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The design of artificial reefs must be based on the criteria of both durability and serviceability. In this respect, the seabed subsidence rate related to the weight of the reefs and of their foundation system should be limited. The horizontal drift of the reefs during their life should be small too. In this study, pertaining to the behavior of artificial reefs made of microsilica concrete and realized with foundations in bamboo near the international airport of Hong Kong, 1-year monitoring data and calculations of reef foundation settlements are shown and discussed to assess the performance of the adopted mixed foundation and to deduce the nature of the long-term subsidence. The subsidence related to the settlements of the foundations was monitored using a Multibeam Echo Sounder System. It was found that the observed subsidence rate cannot be justified by the primary consolidation of the soils forming the seabed. Indeed, secondary consolidation seems to play an important role. Overall, after one year of service, the artificial reefs are considered to be effective in terms of limitation of both subsidence and drift. [ABSTRACT FROM AUTHOR]

Global degradation of coral reefs is reflected in the destruction of shelters in various environments and threatens the stability of marine ecosystems. Artificial shelters offer an alternative, but their design could be more challenging due to limited knowledge regarding desired inhabitants' shelter characteristics and preferences. Investigating these preferences is resource-intensive, particularly regarding small shelters that mimic natural reef conditions. Furthermore, for statistical analysis in small shelters, fish abundance may need to be higher. We propose a method to characterize the species-specific shelter preferences using low-volume data. During a study conducted from January 2021 to April 2022, round clay artificial shelters (RAS) were deployed on an abandoned oil pier to examine a coral reef fish community. We recorded 92 species from 30 families and grouped them into systematic (families) and functional (dietary group) classes. Grouping enabled us to examine each group's preference, while crossing these group preferences revealed species-specific preferences, which matched field observations. This approach proved effective in profiling the shelter preferences of 17 species while having limited resources. These profiles may later allow the establishment of ecological-oriented artificial reefs. Moreover, this method can be applied to other applications using other shelter designs, sizes, and research sites. [ABSTRACT FROM AUTHOR]

Suitable colonization materials are a pursued target in marine restoration programs. Known for making nutrients available while reducing pollutants and the risk of pathogens in terrestrial ecosystems, Biochar and Bioferment materials of organic origin were tested during a two-year experiment. We tested the efficacy of these materials for restoration purposes through experimental concrete tiles treated with Biochar (B) and Bioferment (F) and tiles made of concrete, which were used as controls (Ct) for the colonization of marine organisms in the marine protected area of Porto Cesareo, Southern Italy (20 m depth). Tiles were monitored for photographs from October 2019 to September 2021. Initially, Biochar treatment presented a higher percentage of total benthic cover (81.23 ± 2.76, median ± SE), differing from Bioferment treatment and control tiles (45.65 ± 5.43 and 47.95 ± 3.69, respectively). Significant interaction between treatments and times suggests changes in community structure related to Polychaeta cover increase in Bioferment and control materials from the second monitoring time. Furthermore, the underwater instability of Bioferment on the tiles could explain the similarity with control tiles in marine organisms' covers. Hence, Biochar is shown to be a material with optimal stability in seawater, demonstrating greater capacity for marine organisms' colonization in less time compared to the other two materials. [ABSTRACT FROM AUTHOR]

The combined release of artificial reefs in different quantities and arrangements leads to different flow field effects. This study designs a small trapezoidal artificial reef. To optimize the quantity and layout of these reefs, trapezoidal reefs in three different layouts were selected for analysis at five different velocity gradients (0.1, 0.5, 1.0, 1.5, and 2.0 m/s). The effects of disposal spacing and layout on the flow field effect of trapezoidal artificial reefs at different flow velocities were simulated using Ansys Fluent. According to the findings: after simulation, flow velocity could indirectly reflect the distribution of upwelling and back eddy, the scale and strength of upwelling increased as flow velocity increased, and the back eddy showed no obvious variation with flow velocity. In transverse combination mode, both the scale and strength of the upwelling and back eddy were maximized when the reef spacing was 1.0 L; in longitudinal combination mode, upwelling and back eddy reached maximum scale and strength when the disposal spacing of the reefs was 1.5 L of a single reef. In 2020, flow mapping and fishery surveys were carried out in the engineering pilot area. The results showed that the number and species of fish populations with 1.5 L spacing in the vertical combination method were significantly higher than those in other forms, and the structure of the fish reef was stable without any flipping or sliding phenomenon. This study can provide a theoretical reference for the design and the actual deployment of artificial reefs to improve the ecological restoration of the water. [ABSTRACT FROM AUTHOR]

This study aimed to understand the structure and function of the artificial reef ecosystem of the Sea of Oman and its stability and maturity. For this study, the trophic model of the Sea of Oman's artificial reef ecosystem was described using the Ecopath with Ecosim (EwE) ecosystem modeling software (Version 6.6.7). The essential characteristics of the aquatic system were identified using a total of 38 fish species/functional groups, spread across an area of 140 km2 of artificial reef farm. The mean trophic level of the artificial reef ecosystem of the Sea of Oman was 3.039. Sharks were the keystone species of the studied ecosystem. Heniochus acuminatus and Chaetodon gardneri were the species with the highest niche overlap, whereas Acanthurus sohal and other crustaceans, and Terapon puta and Saurida undosquamis were the species with the lowest niche overlap. It was found that the ratio of total primary production to total respiration of the ecosystem studied was more than one, indicating that the system produces more energy than it uses to respire, and the ecosystem of the Sea of Oman can be regarded as a developing system because of its low degree of stability and maturity. The omnivory index was 0.260, the connectance index was 0.159, the total biomass to total throughput ratio was 0.006, Finn's cycling index was 5.41, the total primary production to total biomass ratio was 64.895, and the total primary production to total respiration ratio was 4.424. The results indicate that the artificial reef ecosystem in the Sea of Oman can be categorized as immature (in the early developmental stage). Further study is needed to improve the input data and track ecosystem health, as well as exploring other management strategies. Based on the outcomes of the study, it is suggested that environmental management of the reef ecosystem, along with the fish catch data, should be taken into consideration for future research. [ABSTRACT FROM AUTHOR]

Artificial reefs act as islands of biodiversity that provide substrate where sessile organisms can settle and mobile invertebrates and fishes can find shelter and food. Though these structures are common and widespread in the Gulf of Mexico, their community composition is not well understood. We aimed to ameliorate understanding of the invertebrate communities living on artificial reefs in the northeastern Gulf of Mexico by using molecular techniques and morphological examination to describe the biodiversity and genetic connectivity of crabs (Infraorders Anomura and Brachyura) living on and among artificial reefs near Pensacola, FL, USA. Specimens (N = 1,241) were collected from six artificial reefs using Autonomous Reef Monitoring Structures (ARMS) after four, six, and ten months of submergence, respectively, and were identified using DNA barcoding and morphological examination. Spatial and temporal trends in biodiversity were examined by comparing Hill-Shannon and Hill-Simpson diversities, richness, and canonical correspondence analysis. Population genetic analyses were performed on the two most commonly recovered species, Pseudomedaeus agassizii (A. Milne-Edwards, 1880) and Hexapanopeus paulensis (Rathbun, 1930). A total of 11 taxa were identified, and artificial reef shape was found to be influential in shaping spatial patterns of biodiversity. Species turnover was common across the ten months of sampling, and richness peaked at the ten-month mark. Population genetics revealed that there is high gene flow between the six sampling locations. This study is the first to describe the biodiversity of crab communities on artificial reefs in the northeastern Gulf of Mexico. [ABSTRACT FROM AUTHOR]

In October 1970, the city of Genoa was devastated by a major flood. A few weeks later, hundreds of wrecked cars removed from the city's streets were sunk off the coast of Varazze, in the first-ever Italian project to create an artificial reef. This initiative, which was inspired by similar experiences tried out in the United States and other countries, had been aimed at increasing the fish population and protecting the seabed but was carried out without any thorough preliminary scientific study, and produced other effects not in the initial intentions of the project. Nonetheless, this story should be read as one point in the broadest trajectory in the evolution of environmental discourse. This contribution, based on hitherto unpublished visual documentation, is therefore an investigation into the very specific meaning of the environment in Italy at the beginning of the 70s. The first part of the article provides a reconstruction of the operational details involved in creating the new underwater seascape of Varazze while in the second part, the earlier examples of similar initiatives are described, as well as the reactions of the scientific community. In conclusion, we reflect on the legacy of the initiative, both at the environmental level and as a basic step in the relationship between visual media and contemporary environmental discourse. [ABSTRACT FROM AUTHOR]

Artificial oyster reefs provide important spawning and nursery grounds for a variety of fishes and large mobile crustaceans. Between July 2016 and May 2017, seasonal surveys of species composition and community structure were performed in the artificial oyster reef area and control area adjacent to the Luanhe River Estuary in China. During the survey year, 56 species belonging to 50 genera, 45 families, and 19 orders were recorded. The dominant economically important fish and mobile crustaceans were Hexagrammos otakii, Pholis fangi, Sebastes schlegelii, Charybdis japonica, and Oratosquilla oratoria. Resident fishes belonged to the Cynoglossidae, Paralichthyidae, Pleuronectidae, and Gobiidae families. Seasonally important fish species included Lateolabrax japonicus, Konosirus punctatus, Thryssa kammalensis, Hexagrammos agrammus, and Acanthopagrus schlegelii. The ranges of H' values among stations were 1.18–2.16, 0.65–1.75, 1.18–2.06, and 0.62–1.92 in spring, summer, autumn, and winter, respectively. The benthic organisms present in the community of artificial oyster reef areas can be classified into groups according to month and season. The abundance biomass curves showed that the oyster reef area in spring, autumn, and winter experienced low disturbance, whereas the community structure in summer was subject to large variations from external disturbance. We also found that as the age of the oyster reefs increased, the percentage of oysters in the low shell height group (< 40 mm) decreased. The oyster density was 324 ind/m2 for the reef created in 2016, 724 ind/m2 for the reef created in 2015, and 364 ind/m2 for the reef created in 2013. These findings can be used to develop suitable management strategies for the sustainable maintenance of artificial oyster reef ecosystems. [ABSTRACT FROM AUTHOR]

Artificial floating reefs are an important supplement to bottom reefs in marine habitat construction, which provide a good environment for fish to survive, breed and habituate in the middle and upper layers of water. They can adapt to the silt bottom of the East China Sea. To make full use of the water space and improve the effective space of the floating reef, based on the field tidal current data, an upper- and lower-layered artificial floating reef has been designed in this study. The connection method of the upper and lower reefs has been described in detail and a hydrodynamic numerical model has been established. At the same time, the effects of floating reef structure ratio, wave height and wave steepness on its force and motion are discussed under the action of tidal current and wave current. The result shows that, at a specific flow rate, the change of the proportion of the layered floating reef structure had little effect on the roll of the upper and lower reefs. The maximum roll angle does not exceed 15°, and the tilt angle of the upper and lower reefs is consistent, which ensures the good flow resistance and stability of the floating reef. Under the specific length of the connecting cable and the main mooring, the hydrodynamic characteristics of the layered floating reef are better when the ratio of the sum height of the lower reef and the connecting cable to the height of the upper reef is not greater than one and the extreme proportion structure is not considered. The tension of the stratified floating reef is proportional to the wave height and wave steepness under the action of wave and current. The main mooring rope is the most stressed, and the rolling motion of the upper and lower reefs is consistent. Above all, results can provide a theoretical basis for the optimization design of the artificial floating reef structure. [ABSTRACT FROM AUTHOR]

Artificial reefs (ARs) are designed to mimic natural habitats and promote marine life. Their effectiveness is however debatable and can depend on factors such as structural complexity and construction material. Old artificial reefs (OARs) were made of concrete mold of simple geometric shapes, limiting their ability to mimic the complexity of natural reefs. Recent advancements in three‐dimentional (3D)‐printing technology have enabled the creation of 3D‐printed artificial reefs (3DRs) with biocompatible material and complex structures that can better simulate the natural habitats. We employed underwater hyperspectral technology to estimate the performance of these reefs and compare the benthic photosynthetic signal of natural reefs (NATs) with those of ARs (OARs and 3DRs) in coastal area of the north‐western Mediterranean (France and Monaco Principality). We expected differences in reflectance signals between OARs and NATs, and signals closer to NATs in 3DRs than OARs. Underwater hyperspectral technology was able to detect higher chlorophyll‐a derived signals on NATs than OARs. Moreover, the magnitude of differences between 3DRs and NATs was smaller than that between OARs and NATs. Although ARs were not capable of mimicking natural reefs, the use of 3D‐printed ARs might ameliorate their effectiveness for coastal reconciliation. [ABSTRACT FROM AUTHOR]

Cold‐water corals (CWCs) are important species that provide habitat for other taxa but are sensitive to mechanical damage from bottom trawling. CWC conservation has been implemented in the form of marine protected areas (MPAs), but recovery from impact may be particularly slow in the deep‐sea environment; consequently, the use of restoration techniques has been considered. To gain some insight into CWC recruitment and growth, in 2011 we deployed small seabed moorings in the Darwin Mounds MPA (~1,000 m water depth). This site hosts hundreds of CWC mounds, that had previously (until 2003) been impacted by deep‐water trawling. In 2019, we carried out in situ visual surveys of these moorings and the surrounding seabed environment, then recovered two of the moorings. The mooring buoys, glass floats with plastic covers, were extensively colonized by a diverse epifauna that included the CWCs Desmophyllum pertusum and D. dianthus. The presence of coral recruits indicated that environmental conditions, and larval supply, remained favorable for the settlement and growth of CWCs within the MPA. Based on our observations, we consider four possible restoration methods, together with a "do‐nothing" option, for the Darwin Mounds CWCs that have shown little, if any, natural recovery despite 16 years of protection. We conclude that seabed emplacement of high‐relief artificial substrata is likely to be the most efficient and cost‐efficient means of promoting enhanced recovery of the CWCs. [ABSTRACT FROM AUTHOR]

With the recent development from grey infrastructures to green infrastructures, artificial reefs become more popular in coastal protection projects. To investigate the responses of beach profile evolution to the presence of an artificial reef, a non-hydrostatic model is established. Both hydrodynamic and morphodynamic evolution for the beach with and without an artificial reef are compared under regular wave conditions. In addition, the protected beach profile evolution by an artificial reef is discussed under irregular wave conditions. Three key parameters in non-hydrostatic simulation are considered for sensitivity analysis, including maximum wave steepness criterium (maxbrsteep), water depth factor (depthscale), and equilibrium sediment concentration factor (sedcal). The numerical results under regular wave conditions indicate that the artificial reef enhances wave attenuation by inducing wave breaking. In addition, the artificial reef reduces local flow velocity and offshore sediment transport by 51%, therefore decrease the total erosion by 53%. Over the artificial reef, wave skewness and asymmetry go through a drastic change. Under irregular wave conditions, short waves contribute to the wave energy mainly and reflection-induced standing wave effects decline considerably. It demonstrates that the artificial reef can protect the beach from regular and irregular waves by reducing erosion and offshore transport of suspended sediments. Moreover, in the wave breaking area, the increase of maximum wave steepness criterium may give arise to the wave height. The morphological evolution is more sensitive to water depth factor than equilibrium sediment concentration factor, because the former is a controlling factor for beach profile characteristics while the latter forms the sandbar varying irregularly in shape. [ABSTRACT FROM AUTHOR]

Partial effects indicate the effect of the independent variable on the response variable while all other independent variables are held constant Graph: SI Fig. Partial effects indicate the effect of the independent variable on the response variable while all other independent variables are held constant Graph: SI Fig. [Extracted from the article]

Algal Turf Scrubbers (ATS) are designed to remediate polluted waters where wastewater and agricultural runoff have caused eutrophication and the non-point source of excess nutrients cannot be determined. These ATS systems improve water quality by encouraging algal growth on flow-way surfaces rather than forming harmful blooms in open waters. Excessive nutrients from the water accumulate in the flow-way’s lawn of algae, and unless the algal biomass is repurposed, it is discarded in landfills as waste. In this article, we outline a simple methodology to utilize waste algal biomass as a novel source of clay. Raw algal waste contains minerals which can be used as a sustainable and more environmentally-friendly alternative to industrially-mined clays. When algae-based clay sculptures are kiln fired, they resemble terracotta brick in their color, durability, and porosity. In addition to the aesthetic and artistic potential of algae-based clay, this medium provides an excellent opportunity for educators to engage students with hands-on crafting activities while learning about eutrophication and environmental restoration of aquatic habitats.

To better understand the habitat preferences and behavioural ecology of Sparus latus, we performed an experiment using box-shaped reefs as habitat enrichment materials, allowing us to determine the behavioural strategies and drivers involved in the response to different enrichment structures. The results showed that the first contact time of S. latus was negatively correlated (Pearson’s correlation, p < 0.005) with the distribution rate in the artificial reef area. Enrichment structures affected the habitat preferences of S. latus, and there was a significant difference in the average distribution rate between the control and treatment groups (Adonis, p < 0.001). The opening ratio (Adonis, R2 = 0.36) explained the distribution difference of S. latus better than the opening shape (Adonis, R2 = 0.12). In the absence of an enrichment structure, S. latus remained more active during the daytime, exhibiting poor clustering, while in the presence of an enrichment structure, S. latus exhibited clustered movement at night. The opening ratio was negatively correlated with the average interindividual distance (Spearman’s correlation, p < 0.01) and showed a significant positive correlation with the average distribution rate in the reef area (Spearman’s correlation, p < 0.001), indicating that the reef opening ratio significantly affected the reef-tropism and clustering behaviours of S. latus. The light intensity was negatively correlated with the average distance moved, and the average speed (Spearman’s correlation, p < 0.05) was significantly positively correlated with the reef first contact time (Spearman’s correlation, p < 0.001), indicating that the light intensity affected the exploration and activity patterns of S. latus. These results provide a research basis for analysing the pattern and process of fish proliferation induced by artificial reef habitats.

Artificial reefs are man-made structures submerged in the ocean, and the design of these structures plays a crucial role in determining their effectiveness. Precisely measuring the configuration of artificial reefs is vital for creating suitable habitats for marine organisms. This study presents a novel approach for automated detection of artificial reefs by recognizing their key features and key points. Two enhanced models, namely, YOLOv8n-PoseRFSA and YOLOv8n-PoseMSA, are introduced based on the YOLOv8n-Pose architecture. The YOLOv8n-PoseRFSA model exhibits a 2.3% increase in accuracy in pinpointing target key points compared to the baseline YOLOv8n-Pose model, showcasing notable enhancements in recall rate, mean average precision (mAP), and other evaluation metrics. In response to the demand for swift identification in mobile fishing scenarios, a YOLOv8n-PoseMSA model is proposed, leveraging MobileNetV3 to replace the backbone network structure. This model reduces the computational burden to 33% of the original model while preserving recognition accuracy and minimizing the accuracy drop. The methodology outlined in this research enables real-time monitoring of artificial reef deployments, allowing for the precise quantification of their structural characteristics, thereby significantly enhancing monitoring efficiency and convenience. By better assessing the layout of artificial reefs and their ecological impact, this approach offers valuable data support for the future planning and implementation of reef projects.

Rockfishes (Sebastes spp.) are a long-lived, understudied, multi-species fish assemblage in inland Washington (USA) waters. Driven by large-scale fishery removals in the 1970s, their numbers declined and have yet to recover, perhaps due to slow maturation and rare recruitment success. Since then, rockfish fishing restrictions have increased within Puget Sound, culminating in a 2010 total ban. Here, we analyze rockfish community trends (abundance and Shannon Diversity) within Puget Sound from 2009 to 2023. Our dataset includes 157 recorded dive transects from nine rocky or artificial reef habitats at depths 5–24 m throughout four Puget Sound basins: Admiralty Inlet (2 sites), Central Puget Sound (4 sites), Hood Canal (2 sites), and South Puget Sound (1 site). Significant differences in community species composition between basins were observed; we noted more Black (S. melanops), Yellowtail (S. flavidus), and Puget Sound (S. emphaeus) rockfish and fewer Brown rockfish (S. auriculatus) at sites in Admiralty Inlet vs. Central Puget Sound. Adult rockfish counts and Shannon Diversity varied seasonally, with higher rockfish counts and diversity indices in summer/autumn vs. winter/spring. Notably, we observed that total adult rockfish count per survey tended downward over time, driven partly by significant downward trends in Hood Canal Copper rockfish (S. caurinus) counts. We recommend continued monitoring and additional investigation into what factors besides fishing may be driving the trends reported here. [ABSTRACT FROM AUTHOR]

Artificial reefs are now commonly used as a tool to restore degraded coral reefs and have a proven potential to enhance biodiversity. Despite this, there is currently a limited understanding of ecosystem functioning on artificial reefs, and how this compares to natural reefs. We used water sampling (bottom water sampling and pore water sampling), as well as surface sediment sampling and sediment traps, to examine the storage of total organic matter (as a measure of total organic carbon) and dynamics of dissolved inorganic nitrate, nitrite, phosphate and ammonium. These biogeochemical parameters were used as measures of ecosystem functioning, which were compared between an artificial reef and natural coral reef, as well as a degraded sand flat (as a control habitat), in Bali, Indonesia. We also linked the differences in these parameters to observable changes in the community structure of mobile, cryptobenthic and benthic organisms between habitat types. Our key findings showed: (1) there were no significant differences in inorganic nutrients between habitat types for bottom water samples, (2) pore water phosphate concentrations were significantly higher on the artificial reef than on both other habitats, (3) total organic matter content in sediments was significantly higher on the coral reef than both other habitat types, and (4) total organic matter in sediment traps in sampling periods May and September were higher on coral reefs than other habitats, but no differences were found in November. Overall, in terms of ecosystem functioning (specifically nutrient storage and dynamics), the artificial reef showed differences from the nearby degraded sand flat, and appeared to have some similarities with the coral reef. However, it was shown to not yet be fully functioning as the coral reef, which we hypothesise is due its relatively less complex benthic community and different fish community. We highlight the need for longer term studies on artificial reef functioning, to assess if these habitats can replace the ecological function of coral reefs at a local level. [ABSTRACT FROM AUTHOR]

There is currently limited research assessing the ecological potential of coral restoration programmes of habitat enhancement and restoration of benthic and mobile populations for influencing the attitudes (and subsequent behaviours) of the communities where they are based. Our qualitative study investigated the impact of a coral reef restoration programmes on local environmental attitudes in a rural fishing community in north Bali, Indonesia. We conducted semi-structured interviews with individuals and multi-stakeholder focus groups (n = 31) in Tianyar Village, where the NGO 'North Bali Reef Conservation' ('Yowana Bhakti Segara') was based. Our results highlight several factors that influenced environmental behaviours, including perceived value of coral reefs (e.g.,changes in fishing yield), drivers of support for coral reef restoration (e.g., local leaders' influence) and barriers to coral reef restoration support (e.g., lack of investment). Overall, our data indicate that the restoration programme has influenced positive environmental attitudes within the community through improvements in waste management, increased support for restoration work, and the establishment of new environmental regulations. Based on our results, we make five recommendations: (1) continuing environmental education within the community, (2) strengthening regulations and improving enforcement, (3) increasing financial and logistical support for waste management and ecotourism, (4) continuing the construction and deployment of artificial reefs, ensuring 'best practice' recommendations are followed, and (5) utilising the influence of local leaders to create positive environmental behaviours. [ABSTRACT FROM AUTHOR]

The long-spined sea urchin Diadema antillarum controls reef dynamics by grazing on algae and increasing coral recruitment. Populations of Diadema never recovered after a mass-die off in 1983 and 1984, and numbers were further reduced by a more recent die-off in 2022. To restore grazing pressure and thereby the resilience of Caribbean coral reefs, multiple Diadema restocking efforts have been performed. Although results vary, relatively low retention is one of the reasons restocking is not considered more often. If causes for the low retention can be identified, suitable measures may be able to increase restocking success. In this study, we monitored restocked lab-reared and wild juvenile Diadema on artificial reefs around Saba, Caribbean Netherlands. To assess the retention of Diadema over time, we conducted diver surveys and used underwater photo time lapse during daylight. Retention of uncaged lab-reared and wild Diadema decreased steadily with less than 30% surviving after 10 days. In total, 138 predator-prey interactions were recorded, of which 99% involved the queen triggerfish Balistes vetula, although other potential predators were present in the area. None of the recorded predator-prey interactions was successful, which suggests that artificial reefs with incorporated shelters may be suitable for juveniles as daytime refuge. However, Diadema that were more often attacked during the day were more likely to be absent the next morning. Because queen triggerfish often visited the experimental site in the first or last hour of daylight, it could be that they were more successful in their attacks when it was too dark to see anything on the photos and when Diadema came out to feed or to look for better shelter opportunities. If Diadema migrated off the artificial reef, they were probably predated during the process, because no Diadema were found on surrounding reefs. Wild Diadema were attacked significantly more often than lab-reared Diadema, possibly because the wild urchins were larger, but this did not significantly affect retention. Future restocking should be performed on natural or artificial reefs with deeper shelters, so Diadema can retract farther into their crevice, and should include night-time monitoring to identify the remaining unknown factors that cause low retention, including migration and nocturnal predation. This knowledge is urgently needed to coral reef managers so they can increase Diadema restocking success by selecting reefs with a lower predator density, protect urchins during an acclimatization period and/or conduct temporary predator control measures. [ABSTRACT FROM AUTHOR]

The fluctuating asymmetry (FA) of fish otoliths can reflect the difference in the growth and development of fish in sea areas greatly affected by environmental pressure, thus enabling the assessment of different habitats. In this study, using 113 Collichthys lucidus samples collected from different functional areas (estuary area, aquaculture area, artificial reef area and natural area) in Haizhou Bay, the square coefficient of asymmetry variation (CV2a) of four characters (length, width, perimeter and area) of the left and right sagittal otoliths was calculated. The results showed that the CV2a value of otolith width was the lowest and that of otolith length was the highest. The CV2a value had no obvious regularity with increasing fish body length. In addition, the CV2a values of the four characteristics reached their lowest values in the artificial reef area, indicating that the construction of marine ranching dominated by artificial reefs may partly improve the aquatic environment in this functional area. We consider that the otolith FA of C. lucidus can be used as a characteristic of environmental stress between different areas/regions/habitats. [ABSTRACT FROM AUTHOR]

Coral reef habitat quality is declining in many locations because of heatwaves (coral bleaching) and other disturbances. Reef‐building corals provide refuge from predation, so declining complexity restricts the transfer of energy to upper trophic levels.We use a size‐based ecosystem model to test systematically the effects of refuge at specific sizes and the impacts of distributions of refuges that vary in size. Outcomes are assessed in terms of ecosystem service provision.Simulations indicate that refuge sheltering fish between 5 and 10 cm in length enhances fish biomass and fisheries productivity, for example, increasing herbivore biomass by up to 80%.We identify and present a range of refuge profiles that can theoretically improve ecosystem service provision by as much as sixfold. Profiles where refuge availability decreases with increasing fish size consistently outrank other designs.Synthesis and application: These results highlight how critical small‐scale refuge is for coral reefs, and how we might design artificial reefs to maximise service provision. [ABSTRACT FROM AUTHOR]

The impact of temporal factors and physiochemical properties on the quantities and biomass of fish in the Thermaikos Gulf and adjacent habitats around the Pieria artificial reef complex in Northern Greece was evaluated. Data were collected from edge habitats of an artificial reef made of submerged concrete blocks located offshore of Kitros. Between 2015 and 2017, sampling excursions took place in the spring, summer, and fall of each year. The artificial reef complex is positioned 11.5 km offshore from Kitros, near the delta of the Aliakmonas River, and is influenced by freshwater from the Axios, Aliakmonas, Ludias, and Gallikos Rivers. To estimate the biomass and numbers of the primary benthopelagic commercial fish in the region, nine experimental samples were taken from 2015 to 2017, employing a bottom trawl with a mesh size of 10 mm. Each trawl sample lasted for 30 min to reduce the environmental impact of fishing in the areas under study. The sampling schedule was aligned with factors like the breeding times of the dominant species and the seasonal changes in the thermocline zone. Analysis showed seasonal differences in average abundance and biomass values across the 3 years of the study. Mullus barbatus, recognized as the most commercially significant species caught, demonstrated the greatest abundance and biomass during the second sampling season. Conversely, Pagellus erythrinus, the second most vital commercial species caught, exhibited its highest abundance in the first season and reached its peak biomass during the third sampling season. Hierarchical cluster analyses showed that the two major resulting clusters of species proliferated in numbers over the 3-year period, while undergoing a concurrent reduction in their individual sizes. [ABSTRACT FROM AUTHOR]

Coral nurseries and associated techniques are the most common and widespread reef restoration methods worldwide. Due to the rapid decline of coral reefs, coral nurseries need to be eco-friendlier and adapted for effective upscaling to support large restoration projects. We suggest new design and fabrication processes associated with coral gardening and transplantation with 3D printing technology to offer a beneficial solution for growing coral fragments in on-land and underwater nurseries. We describe multiple combinations of building nurseries through the integration of biomimetic substrates and novel solutions for attaching coral fragments. Our methods are supported with supplemental testing of two hybrid substrate designs and coral mounting structures, building upon previous studies in the Gulf of Eilat/Aqaba (GoE/A), Red Sea. We identified and quantified marine invertebrates colonizing the surfaces of our substrates with environmental DNA (eDNA) by targeting the mitochondrial COI gene. We evaluated our coral fragments with and without our mounting structures to obtain an indication of total protein as a proxy for tissue health. We demonstrate the ability to design hybrid nurseries with custom mounting structures using biomimetic substrates, such as large ceramic artificial reefs, or with an interlocking mesh for holding numerous fragments to maximize out-planting efforts. We propose several methods for both land and underwater nurseries catered to various restoration initiatives for cost-effective up-scaling to meet the demands of global reef restoration. [ABSTRACT FROM AUTHOR]

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In this paper, the flow characteristics induced by a cubic artificial reef with diversions (DCAR) were investigated using computational fluid dynamics (CFD). The results showed that the design of a DCAR can greatly improve the flow field range compared to typical cubic artificial reefs. The upwelling volume of the DCAR was more than 16 times that of a typical cubic artificial reef. The flow field effect produced the best results when the cut-opening ratio (COR) was 0.1–0.2 with constant flow. The parameters of the upwelling and back vortex increased with an increase in the flow velocity, and it decreased with an increase in the COR. The drag coefficient was less affected by the flow velocity, which remained between 1.32 and 1.44. The new type of artificial reef can improve the flow characteristics around the reefs. [ABSTRACT FROM AUTHOR]

The rapidly expanding built environment in the northern Gulf of Mexico includes thousands of human built structures (e.g. platforms, shipwrecks) on the seabed. Primary-colonizing microbial biofilms transform structures into artificial reefs capable of supporting biodiversity, yet little is known about formation and recruitment of biofilms. Short-term seafloor experiments containing steel surfaces were placed near six structures, including historic shipwrecks and modern decommissioned energy platforms. Biofilms were analyzed for changes in phylogenetic composition, richness, and diversity relative to proximity to the structures. The biofilm core microbiome was primarily composed of iron-oxidizing Mariprofundus, sulfur-oxidizing Sulfurimonas, and biofilm-forming Rhodobacteraceae. Alpha diversity and richness significantly declined as a function of distance from structures. This study explores how built structures influence marine biofilms and contributes knowledge on how anthropogenic activity impacts microbiomes on the seabed. [ABSTRACT FROM AUTHOR]

The ecological succession has been widely studied by means of biofouling assemblages among different substrates, and mainly targeted in early stages on artificial ones. The present study focuses on biofouling that colonizes carbonated structures, a material similar to the natural substrate produced by the electrolysis of seawater, which is relatively very little studied. We have observed the colonization of sessile macrofouling of the port of Alicante (SE Spain, Western Mediterranean) on two types of substrates (electrolytic carbonated and steel) over 12 months of succession. The assemblages of both substrates have been analyzed by means of diversity indexes and multivariate analysis (PERMANOVA and SIMPER) in order to see the differences over time. The carbonated substrate has presented a community with higher values of biological diversity, structure and complexity, although the differences in species composition between substrates are not evident during all immersion periods. Thus, these results seem to indicate that, even after 12 months of immersion, communities are still in a dynamic successional stage.

Epiphytic microalgae are important contributors to the carbon and nutrient cycles yet are often overlooked during ecological surveys. In reef habitats, epiphytes are often found living on host organisms, including seaweeds or corals, and can influence community composition of higher trophic level taxa. Hence, understanding how epiphytes respond to different reef substrate materials can help inform designs of substrates intentionally deployed to form artificial reefs which can encourage high biodiversity and ecological functioning. One such epiphyte, Gambierdiscus spp., is a harmful benthic dinoflagellate which produces toxins that bioaccumulate and cause ciguatera fish poisoning (CFP) when contaminated fish is consumed by humans. CFP is one of the most frequently reported seafood-associated illnesses around the world, occurring most often near tropical reefs. We surveyed the epiphytes amongst 13 natural and artificial reef sites located off the coast of North Carolina to determine the role of the reefs’ foundational substrate (e.g., natural marl, steel or concrete) on structuring the epiphyte community with an emphasis on Gambierdiscus spp. abundance. No Gambierdiscus spp. were detected among the sampled reefs, likely due to suboptimal water temperatures. An ex-situ substrate preference experiment for Gambierdiscus spp. was performed using marl to represent natural rocky reefs, and steel and concrete to represent artificial reefs. Experimental results indicated that Gambierdiscus spp. grew fastest in the presence of marl and density decreased significantly when exposed to steel. However, steel artificial reefs had the highest average epiphyte biomass and species richness amongst the sampled reefs. 18s rRNA gene sequence analysis revealed that natural reefs were more likely to be dominated by dinoflagellates, whereas steel and concrete reefs were dominated by diatoms. We found that epiphyte composition was related to material at a phylum level, but seaweed hosts played a more significant role at the species level. These findings suggest that CFP risk is relatively low on the reefs studied but natural reefs would likely be preferentially colonized by Gambierdiscus spp. should ambient conditions become appropriate.

As offshore wind energy developments increase globally in response to climate change, it is important to gain an understanding of the effects they are having on the marine environment. Whilst there is growing information on the types of organisms present within these sites, our knowledge of how species interact with these sites is limited. For the first time we examined the movements and habitat utilization of a temperate decapod, the European Lobster Homarus gammarus , using acoustic telemetry within an offshore wind farm (OWF). Innovasea V9 acoustic transmitters were externally attached to 33 individuals (carapace length = 87–113  mm) at three turbine locations within an offshore wind farm in the Irish Sea. Individuals were found to exhibit high residency to the tagging sites, with over half of tagged lobsters present at the tagging sites for 70% of the study period. Individual home ranges and core territories were calculated using 95% and 50% kernel density, respectively. Home ranges ranged from 9313.76 to 23 156.48m2 while core territories ranged from 1084.05 to 6037.38m2. Over 50% of all detections were recorded within 35 m of the scour protection. These results suggest that particular areas of habitat within fixed-turbine OWFs provide a suitable habitat for lobsters. We postulate that this is likely the result of artificial reef effects arising from the addition of artificial hard substate into previously soft sediment dominated habitats. Therefore, future fixed-turbine OWF developments across Europe may provide potential fishery opportunities as a result of artificial reef effects. [ABSTRACT FROM AUTHOR]

Dredging materials from reef flats have become an important source of sand and aggregates for meeting the infrastructure needs of coral-lined shores in subtropical and tropical regions, especially for low-lying atoll islands. Dredging at the reef flats can generate artificial excavation pits, which not only have profound influences on coral ecological stability but also deeply affect the hydrodynamic characteristics of coral reefs. To deepen the understanding of the influence of excavation on the wave hydrodynamics of fringing reefs, the wave propagation, wave transformation, wave setup, and wave runup processes of regular waves on fringing reefs with artificial pits have been systematically analyzed using a non-hydrostatic numerical wave solver (NHWAVE). The effects of some significant factors have been carefully investigated. According to the study findings, the existence of artificial pits can result in a slight decrease in the wave height around the artificial pit. The time-mean maximum of wave runup height at the backreef slope can be reduced to some extent when the artificial pit is present. When placed close to the reef edge, the artificial pit can have noticeable effects on the hydrodynamic characteristics of fringing reefs, particularly the wave setup along the reef flat. It is hoped that the study findings can provide further reference for evaluation of the influences of artificial pits on the wave hydrodynamics of fringing reefs. [ABSTRACT FROM AUTHOR]

The design of an artificial reef (AR) module for improving the fishing productivity of cephalopod molluscs in the Ares-Betanzos estuary (Galicia, NW Spain) is addressed in this study. At the time of deciding on a suitable AR design, it is first necessary to assess how the different marine species use ARs so that it is possible to define the complexity of the design: its size and shape, as well as the number of nest cavities it should present and the dimensions of these cavities. Thus, two different cubic modules are proposed, both with an edge of 1500 mm. One of them can be considered as the standard design, while the other has been modified to include four open cylindrical holes. Several tools are employed to assess both proposals. Moreover, a CFD (computational fluid dynamics) model is performed. The results suggest that the flow in the interior of the tubes provides a suitable environment for cephalopod molluscs, given that circulation is produced, guaranteeing nutrient renewal. As further contributions, the present work determines how the capture of cephalopods and other species in Galician fish markets has evolved and reviews the habitat preferred by cephalopods in Galicia. It also proposes and compares two AR modules. [ABSTRACT FROM AUTHOR]

Spatiotemporal changes in the concentration of UV filters were investigated along the shore according to increasing distance from breakwaters, from the shoreline, as well as according to seasonality in three locations of different anthropogenic pressures, involving those from cosmetic products being released during touristic activity. Nine organic UV filters (benzophenone-1 (BP-1), benzophenone-2 (BP-2), benzophenone-3 (BP-3), octocrylene (OCR), 4-methoxy benzylidene camphor (4-MBC), ethylhexyl methoxycinnamate (EHMC), ethylhexyl salicylate (EHS), homosalate (HMS), and butyl methoxydibenzoylmethane (BMDM)) were determined in core sediments, and the range of determined concentrations above the limit of quantification was between 19.2 ng·kg−1 d.w. (HMS) and 539.5 μg·kg−1 d.w. (4-MBC). Unexpectedly, contrary to the level of anthropogenic pressure, the concentrations of four (BP-1, BP-2, BP-3, OCR) UV filters decreased in the following order: Darłówko > Ustka > Rowy. Higher concentrations of BP-1, BP-2, BP-3, and OCR were determined in spring than in summer and autumn. The maximal concentration of HMS and EHMC/EHS was found in the summer and in the autumn, respectively. BMDM was determined occasionally only in two samples collected in Ustka. The higher maximal concentration range of all UV filters was determined in core sediments taken from the eastern (539.5 μg·kg−1 d.w.) rather than from the western (11.3 μg·kg−1 d.w.) parts of the beaches. According to increasing distance from the breakwaters, higher concentrations of UV filters were determined in sites located up to 100 m away in all locations and seasons. Spatial variation in the concentration of UV filters was observed in profiles perpendicular to the water line. Typically, higher concentrations were determined at sites having contact with water, although incidentally, high concentrations were also noticed at sites located further into the beach. The Polish coast of the Baltic Sea is not free from organic UV filters, and expectations concerning the abundance of UV filters in a given location are far from recorded data due to the impact of hydro-technical treatments (i.e., stony and wooden breakwaters, artificial reefs, nourishment) and coastal littoral drift. [ABSTRACT FROM AUTHOR]

Over the past decade, there has been increasing interest in marine restoration, requiring a consideration of various approaches for optimal success. Artificial reefs (ARs) have been employed for marine restoration and fisheries management, but their effectiveness in restoring ecosystems lacks well-defined ecological criteria and empirical evidence. A systematic review of the literature on ARs articles between 1990–2020, a meta-analysis of their effectiveness based on the similarity of species composition with reference natural reefs (NRs), as well as bias risk analyses were carried out. Research on ARs primarily focused production of marine communities (n = 168). There are important information gaps regarding socioeconomic aspects; design, materials, and disposal in the selected habitats; legal, management, and planning aspects considering long-term monitoring. Regarding effectiveness, few articles (n = 13) allowed comparisons between ARs and NRs, highlighting the need to apply proper reference sites in AR implementations. Meta-analysis showed that ARs are not similar to reference NRs (p = 0.03, common effect and p = 0.05 random effect models). However, a high index of heterogeneity (88%) suggests that this relation may be influenced by factors other than the reef type. Thus, further analysis can disguise variables conditioning this AR–NR similarity as a measure of restoration for degraded marine ecosystems. [ABSTRACT FROM AUTHOR]

Poor survival of seeds reduces the production efficiency of the sea cucumber Apostichopus japonicus in pond culture. We investigated the effects of sea mud on the movement-related behaviors of A. japonicus with different body sizes. Mud significantly decreased crawling behavior and wall-reaching behavior in small seeds (~ 1 g of body weight), but not in the large ones (~ 2.5 g of body weight). These behaviors were significantly greater in the large seeds of A. japonicus than those in the small individuals when they were both on the mud. This clearly suggests that mud has negative effects on the movement-related behaviors of small seeds, but not on large individuals. We further assessed the effects of inevitable transport stress on the movement-related behaviors of A. japonicus on mud. Significantly poorer performances in crawling behavior, wall-reaching behavior and struggling behavior were observed in stressed A. japonicus (both sizes) than those in unstressed groups. These new findings indicate that transport stress further increases the adverse effects on the movement-related behaviors of A. japonicus on mud. Moreover, we investigated whether adverse effects can be reduced when individuals are directly seeded onto artificial reefs. Crawling behavior, wall-reaching behavior and struggling behavior in stressed A. japonicus (both sizes) seeded onto artificial reefs were significantly greater than those on mud, whereas artificial reefs did not significantly improve the crawling and struggling behaviors of unstressed small seeds. These results collectively indicate that mud and transport stress show negative impacts on the movement-related behaviors of sea cucumbers. Artificial reefs greatly reduce these adverse effects and probably contribute to improving the production efficiency of sea cucumbers in pond culture. [ABSTRACT FROM AUTHOR]

The development of modern tropical marine ranching is an important means to conserve fishery resources and protect the marine ecological environment in the South China Sea, which has far-reaching significance for the conservation and scientific utilization of fishery resources in the South China Sea. Artificial reefs are one of the important tools to create marine ranching habitats. However,due to the deep water in the South China Sea,conventional reefs are difficult to play a role,whereas floating reefs can make use of the water space in the middle and upper layers,and are the best facilities to create deep water fishing grounds. This study reviews the types,functions,and application scenarios of floating fish reefs,summarizes relevant research and current status both domestically and internationally,and looks forward to the future of floating fish reefs in the South China Sea,including their role in information-based monitoring of ocean ranching,recreational fishing, conservation of upper-middle level fishery resources,and the construction of offshore ocean ranching. [ABSTRACT FROM AUTHOR]

The construction of acoustic-tamed marine ranching is of great significance to the proliferation of fishery resources,the protection of the marine environment,and the sustainable development of fishery. The study of the effective range of acoustic taming can provide a scientific and reasonable reference for the site selection of artificial reefs in marine ranching. In this study,the sound playing parameters for acoustic taming of Sebastes schlegelii were set concerning the T/ SCSF 0009—2021 technical regulations of fish acoustic taming in marine ranching. In the marine ranching demonstration area,300 Hz sine waves were played underwater to simulate the field acoustic taming. The underwater noise attenuation model was established through calculation. The results show that the horizontal attenuation formulas of 1 m,5 m,and 10 m underwater are:TTL =1. 73×10 logs(r); TTL =1. 58×10 log(r); TTL = 1. 70×10 log(r),and the underwater noise attenuation is spherical attenuation. In the marine ranching demonstration area,the effective radius of acoustic taming of the sine wave with the parameter of 300 Hz,155 dB for Sebastes schlegelii is 500 m,and the optimal radius of acoustic taming is 250 m. [ABSTRACT FROM AUTHOR]

In order to comprehensively utilize ocean resources and renewable energy, a novel modular floating structure (MFS) system with multi-direction expansibility has been proposed, which includes inner hexagonal tension leg platform (TLP) modules and outermost floating artificial reef modules coupled with the function of the wave energy converter (WEC). Considering both the hydrodynamic interaction effect and the mechanical coupling effect, the main dynamic responses of the MFS system have been analyzed under different incident wave directions, and the corresponding physical mechanism has been clarified. Results indicate that connector loads slightly increase, but motion responses of the MFS system are more stable when the outermost floating artificial reefs serve as the up-wave modules. Outermost floating artificial reef modules have shown good wave-attenuation capacity for inner TLP modules, as well as producing considerable output wave power. The effect of key power take-off (PTO) parameters on the WECs' performance has been investigated, and the optimal PTO damping coefficient has been suggested. In addition, extreme responses of the proposed MFS system have been further studied, and its safety has been well verified under typical extreme sea conditions. The main results of this work can serve as a helpful reference for the construction of future offshore floating cities. [ABSTRACT FROM AUTHOR]

Artificial reefs (ARs) have been advocated for and implemented as management tools for recreational fisheries, species conservation, and habitat replacement; however, the research that includes attracting marine species of floating ARs remains in its early stages. Here, two types of floating ARs were designed to evaluate the attractive effects using the occurrence rate and attracting index for six commercially important species (Lateolabrax maculatus, Liza haematocheila, Sebastes schlegelii, Acanthopagrus schlegelii, Litopenaeus vannamei, and Amphioctopus fangsiao) in the Bohai Bay of China; their combined ARs were meanwhile compared with two variants of artificial seagrass beds (SA and SB) and the traditional double-frame artificial reef (TD). All of the designed ARs were effective in attracting experimental species. The ARs with higher shelter areas (SB and TD) showed a better attracting effect. The efficiency of the ARs in attracting different species depended on their life histories. The bottom-mounted ARs were more efficient in attracting demersal species, while the floating ARs attracted epipelagic fish. In addition, the combined reefs had a better attractive effect than single ARs did. Overall, floating ARs and their combined ARs show the potential to deploy especially for attracting epipelagic fishes, although further study is needed. [ABSTRACT FROM AUTHOR]

The magnetic anchoring system (MAS) for reef limestone reinforcement is proposed in this paper. The mix proportion of the artificial reef limestone was designed, and the parameters of the MAS were determined through orthogonal tests. The effect of the magnetic field on the anchoring materials was analyzed using XRD and the nitrogen adsorption method. The results indicate that the designed artificial reef limestone can be used in place of in situ rock samples for laboratory tests. In air, the bond samples of the anchoring material and reef limestone experienced cohesion failure of the artificial reef limestone. However, in seawater, it was cohesion failure of the reef limestone and interface adhesion failure. During the pull-out test, the reef limestone specimen reinforced by MAS showed interface failure between the anchoring material and the rock mass. The Fe3O4 powder present in the anchoring material has the ability to migrate towards the anchor, thereby enhancing the density of the anchoring material. This, in turn, helps to eliminate the free water present in the anchor hole, and consequently, improves the bonding effect of the interface. The reinforcement effect of MAS is particularly advantageous for rock reinforcement under complex working conditions. [ABSTRACT FROM AUTHOR]

Summer mortality and morbidity are serious environment-related problems in cultured sea cucumbers (Apostichopus japonicus). Air exposure probably worsens the impact of high temperature on cultured sea cucumbers. In this present study, two laboratory experiments were designed to investigate the effects of artificial reefs on mortality, morbidity, crawling, feeding, and adhesion behaviors of small sea cucumbers (~1 g of wet body weight) after air exposure and disease outbreaks at 25 °C, respectively. Significantly lower mortality and morbidity occurred in the group with artificial reefs compared with those in the group without artificial reefs in the two experiments. This present study found that the stressed sea cucumbers cultured inside artificial reefs showed a significantly higher adhesion index, feeding behavior, and crawling frequency than those cultured without artificial reefs. In disease challenge assays, small sea cucumbers cultured inside the artificial reefs showed a significantly higher adhesion index and crawling frequency than those cultured without artificial reefs at 25 °C. Feeding, crawling, and adhesion behaviors of sea cucumbers cultured outside artificial reefs were not significantly different from those cultured without artificial reefs. The experimental results indicate that sea cucumbers with good fitness-related behaviors may be less affected by the disease and more likely to move into the crevices of artificial reefs. Fitness-related behaviors were poor in sea cucumbers cultured outside artificial reefs, so we considered them as affected individuals. Thus, artificial reefs provide a place to reduce the physical contact between unaffected and diseased/affected individuals, showing a potential to reduce disease transmission. Our present study establishes a cost-effective approach to increasing the survival of small sea cucumbers in seed production at high temperatures. [ABSTRACT FROM AUTHOR]

On account of their critical importance, corals are protected in India under Schedule I of the Wildlife Protection Act, 1972, Govt. of India. In spite of that, reports of coral smuggling arise from the Indian reef areas, sporadically. Corals being delicate animals, the restoration of corals seized from smugglers is difficult because of the delay involved in legal proceedings, transportation and the fragile nature of the corals. The present study reports the first successful effort in restoring seized live corals in the Gulf of Mannar, Southeast India. Fifty fragments of seized corals belonging to nine genera have been successfully transplanted on perforated trapezoidal artificial reefs deployed around Vaan Island of the Gulf of Mannar with an average survival rate of 62 % after 22 months. The growth rate of these surviving transplants ranged between 1.28±0.12 and 8.56±0.11 cm year-1. The present attempt sets an example in the enforcement history of India, where sensitive marine organisms like corals can be saved after seizure if conservation authorities and researchers work together. However, proper network and coordination between these is critical to restore delicate marine organisms if seized alive. [ABSTRACT FROM AUTHOR]

In 2020 marine heatwaves elicited severe bleaching on many of Earth's coral reefs. We compared coral reef benthic community composition before (April 2020), during (September 2020), and after (December 2020–September 2021) this event at five fringing reefs of Southern Taiwan. The four shallow (3 m) reefs were hard coral-dominated in April 2020 (cover = 37–55%), though non-bleached coral cover decreased to only 5–15% by December 2020. Coral abundance at the two shallow (3 m), natural reefs had failed to return to pre-bleaching levels by September 2021. In contrast, coral cover of two artificial reefs reached ~45–50% by this time, with only a small drop in diversity. This is despite the fact that one of these reefs, the Outlet, was characterized by temperatures >30 °C for over 80 days in a six-month period due not only to the bleaching event but also inundation with warm-water effluent from a nearby nuclear power plant. Only the lone deep (7 m) reef was spared from bleaching and maintained a coral/algal ratio >1 at all survey times; its coral cover actually increased over the 18-month monitoring period. These data suggest that (1) the natural deep reef could serve as a refuge from thermal impacts in Southern Taiwan, and (2) the remaining corals at the Outlet have either adapted or acclimatized to abnormally elevated temperatures. [ABSTRACT FROM AUTHOR]

Abstract Background Many marine man-made structures (MMS), such as oil and gas platforms or offshore wind turbines, are nearing their ‘end-of-life’ and require decommissioning. Limited understanding of MMS decommissioning effects currently restricts the consideration of alternative management possibilities, often leaving complete removal as the only option in certain parts of the world. This evidence-base describes the ecosystem effects of marine MMS whilst in place and following cessation of operations, with a view to informing decision-making related to their potential decommissioning. Method The protocol used to create this map was published a priori. Systematic searches of published, literature in English were conducted using three bibliographic databases, ten specialist organisational websites or repositories, and one search engine, up to early 2021. A total of 15,697 unique articles were identified as potentially relevant to our research questions, of which 2,230 were screened at the full-text level. Of that subset, 860 articles met all pre-defined eligibility criteria. A further 119 articles were identified through “snowballing” of references from literature reviews. The final database consists of 979 articles. For each article included, metadata were extracted for key variables of interest and coded into a database. Review findings The vast majority of eligible articles related to the presence of MMS (96.2%), while just 5.8% considered decommissioning. Overall, articles mainly considered artificial reefs (51.5% of all articles) but increasingly oil and gas (22%), shipwrecks (15.1%) and offshore wind (13.1%). Studies were distributed globally, but the majority focused on the United States, single countries within Europe, Australia, Brazil, China, and Israel; 25 studies spanned multiple countries. Consequently, the bulk of the studies focused on the North Atlantic (incl. Gulf of Mexico, North Sea, and Mediterranean Sea) and North Pacific Oceans. A further 12 studies had a global scope. Studies in majority reported on fish (53%) and invertebrates (41%), and were disproportionately focused on biological (81%) and ecological (48%) impacts. Physico-chemical (13%), habitat (7%), socio-cultural (7%), economic (4%) and functional (8%) outcomes have received less attention. The number of decommissioning studies has been increasing since ca. 2012 but remains noticeably low. Studies mostly focus on oil and gas infrastructures in the USA (Gulf of Mexico) and Northern Europe (North Sea), covering 9 different decommissioning options. Conclusions This systematic map, the first of its kind, reveals a substantial body of peer-reviewed evidence relating to the presence of MMS in the sea and their impacts, but with considerable bias toward biological and ecological outcomes over abiotic and socio-economic outcomes. The map reveals extremely limited direct evidence of decommissioning effects, likely driven at least in part by international policy preventing consideration of a range of decommissioning options beyond complete removal. Despite evidence of MMS impacts continuing to grow exponentially since the early 1970s, this map reveals key gaps in evidence to support best practice in developing decommissioning options that consider environmental, social and economic effects. Relevant evidence is required to generate greater understanding in those areas and ensure decommissioning options deliver optimal ecosystem outcomes.