Reef Areas Research Articles

Status of Coral reef around Swaraj Dweep (Havelock Island), Andaman, India

The study was carried out in selected reef sites at Swaraj Dweep (Havelock Island) to assess the status of live coral diversity with related fauna by using the line intercept transects (LIT) survey method. Three sites were selected for this study viz (1) Vijayanagar beach, (2) Elephant beach and (3) Radha Nagar Beach. The average length of entire LIT and reef area of each site were 1098 m, 141.3m and 215 m & 675.3 m, 103.3m and 133m respectively. The average of live corals was found dominant in the entire LIT at site 2 (37.7%) followed by site 1 (16.2%), and site 3 (14%) and dead corals were found dominant at site 3 (44.7%) followed by site 2 (33.2%) and site 1 (13.8%). Similarly reef area of live coral was found dominant at site 2 (50.8±2.5%) followed by site-1 (26.9±0.2%) and site 3 (23.7±6.2%). Altogether 80 species of live coral were recorded under 31 genera and 11 family at all LIT in which the family Poritidae was dominant in site 1 (55.1±4.9%) and site 2 (55.2±2.5%). The family Acroporidae was dominant in site 3 (35.2±4.1%). The environmental parameters of all three sites were analyzed that there were little variations observed except CO2 which remained consistent (0) during the study period.

Benthic Mapping of Coral Reef Areas at Varied Water Depths Using Integrated Active and Passive Remote Sensing Data and Novel Visual Transformer Models

Benthic Mapping of Coral Reef Areas at Varied Water Depths Using Integrated Active and Passive Remote Sensing Data and Novel Visual Transformer Models

New genera and new species of Catenulaceae (Bacillariophyta) from Coral Reef habitat of two Indonesia islands-Bawean and Sulawesi-A morphological approach.

Indonesia is listed as a region with high marine biodiversity, especially when considering the three large tropical ecosystems: seagrass beds, mangroves and coral reefs. It is likely that the biodiversity of diatoms in this area is also high. Samples for this research were taken from the remote area of Bawean Island and Tomini Gulf in Central Sulawesi. In this research, we explored marine benthic diatoms from coral reef areas and presented two new genera: Paracatenula and Wallaceago, and seven new species: Paracatenulaporostriata sp. nov., Wallaceagoporostriatus sp. nov., Catenulaboyanensis sp. nov., C.komodensis sp. nov., C.decusa sp. nov., C.densestriata sp. nov., and Catenulopsisbaweana sp. nov. The new genus Paracatenula is characterized by its perforated cingulum, and the genus Wallaceago is distinguished by its proximal and apical raphe ends bent to the ventral side and the presence of a stauros in the mantle.

“Accidental” artificial reefs — lessons from Singapore for coral and seagrass restoration along urban shorelines

Due to rapid urbanization and coastline modification, the city-state of Singapore has lost nearly three-quarters of its intertidal coral reef area and nearly 90% of its subtidal coral reef area since pre-colonial times. However, the recolonization of coral communities has occurred naturally on seawall structures despite the lack of any deliberate planning or intervention. Recent mapping of coastal habitats shows that seawall reefs now form a significant proportion of habitat occupied by hard corals in Singapore, including areas where there were historically no coral reefs, and often exist side-by-side with other regenerated marine habitats such as seagrass meadows. These “accidental” artificial reefs demonstrate that new hard coral and seagrass communities can establish along highly urbanized shorelines, albeit in a novel form, and provide ecosystem services to urban communities. Key lessons can be drawn from these case studies, particularly relating to landscape design of urban shorelines to facilitate ecological coral and seagrass restoration. These include constructing seawalls with optimal slope profiles, providing creviced berms at the lower intertidal of seawalls, co-locating seawalls with artificial intertidal lagoons, and considering coral larvae supply in choosing sites for restoration using seawalls. Most importantly, these case studies illustrate the potential of using seawalls to restore hard coral and seagrass habitat on a landscape-scale, especially in urban environments.

High-resolution imagery of the coral reefs of Gorgona Island, Colombian Pacific Ocean: An improved view for monitoring and research

The shape and size of a coral reef are both key factors influencing its ecology and biodiversity. These parameters play a fundamental role in the creation of specific habitats that support a rich biodiversity. They also greatly influence its resilience to climatic events and external influences. Here we present a practical example of photogrammetric reconstruction of the best developed coral reefs of the Colombian Pacific, located at Gorgona Island. Using unoccupied aerial vehicles (drones) and Geographic Information Systems (GIS), we produced high resolution orthophotomosaics and precise contour maps of four reefs and updated estimates of reef areas. We illustrate the improved accuracy of these maps in comparison with maps obtained from satellite imagery and conclude by highlighting the usefulness of drones to locate, measure, and monitor small coral reefs.

AI-Powered Tracking for Sustainable Marine Ecosystem Resource Management Projects

Ecosystems are our planet's life-support systems that facilitate sustainable development. Within the marine ecosystem, oysters serve as a keystone species. Numerous oyster restoration projects have been launched with a crucial element involving precise assessment of oyster population sizes within specific reef areas. However, the current methods of tracking oyster populations are approximate and lack precision. To address this research gap, the authors developed an AI-empowered project for oyster detection. Specifically, they created a dataset of wild oysters, utilized Roboflow for image annotation, and employed image augmentation techniques to augment the training data. Then, they fine-tuned a YOLOv8 computer vision object detection model using their dataset. The results demonstrated a mean average precision (mAP) of 85.2 percent and an accuracy of 87.7 percent for oyster detection. This approach improved upon previous attempts to detect wild oysters, offering a more effective solution for population assessment, which is a fundamental step toward sustainable oyster restoration project management.

Temporal and spatial variation in the food web structure in artificial reef areas and adjacent habitats in Haizhou Bay

Artificial reef is regarded as an effective tool for restoring habitats and supporting the marine ecosystem. While the energy flow and material exchange in the food web of artificial reef ecosystem still remain vacant and should be further understood. In this study, stable isotopic characteristics (δ13C and δ15N) were used to identify the trophic niches and potential carbon sources of consumers (fish and invertebrates) in artificial reef areas and adjacent habitats in Haizhou Bay (the estuary area (EA), the aquaculture area (AA), the artificial reef area (AR), the natural area (NA) and the comprehensive effect area (CEA)) in spring and autumn. The results showed that the average δ13C for all consumers decreased from − 16.99 ± 2.07‰ to − 21.81 ± 1.66‰, and the average δ15N ranged from 11.37 ± 0.35‰ to 14.69 ± 0.64‰ in all seasons. A SIBER model revealed highly similar trophic niche among habitats in autumn, and lower overlap in spring. The SIMMR model showed that phytoplankton and sedimentary organic matter (SOM) were the major contributors to consumers, and particulate organic matter (POM) accounted for less contribution. In AA and NA phytoplankton and SOM generally contributed fairly equally to most fish, while single SOM sources were major contributors to nearly all the species in AR and CEA. Our findings reveal that ARs can serve as seascape mosaics to increase fish community diversity because of their high variation in the δ13C value and the trophic niches from EA to the NA. Preliminary multidisciplinary studies are needed for the mitigation of effects before any implementations deployed to the offshore waters that influence habitat connectivity, especially some habitat–specific migratory species.

Sea urchin Arbacia punctulata feeding preference for algal turf over kelp in a degraded kelp forest ecosystem

Climate change is driving a shift in the distribution of global kelp forests, with the contraction of kelp habitats occurring at warm range edges. Declining kelps often have been replaced by novel algal turf assemblages, which are reinforced by ecological feedback mechanisms and provide fewer ecosystem services. Trophic interactions among marine herbivores, algal turfs, and kelps on algal turf-dominated reefs remain poorly resolved but could have important implications for the stability of algal turf reefs and the potential for kelp forest recovery. Here, we examine herbivory by the Atlantic purple sea urchin, Arbacia punctulata, in a degraded kelp forest ecosystem dominated by algal turf in southern New England, USA. In a localized field survey, we observed lower algal turf cover on reef areas containing A. punctulata (mean ± SE: 62 ± 12% turf cover) as compared to areas with no sea urchins present (92 ± 4% turf cover). Reef areas with and without sea urchins had similarly low cover of the previously dominant kelp, Saccharina latissima (6–8% kelp cover). In laboratory and field experiments, individuals or groups of A. punctulata enclosed with a diet choice of algal turf versus kelp had higher grazing rates on the algal turf. A. punctulata in the laboratory also exhibited greater attraction to algal turf over kelp, physically moving towards this food source. In combination, the results provide evidence that A. punctulata has a feeding preference for algal turf over kelp in southern New England. Future research is warranted to further examine the grazing ecology of A. punctulata, particularly in the context of ongoing kelp forest restoration efforts in this region.

Seasonal dynamics response mechanism of benthic microbial community to artificial reef habitats

Artificial reefs (ARs) have been globally deployed to enhance and restore coastal resource and ecosystems. Microorganisms play an essential role in marine ecosystems, while the knowledge regarding the impact of ARs on microecology is still limited, particularly data concerning the response of benthic microbial community to AR habitats. In this study, the seasonal dynamics of benthic microbial community in AR and adjacent non-artificial reef (NAR) areas surrounding Xiaoshi Island were investigated with high-throughput sequencing technology. The results revealed that the diversity and structure of microbial community between AR and NAR both displayed pronounced seasonal dynamics. There was a greater influence of season factors on microbial communities than that of habitat type. The microbial communities in AR and NAR habitats were characterized by a limited number of abundant taxa (ranging from 5 to 12 ASVs) with high relative abundance (8.35–25.53%) and numerous rare taxa (from 5994 to 12412 ASVs) with low relative abundance (11.91%–24.91%). Proteobacteria, Bacteroidota and Desulfobacterota were the common predominant phyla, with the relative abundances ranging from 50.94% to 76.76%. A total of 52 biomarkers were discovered, with 15, 4, 6, and 27 biomarkers identified in spring, summer, autumn and winter, respectively. Co-occurrence network analysis indicated that AR displayed a more complex interaction pattern and higher susceptibility to external disturbances. Furthermore, the neutral model and βNTI analyses revealed that the assembly of microbial communities in both AR and NAR is significantly influenced by stochastic processes. This study could provide valuable insights into the impact of ARs construction on the benthic ecosystems and would greatly facilitate the development and implementation of the future AR projects.

Outplants of the Threatened Coral Acropora cervicornis Promote Coral Recruitment in a Shallow-Water Coral Reef, Culebra, Puerto Rico

The numerous socioeconomic and ecological challenges that coral reef degradation poses in the Greater Caribbean have led to a surge in restoration efforts. In this context, outplanting nursery-reared coral colonies has emerged as one of the most common strategies used to rejuvenate degraded reefs and reinstate critical ecosystem processes such as coral recruitment. However, the extent to which coral outplanting promotes the recruitment of coral species remains a subject of ongoing debate. This study tested the hypothesis that reintroducing the threatened coral Acropora cervicornis to a degraded coral reef promotes coral recruitment. To test our hypothesis, a series of recruitment quadrats were established in an area populated with A. cervicornis outplants and in a reference location devoid of the coral. To further investigate the relationship between A. cervicornis and coral recruitment, an experiment was implemented in which half of the quadrats in the restored area received a coral outplant, while the other half were left undisturbed. After one year, all coral recruits located within the quadrats were counted and identified. It was found that in the restored area the mean recruit density exceeded that of the reference location by a factor of 2.15. Results also unveiled a positive association between coral recruitment and the presence of A. cervicornis. Specifically, the mean recruit density in quadrats that received an A. cervicornis colony was 2.21 to 4.65-times higher than in the quadrats without coral outplants. This intriguing observation underscores the pivotal role of A. cervicornis in shaping the recruitment dynamics of corals within degraded reef areas, highlighting the potential of active coral outplanting to enhance the resilience of deteriorating coral reef ecosystems.

PEMBERDAYAAN MASYARAKAT BERBASIS EDUWISATA BAWAH AIR PADA WILAYAH KELOLA HUKOM ADAT LAOT (WK-HAL) LHOK LAMTEUNGOH SINERGISME DENGAN USK DALAM MENDUKUNG KAMPUS PTNBH

The Laot Lhok Lamteungoh traditional legal management area has marine natural characteristics consisting of shallow sea areas with coral reef ecosystems in several places, one of which is on Tuan Island, and several other points to the west-south in Peukan Bada District, Aceh Besar Regency. Coral reef areas are resources that must be conserved and provide income for the surrounding communities. PKMBP 2023 seeks an integrated program which will ultimately produce prospective entrepreneurs in the marine or maritime services sector, especially underwater tourism from traditional fishing communities. Service activities have been carried out for approximately 6 months June-November 2023 with socialization activities, FGDs, and a number of trainings and product placements in designated locations. The outputs produced in this activity include IPRs in the form of Copyright certificates, artificial reef prints, artificial reef products, mass media publications, and service journal publications. All targets were achieved as planned.

Estimating and comparing the direct economic contributions of reef fisheries and tourism in the Asia-Pacific

Global estimates of the economic value of coral reefs have been made using benefit transfer and other valuation methods, but it is unclear whether these estimates match actualized values (e.g. market values of reef fish and reef tourism) or how they scale to specific regions. Here we empirically estimated the (actualized) direct economic contribution of fishing and tourism on coral reefs (i.e., direct use values) in the Asia-Pacific (APAC) region, which includes a majority (∼80%) of the global reef area. We found that coral reefs in the APAC region directly contributed $25 billion annually on average over the years 2008–2012 to the region’s economy from fishing and tourism alone. The majority of direct economic contributions (US$19.5 billion) was provided by reef tourism, while the remainder was divided between artisanal (US$2.4 billion) and industrial (US$3.2 billion) fisheries. The average economic productivity of coral reefs was estimated at US$112,000 per square kilometer of coral reef, although there were large deviations between countries in terms of economic utilization of their reefs. Our findings suggest that a highly-cited prior estimate of the global potential value of coral reefs (Cesar et al., 2003) is likely a significant underestimation of actual economic contributions. We discuss some of the implications for reef management. Most notably, our results indicate that the non-consumptive direct use of reef resources provide substantially more economic benefits than consumptive uses.

Effect of fragment size on growth and survival rate of Sarcophyton sp.

The Sarcophyton sp. are very strong and dominant in many coral reef areas. Sarcophyton species are characterized by a distinct sterile stalk, a broad, flared, smooth, mushroom-shaped top, with a wide distribution and dominance in numerous coral reef areas extending from the Red Sea and eastern Africa to the western Pacific Ocean. They are cherished in marine aquariums for their diverse colors and adaptability. However, their excessive exploitation has significantly impacted resources and disrupted the balance of the soft coral biome that inhabits coral reefs. The objective of the current study was to assess the impact of fragment size (0.5 × 0.5; 1.0 × 1.0; 1.5 × 1.5; 2.0 × 2.0, and 2.5 × 2.5 cm) on survival rate, growth rate and time of attachment of coral Sarcophyton sp. in a closed seawater system. Each treatment involved three replicates with 20 cuttings per replicate, and the experimental period was 90 days. The experiment showed that the fragment size did not influence the growth rate of oral disc diameter, pedal disk diameter, and the time attachment of Sarcophyton sp. However, the size of the fragment affects the survival rate, height growth rate, and weight of Sarcophyton sp. colonies. These findings collectively suggest that the initial coral fragment size of 1.5 cm was suitable in laboratory conditions.

Complex drivers of invasive macroalgae boom and bust in Kāne'ohe Bay, Hawai'i

Invasive macroalgae Eucheuma sp. and Kappaphycus spp. (E/K) became a dominant benthic feature in Kāne'ohe Bay throughout the past four decades - occurring on up to 74 ha of reef area and growing up to three meters thick, which prompted intensive management action. In 2013, E/K cover began decreasing at managed and unmanaged sites. This study examined the extent and timing of the E/K decline and evaluated environmental and ecological drivers beyond management contributing to the decline. E/K continued to recede into 2017 and remains sparse in Kāne'ohe Bay today. Increasing over the sampling period, herbivore biomass was negatively correlated with E/K cover, and other significant, non-linear relationships emerged between E/K cover and coral cover, sea surface temperature, wind, and rainfall. This study uncovers several possible mechanisms explaining a boom and bust in E/K abundance, emphasizes the importance of herbivory, and highlights the resilience of coral reefs in Kāne'ohe Bay.

Reduced small-scale structural complexity on sponge-dominated areas of Indo-Pacific coral reefs

Corals provide a complex 3D framework that offers habitat to diverse coral reef fauna. However, future reefs are likely to experience reduced coral abundance. Sponges have been proposed as one potential winner on future coral reefs, but little is known of how they contribute to reef 3D structure. Given the ecological importance of structural complexity, it is critical to understand how changes in the abundance of structure-building organisms will affect the three-dimensional properties of coral reefs. To investigate the potentially important functional role of coral reef sponges as providers of structural complexity, we compared the structural complexity of coral- and sponge-dominated areas of an Indonesian coral reef, using 3D photogrammetry at a 4 m2 spatial scale. Structural complexity of 31 4 m2 quadrats was expressed as rugosity indicating reef contour complexity (R), vector dispersion indicating heterogeneity of angles between reef surfaces (1/k), and fractal dimension indicating geometrical complexity at five different spatial scales between 1 and 120 cm (D1–5). Quadrats were identified as high- or low-complexity using hierarchical clustering based on the complexity metrics. At high structural complexity, coral- and sponge-dominated quadrats were similar in terms of R and 1/k. However, smallest-scale refuge spaces (1–5 cm) were more abundant in coral-dominated quadrats, whereas larger scale refuge spaces (30–60 cm) were more abundant in sponge-dominated quadrats. Branching and massive corals contributed the most to structural complexity in coral-dominated quadrats, and barrel sponges in sponge-dominated quadrats. We show that smaller-scale refugia (1–5 cm) are reduced on sponge-dominated reefs at the spatial scale considered here (4 m2), with potential negative implications for smaller reef fauna.

Living on the Coast in Harmony with Natural Processes

The coastal zone is a fascinating place that comprises the interface between sea and land. This interface, which is both very dynamic and sensitive, has been affected by strong urban and industrial pressures, and an increase in both traffic and recreational uses, leading to the deterioration of natural habitats and the growing instability of residential areas. Added to this disruption is ongoing climate change, which will lead to rising sea levels and increased wave action. Another problem we are increasingly concerned about is ocean pollution, which has been one of the main causes of threats to deep-water coral reef areas. The main sources of pollution include oil spills and offshore oil drilling. The effects of pollution caused by oil spills can not only seriously affect the global environmental balance of our planet but can also, on a different scale, seriously affect the economy of countries whose main resources depend heavily on the sea. Wave energy has the potential to alleviate the world's dependence on depleting fossil energy resources. With regard to coastal protection, the development of ecological solutions to preserve ecosystems and address coastal processes as an alternative to traditional coastal protection structures (seawalls, groins and breakwaters) is becoming increasingly important. These structures, generally referred to as passive measures, are usually built to alter the effects of sea waves, currents and the movement of sand along the coastline, with the aim of protecting beaches, ports and harbors. The concerns outlined are critically addressed throughout this review article. All of them are highly relevant today and, as demonstrated throughout this article, are expected to grow even more and with much more pronounced consequences starting from the middle of the current century.

Towards enhancing the durability of seawater coral aggregate concrete under drying-wetting cycles with slag-based geopolymers

The utilization of marine resources (e.g. seawater, coral sand or sea sand, and coral coarse aggregate) for the preparation of seawater coral aggregate concrete (CAC) in reef or island areas contributes to the decreased construction periods and costs for offshore projects. Nevertheless, the high porosity and brittleness of coral aggregates affect the mechanical characteristics and durability of CAC and its structures. In this study, slag-based geopolymers were utilized as substitutes for ordinary Portland cement for preparing geopolymer-based seawater coral aggregate concrete (GPCAC). The mechanical properties of GPCAC and CAC under seawater drying-wetting cycles were explored, and their degradation mechanisms in terms of mechanical characteristics were estimated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results pointed out that GPCAC exhibited better resistance to seawater attack than CAC after being subjected to seawater drying-wetting cycle environments. When subjected to 60 °C seawater corrosion in drying-wetting cycles for 12 months, the cubic compressive strength, elastic modulus, and axial compressive strength of CAC degraded by 14.4%, 13.0%, and 16.9%, respectively, while those of GPCAC only reduced by 5.4%, 11.8%, and 3.1%, respectively. It is concluded that the excellent pore structure, dense microstructure, and stabilized hydration products of geopolymers are responsible for their superior resistance to seawater attack compared to cement-based materials.

Environment security perspective to coral reef protection and management: a comparative study of India and Australia

ABSTRACT Coral reefs are home to a variety of flora and fauna and carry huge potential in serving the national interests of the coastal states that host them. The research uses an environment security theoretical framework to understand how it is the state’s prerogative to protect coral reefs to protect its own national interest. Active state involvement in the protection of reef ecosystems is the most practical option in the face of global warming and climate change, with limited consensus on this environmental problem within the international community. The research explains how a state can actively engage in coral reef management by focusing on pollution control related to tourist activity in the reef areas. A comparative analysis of coral reef management by India and Australia shows how active coral reef management can help protect reef structures, giving maximum return benefits to the state.

High-resolution optical remote sensing geomorphological mapping of coral reef: Supporting conservation and management of marine protected áreas

Brazilian corals are unique ecosystems with high endemism and low functional redundancy. Hence, mapping its geomorphology is an important step to inferring analyzes on benthic habitats. We observe several difficulties during this mapping of coastal areas by remote sensing and a lack of fine-scale depth data for reef areas in Brazil. The present study aims to present the bathymetry extracted by satellite imagery in murky waters using a mosaic of Sentinel-2 images in Google Earth Engine (GEE) calibrated with field samples. We used the satellite extracted DBM to map the bottom geomorphology through BTM (Benthic Terrain Modeler). We then present the first detailed geomorphological map for the largest marine coastal protected area in Brazil- MPA Costa dos Corais. The geomorphological raster was differentiated into seven classes: Flat Plains, Depressions, Gentle Slopes, Slopes, Terrestrial Reef Flat, Reef Flat, and Crest. Altogether, we estimate >275 km2 of area representing reef structures (coral reef or beachrocks), or about 48% of the total MPA area. Mapping coral reefs can contribute to conservation, particularly in selecting areas for in situ monitoring activities and in prioritizing the application of remedial actions in the event of environmental disasters or threats to coral health, such as oil spills and bleaching episodes. Our findings encourage the applicability of these methodologies in other reef areas and collaborate for the management and monitoring of marine protected areas. In addition, all mapping is available online for any user.

Distinct coral environments shape the dynamic of planktonic Vibrio spp.

BackgroundCoral reefs are one of the most biodiverse and productive ecosystems, providing habitat for a vast of species. Reef-building scleractinian corals with a symbiotic microbiome, including bacteria, archaea, viruses and eukaryotic microbes, are referred to coral holobionts. Among them, coral diseases, mainly caused by Vibrio spp., have significantly contributed to the loss of coral cover and diversity. Habitat filtering across the globe has led to a variety structure of marine bacterial communities. Coral species, quantity and characteristics are significant differences between the Xisha Islands and Daya Bay (Guangdong Province). Thus, the Vibrio communities may be distinct between coral rich and poor areas.ResultsThrough comparison of Vibrio dynamics between coral-rich (Xisha Islands) and coral-poor (Daya Bay) locations, we uncovered differences in Vibrio abundance, diversity, community composition and assembly mechanisms associated with corals. The higher abundance of Vibrio in coral rich areas may indicate a strong interaction between vibrios and corals. V. campbellii, Paraphotobacterium marinum and V. caribbeanicus were widely distributed in both coral rich and poor areas, likely indicating weak species specificity in the coral-stimulated growth of Vibrio. Random-forest prediction revealed Vibrio species and Photobacterium species as potential microbial indicators in the coral rich and coral poor areas, respectively. Ecological drift rather than selection governed the Vibrio community assembly in the Xisha Islands. Comparatively, homogenizing selection was more important for the Daya Bay community, which may reflect a role of habitat filtration.ConclusionThis study revealed the different distribution pattern and assembly mechanism of Vibrio spp. between coral rich and poor areas, providing the background data for the research of Vibrio community in coral reef areas and may help the protection of coral reef at the biological level. The main reasons for the difference were different number and species of corals, environmental (e.g., temperature) and spatial factors. It reflected the strong interaction between Vibrio and corals, and provided a new perspective for the investigation of Vibrio in coral reef ecosystem.