Search Results (174)

Coral reef degradation has accelerated the development of active restoration approaches, including the use of mid-water coral nurseries (Floating Reef Devices; FRDs) designed to enhance coral growth and survival. Although primarily used for coral propagation, the broader ecological roles of FRDs remain poorly understood. We assess the biodiversity and ecological structure of a long-term FRD deployed in the Gulf of Eilat over two decades as an active coral nursery. We surveyed naturally recruited sessile organisms and associated fish communities, quantifying taxonomic breadth and distinctness (Δ+), functional diversity, and trophic structure. The FRD supported a diverse community spanning eight phyla and 128 genera, with high taxonomic distinctness and wide functional trait representation across multiple trophic levels. Despite lower genus richness compared to natural habitats, coral and fish assemblages exhibited taxonomic and functional patterns that fell within the range observed for the adjacent natural reef. Functional analyses showed that the FRD’s coral assemblage occupied nearly the full regional trait space, while fish biomass was dominated by planktivores and secondary consumers, indicating a differently structured trophic organization. These findings demonstrate that long-term floating nursery systems can develop into structurally complex, multi-trophic communities, providing ecological and conservation values and ecosystem services beyond their original restoration role. These findings provide an ecological foundation for future studies of floating restoration systems and their associated ecological roles, while also informing their design, implementation, and evaluation as practical tools for enhancing ecosystem recovery and associated ecological functions. Full article

Nature-based Solutions (NbS) are increasingly recognised as effective approaches for enhancing coastal resilience while simultaneously supporting biodiversity, ecosystem services, and, where appropriate, climate-change mitigation. Their importance is particularly evident in the Mediterranean Basin, a climate-change hotspot exposed to sea-level rise, coastal erosion, land subsidence, sediment deficits, and intense anthropogenic pressures. This review provides a structured evidence synthesis of NbS for Mediterranean coastal adaptation, integrating ecological, hydrodynamic, geomorphological, biodiversity, governance, and implementation perspectives. We examine the principal NbS typologies, including vegetated habitats, biogenic reefs, sediment-based interventions, and hybrid approaches, with particular attention to vulnerable microtidal systems such as coastal lagoons and subsiding shorelines, including the Venice Lagoon and the Emilia-Romagna coast. Drawing on peer-reviewed literature together with evidence from European LIFE projects and restoration initiatives, the review highlights how process-based interventions can restore ecosystem functioning, strengthen coastal resilience, and provide multiple ecosystem services. At the same time, the analysis emphasises that NbS are inherently context-dependent, with their effectiveness influenced by local geomorphology, sediment availability, hydrodynamic conditions, governance capacity, and long-term management. Although important scientific uncertainties remain, wider implementation is increasingly constrained by economic, institutional, and governance barriers. The review concludes that NbS should not be regarded as stand-alone alternatives to conventional engineering, but as key components of integrated and adaptive hybrid coastal management strategies capable of supporting resilient Mediterranean coastal systems under future climate change. Full article

The Jobos Bay National Estuarine Research Reserve (JBNERR) includes the largest bay on the southern coast of Puerto Rico. The reserve includes diverse habitats ranging from mangrove forests, shallow lagoons, seagrass beds, cays and coral reefs, with a broad range of environmental gradients between the populated coastal plain and the oligotrophic Caribbean Sea. As the only research reserve in the region, resource managers seek cost-effective and reliable processes to restore and promote ecosystem health in the reserve. Benthic foraminiferal assemblages are widely applied bioindicators for assessing coastal environments, notably coral reefs and seagrass ecosystems. This study evaluated the applicability of three indices, the FoRAM Index (FI), the Epiphytic FoRAM Index (FI′), and the Long vs. Short Life-Span Index (I_LS), to assess bayside and reef habitats bordering three cays of Jobos Bay. Surficial sediment samples were collected in 2018 and 2019. Environmental data included sediment composition (e.g., texture, total organic content) and water quality (e.g., nutrients and pH). From a total of 57 samples, 4671 individuals were counted, representing 35 genera. Cluster analysis based on genus-level relative abundances revealed four main groups: Dominant (>10%), Common (5–10%), Occasional (1–4%), and Rare (<1%). Dominant genera included Quinqueloculina (24%) and Amphistegina (18%). Common taxa included smaller rotaliids such as Rotorbinella (6%) and miliolids such as Pyrgo (5%). Twelve genera were occasional, including Triloculina (4%) and Elphidium (3%). Tests of 16 genera occurred rarely (<1%), including agglutinated taxa such as Textularia and stress-tolerant forms like Bolivina. In total, FI values ranged from 1.3 to 9.6, FI′ from 1.9 to 9.7, and I_LS from 0.5 to 30.6. Bayside samples scored generally lower compared to reef samples. In summary, foraminiferal assemblages and associated bioindices indicated that environmental conditions supported Foraminifera that host algal symbionts in the reef environments and the prevalence of macroalgae and seagrass in the bayside benthos. Full article

Background/Objectives: The long-spined sea urchin Diadema antillarum is a keystone herbivore whose grazing maintains Caribbean coral reefs; basin-wide mass mortalities in 1983–1984 and 2022 have made genomic resources a conservation priority, yet no nuclear genome existed for the species. We aimed to generate the first nuclear reference and to resolve the high heterozygosity that complicates genome assembly in broadcast-spawning marine invertebrates. Methods: For the assembly, we combined PacBio HiFi, Oxford Nanopore, and Illumina sequencing. Genome size and heterozygosity were estimated by k-mer profiling. We compared standard and haplotype-aware assembly strategies (hifiasm), evaluated completeness with BUSCO, and annotated repeats using a species-specific RepeatModeler library. Results: k-mer profiling estimated a haploid genome of ~703 Mb with 2.52% heterozygosity. Standard assembly then produced an inflated 1.75 Gb assembly (98.4% BUSCO-complete but 84.4% duplicated), indicating retention of both haplotypes. Haplotype-aware reassembly separated this into a collapsed primary assembly (1.03 Gb) and two phased haplotypes (0.95 and 0.89 Gb), each comparable in size to the chromosome-level congener D. antillarum (886 Mb). BUSCO completeness reached 99.0%, with single-copy orthologs rising to 85–90%, and reference-free consensus quality reached QV 44.5 (Merqury; initial assembly). This genome is repeat-rich (42.84% repetitive; 29.96% unclassified). Conclusions: We provide the collapsed primary assembly together with both phased haplotypes as a haplotype-resolved reference for D. antillarum, establishing a foundation for immunogenomic, comparative, and population-genetic studies and for monitoring and restoration of this ecologically critical species. More broadly, the study shows that haplotype-aware assembly is essential for resolving such highly heterozygous genomes and delivers the genomic foundation needed to guide the conservation of this keystone Caribbean reef species. 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

Sandy coastal ecosystems are among the most widespread yet ecologically simplified marine habitats, particularly where anthropogenic pressures and the scarcity of structurally complex habitats limit biodiversity. This study evaluated the ecological effects of eco-engineered submerged reefs deployed in 2021 along the sandy coast of Lido degli Scacchi (northern Adriatic Sea, Italy). Twenty-one fully submerged eco-engineered Tecnoreef^® modules were installed within the gaps between existing detached breakwaters, introducing a highly porous and architecturally complex habitat into a shallow sedimentary environment. Benthic communities were monitored over two years through the assessment of soft-bottom infaunal and hard-substrate epifaunal assemblages. Community development on Tecnoreef modules was compared with that occurring on adjacent limestone breakwaters under both windward and leeward exposure conditions. Infaunal assemblages were primarily influenced by hydrodynamic exposure and showed limited differentiation between habitat types, although abundance and diversity increased around the submerged structures over time. In contrast, epifaunal communities exhibited marked temporal changes and developed compositions distinct from those observed on breakwaters. Among the taxa contributing most strongly to community differentiation was the reef-building polychaete Sabellaria spinulosa. The progressive establishment of this ecosystem-engineering species suggests that the eco-engineered modules provided favorable conditions for the early stages of secondary biogenic habitat development, although longer-term monitoring will be required to determine whether these developing habitats persist and evolve into stable ecological systems. Our results provide encouraging evidence that structurally complex submerged reefs can increase habitat heterogeneity and support the development of diverse benthic assemblages in highly modified sandy coastal environments. Although longer-term monitoring is required to assess habitat persistence and ecosystem-level effects, these findings highlight the potential of eco-engineered reefs as nature-based tools for supporting biodiversity enhancement and habitat development in tourism-dominated coastal landscapes. Full article

Community-based oyster reef restoration historically involved deploying plastic-based restoration units. However, many practitioners now seek to eliminate plastic usage due to environmental concerns. Scientific investigation into the efficacy and environmental safety of novel, non-plastic restoration products is limited. Four non-plastic shell bag materials (three biopolymers, one basalt fiber) were tested in field and laboratory studies, using plastic controls. In Mosquito Lagoon, FL, USA, a subtropical estuary, units at four restored reefs were monitored quarterly for one year. A 12-month laboratory study examined these same materials and their potential to shed microparticles. In the field, all biopolymers exhibited low persistence (≤17% remaining after 12 months). Basalt had high persistence (96%), but developed large rips by the end of the study. Oyster recruitment was negatively associated with damage to shell bags due to substrate loss. In the laboratory, basalt fiber shed high numbers of thin, rod-like microparticles (1987.4 microparticles/year ± 256.4 SE). Other materials shed <5 microparticles/year on average. Low durability of experimental materials emphasizes the need for more resilient restoration products that can withstand conditions in subtropical marine ecosystems. It is unknown if basalt microparticles impact marine environments, but further study is imperative given the high volume that was shed. Full article

Oysters, as sessile organisms, are highly influenced by environmental conditions affecting their growth and reproduction. Therefore, unfavorable conditions can directly compromise the effectiveness of oyster reef restoration efforts. The study applied the dynamic energy budget (DEB) theory to model the growth of the Suminoe oyster (Crassostrea ariakensis) and estimated the model’s main parameters through linear and nonlinear regression methods. Meanwhile, the parameters of the existing DEB models for the Pacific oyster (Crassostrea gigas) and the Portuguese oyster (Crassostrea angulata) were optimized to improve the model performance. Model accuracy was confirmed by comparing the simulated and observed values of shell height and wet weight for three oyster species. The validated models were subsequently applied to three distinct habitats: Qianhu Bay, the Yangtze River Estuary, and Jiaozhou Bay, to simulate the individual dynamic growth and survival processes of the three oyster species. The simulations of shell height and wet weight for the three oyster species showed strong agreement with observations, with a mean coefficient of determination (R²) of 0.98. The mean NRMSE value of the three models was 0.16, indicating low model-prediction error. The simulation of various habitat scenarios suggested that C. ariakensis exhibited faster growth in the Yangtze River Estuary and Qianhu Bay, and C. gigas in the Yangtze River Estuary. Additionally, C. angulata experienced mortality in the Yangtze River Estuary (February) and Jiaozhou Bay (January). The findings of this study can provide scientific guidance on selecting species for oyster reefs across various marine environments to effectively enhance their ecological restoration outcomes. Full article

Elkhorn coral (Acropora palmata) is a threatened reef-building species that plays a critical role in Caribbean coastal ecosystems. Efficient, large-scale monitoring of A. palmata is essential for evaluating restoration success, yet traditional in situ surveys remain costly and spatially constrained. In this study, we acquired high-resolution (1.8 cm) uncrewed aerial vehicle (UAV) imagery of a coral reef within the United States Virgin Islands’ (USVI) St. Croix East End Marine Park (STXEEMP) and applied deep learning object detection to identify individual A. palmata colonies. We utilized two convolutional neural network architectures, FasterRCNN and MaskRCNN. FasterRCNN was used as an initial screening tool to identify the optimal imagery dataset from several candidates. After identifying the dataset, we used MaskRCNN with an iterative annotation refinement procedure in which initial model predictions were used to augment the training data and achieved an F1 score of 0.78. Detection accuracy was strongly influenced by colony size and apparent water depth, with markedly high accuracy for corals wider than 0.3 m (F1 = 0.87) and located in shallower waters (F1 = 0.81). Beyond detection, MaskRCNN’s polygon outputs enabled the measurement of the individual colony area and the generation of high-resolution coral density maps. These products complement broader-scale prediction and mapping approaches and provide fine-scale, management-relevant information. Although this study was conducted at a single reef site during one acquisition period, the results suggest that UAV-based deep learning workflows offer a promising approach for coral reef monitoring that could support restoration assessments and conservation decision-making, pending validation across additional sites, seasons, and environmental conditions. Full article

Tidal flats are shrinking and eroding due to sea-level rise and human activities. Ecological submerged breakwaters (ESBs) offer a novel solution combining coastal protection and ecological restoration, but their effects on sediment dynamics lack field evidence. This study presents synchronous in situ measurements from an inner tidal flat (WN01) and an outer shallow area (WN02) of a newly built riprap slope-type ESB on the northern coast of the Sheyang River Estuary, Jiangsu, China. Using Acoustic Doppler Velocimeters (ADVs) and wave-tide gauges, we examined hydrodynamics, suspended sediment concentration (SSC), bed shear stress, erosion–accretion, and sediment transport under normal-weather and strong wave events. Within the constraints of a 14-day observation at two stations, our results indicate that: (1) The ESB reduced wave height and weakened currents, shifting dominant bed shear stress from wave-dominated outside to tide-dominated inside. Under normal weather, both sides were accretive. (2) Strong wave events caused sharp increases in bed shear stress, net erosion on both sides, and a 2–3-fold SSC rise, breaking the normal balance. (3) Suspended sediment transport direction remained northwest inside during strong wave events but shifted to northeast/southeast outside, demonstrating effective isolation of wave-driven anomalies. Bedload was trapped inside, resulting in no net sediment loss, in contrast to the unprotected southern tidal flat. (4) We recommend moderately lowering the ESB crest elevation to prevent excessive accretion and implementing “grey-green” restoration (salt marshes or oyster reefs) to enhance coastal resilience against sea-level rise. Full article

This study investigates the reuse of mussel shell waste as a secondary raw material in bio-cement mortars designed for the additive manufacturing of artificial reefs for marine habitat restoration. The novelty of the research lies in combining a high recycled shell content (60 wt.%), low-clinker cement, and two 3D-printing techniques: Extruded Material Systems (EMS) and Powder-Based Systems (PBS). Mechanical performance was evaluated through flexural and compressive tests after 7, 28, and 91 days under both air and freshwater curing conditions, while environmental impacts were assessed through Life Cycle Assessment (LCA). The LCA evaluated both the environmental performance of shell-based mixtures compared with conventional materials and the impacts associated with the investigated fabrication techniques. The best-performing bio-mixtures achieved compressive strengths up to 46.01 MPa and flexural strengths up to 9.91 MPa after freshwater curing, demonstrating the suitability of shell-based mortars for submerged applications. LCA results showed reduced impacts in land use and mineral resource depletion compared with conventional mixtures, despite slightly higher energy and water demands associated with shell pre-treatment. The results demonstrate the technical and environmental feasibility of integrating aquaculture waste into sustainable 3D-printed marine restoration solutions. Full article

The current approach to coastal oyster reef restoration currently relies on conventional plastics, raising concerns about plastic pollution. Therefore, developing biodegradable alternatives, such as nano-montmorillonite-modified polylactic acid materials (PLA), has become a priority. This study compared oyster recruitment on PLA substrates with that on four conventional plastic substrates (polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET) and polyvinylidene chloride (PVDC)) through field experiments, examining how PLA substrate thickness and surface roughness influence oyster recruitment. Additionally, we evaluated the responses of oyster populations and associated macroinvertebrate communities after ten months of restoration using PLA-based versus polyethylene (PE) shell-bag reefs. The results showed no significant difference in oyster recruitment between PLA and conventional plastic substrates (p > 0.05). However, increasing the thickness and surface roughness of the PLA substrates significantly enhanced the recruitment of juvenile oysters (p < 0.05). After ten months, there was no significant difference in oyster abundance between PLA and PE shell bag reefs; however, there was a significant difference in resident macroinvertebrate abundance, with abundances markedly higher on PLA reefs (1372 ± 220 ind./m² vs. 545 ± 90 ind./m²; p < 0.05). This study highlights the potential of PLA as a promising alternative to conventional plastics. However, its rapid degradation limits its applicability in high-energy environments. Furthermore, given that a comprehensive assessment of the microplastic risks associated with its degradation has not yet been conducted, large-scale application is not currently recommended. Full article

The city of Veracruz preserves buildings mainly constructed during the 16th and 17th centuries, where carved madreporic coral was used as ashlar and as a component in mortars. These historic structures, now part of Mexico’s built heritage, show various degrees of deterioration caused by erosion and prolonged exposure to environmental elements. Restoration using original materials is currently nearly impossible due to ecological restrictions protecting coral reefs. In this context, and under the principles of the tailor-made technique, the present research revisits physico-mechanical and chemical studies conducted on the corals used in the construction of one of the most representative buildings in the city. The results were compared with those obtained from the formulation of experimental mortars using readily available materials—such as air lime, siliceous aggregates, and calcium carbonate—with the aim of reproducing the physical, mechanical, and chemical properties observed in the original corals. Laboratory tests allowed evaluation of their compatibility and performance, seeking to develop alternative materials that enable conservation interventions without compromising the integrity of the base material or the historic structures. The design of mortars is intended to be used in the restoration processes of buildings that are part of the built historical heritage. This is the starting point for understanding the characteristics of the mortar and its compatibility with the substrate, which could be used for repairing stone blocks and for preparing new mortars for masonry and plastering, since research on restoration mortars has largely overlooked this type of building with coral masonry due to its rarity. Therefore, this research is of particular interest. The mixtures formulated with calcareous sand were the most compatible with the reference coral material, while those made with silica sand exhibited properties superior to the corals, and marine sands showed very poor behavior, potentially compromising the integrity of the buildings. In physical–mechanical tests, formulations that include calcareous sand and silica sand (2 mm) demonstrated behavior closest to that of coral, consistent with chemical analysis results, where mortars formulated with calcareous sand registered the highest contents of CaO and portlandite. Mercury intrusion porosimetry indicated that the mortar formulated with silica sand (2 mm) has a porosity only 4.07% lower than that of the coral, while mortars formulated with calcareous sand and lime paste are between 11.17% and 16.87% lower. Therefore, one of the mixtures that stands out as the best option due to its similarity in physical–mechanical and chemical results is the composite that is not found at the extremes of the results obtained in the various tests carried out. The use of calcareous sand, as previously mentioned, enhances its behavior and affinity with the coral masonry, as demonstrated in the tests. Full article

Against the backdrop of global coral reef degradation, benthic resource structure is shifting from coral dominance to turf algae and detritus-dominated epilithic algal matrix (EAM). As a typical detritivorous reef fish, Ctenochaetus striatus (Quoy & Gaimard, 1825) plays an important ecological role in regulating the functioning of degraded coral reef ecosystems. Using stable isotope analysis (δ¹³C and δ¹⁵N), this study systematically compared the trophic niche characteristics of different size classes of C. striatus across four reef habitats in the Xisha Islands, South China Sea, representing a gradient of disturbance (Qilianyu Island > Lingyang Reef > North Reef > Langhua Reef), in order to elucidate habitat-specific ontogenetic shifts and their adaptive features. The results showed that C. striatus from Qilianyu Island and Lingyang Reef exhibited overall higher δ¹⁵N values, suggesting an overall pattern consistent with stronger nitrogen enrichment at the more disturbed reefs, whereas individuals from Langhua Reef had significantly lower δ¹³C values, indicating a stronger reliance on offshore-derived carbon pathways. Across size classes, the trophic niche area (SEAc) and intraspecific trophic heterogeneity, measured as mean nearest neighbor distance and standard deviation of nearest neighbor distance, of populations from Qilianyu Island, Lingyang Reef, and North Reef generally decreased with increasing body size, revealing a pattern of trophic convergence toward core resources. In contrast, the Langhua Reef population exhibited a distinct expansion–contraction pattern, suggesting flexible resource use across developmental stages under conditions of low human disturbance and high resource heterogeneity. Although smaller size classes generally showed high probabilities of niche overlap among reefs, overlap declined markedly in the largest size class, with most values falling below 50%, indicating that resource assimilation strategies increasingly reflected reef-specific resource backgrounds. These findings demonstrate that ontogenetic trophic niche shifts in C. striatus are not fixed, but are highly dependent on local resource context and habitat conditions. In degraded reefs with simplified resource structure, individuals tend to converge on core resource spectra to maintain survival, whereas in healthier reefs with greater habitat heterogeneity, they tend to show greater variation in major food sources and resource use. This study provides a theoretical basis for coral reef ecological restoration. Full article

Oyster reef restoration projects have been developed to provide habitat for fish and crustaceans. Some novel restoration structures employ greater complexity in attempts to better restore oyster reef habitat along degraded shorelines. The Pervious Oyster Shell Habitat (POSH) was created with greater structural complexity and strength to enhance oyster reef habitat for fish and crustaceans in energetic systems. The purpose of this study was to assess the POSH’s short-term ability to provide oyster reef habitat by measuring utilization of the POSH by fish and decapod crustaceans. Nekton abundances, diversity indices, and community similarity were compared between POSH structures, Reef Innovations’ “Oyster Ball”, and a natural oyster reef control. Artificial reef modules were sampled using 2 m² bottomless lift nets, over one year, along two energetic shorelines in northeast Florida. Fish abundances were low and variable among treatments, with no significant differences detected. Crustacean abundances were greater on the POSH than the Oyster Ball, aside from winter at one site, with significant differences detected for all but two measurements. Nekton community analyses were similar among all treatments and sites. The POSH’s design provided more interstitial space for utilization by common benthic crustaceans. Stakeholders attempting to restore degraded shorelines should consider employing the method. Full article