Coral Reef Research Articles

3D printed artificial coral reefs: design and manufacture

Applying 3D concrete printing (3DCP) technology to design and manufacturing can create a diverse configuration of the marine landscape. However, this combination of 3D technology and artificial coral products is still in the initial stage of research and application. Therefore, this study introduces a novel design shape model, bridging theory and experimental models. Two innovative design models have been presented, and one has been manufactured and assembled based on the optimal assembling process. The paper aims to propose a design shape model for artificial coral reefs that employs innovative 3D concrete printing technology to create rough surfaces with openings and cavities similar to those found in natural rocks. The proposed design shape for artificial coral reefs, successfully trialed in this research, can be used as a reference model. The procedure for essential works, including drawing, printing, assembling, and some techniques, is helpful for understanding and implementing the works presented in the study. The application of 3D concrete printing technology to an artificial reef fulfills an identified need and plays a crucial role in marine ecosystem restoration and protecting endangered habitats, thereby making a significant social impact while promoting sustainable development in construction. This paper fulfills an identified need to apply 3D concrete printing technology to manufacturing artificial coral reefs.

Signatures of Natural and Human Activities Revealed from Sediment Archives: A Case Study of the Kenyan Coral Reef Ecosystems

Signatures of Natural and Human Activities Revealed from Sediment Archives: A Case Study of the Kenyan Coral Reef Ecosystems

Telomere-to-telomere gapless genome assembly of the giant grouper (Epinephelus lanceolatus)

The giant grouper (Epinephelus lanceolatus) is a large coral reef fish distributed in the Indian Ocean and the Pacific Ocean. With a high market value, this species can grow up to approximately 2.7 meters in length and weigh 440 kilograms. With the rapid development of bioinformatics, higher standards of genome analysis are now required compared to previous reference genomes. This study presents a gapless assembly of the giant grouper genome, which has a length of 1.03 Gb. The sequences were assembled onto 24 chromosomes with a coverage of over 99% (1.02 Gb), and telomeres were detected on 24 chromosomes. Analysis using Merqury indicated a high level of accuracy, with an average consensus quality value of 59.24. The ONT ultralong and PacBio HiFi data were aligned with the assembly using minimap2, resulting in a mapping rate of 99.9%. The study inferred 25,815 protein-coding genes. These results lay a foundation for exploring the evolution and biology of the giant grouper, and advancing molecular breeding techniques.

Coral reef rehabilitation following Hurricane Irma using nano-engineered artificial reefs in Sint Maarten

Artificial reefs are being increasingly deployed as a coral reef restoration strategy. Additional reef habitats made from conventional substrates (e.g., metal, concrete, etc.) have had limited success in addressing conservation objectives on degraded coral reefs due to structure size and lack of standardized monitoring, and inability to enhance select ecological, and species variables. Technological advances and new restoration methods must be quickly tested and applied on a large scale to curb further deterioration of coral reefs. Here, we present the results of the first deployment of Oceanite artificial reefs (ARs). We compare the composition of the benthic community and associated fish assemblages on Oceanite ARs 14 months after deployment in a marine protected area (MPA) and two unprotected sites in Philipsburg, Sint Maarten. We also examined fish abundance and behaviour on the ARs. The initial results from this pilot study suggest that Oceanite mineral matrices can enhance local biodiversity, attract coral recruits, provide food and protection for large fish communities, and develop an early stage, healthy coral reef community in 14 months. We suggest that further research and testing of Oceanite capabilities will allow us to develop site-, species-, and function-specific nanotechnology-enabled substrates to optimize AR conservation goals. Oceanite mix designs can be tuned to precise parameters to promote reef restoration and stressor mitigation (e.g., pH, leachate emissions, surface texture, porosity, void structure, and hydrophobic, heat-absorbing, and disease-fighting properties). Using both bottom-up and top-down restoration processes, we suggest that deploying bio-enhancing habitats with targeted microclimate stressor treatments on the world’s critical reefs will allow to build global refuges resilient to climate change and provide much needed ecosystem services.

Macroalgae of the Campeche Bank, Gulf of Mexico

The coastal habitats in the southern Gulf of Mexico face multiple threats, such as rising water temperatures, acidification, increased turbidity, invasive species and pollutants. This imperils the biodiversity of beaches, wetlands and coral reefs. To address this, there is a need for comprehensive baseline information on marine biodiversity. Several reefs in the Gulf of Mexico have been extensively studied, yet smaller reefs on the Yucatan continental shelf lack thorough exploration despite their ecological significance. These reefs serve as crucial biodiversity hotspots influenced by environmental characteristics, receiving diverse taxa from the Gulf of Mexico. The macroalgae study at the Bank of Campeche dates back to the 1950s, but comprehensive investigations have been sporadic. The recent study aims to fill this gap, contributing to the taxonomic inventory of the area's benthic macroflora. Methodologically, extensive sampling across eight reefs was conducted, collecting and preserving macroalgae samples for identification in the laboratory. The study documented 90 infrageneric taxa across the reefs, with Cayo Arenas exhibiting the highest species count. Additionally, three new distribution reports for Mexico were identified in the region. The distribution of species varied amongst locations, with few species in common even amongst geographically proximate reefs. The diversity found in these reefs slightly trails behind other studied regions, but surpasses previous reports for the Campeche Bank. It is important to emphasise that the significance of this study lies in its focus on remote reefs with complicated and costly access logistics. Additionally, it is one of the first publicly available datasets published for this region. The study aligns with existing literature on prevalent families in reef environments and highlights differences in species distribution, based on depth variations amongst reefs. The findings of new distribution records in the region and the distinctiveness of localities despite their proximity underscore the unique ecological dynamics of these reefs. These reefs are located in remote and difficult-to-access areas, highlighting the importance of the data obtained on their biodiversity and conservation status. This work presents for the first time a list of macroalgae for the reefs of Banco Nuevo, Banco Obispo, Banco Pera and Serpientes Reef. Three new distribution reports for Yucatan were identified at the Banco Obispo reef: Botryocladia shanksii E. Y. Dawson, Ceratodictyon scoparium (Montagne & Millardet) R. E. Norris and Asteromenia peltata (W. R. Taylor) Huisman & Millar and a new report for the Mexican Atlantic, Herposiphonia parca Setchell at the Triángulo Oeste reef. This results in distinct algal communities compared to other reefs in the region, emphasising their ecological significance and the need for continued research and conservation efforts. To our knowledge, this is one of the first interoperable datasets being published on the marine algae of the southern Gulf of Mexico reef ecosystems.

Validating CYGNSS Wind Speeds with Surface-Based Observations and Triple Collocation Analysis

Existing validation of mean wind speed estimates via reflectometry from global navigation systems of satellites (GNSS-R)—has been largely limited in spatial coverage to equatorial buoys or tropical cyclone events near continental United States. Two alternative validation techniques are presented for the Cyclone GNSS (CYGNSS) mission using surface-based observations along coasts and coral reefs instead of buoys, and triple collocation analysis (TCA) instead of a 1:1 gridded comparison for tropical cyclone (TC) events. For the surface-based analysis, Fully Developed Seas (FDS) v3.2 and NOAA v1.2 were compared to anemometer data provided by the Australian Bureau of Meteorology across the Australia and Pacific regions. Overall, the products performed similarly to previous studies with NOAA having higher correlations and lower errors than FDS, though FDS performed better than NOAA over the Australian dataset for high wind speed events. TCA was used to validate NOAA v1.2 and Merged v3.2 datasets with other satellite remotely sensed products from the Soil Moisture Active Passive (SMAP) mission and Synthetic Aperture Radar (SAR). Both additive and multiplicative error models for TCA were applied. The performance overall was similar between the two products, with NOAA producing higher errors. NOAA performed better than Merged for mean winds above 17 m/s as the large temporal averaging reduced sensitivity to high winds. For SMAP winds above 17 m/s, NOAA’s average bias (−2.1 m/s) was significantly smaller than the average bias in Merged (−4.4 m/s). Future ideas for rapid intensification detection and constellation design are discussed.

A long-term dataset of <i>in-situ</i> temperature data reveals wind-induced up- and downwelling in the coastal waters of Nha Trang, South Central Vietnam

In order to implement successful coastal management and protect corals, it is imperative to understand the Nha Trang Bay’s coastal processes and take adequate measures to protect corals and reef structure. This paper aimed to analyze whether sudden variations in physical parameters, such as temperature, could be potentially harmful to coastal coral reefs, in addition to anthropogenic factors such as pollution and intensive fishing. In this paper, the first long-term observation (2008–2019) of temperatures, not only from SST data, but also in situ in coral reefs (10 and 18 m depth) at Nha Trang Bay, South Central Vietnam, was investigated. The data showed that wind-induced upwelling during summer mainly govern the coastal region. In contrast, wind-induced downwelling was found during winter, visible in all three investigated water layers (SST, 10 and 18 m). In winter, the vertical mixing is strong and there is virtually no time-lag between the layers. In summer a scattering layer was formed, the phenomenon where a layer of water with different properties (such as temperature or salinity) is formed, blocking the sinking of water. In summer, correlations with air temperature were not significant, nor were correlations with night cooling, thus having implications for the distribution of nutrients and the health of the coral reefs. However, this was only the situation near the coast. Wavelet analysis shows that the short-term variability is significantly more substantial, caused by the shallow depth of the thermocline, which is much stronger affected by tidal and weather events than in winter. As a result of the combination of large yearly temperature variations (21oC to 31oC) plus increased sediment deposition in the rainy seasons, reefs close to the shore are generally not well-developed. This paper strongly advocates for science-based monitoring of coral reef conditions and underscores the need for law enforcement within the Marine Protected Area of Nha Trang Bay.

Bargibant’s pygmy seahorse Hippocampus bargibanti in Taiwan Bank: hidden biodiversity of Taiwan Strait

During a scientific expedition in the Taiwan Bank in the southern Taiwan Strait in 2021, five pygmy seahorses, measuring between 18.1 mm and 28.3 mm in standard length, were inadvertently collected along with Muricella sea fans. Morphometric measurements of these pygmy seahorse specimens coincided with the previous data on H. bargibanti, but they had a proportionally greater head depth and snout length. Genetically, DNA marker analysis of partial mitochondrial COI sequences confirmed that our specimens belonged to the same lineage as H. bargibanti, with a p-distance of 0.54% among populations. This discovery enhances our knowledge of the limited biodiversity in the Taiwan Bank, which includes a complex geomorphology of both reef banks and sandy substrates, and highlights the importance of strict laws prohibiting fishing with inadequate gear, invasive or illegal fishing, and sand dredging to protect unexplored coral reef biodiversity in the area.

Coral Reef Restoration for Coastal Protection: Water Quality Monitoring in Indonesia Coral Reef Garden Nusa Dua, Bali

The Indonesia Coral Reef Garden (ICRG) is a coral reef restoration program with Nusa Dua as one of five sites in Bali. A plantation program has been done by 2020, but it is necessary to monitor the condition. A field survey in Nusa Dua was carried out on October 3-4, 2022 to measure and check ocean parameters that are suitable for coral life and diving in artificial coral reefs installed. In the survey, several points had been measured through CTD Valeport Midas+ prior to measuring ocean parameters in the same location as a preliminary survey done two years in advance. The sea condition of temperature, salinity, pH, turbidity, and DO is 24.89 - 28.69 °C, 33.75 - 34.22 psu, 8.0 - 8.1, 1.19 - 4.27 FTU, and 4.47 - 5.24 mg/L, respectively. Based on the conformity of water quality, the water condition is good for coral growth. A total of 15 locations are used to put artificial coral reefs in many forms or structures. The coral plantation program in Nusa Dua shows promising progress in qualitatively consisting of species of Montipora sp., Acropora sp., and Alcyonacea sp. A continuous measurement is demanded to monitor the condition of coral growth quantitatively.

An updated checklist of fishes of Dongsha Island, Taiwan, northern South China Sea.

Dongsha Island, situated in the northern part of the South China Sea, is surrounded by coral reefs and deep-sea habitats. The coastal areas of the atoll, a marine protected area, serve as important nursery habitats for many reef fish species. At the same time, the offshore deep-sea continental slopes are historically important fishing grounds. Although previous inventories primarily focused on coral reef fishes within the atoll listing 652 species from 73 families, comprehensive surveys of fishes from deeper waters have been incomplete. In this study, the species composition of the fish fauna around Dongsha was updated by analyzing large volumes of frozen bycatch from commercial deep-sea trawlers operating in the area for the past four years and reviewing the existing literature. The species list increased to 1087 species belonging to 167 families, including several documented as new records and potentially undescribed species. This updated checklist also includes images of each species and most of their sagittal otoliths. This will assist further taxonomic work and significantly enhance understanding of marine biodiversity in the South China Sea.

Census-based estimates of Mediterranean Oligocene–Miocene reef carbonate production

Census-based approaches to reefal carbonate budgets are increasingly being used to project the near-future fate of tropical coral reefs. Some of the census parameters are difficult to achieve in fossil reef systems, which may be the reason why no census-based estimates of fossil reef carbonate production have been published until now. Here, we apply a census-based estimate of gross carbonate production in two reef systems from southeastern Italy to (1) test if reasonable estimates are possible and (2) assess the variability of carbonate production rates over time and reef environment. We confirm that estimates of late Oligocene and late Miocene reef gross carbonate production are within the range of modern coral reefs with the late Oligocene reef front showing the greatest carbonate production (6.1 ± 1.3 kg CaCO3 m−2 year−1) and the late Miocene reef front exhibiting the lowest production (1.7 ± 0.5 kg CaCO3 m−2 year−1). The decline of reef carbonate production from the Oligocene to the Miocene is accompanied by a decline of reef builder biodiversity but driven by the lower coral cover and coral growth rates in the Miocene. The decline of reefal carbonate production may be related to late Cenozoic cooling.

Emergent coral reef patterning via spatial self-organization

Emergent coral reef patterning via spatial self-organization

Evaluating Climate Change Impacts to Qatar’s Marine Life: A Risk Assessment for SDG 14 (Life Below Water)

Marine life is integral to Qatar and the broader Arab region, serving as a cornerstone for biodiversity, economic activity, and cultural heritage. Despite the ambitious targets set by Sustainable Development Goal (SDG) 14, climate change is placing mounting pressure on conservation efforts. Recognizing that climate change cannot be entirely stopped, the focus should be on mitigating its effects through sustainable strategies. This study identifies twelve climate-related risks that impede Qatar's progress towards achieving SDG 14 - Life Below Water. To understand the region-specific climate risks, this study engaged in a focus group discussion with representatives from the government, NGOs, private sector, and academia. The Climate Change Risk Assessment (CCRA) identified the most severe risks as flooding associated with rising sea levels, modified species biogeography, and compromised coral reef health. While other risks were rated low, such as risks to seagrass meadows driven by increasing sea temperatures. Other significant findings include the need for increased awareness of climate change impacts on both the local and global administrative platforms. This risk assessment provides insights into the vulnerable facets of Qatar's marine environment, intending to guide forthcoming strategies for achieving SDG-14.

Variation in coral rubble cryptofauna is scale-dependent and driven by small-scale habitat characteristics

Motile cryptofauna living in dead coral rubble represent some of the greatest biodiversity and basal energetic resources on tropical coral reefs. Yet we know relatively little about how and why coral rubble cryptofauna communities change over space and time. As human impacts increase the degradation of living hard corals to dead coral rubble on many reefs worldwide, understanding the communities that will succeed in these degraded environments and the factors paramount to their success becomes increasingly central to coral reef ecology and conservation. Using a remote and uninhabited oceanic atoll in the Pacific Ocean, we quantified the natural spatial variability in motile cryptofauna diversity and community structure in coral rubble across scales (m to km) and tested whether variability at smaller scales could be explained by gradients in microhabitat. We show that coral rubble cryptofauna communities are most variable at intra-site scales (m) rather than inter-site scales (100s m) or between reef zones (km scales). We also show that a substantial amount of variation in cryptofauna density (55%) and phyla-level community structure (31%) is explained by small-scale habitat characteristics, specifically the substrate type below the rubble and the variability in macroalgal cover on individual rubble pieces. Our findings highlight the need to study small-scale processes that are relevant to motile cryptofauna and their community interactions if we are to elucidate the structuring forces of these diverse cryptic assemblages on coral reefs.

Host distribution, size and habitat as determinants of population density and group size in a coral reef sea whip goby

Coral reefs are complex habitats that support a diversity of fish species, some of which live in specialised relationships with particular coral taxa. The ecology and social organisation of these habitat specialists can be shaped by characteristics of their host coral. Here, we quantified the distribution, density, size, dispersion and health of the gorgonian sea whip Junceella fragilis and examined their influence on population density and group size of the sea whip goby Bryaninops amplus. Visual surveys of sea whips and resident gobies were conducted in 30 m × 4 m belt transects at 16 fringing reef sites in the Palm Island Group, Queensland, Australia, across 3 depths (5, 10 and 15 m) and 4 replicates. To examine if distributions of J. fragilis and their goby inhabitants were related to current speed, a current meter was deployed at each site and depth for a 6 d period. The spatial distribution and density of B. amplus positively related to that of sea whips, and group size positively related to sea whip surface area. B. amplus density positively related to current speed, and group sizes were highest on solitary sea whips in sandy habitats. Surprisingly, group sizes were not affected by sea whip condition, with large groups found on sea whips with high proportions of damaged tissue. Host distribution, configuration and size are clearly major determinants of sea whip goby density and group size. While goby populations may ultimately be threatened by the loss of their host, they do appear to be resilient to the early stages of degradation.

Local coral connections within an atoll reef system underlie reef resilience and persistence

AbstractThe recovery of isolated reef systems is a complex process that is usually associated with the supply of coral larvae from distant reefs (or large‐scale connectivity). However, a frequently neglected process is the potential for supply within the reef itself (or local connectivity). In this study, we quantify and characterize the role of local connectivity over 21 yr of simulated annual coral spawning on an isolated coral reef atoll using outputs from a high‐resolution biophysical model (< 150 m horizontal resolution) along with network analysis. We find that approximatively half of the coral reef larvae dispersal remains local (within 100 s m to 10 s km of release location), while the remaining half contributes to long‐distance dispersal (> 100 s km) and is exported away from the system. Local dispersal plays a pivotal role in creating a highly‐connected network across the reef, enhancing exchanges of larvae within the same reef patches (local retention), across reef zones (e.g., lagoon, reef flat), and across the larger reef system. Finally, we show that this highly‐connected network exhibits a certain level of robustness, even when exposed to environmental stressors such as thermal‐induced mortality. Our findings highlight the previously overlooked role of local scale dispersal in driving recovery of isolated reef systems and emphasize the importance of targeted local management actions, indicating that efforts directed at enhancing and preserving local connectivity can have a substantial impact on the overall health and resilience of isolated reef ecosystems.

European Native Oyster Reef Ecosystems Are Universally Collapsed

ABSTRACTOyster reefs are often referred to as the temperate functional equivalent of coral reefs. Yet evidence for this analogy was lacking for the European native species Ostrea edulis. Historical data provide a unique opportunity to develop a robust definition for this ecosystem type, confirm that O. edulis are large‐scale biogenic reef builders, and assess its current conservation status. Today, O. edulis occur as scattered individuals or, rarely, as dense clumps over a few m2. Yet historically, O. edulis reef ecosystems persisted at large scales (several km2), with individual reefs within the ecosystems present at the scale of several hectares. Using the IUCN Red List of Ecosystems Framework, we conclude the European native oyster reef ecosystem type is collapsed under three of five criteria (A: reduction in geographic distribution, B: restricted geographic range, and D: disruption of biotic processes and interactions). Criterion C (environmental degradation) was data deficient, and Criterion E (quantitative risk analysis) was not completed as the ecosystem was already deemed collapsed. Our assessment has important implications for conservation policy and action, highlighting that the habitat definitions on which conservation policies are currently based reflect a highly shifted baseline, and that the scale of current restoration efforts falls far short of what is necessary for ecosystem recovery.

ECoral: How Electrolysis Could Restore Seawater Conditions Ideal for Coral Reefs.

Coral reefs suffer from climate change, including long-term ocean acidification (OA) and warming and short-term bleaching, tropical storms, and pollution events, all of which are increasing in frequency and severity. It is urgent yet unclear how to intervene to save coral reefs. Reversal of the ocean pH to preindustrial levels could restore coral reefs to their preindustrial growth rates; however, strategies to reverse OA on environmentally relevant scales have not been established. Anecdotally, electrolysis seems to help coral reefs recover from acidification and short-term events, but few uncontrolled studies support such claims. Here, using two independent continuum simulation approaches (COMSOL and CrunchFlow), we show the effect of electrolysis on seawater chemistry relevant to coral reef survival and growth. We conclude that near the negative electrodes, the cathodes, seawater pH, supersaturation, and carbonate concentration all increase significantly. Electrolysis of seawater, therefore, can be used to restore preindustrial ocean conditions locally to save coral reefs, an approach termed eCoral here. We anticipate these simulation results to be the starting point for controlled experiments to test whether seawater electrolysis promotes coral reef growth and restoration, as these simulations predict.

Fish and invertebrate communities show greater day-night partitioning on tropical than temperate reefs.

Diel partitioning of animals within ecological communities is widely acknowledged, yet rarely quantified. Investigation of most ecological patterns and processes involves convenient daylight sampling, with little consideration of the contributions of nocturnal taxa, particularly in marine environments. Here we assess diel partitioning of reef faunal assemblages at a continental scale utilizing paired day and night visual census across 54 shallow tropical and temperate reefs around Australia. Day-night differences were most pronounced in the tropics, with fishes and invertebrates displaying distinct and opposing diel occupancy on coral reefs. Tropical reefs in daytime were occupied primarily by fishes not observed at night (64% of all species sighted across day and night, and 71% of all individuals). By night, substantial emergence of invertebrates not otherwise detected during sunlit hours occurred (56% of all species, and 45% of individuals). Nocturnal emergence of tropical invertebrates corresponded with significant declines in the richness and biomass of predatory and herbivorous diurnal fishes. In contrast, relatively small diel changes in fishes active on temperate reefs corresponded to limited nocturnal emergence of temperate invertebrates. This reduced partitioning may, at least in part, be a result of strong top-down pressures from fishes on invertebrate communities, either by predation or competitive interference. For shallow reefs, the diel cycle triggers distinct emergence and retreat of faunal assemblages and associated trophic patterns and processes, which otherwise go unnoticed during hours of regular scientific monitoring. Improved understanding of reef ecology, and management of reef ecosystems, requires greater consideration of nocturnal interactions. Without explicit sampling of nocturnal patterns and processes, we may be missing up to half of the story when assessing ecological interactions.

Unravelling the Universal Spatial Properties of Coral Reefs

ABSTRACTAimTo characterise the size and geometry of coral reefs on a global scale.LocationGlobal.Time PeriodPresent.Major Taxa StudiedCoral reefs.MethodsWe process the Allen Coral Atlas database of shallow‐water tropical reefs to obtain a comprehensive and unprecedented inventory of coral reefs worldwide. We analyse different macroecological and morphological patterns, including size distribution, the area‐perimeter relationship, inter‐reef distance distribution, and the fractal dimension of individual reefs and coral provinces.ResultsWe identified a total of 1,579,772 individual reefs worldwide (> 1000 m2), extending over a total of 52,423 km2 of ocean area with mean and median sizes of 3.32 and 0.3 ha, respectively. We unravelled three universal laws that are common to all coral reef provinces: the size‐frequency distribution and the inter‐reef distance distribution follow power laws with an exponent of 1.8 and 2.33, respectively. At the same time, the area‐perimeter relationship conforms to a power‐law with an exponent of 1.26. Furthermore, we demonstrate that coral reefs develop fractal patterns characterised by a perimeter fractal dimension of and a surface fractal dimension of . Our analysis suggests that coral reefs tend to evolve from simple rounded filled shapes to more complex, elongated and less compact forms, developing into fractal structures with a consistent surface fractal dimension and an increasing perimeter fractal dimension as they grow.Main ConclusionsCoral reefs display intricate fractal‐like geometries and exhibit universal macroecological patterns, largely independent of their geographical location. The universality of the observed patterns suggests that these features possibly stem from the highly conserved interactions of biological, physical and chemical processes. Over geological scales, these processes lead to reef landscape patterns common among all provinces, providing new information relevant to reef growth modelling.