment above fair-weather wave base; (2) the coralline algal biofacies (BFB), deposited within a mesophotic setting and representing the deepest biofacies among the three recognized ones; and (3) the large benthic foraminiferal and coralline algal biofacies (BFC), subdivided into two sub-biofacies, namely (a) the miogypsinid, thin and flat large benthic foraminiferal and coralline algal sub-biofacies (BFC1), indicative of deeper setting, comprised between BFA and BFB, and (b) the miogypsinid and coralline algal sub-biofacies (BFC2), indicative of shallower settings than BFC1, and bearing evidence of paleo-seagrass meadows. All these biofacies were developed within the photic zone, in a relatively flat seafloor punctuated by patch reefs and seagrass meadows and characterized by a notable nutrient influx. Foraminiferal-based experimental paleobathymetric parameters, including the lepidocyclinids/miogypsinids, the flat nummulitids/lepidocyclinids, and the hyaline/porcelaneous foraminifera ratios, were tested and confirmed as reliable tools for paleodepth and paleoenvironmental reconstructions. Full article

This study presents an innovative approach to automated coral reef monitoring using satellite imagery, addressing challenges in image quality assessment and correction. The method employs Principal Component Analysis (PCA) coupled with clustering for efficient image selection and quality evaluation, followed by a machine learning-based cloud removal technique using an XGBoost model trained to detect land and cloudy pixels over water. The workflow incorporates depth correction using Lyzenga’s algorithm and superpixel analysis, culminating in an unsupervised classification of reef areas using KMeans. Results demonstrate the effectiveness of this approach in producing consistent, interpretable classifications of reef ecosystems across different imaging conditions. This study highlights the potential for scalable, autonomous monitoring of coral reefs, offering valuable insights for conservation efforts and climate change impact assessment in shallow marine environments. Full article

Coral reefs thrive in nutrients-poor waters, and their survival strategy in such oligotrophic marine environments remains largely unexplored. Current coral research has focused on the interplay between the animal hosts, symbiotic Symbiodiniaceae, and associated bacteria, with little attention given to their individual interactions. Here, we integrated biochemical, transcriptomic, and metabonomic analyses of the clade D Symbiodiniaceae strain AG11 to investigate the growth-assisting mechanisms of symbiotic bacteria. Our findings indicate that metabolic trophallaxis between Symbiodiniaceae and symbiotic bacteria plays a crucial role in enhancing survival and population growth under nitrogen-depleted conditions, commonly found in typical coral habitats. Notably, the exchange of organic compounds between Symbiodiniaceae and bacteria significantly boosts nitrogen uptake in their free-living state. Furthermore, we demonstrated how beneficial bacteria influence the survival of Symbiodiniaceae in response to environmental changes, which are vital for coping with nitrogen-depleted conditions where coral reefs are particularly vulnerable. Full article

The diurnal cycle of light significantly impacts microbes, making diurnal investigations crucial for understanding microbial communities. Zhubi Reef is known to harbor exceptionally rich biodiversity, with both zooplankton and seawater properties demonstrating diurnal patterns. However, microbial community structures and their potential diurnal dynamics remain largely unexplored. This study is the first to utilize flow cytometry and high-throughput sequencing to investigate prokaryotic and microeukaryotic communities in the Zhubi lagoon, focusing on diurnal variations under different light intensities. The picophytoplankton cell abundance and the microbial community structures both exhibit clear diurnal variations. Light is identified as the primary driver of diurnal variations in the picophytoplankton cell abundance. The diurnal variation in microbial community diversity is driven by changes in the cell abundance of two dominant picocyanobacterial groups. Our findings reveal the diurnal variation in microbial community structures is mediated by the light-driven fluctuation of dominant cyanobacterial populations, and the diurnal variation patterns of specific populations may vary with habitats and sampling timepoints. This research provides valuable insights into the microbial community structure within the Zhubi lagoon. Full article

Nitrification is the key process linking the oxidized and reduced forms of reactive nitrogen, playing an important role in the nitrogen biogeochemical cycle. Quantifying the nitrification rate and evaluating its environmental regulators in different aquatic environments at both regional and global scales has received increasing attention. However, the spatiotemporal variations in nitrification rates in coastal waters, particularly with different trophic states, remain unclear. By using the ¹⁵N-labeling technique, here, we quantified the nitrification rates under dark and light conditions in the surface waters of Shenzhen Bay and Dapeng Bay, representing eutrophic and oligotrophic environments, respectively. The nitrification rates were 2–3 orders of magnitude higher in Shenzhen Bay (eutrophic) than those in Dapeng Bay (oligotrophic). The concentrations of ammonium and total suspended matter play key roles in regulating the spatiotemporal distribution and difference in nitrification in these two coastal bays. The nitrification rate under the dark condition (0.13–49.37 nmol N L⁻¹ h⁻¹) was greater than that under light incubation (0–10.15 nmol N L⁻¹ h⁻¹), indicating light inhibition of 33–100% in the surface water. Such results imply that daily integrated nitrification based on the rates under dark incubation may have been overestimated. An environment with high turbidity is preferable for nitrification, as it reduces the damage caused by light to ammonia-oxidizing microbes. Collectively, the differences in nitrification rates further result in a distinct composition of dissolved inorganic nitrogen, with Shenzhen Bay dominated by nitrate and Dapeng Bay dominated by ammonium. Our results provide scientific references for the mitigation of nitrogen pollution in different trophic coastal bays. Full article

Coral reefs are vital ecosystems facing rapid degradation. This research explores architectural design solutions for bio-enhancing modular prototypes to support coral attachment and growth. Inspired by coral polyps, nine biomimetic designs were created using Maya and Rhinoceros 3D to optimise surfaces for coral settlement. A total of 75 prototypes (15 × 15 cm) were fabricated, incorporating four materials—PETG, concrete, oyster concrete, and clay—and seven colour variations—sand, translucent green, translucent brown, red, pink, grey, and reddish. The findings indicate that 3D printing with PETG was the most efficient fabrication method but required structural support and long-term underwater testing, while oyster concrete demonstrated potential for self-sustaining structures. This study highlights the role of architectural design in marine restoration, promoting biodiversity and resource-efficient solutions. By integrating corals into the design, these structures can self-grow and adapt, reducing material consumption and long-term maintenance. Full article

Coral reef and their ecological services of food production and shoreline protection are threatened by unsustainable use. To better understand their status, multiple approaches to estimating fisheries sustainability were compared, namely fisheries-independent stock biomass and recovery rates, fisheries-dependent landed catches, balanced harvest and gear use metrics, and fish length measurements. A community biomass recovery was established over a 45-year no-fishing stock recovery time series from seven fisheries reserves and compared to catch- and length-based estimates of sustainability. The logistic production rates (r = 0.09 ± 0.06 95% confidence interval (CI)) and maximum equilibrium total biomass (~150 ± 30 tons/km²) indicated a broad range of potential maximum sustainable yields, with a likely range of 1.1 to 3.9 (95% CI; mean = 3.8) tons/km²/year. In contrast, the mean annual linear biomass growth rates in reserves were lower but less variable than logistic surplus production estimates, ranging from 2.1 to 3.5 (mean = 2.8 tons/km²/year). Realized catches at landing sites were lower still, ranging from 1.43 to 1.52 (mean = 1.48 ± 0.2 tons/km²/y). Differences between production estimates and capture were largely attributable to changes in taxonomic composition and an imbalance in the estimated proportionality of production potential versus actual capture rates. Lost potential capture was likely due to differences in the vulnerability of taxa to fishing and a lack of compensatory increased production among fishing-resistant taxa. Large proportional losses of catch were measured among snappers, unicorn fish, sweetlips, goatfish, and soldierfish, while smaller proportional gains in the catch samples were found among resident herbivorous rabbitfish, parrotfish, and groupers. Many of these declining taxa have vulnerable schooling life histories that are likely to require special habitat and reserve characteristics. Evaluations of sustainability from length measurements found 17 or 7% of total and 12% of caught species had sample sizes minimally sufficient for evaluation (>30 individuals from 413 catches, 2284 captured individuals composed of 144 species) of length and spawning metrics of sustainability. Seven of these species met length-based and three met spawning potential ratio thresholds for sustainability. Consequently, length-based evaluations had poor species coverage and therefore we were unable to evaluate the sustainability of the larger fish community. Recommendations for future research include a better understanding of the consequences of variability in spillover and proportionality of production potential for sustainability. Management recommendations are to focus management on the recovery of species abundant in unfished locations but not contributing to fisheries yield. Full article

Pacific crown-of-thorns starfish (Acanthaster solaris) outbreaks pose a significant threat to coral reef ecosystems, with climate change potentially exacerbating their distribution and impact. However, there remains only a small number of predictive studies on how climate change drives changes in the distribution patterns of A. solaris, and relevant assessments of the impact of these changes on coral reef areas are lacking. To address this issue, this study investigated potential changes in the distribution of A. solaris under climate change and its impact on Acropora coral habitats. Using a novel two-step framework, we integrated both abiotic and biological (Acropora distribution) predictors into species distribution modeling to project future shifts in A. solaris habitats. We created the first reliable set of current and future global distribution maps for A. solaris using a comprehensive dataset and machine learning approach. The results showed significant distribution shifts under three climate change scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5), with expanded ranges under all scenarios, and the greatest expansion occurring near 10° S. Asymmetry in the latitudinal shifts in habitat boundaries suggests that the Southern Hemisphere may face a more severe expansion of A. solaris. Regions previously unsuitable for A. solaris, such as parts of New Zealand, might experience new invasions. Additionally, our findings highlight the potential increase in predatory pressure on coral reefs under SSP2-4.5 and SSP5-8.5 scenarios, particularly in the Western Coral Triangle and Northeast Australian Shelf, where an overlap between A. solaris and Acropora habitats is significant. This study provides critical insights into the ecological dynamics of A. solaris in the context of climate change, and the results have important implications for coral reef management. These findings highlight the need for targeted conservation efforts and the development of mitigation strategies to protect coral reefs from the growing threat posed by A. solaris. Full article

An epilithic algal matrix (EAM) exhibits rapid expansion, recovery capacity, and high adaptability, leading to widespread distribution in degraded coral reef habitats. However, limited research on the dynamic processes of succession hinders a comprehensive understanding of EAM formation. To examine the influence of succession processes and environmental factors on the composition of EAM microbial communities, a three-factor (time × depth × attached substrate type) crossover experiment was conducted in the Luhuitou Reef Area, Sanya, China. Microbial community compositions were analyzed through 16S rRNA gene amplicon sequencing. The community was predominantly composed of proteobacteria (61.10–92.75%), cyanobacteria (2.47–23.54%), bacteroidetes (0.86–8.49%), and firmicutes (0.14–7.76%). Successional processes were found to significantly shape the EAM-associated microbial communities in the Luhuitou Reef Area. Proteobacteria played a crucial role in biofilm formation during this process, while cyanobacteria contributed to the structural complexity of microhabitats within the EAM. A chaotic aggregation stage of approximately one month was observed before transitioning into an expansion stage, eventually stabilizing into a low-diversity community. Although the relatively smooth substrate supported high biodiversity, microorganisms displayed no preference for the three different substrates. While no significant differences in community composition were observed at small-scale depths, cyanobacteria and bacteroidetes showed positive correlations with light and temperature, respectively. The EAM-associated microbial community exhibited higher complexity in the shallower regions under increased light intensity and temperature. Given the characteristics of the microbial community succession process, continuous monitoring of changes in microbial community structure and key taxa (such as proteobacteria and cyanobacteria) during EAM formation is recommended. Full article

The coral reefs in the Philippines are facing an unprecedented crisis. This study, based on a comprehensive analysis of marine heatwaves (MHWs), degree heating weeks (DHWs), and ocean acidification (OA) indices derived from satellite observations and reanalysis data, reveals how thermal stress and OA have progressively eroded coral ecosystems from 1985 to 2022. This study analyzed 12 critical coral habitats adjacent to the Philippines. The monthly average sea surface temperature (SST) in the study area ranged from 26.6 °C to 29.3 °C. The coast of Lingayen Gulf was identified as the most vulnerable coral reef site in the Philippines, followed by Davao Oriental and Polillo Island. The coast of Lingayen Gulf recorded the highest total MHW days in 2022, amounting to 293 days. The coast of Lingayen Gulf also reached the highest DHW values in July and August 2022, with 8.94 °C weeks, while Davao Oriental experienced the most extended average duration of MHWs in 2020, lasting 90.5 days per event. Large-scale climate features such as the El Niño–Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) significantly influenced the study area’s SST anomalies and MHW events. High-risk coral bleaching periods, such as 1988–1989, 1998–1999, 2007–2008, and 2009–2010, were characterized by transitions from El Niño and positive PDO phases, to La Niña and negative PDO phases. However, since 2015, global warming has led to high cumulative heat stress without specific climate background patterns. We propose a Coral Marine Environmental Vulnerability Index (CoralVI) to integrate the spatiotemporal dynamics of warming and acidification and their impacts on coral habitats. The data show a rapid increase in the marine environmental vulnerability of coral habitats in the Philippines in recent years, extending to almost the entire coastline, posing significant threats to coral survival. Full article

Gera Gulf, a relatively small embayment on the island of Lesvos, serves as a representative example of a semi-enclosed, shallow marine system in Greece. Previous studies revealed that the gulf seafloor is occupied by numerous small reefs that are evenly distributed. Recently, seismic surveys together with gravity coring have shown numerous relict reefs within a fine-grained matrix, hosted at different stratigraphic levels above the inferred Holocene/Pleistocene boundary and locally extending up to the present seabed. The reefs are primarily engineered by the bivalve Ostrea edulis, with additional colonization by other marine organisms such as the coral Cladocora caespitosa. Key features identified in the seismic profiles include the widespread distribution of buried reef structures, erosional surfaces and unconformities also related to a paleolake, extensive fluid concentrations, and a major fault system paralleling the northeastern coast. Seismic record analysis and sediment dating suggest that the flooding of Gera Gulf began approximately 7500 BP, with O. edulis colonizing the seabed shortly thereafter. Buried reef structures were identified within the transgressive and highstand system tracts, characterized by varying sedimentation rates. These variations reflect changing environmental conditions, probably linked to specific climatic events during the Holocene epoch, which contributed to the evolution and shaping of the oyster reef terrain. Given the limited studies on recent or buried oyster reefs in similar environments, this study provides critical insights into the Holocene evolution of oyster reef terrains and their response to climate changes. Full article

The infraclass Euthyneura (Mollusca, Heterobranchia) exhibits significant diversity in morphology, size, life habits, and color. Several species are important for research in evolution, ecology, chemistry, and pharmacology. Despite Colombia’s expansive Pacific and Caribbean coasts, which host ecosystems such as rocky shores and coral reefs, key habitats for sea slugs and sea hares, the biodiversity of Euthyneura remains largely understudied. This study aims to expand the inventory of Euthyneura diversity in intertidal and shallow subtidal rocky and coral reef environments in Colombia’s Pacific (Uramba Bahía Málaga National Natural Park) and Caribbean (Seaflower Biosphere Reserve) areas. Rapid biodiversity assessments using snorkeling and errant scuba diving at depths of 1–40 m resulted in the documentation of 31 species (14 in Caribbean coral reefs and 17 in Pacific intertidal and shallow subtidal rocky shores and reefs). Eleven species were new records. The family Aplysiidae was the richest with five species, followed by Facelinidae with four, and Aeolidiidae, Discodorididae, Chromodorididae, and Plakobranchidae with three each. Given the limited sampling effort (~40 h in the Caribbean and ~20 h in the Pacific) and the substantial new data collected, it is evident that there is still much to learn about this group in these areas. Increased efforts, combined with detailed morphological and molecular techniques, will enhance our understanding and documentation of Euthyneura diversity in Colombia. Full article

This study introduces a novel approach for the multi-model analysis of complex water distribution networks (WDNs). The research focuses on designing and optimizing various WDN configurations while adhering to hydraulic constraints. Several key parameters and criteria are considered to achieve an efficient design. Additionally, different network layouts are evaluated, including looped and non-looped systems with varying numbers of reservoirs. Next, an analytical approach is developed to optimize the proposed WDNs, taking into account pipe type, length, and diameter, as well as nodal demands, elevations, pressure losses, and water velocities. Cost analysis reveals that a single-reservoir, non-looped WDN has the lowest cost (USD 26,892), while a two-reservoir, looped WDN has the highest (USD 30,861). The design inflows vary linearly, ranging from 0.0212 to 0.205 m³/s for a 0.3 m pipe diameter and from 0.0589 to 0.5694 m³/s for a 0.5 m pipe diameter. Further, a new approach based on the Coral Reef Algorithm (CRA) is developed and implemented to improve the technical and economic viability of the designed WDNs. The CRA effectively showcases its capacity to iteratively enhance network design by reducing overall costs significantly. Notably, higher demand multipliers yield even more efficient solutions, suggesting the algorithm’s adaptability to varying demand scenarios. Full article

The coral microbiome is highly related to the overall health and the survival and proliferation of coral reefs. The Red Sea’s unique physiochemical characteristics, such a significant north–south temperature and salinity gradient, make it a very intriguing research system. However, the Red Sea is rather isolated, with a very diversified ecosystem rich in coral communities, and the makeup of the coral-associated microbiome remains little understood. Therefore, comprehending the makeup and dispersion of the endogenous microbiome associated with coral is crucial for understanding how the coral microbiome coexists and interacts, as well as its contribution to temperature tolerance and resistance against possible pathogens. Here, we investigate metagenomic sequencing targeting 16S rRNA using DNAs from the sediment samples to identify the coral microbiome and to understand the dynamics of microbial taxa and genes in the surface mucous layer (SML) microbiome of the coral communities in three distinct areas close to and far from coral communities in the Red Sea. These findings highlight the genomic array of the microbiome in three areas around and beneath the coral communities and revealed distinct bacterial communities in each group, where Pseudoalteromonas agarivorans (30%), Vibrio owensii (11%), and Pseudoalteromonas sp. Xi13 (10%) were the most predominant species in samples closer to coral (a coral-associated microbiome), with the domination of Pseudoalteromonas_agarivorans and Vibrio_owensii in Alshreah samples distant from coral, while Pseudoalteromonas_sp._Xi13 was more abundant in closer samples. Moreover, Proteobacteria such as Pseudoalteromonas, Pseudomonas and Cyanobacteria were the most prevalent phyla of the coral microbiome. Further, Saweehal showed the highest diversity far from corals (52.8%) and in Alshreah (7.35%) compared to Marwan (1.75%). The microbial community was less diversified in the samples from Alshreah Far (5.99%) and Marwan Far (1.75%), which had comparatively lower values for all indices. Also, Vibrio species were the most prevalent microorganisms in the coral mucus, and the prevalence of these bacteria is significantly higher than those found in the surrounding saltwater. These findings reveal that there is a notable difference in microbial diversity across the various settings and locales, revealing that geographic variables and coral closeness affect the diversity of microbial communities. There were significant differences in microbial community composition regarding the proximity to coral. In addition, there were strong positive correlations between genera Pseudoalteromonas and Vibrio in close-to-coral environments, suggesting that these bacteria may play a synergistic role in Immunizing coral, raising its tolerance towards environmental stress and overall coral health. Full article

Background: The Merulinidae family belonging to the order Scleractinia is mainly distributed in the Indo-Pacific and Caribbean regions and often constitute the most dominant species of coral reefs. Mitochondrial genome is a key tool for studying the phylogeny and adaptation. Only a few studies have conducted the characteristics analyses of mitochondrial genome in the Merulinidae family. Methods: Therefore, we used high-throughput sequencing technology to describe the mitochondrial genome of Platygyra daedalea, a member of this family. Bioinformatics was used to analyze the composition characteristics of the mitochondrial genome of 10 Merulinidae species. Results: The mitochondrial genome of P. daedalea had a total length of 16,462 bp and a GC content of 33.0%. Thirteen unique protein-coding genes (PCGs), two transfer RNA (tRNA) genes, and two ribosomal RNA (rRNA) genes were annotated. Each species of Merulinidae had 13 unique PCGs in the mitochondrial genome. In contrast, the number of tRNAs and rRNAs significantly varied in Merulinidae species. Collinearity and gene rearrangement analyses indicated that the mitochondrial evolution of species in the Merulinidae family was relatively conserved. Divergence time analysis indicated that Merulinidae originated in the Oligocene, whereas the Platygyra genus originated in the Miocene. The formation and intraspecific divergence of coral species were consistent with geological changes in the ocean. Conclusions: The results of this study help better understand the characteristics of the mitochondrial genome in the Merulinidae family and provide insights into the utility of mitochondrial genes as molecular markers of phylogeny. Full article