Reef Condition Research Articles

Distribution and Condition of Hard Coral (Scleractinian) Species in the Waters of Airlouw and Seri Village

The waters of Air Louw and Seri Village are located in the southern part of Ambon Island and are classified as high in human activity due to their high biodiversity. In Airlouw waters, beach and marine tourism activities are part of the life of the local community, while Seri waters tend to be high in fishing activity. This condition can lead to the degradation of coral reef ecosystems, and we need a good database on the types of corals, their distribution, and the conditions of coral reef ecosystems. Data was collected by combining the Line Intercept Transect (LIT) and Photo Transect methods and carried out at 3 and 10 meters deep. The distribution of hard coral species at the two study sites resulted in 87 species of hard coral (Scleractinia) from 27 genera, 12 families. Fifty-seven scleractinian species were found at the intersection of the transect lines and 30 other species around the transect lines. In general, the condition of coral reefs at Airlouw station is classified as Medium (28. 25%), with the dominant growth forms at a depth of 3 m and 10 m being Acropora Branching and Coral Encrusting. At the Seri station, the condition of coral reefs is also categorized as moderate, namely 38. 25%, with the dominant growth forms, namely Coral Massive and Coral Branching. The condition of the coral reefs in both locations needs attention to manage the ecosystem further.

Applying coral breeding to reef restoration: best practices, knowledge gaps, and priority actions in a rapidly‐evolving field

Reversing coral reef decline requires reducing environmental threats while actively restoring reef ecological structure and function. A promising restoration approach uses coral breeding to boost natural recruitment and repopulate reefs with genetically diverse coral communities. Recent advances in predicting spawning, capturing spawn, culturing larvae, and rearing settlers have enabled the successful propagation, settlement, and outplanting of coral offspring in all of the world's major reef regions. Nevertheless, breeding efforts frequently yield low survival, reflecting the type III survivorship curve of corals and poor condition of most reefs targeted for restoration. Furthermore, coral breeding programs are still limited in spatial scale and species diversity. Here, we highlight four priority areas for research and cooperative innovation to increase the effectiveness and scale of coral breeding in restoration: (1) expanding the number of restoration sites and species, (2) improving broodstock selection to maximize the genetic diversity and adaptive capacity of restored populations, (3) enhancing culture conditions to improve offspring health before and after outplanting, and (4) scaling up infrastructure and technologies for large‐scale coral breeding and restoration. Prioritizing efforts in these four areas will enable practitioners to address reef decline at relevant ecological scales, re‐establish self‐sustaining coral populations, and ensure the long‐term success of restoration interventions. Overall, we aim to guide the coral restoration community toward actions and opportunities that can yield rapid technical advances in larval rearing and coral breeding, foster interdisciplinary collaborations, and ultimately achieve the ecological restoration of coral reefs.

Elemental Fractionation in Sabellariidae (Polychaeta) Biocement and Comparison with Seawater Pattern: A New Environmental Proxy in a High-Biodiversity Ecosystem?

The polychaete worm Sabellaria alveolata builds shallow-water aggregates of tubes by agglutinating sands using a secreted glue. Sabellarid bioconstructions represent fragile and dynamic habitats that host numerous associated organisms, playing a key ecological role. A two-year study on bioconstructions from three Sicilian sites (Simeto, Portopalo, and Falconara) investigated the balance between reef status and environmental parameters through a geochemical comparison of biocement tube portions and the surrounding waters. Water pollution by heavy metals, which is monitored in marine waters, is a result of river, domestic, and industrial discharges. The major constituents from the biocements of the three sites showed concentrations comparable to those in the seawater, while trace elements (Cr, Ni, Cu, Zn, and As) showed concentrations significantly higher than the mean seawater composition. These similar trends confirm a close dependence between the presence of trace elements (metals) in the seawater and the subsequent bioaccumulation in the biocement produced by the worm. The results also showed that Ca and Mg are fractionated by biocement independent of their water concentrations, in contrast to the trace elements. Further studies addressing the biomineralization processes and the relative fractionation of trace elements in Sabellaria biocement will allow it to be validated as a valuable proxy for short- and long-term environmental studies.

Coral reef degradation at an atoll of the Western Colombian Caribbean.

Coral reef decline is an issue of concern around the globe. Remote and uninhabited coral areas are not exempt from facing changes in species composition and functionality due to global drivers. Quitasueño is a remote atoll within the Seaflower Biosphere Reserve, in the Southwestern Caribbean Sea. To evaluate the current status of the coral reefs in Quitasueño we sampled 120 stations through Rapid Ecological Assessment and evaluated four stations through Planar Point Intercept to compare the current percent cover of benthic groups with previous studies in the area. We found pronounced changes in coral and macroalgae covers in time, and great conspicuousness of multiple conditions of deterioration along Quitasueño, including diseases, coral predation, and aggression and invasion of coral colonies by macroalgae and sponges. The reef ecosystem seems to be facing a phase shift, in which the benthic cover previously dominated by hard corals is currently dominated by fleshy macroalgae. It is essential to evaluate the possible drivers of the extent of degradation of Quitasueño to understand the process of deterioration and mitigate the impacts.

Drone lidar-derived surface complexity metrics as indicators of intertidal oyster reef condition

Eastern oysters (Crassostrea virginica) generate structurally complex reef systems that offer diverse ecosystem services. However, there is limited understanding of how reef structure translates into reef condition. This knowledge gap might be better addressed if oyster reef structure could be more rapidly assessed. Conventional in situ monitoring techniques are often time-intensive, invasive, and do not provide spatially continuous information on the reef structure. Unoccupied Aircraft Systems (UAS), commonly referred to as drones, equipped with optical sensors can rapidly and non-invasively map intertidal oyster reef surfaces. We demonstrate how a digital surface model from UAS-based light detection and ranging (lidar) can enable very high-resolution characterization and monitoring of intertidal oyster reef surface morphology. Generalized linear models (GLMs) identified relationships between in situ live oyster counts and surface complexity metrics derived from digital surface models produced from lidar point clouds. Statistically significant relationships between surface complexity metrics (e.g., gray level co-occurrence features, volume to area ratio, skewness of elevation) and live oyster counts suggest that surface complexity provides useful proxies for reef condition. Advancing the application of remote sensing to intertidal oyster reefs can help identify reefs that are prone to degradation and inform conservation and restoration strategies.

Implementing a transformative approach to the coral reefs' recovery phase

Mitigation and rehabilitation are responses to climate change and human misuse. However, many regions worldwide still lose coral reefs even after implementing these responses. We chose Hurghada city, on the Red Sea, and Weizhou island, on the South China Sea, as sample regions to assess their various modes of coral community structure loss against the combined climatic and human impact drivers that led to this shift. Despite the former being considered a regional coral refuge, while the latter was limited, both regions have previously intervened with coral restoration. We found that even after three decades of impact cessation by forcing laws, most coral reef states are still declining (about a third and a half in both cities), have not harnessed the existing crowded larval density, and are unrecovered. Such findings imply that the combined impacts will persist, necessitating a broad connectivity analysis that enables a suitable intervention (hybrid solutions hypothesis).Each state of coral categories was connected to certain combined stressor factors using our broad connectivity analysis to grasp the extent and relative contribution of coral community shift since our data obtained from comparable sites were widely varied. Moreover, destructive emerged changes have transformed the coral community structure under the forced adaptation scenario of the community structure, boosting those who can resist at the expense of others.To prove our hypothesis, we used the connectivity findings in determining the optimal technique and spots for coral rehabilitation around the two cities. We then compared our findings with the outcomes of two other existing adjacent restoration projects related to other endeavors. Our hybrid approach harvested coral larvae that had been wasted in both cities. Thus, hybrid solutions are globally required for such cases, and proper early interventions are needed to maintain the genotype power to boost coral adaptability throw global ecological settings.

Legacy effects of anthropogenic disturbances modulate dynamics in the world's coral reefs.

Rapidly changing conditions alter disturbance patterns, highlighting the need to better understand how the transition from pulse disturbances to more persistent stress will impact ecosystem dynamics. We conducted a global analysis of the impacts of 11 types of disturbances on reef integrity using the rate of change of coral cover as a measure of damage. Then, we evaluated how the magnitude of the damage due to thermal stress, cyclones, and diseases varied among tropical Atlantic and Indo-Pacific reefs and whether the cumulative impact of thermal stress and cyclones was able to modulate the responses of reefs to future events. We found that reef damage largely depends on the condition of a reef before a disturbance, disturbance intensity, and biogeographic region, regardless of the type of disturbance. Changes in coral cover after thermal stress events were largely influenced by the cumulative stress of past disturbances and did not depend on disturbance intensity or initial coral cover, which suggests that an ecological memory is present within coral communities. In contrast, the effect of cyclones (and likely other physical impacts) was primarily modulated by the initial reef condition and did not appear to be influenced by previous impacts. Our findings also underscore that coral reefs can recover if stressful conditions decrease, yet the lack of action to reduce anthropogenic impacts and greenhouse gas emissions continues to trigger reef degradation. We uphold that evidence-based strategies can guide managers to make better decisions to prepare for future disturbances.

Toward a New Era of Coral Reef Monitoring.

Coral reefs host some of the highest concentrations of biodiversity and economic value in the oceans, yet these ecosystems are under threat due to climate change and other human impacts. Reef monitoring is routinely used to help prioritize reefs for conservation and evaluate the success of intervention efforts. Reef status and health are most frequently characterized using diver-based surveys, but the inherent limitations of these methods mean there is a growing need for advanced, standardized, and automated reef techniques that capture the complex nature of the ecosystem. Here we draw on experiences from our own interdisciplinary research programs to describe advances in in situ diver-based and autonomous reef monitoring. We present our vision for integrating interdisciplinary measurements for select "case-study" reefs worldwide and for learning patterns within the biological, physical, and chemical reef components and their interactions. Ultimately, these efforts could support the development of a scalable and standardized suite of sensors that capture and relay key data to assist in categorizing reef health. This framework has the potential to provide stakeholders with the information necessary to assess reef health during an unprecedented time of reef change as well as restoration and intervention activities.

Oceanographic conditions and sedimentation in the Kawal river Bintan Island and impact on the prevalence of coral disease

In river mouths and coastal areas, sediment carried by water flows often clogs the estuaries and causes silting lagoons, impacting the prevalence of coral disease. Ten sediment traps were installed in the river 25 cm from the bottom to record the data for 21 days in Kawal River. Oceanographic and current flow data were collected using CTD and a Current meter using the Eulerian method with a depth interval installation of 0.25 to 0.75 from the river surface. The Underwater Photo Transect (UPT) is a method to analyze the condition of coral reefs and coral disease. CTD the temperature data ranged from 30.471 ± 0.001 °C to 31,609. ±0.001°C, salinity value ranges from 29.643 ± 0.001 PSU to 32.336 ± 0.001 PSU and current flow ranged from 0.063 ± 0.010 m/s to 0.281 ± 0.012 m/s. The results of the sediment trap, the dry weight value of sediment deposited in the sediment traps ranges from 0.89 grams, and for the largest of 48.45 grams, the turbidity ranged from 0.77 NTU to 4.22 NTU. The prevalence of coral disease was 56.40%. The conclusion indicates that excessive sedimentation rates at river mouths can result in a high incidence of coral disease.

Diversity of Microbial Communities Associated with Epilithic Macroalgae in Different Coral Reef Conditions and Damselfish Territories of the Gulf of Thailand

Reef degradation and algae-farming fish alter the structures and compositions of coral-algal-microbial communities. We collected epilithic macroalgae in different reef conditions and damselfish territories. The microbial communities were characterized by subjecting the V3-V4 hypervariable region of the 16S rRNA gene to amplicon sequencing. Metagenomic analysis revealed 2 domains, 51 phyla, 112 orders, and 238 families and the dominance of Proteobacteria and Bacteroidota in both fair and degraded reefs inside and outside territories. Chloroflexi on the degraded reef was dominant and its proportion was almost two and a half times compared to the fair reef, whereas Cyanobacteria was low on the degraded reef. Bacteroidota was dominant on the fair reef, whereas Actinobacteriota was scarce on this reef. For the damselfish territories, Chloroflexi was dominant inside the territory, whereas Bacteroidetes were found outside the territory. Differences in the microbial species diversity and richness were not apparent between all sites; however, species evenness was higher on the degraded reef condition and lower outside the territory. Important potential pathogens of reef organisms, such as Vibrio, Photobacterium, and Phormidium, were found on the degraded reef areas inside the damselfish territory. The farming behaviors of damselfish influenced microbial communities by changing the epilithic algal matrix that harbors many microbial communities. This study provides useful information on microbial biota in coral reef habitats which is further applicable to reef conservation and coastal management.

Zoning Effectiveness of Marine Nature Reserve Conservation Areas (SAP) Raja Ampat Islands Against Coral Reef Protection

Raja Ampat Islands have been designated as a Marine Nature Reserve (SAP) since 2014, and community activity in these waters remains high for tourism, fishing and sea transportation activities. All of these activities have the potential to suppress the condition of the coral reefs there. Therefore, it is necessary to evaluate the effectiveness of zoning in terms of social and ecological indicators. This research was conducted using the Underwater Visual Census (UVC) method for coral reef fish and the Underwater Photo Transect (UPT) method for coral cover at a depth of 5-7 m. The set critical threshold value is used to evaluate the success of the zoning taken by interviewing fishermen. The results of the study found that the core zone had unfavorable conditions compared to the other zones. Based on an analysis of ecological indicators, the percentage of coral cover was only 20.9% and an abundance of reef fish of 28 ind/m2. The results of the social analysis of the community, Waisilip Village has the lowest level of compliance with a value of 56%. Meanwhile, 77% of respondents agree with zoning, and only 19% understand the zoning management system. The management of SAP Raja Ampat can be said to be effective by taking into the ecological and social indicators of the community. Increase in the percentage of coral cover in the core zone (0.2%), utilization zone (3.9%), sustainable fisheries zone (0.8%) and cultivation zone (5.7%). Most fishermen have good insight and concern for coral reefs and other aquatic resources.

Differential responses of effective quantum yield to acute thermal stress in scleractinian corals including pre- and post-transplanted Acropora muricata

Abstract. Jeetun S, Ricot M, Taleb-Hossenkhan N, Kaullysing D, Flot J-F, Bhagooli R. 2023. Differential responses of effective quantum yield to acute thermal stress in scleractinian corals including pre- and post-transplanted Acropora muricata. Indo Pac J Ocean Life 6: 54-63. Global climate change has had a serious impact on the health status of coral reefs and has led to the use of active reef restoration measures to remediate the decline in coral cover and assist in the recovery of depleted coral populations. This study aimed to assess the thermal photo-physiological responses of Acropora muricata pre- and post-transplantation from reef, lagoon, and nearshore stations to the experimental nearshore station and of four other non-transplanted coral species, namely, Acropora cytherea, Galaxea fascicularis, Pocillopora damicornis and Lithophyllon repanda from the reef. A visual assessment of dinoflagellate symbiont loss was conducted during summer bleaching events in 2011, 2016, and 2019 for A. muricata at the three stations, nearshore, lagoon, and reef, and for the other four corals at the reefs of Belle Mare (BM), Mauritius. The 2016 bleaching event appeared to be more severe for P. damicornis and L. repanda. A first experiment was carried out using pre-transplanted A. muricata from the reef, lagoon, and nearshore, respectively, in 2012, and a second one was conducted with post-transplanted A. muricata from the nearshore station in 2020, and A. cytherea, G. fascicularis, P. damicornis and L. repanda from the reef in both 2012 and 2020. The coral specimens were incubated at 28°C, 30°C, and 32°C for 3hrs. The results showed an enhanced photo-physiological thermo-tolerance through the measurement of the effective quantum yield of A. muricata following transplantation from the reef and lagoon to the nearshore station. Significantly different photo-physiological responses of the other four corals occurring on the reef were also reported between 2012 and 2020. These findings suggest that the nearshore transplanted A. muricata may have acclimatized, leading to enhanced thermo-tolerance when exposed to 30°C and A. cytherea among the test corals may have improved its thermo-tolerance at 30°C and 32°C possibly following several bleaching events. Further studies using longer experimental exposures and involving the symbiont species, antioxidant responses, symbiont cell density, and chlorophyll content along with coral genetics may shed light on possible mechanisms for such enhanced thermo-tolerance.

Condition of Coral Reefs in the Waters of Kalasey Satu Village, Minahasa Regency, North Sulawesi

Condition of Coral Reefs in the Waters of Kalasey Satu Village, Minahasa Regency, North Sulawesi

Macroalgal cover on coral reefs: Spatial and environmental predictors, and decadal trends in the Great Barrier Reef.

Macroalgae are an important component of coral reef ecosystems. We identified spatial patterns, environmental drivers and long-term trends of total cover of upright fleshy and calcareous coral reef inhabiting macroalgae in the Great Barrier Reef. The spatial study comprised of one-off surveys of 1257 sites (latitude 11-24°S, coastal to offshore, 0-18 m depth), while the temporal trends analysis was based on 26 years of long-term monitoring data from 93 reefs. Environmental predictors were obtained from in situ data and from the coupled hydrodynamic-biochemical model eReefs. Macroalgae dominated the benthos (≥50% cover) on at least one site of 40.4% of surveyed inshore reefs. Spatially, macroalgal cover increased steeply towards the coast, with latitude away from the equator, and towards shallow (≤3 m) depth. Environmental conditions associated with macroalgal dominance were: high tidal range, wave exposure and irradiance, and low aragonite saturation state, Secchi depth, total alkalinity and temperature. Evidence of space competition between macroalgal cover and hard coral cover was restricted to shallow inshore sites. Temporally, macroalgal cover on inshore and mid-shelf reefs showed some fluctuations, but unlike hard corals they showed no systematic trends. Our extensive empirical data may serve to parameterize ecosystem models, and to refine reef condition indices based on macroalgal data for Pacific coral reefs.

Growth and Survival Performance of Transplanted Acropora Fragment in a Nursery Floating

The status of the condition of Indonesia's coral reefs is mostly categorized as moderate and damaged. Relatively inexpensive and easy-to-implement rehabilitation methods need to involve the participation of many stakeholders. The method of transplanting coral fragments by hanging (floating) from the surface of the water will be more efficient, especially in their maintenance. This study aims to investigate the most suitable water depth to support the growth and survival of the transplanted coral fragments. A non-factorial Completely Randomized Design (CRD) field experiment with 3 (three) treatments, namely different seedbed depths, 2 m, 4 m, and 6 m respectively. Each treatment was repeated 4 (four) times. The results of analysis of variance showed that the absolute growth rate of coral fragments transplanted by hanging from the surface of the water at different depths (2 m, 4 m, 6 m) showed no significant difference (P-value > 0.05). This shows that the environmental conditions at a depth of 2 m-6 m are relatively the same, so that on average all coral fragments have almost the same growth potential (0.29 cm/month). Meanwhile, the survival rate obtained is also very high (> 90%). These results confirm that the method of transplanting corals by hanging from the sea surface is technically feasible and gives good results. This will help many stakeholders to be involved in optimizing the economic potential value of coral reefs, as well as increasing participation in the conservation and rehabilitation of coral reefs.

Oyster reef habitat depends on environmental conditions and management across large spatial scales

Oyster reefs provide important services to ecosystems and people, with many of these benefits depending on structurally complex reef habitat. Despite the key role of oyster reef habitat, we have yet to understand natural and anthropogenic drivers of subtidal reef habitat over large spatial scales (>200 km). Chesapeake Bay (USA) offers a valuable system to explore how salinity, restoration, and harvest compare in their influence on subtidal oyster reef habitat because of its broad environmental gradient and mosaic of management types. We applied a remote rapid assessment method using underwater photographs to survey oyster reef habitat in 12 tributaries and scored images based on estimates of oyster percent cover and vertical relief. The broad spatial scale (~215 km) of the survey includes reefs that vary in management status and salinity. Bay-wide habitat scores were higher with greater estimated oyster percent cover and vertical relief on unharvested and restored reefs. Salinity also contributed to Chesapeake Bay-wide patterns, but the relationship depended on harvest status. In assessing the separate management jurisdictions, scores were higher on restored reefs in Maryland and on anthropogenic (i.e. artificially supplemented) reefs in Virginia. A time series over 4 yr in 2 Maryland tributaries showed high and persistent habitat scores in restored sanctuaries, but habitat scores increased for all reefs over time. The results highlight the combined roles of the natural environment and management decisions on oyster reef habitat. The effect of harvest and restoration on habitat underscores the importance of local management decisions in determining the future status of oyster reefs.

Using Drone Imagery to Map Intertidal Oyster Reefs along Florida’s Gulf of Mexico Coast

Eastern oyster (Crassostrea virginica) reefs offer vital ecosystem services and support economically and culturally important fisheries. However, environmental and anthropogenic stressors have led to significant decline in oyster reef coverage globally and locally in places like the Suwannee Sound in Florida, USA. Current monitoring methods are insufficient for timely and accurate assessment of oyster resources in the region. Here we demonstrate how drone imagery can be used to delineate intertidal oyster reef coverage rapidly and reliably. The high spatial resolution offered by drone imagery enables accurate delineations. We use a segmentation algorithm to delineate reefs, which produces consistently detailed outlines that are more representative of reef morphology than manual delineations. In total, 1,394 reefs were delineated, which corresponds with 497, 670 m2 of reef area. Of the delineated reefs, 236 (17%) were newly mapped, aligning with 19,848 m2 of newly mapped intertidal oyster reef habitat. The overlapping drone imagery also enabled the production of digital surface models, which were used to calculate volume to area ratio as an indicator of reef condition. These delineations and features serve as accurate baseline data that can be compared to future surveys to monitor how reefs are changing over time in the Suwannee Sound. These methods can also be expanded to other geographical areas and can aid in identifying early signs of decline in oyster reefs.

A dataset of benthic material distribution of coastal coral reefs in Hainan during 2018–2020

Based on the Sentinel-2 high resolution remote sensing image data, we adopted the object-oriented multi-scale segmentation technology and the nearest neighbor algorithm to classify benthic materials of offshore coral reefs in Wenchang City, Danzhou City, Sanya City of Hainan Province during 2018-2020. Then, combining with the remote sensing images of Gaofen-2 satellite and field validation data we verified the accuracy of the classification results. The dataset can be used to analyze the temporal and spatial changes of benthic materials in coastal coral reefs and assess the health status of coral reefs. Moreover, it can serve as a data foundation for the management and protection of coral reefs in Hainan Island.

Impact of Coral Bleaching on Coral Reef Fishes in Sekotong Bay, West Lombok Regency

Coral reef fish is one of the main components making up the ecosystem of coral reefs. There is a strong mutual dependence between reef-forming corals and fish that inhabit coral reefs. Various fish species use coral as a food source and habitat. This article describes the impact of coral bleaching on the diversity, density, and biomass of coral reef fish in the waters of Sekotong Bay, West Lombok. Underwater visual census (UVC) methods are used to obtain data on species, the number of individuals per species, and fish size at transect length 70 meters and width 5 meters. Simple linear regression analysis that is used to assess the impact of coral bleaching on the condition of coral reef fish shows that coral bleaching affects the diversity and density of reef fish. This analysis also showed that coral bleaching affected herbivorous fish biomass but not carnivorous fish. This study concludes that the degradation of coral fish in the Sekotong Bay of West Lombok occurs due to various factors, especially the declining health conditions of coral reefs

Study of Carrying Capacity and Development Strategy of Coral Garden Based Ecoedutourism in Cemara Besar Island, Karimunjawa National Park, Jepara, Central Java

Cemara Besar Island, Karimunjawa National Park, is an important tourist destination in the province of Central Java due to its beautiful beaches and coral reefs. The purpose of this study was to see the area carrying capacity for ecoedutourism based on coral gardens in Cemara Besar Island, analyze development strategies, and find out the recommended spots. The carrying capacity of the area is calculated using three considerations: Physical Carrying Capacity (PCC), Real Carrying Capacity (RCC) and Effective Carrying Capacity (ECC). The results, in PCC>RCC>ECC format, are 2472>97>42 people per day in the utilization zone while 670 > 30 > 15 people per day in the protection zone. Using SWOT analysis, the analysis of tourism development strategies produced 15 alternative regional development strategies, with the top strategic priority being “the development of the concept of coral garden tourism”. Observations on five recommended spots were carried out using a time swimming method, by snorkeling for 10 minutes in an area of 10 m × 10 m per point. The two recommended points in the northern east side of the island, points B and D, are designated as the highly recommended points to apply the concept of ecoedutourism based on coral garden because in these two points the condition of coral reefs is not too good and requires restoration.