Dead Coral Research Articles

Coral reef rehabilitation sites selection based on seasonal waves and environmental quality as ecological supporting system on Mandangin Island

The natural rehabilitation process in the coral reef ecosystem requires a genuinely suitable environment minimum disturbance marine threats. Baby coral is a fragile organism used to increase the quantity of coral reef cover during rehabilitating coral reef ecosystems— determination for coral rehabilitation sites with minimum marine threats for increasing success. The destructive fishing around Mandangin Island induces a declination of live coral coverage. On average, live coral cover around Mandangin Islands is under 10 percent. However, there is high coverage of dead coral that is still functional as a shelter for reef fish in the southeast Mandangin Islands. The dead reef structure can still prevent the coastal area from high seasonal waves hitting the southeast coast from July to September. A large-scale reef structure makes it difficult for small-scale fishers to disturb the rehabilitation area. Water quality indicated that east-to-south coastal areas are considered coral rehabilitation sites. Unique water quality affects the coral adaptation on Mandangin Island. East to Southeast coastal areas are considered coral reef rehabilitation locations based on coral reef cover, water quality, and seasonal waves. The limitation of the coral fragment from Mandangin Islands became the most concerned variable for rehabilitation and reef-structure design to anticipate the seasonal waves.

Branching Lithophyllum Coralline Algae: Dominant Reef Builders on Herbivory-Depressed Tropical Reefs after High Coral Mortality

A unique shift in benthic community composition, where scleractinian corals are replaced by coralline algae, has been observed on coral reefs in Guam in the western Pacific. Guam’s reefs have been subjected to intense fishing pressure and impaired water quality for decades. Since 2013, heat stress has emerged as an additional major threat to the island’s coral reefs. After a severe coral bleaching and mortality event in 2017, branching coralline algae of the genus Lithophyllum rapidly overgrew dead coral skeletons of the ecosystem engineer Acropora abrotanoides and have since become major components of forereef communities over a broad depth range. By now, the persistence of increased Lithophyllum cover meets the temporal criterium of phase shifts, but accurate estimates on the degree of dominance over appropriate spatial scales are lacking due to the absence of reliable baseline data. The ecological impacts of coral reef transitions towards increased coralline cover are unclear. Whereas carbonate budgets and reef growth could remain positive in the long term, the downstream effect of changes in structural complexity, (micro)habitat diversity, and benthic community composition on ecological processes and reef-associated faunal assemblages is unknown.

Wooden traps can replace coral stone traps harvesting the wild lobster seed in mitigating the negative impact on the marine environment

Lobster seacage aquaculture has a significant social-economic contribution to many coastal communities throughout the central provinces of Vietnam. One of the issues of lobster aquaculture is that the industry entirely relies on the wild juvenile lobster (lobster seed) captured using traps made of coral stones, which affects the coastal ecology and environment. The present study was carried out to compare the catch efficiency of traps made of round timber poles (wooden trap) with conventional dead corals (coral stones) during the juvenile lobster fishing season in 2019 in the coastal area of Nha Trang city, Vietnam. Results showed that experimental wooden traps maintained the conventional catch rate level, with a significant proportion of Panulirus ornatus caught at larger carapace length than those caught by the coral stone traps. Our findings show the biological and environmental benefits of using alternative fishing methods would eliminate collecting coral stones to make lobster seed traps and contribute to coastal protection while maintaining the fishing operation and seed supplies for the lobster seacage farmers.

Quantifying the Loss of Coral from a Bleaching Event Using Underwater Photogrammetry and AI-Assisted Image Segmentation

Detecting the impacts of natural and anthropogenic disturbances that cause declines in organisms or changes in community composition has long been a focus of ecology. However, a tradeoff often exists between the spatial extent over which relevant data can be collected, and the resolution of those data. Recent advances in underwater photogrammetry, as well as computer vision and machine learning tools that employ artificial intelligence (AI), offer potential solutions with which to resolve this tradeoff. Here, we coupled a rigorous photogrammetric survey method with novel AI-assisted image segmentation software in order to quantify the impact of a coral bleaching event on a tropical reef, both at an ecologically meaningful spatial scale and with high spatial resolution. In addition to outlining our workflow, we highlight three key results: (1) dramatic changes in the three-dimensional surface areas of live and dead coral, as well as the ratio of live to dead colonies before and after bleaching; (2) a size-dependent pattern of mortality in bleached corals, where the largest corals were disproportionately affected, and (3) a significantly greater decline in the surface area of live coral, as revealed by our approximation of the 3D shape compared to the more standard planar area (2D) approach. The technique of photogrammetry allows us to turn 2D images into approximate 3D models in a flexible and efficient way. Increasing the resolution, accuracy, spatial extent, and efficiency with which we can quantify effects of disturbances will improve our ability to understand the ecological consequences that cascade from small to large scales, as well as allow more informed decisions to be made regarding the mitigation of undesired impacts.

La Niña‐related coral death triggers biodiversity loss of associated communities in the Galápagos

AbstractDuring a cold La Niña period (August 2007–January 2008) in the central Galápagos archipelago, 70% of Pocillopora branching corals were severely bleached across three long‐term monitoring sites, affording an opportunity to examine its impact on the persistence of these corals and their associated community of fish and mobile macroinvertebrates. Using a time series empirical approach, we tagged and tracked the fate of 96 coral heads and their associates. When surveyed in July 2008, recovered live and dead corals that were previously severely bleached supported similar levels of species richness (randomized observed and estimated Chao 1). By contrast, richness on the surviving live corals remained fairly stable, while Chao 1 estimated richness on dead corals underwent a nearly 50% increase between July and January 2009, thereafter declining to 50% of originally surveyed richness by February 2010. This nonlinear change in species richness was largely due to an influx and decline in opportunistic generalists including pencil urchin bioeroders, gastropod snails, and hermit crabs that colonized dead corals and fed on sessile invertebrates and algae that had initially recruited to dead and undefended coral substrate. Thus, dead corals retained high overall species richness until live corals had recovered, after which richness declined as dead corals eroded and disintegrated (July 2011). Live corals attracted a less speciose but stable assemblage of mutualistic xanthid crabs and fishes that increased in abundance over time with the recovery and growth of live coral tissue. Overall, coral status (live/dead), planar area and maximum branch length predicted the number of species associated with each colony. The delayed diversity loss of associated species following La Niña disturbance to a foundation species represents a local extinction debt of 32–49‐month duration. A better understanding of the scale of extinction debt in foundational marine ecosystems is needed to quantify the breadth of impacts of climate oscillations on biodiversity and ecosystem functioning.

Aquaterrestrial Recolonization

In this paper, we introduce the interactive installation Aquaterrestrial Recolonization as an artistic response to rising climate change concerns and trigger the audience's thoughts and discussions. In the project, we are recording and archiving the current state of the dead coral reefs and feeding artificial intelligence with that data to be able to visualize the virtual 3D dimensional recolonized coral reefs, relieved from human devastation and behaviour from the past and conduct changes in the future. We aim to preserve the current state of the Bahamian coral reefs and use artificial intelligence to return to the planet parts mankind has destroyed and affected the future with necessary human behavioural changes. Our AI Environmentalist is designed to be a chronologist, provocateur, and uncompromised planet Earth's protector.

Reconstructing past disturbance in coral communities using U-Th dating of dead coral skeletons

Abstract In the absence of detailed broad-scale studies, both spatially and temporally, the overall status (disturbed, recovering, or in decline) of many of the reefs that make up the Great Barrier Reef remains uncertain. Moreover, of the numerous and varied threats, their relative role in impacting individual reefs is generally unclear. Here, we adopt a novel approach to reliably reconstruct historical disturbance events at Rib and Davies Reefs, two mid-shelf reefs, using uranium-thorium (U-Th) dating of dead corals. Corrected 230Th ages obtained from dead Acropora spp. bracket time periods of lowest coral cover observed during independent ecological surveys in the late 1980s and 2000s at 1988.2 ± 1.3 and 2003.9 ± 6.2 CE, shortly after the arrival of crown-of-thorns starfish (CoTS) at Rib Reef in 1983–1985 and 2000–2002, respectively. At Davies Reef, 230Th ages dated to 1999.2 ± 1.2 CE when coral cover was halved as a result of Cyclone Tessi and an “unknown” disturbance in 2000–2001. Prior to modern surveys, there is remarkable overlap in 230Th ages between reefs, with repeated peaks in the age distribution having a return period of ~10–15 years, akin to the periodicity of modern CoTS outbreaks. Our findings suggest that U-Th dating of dead corals can provide a robust foundation for understanding disturbance history and show promise in contributing to the effective monitoring of coral communities by providing a reliable benchmark with which to assess recovery.

Tool use involving a different prey type, microhabitat and location, and long‐term anvil use, by the graphic tuskfish Choerodon graphicus (De Vis 1885)

AbstractTool use is a remarkable animal behaviour, and the investigation of this phenomenon in fishes is a relatively new and growing field. The graphic tuskfish Choerodon graphicus (De Vis 1885) has previously been documented using anvils but the extent and variability of this tool‐use behaviour remains poorly understood. In this study, we investigated whether C. graphicus breaks open crustaceans and/or sea urchins on anvils in different microhabitats and/or locations. We also inspected two previously identified anvils for evidence of long‐term anvil use. Three individual C. graphicus were observed breaking open sea urchins on dead coral anvils in a coral rubble microhabitat at Île aux Canards, New Caledonia. They produced visual and auditory cues while carrying out tool‐use behaviour and these cues often attracted attendant fishes. Notably, two anvils appeared to have been used by one or more tool‐using C. graphicus for years at Îlot Maître, New Caledonia. These findings suggest that tool‐use behaviour is both innate and learned and is a prey‐handling method of choice used by individuals that learn to specialise in large prey items from a few underutilised hard‐shelled prey species. Furthermore, the findings show that specific anvils can be used long‐term and also suggest that individual wrasses may carry out tool‐use behaviour long‐term. The study provides new insights into the feeding ecology and social behaviour of C. graphicus and underscores the need to further investigate the extent and variability of tool use in fishes.

Spatial distribution of benthic habitats in Kapota Atoll (Wakatobi National Park, Indonesia) using remote sensing imagery

Abstract. Hamuna B, Pujiyati S, Gaol JL, Hestirianoto T. 2023. Spatial distribution of benthic habitats in Kapota Atoll (Wakatobi National Park, Indonesia) using remote sensing imagery. Biodiversitas 24: 3700-3707. This study aims to classify and map benthic habitats in Kapota Atoll, Wakatobi National Park, using Sentinel-2A satellite imagery, that has undergone both atmospheric and geometric corrections. Sentinel-2A satellite imagery was processed using pixel-based classification method. This study used two machine learning algorithms: support vector machine (SVM) and random forest (RF). This study used nine classified benthic habitat classes, namely five homogeneous benthic classes (sand, live coral, dead coral, rubble, and dense seagrass) and four mixed benthic classes (mixed rubble and sand, mixed sand and rare seagrass, mixed medium seagrass and sand, and a mixture of rubble, dead coral, and seagrass). The RF algorithm produced benthic habitat maps with a higher overall accuracy than the SVM algorithm, which was 65.31% and 63.51%, respectively. These accuracy values have met the standards of accuracy for mapping benthic habitats that apply in Indonesia. The SVM algorithm classification results showed that the benthic habitat of the mixed class of medium seagrass and sand was more dominant than other benthic habitat classes. In contrast, the RF algorithm showed the class dense seagrass was more dominant. The selection of the appropriate algorithm for processing satellite imagery was found to be a significant factor in producing an accurate benthic habitat map.

Morphological and molecular analysis of the tropical hermit crab Calcinus vachoni (Decapoda, Diogenidae) and its potential association with colonial anemone.

Calcinus is the colorful hermit crab genus belonging to the family Diogenidae and is often found in coral reefs of the tropical Indo-West Pacific region, including southern Honshu, Japan, which is the northern limit of their occurrence. In the present study, we found C. vachoni for the first time in the intertidal zone of Jeju Island-the southernmost island of South Korea. We examined their morphology and provided a diagnosis of their morphological details with illustrations. In addition, the Korean Calcinus population was genetically characterized using mtDNA cox1 sequences and by placing them into three previously reported regional haplogroups. The phylogenetic tree from maximum likelihood analysis revealed that Korean C. vachoni is assigned to the C. vachoni haplogroups exclusively, one of the three well-supported mitochondrial haplogroups with distinct geographic ranges (i.e., C. vachoni, C. aff. vachoni Cooks, and C. aff. vachoni Mascarenes). This result provides new information on the species distribution of C.vachoni, extending their geographic range further north into the southern coast of Korea. In this study, we also first report the potential association of C. vachoni with their co-occurring colonial anemone species Palythoa aff. mutuki and dead coral head of Pocillopora species based on our on-site observation and a public coral collection database of Calcinus species. However, their ecological association with co-occurring coral species is putatively assumed for now and therefore has to be validated by compelling evidence from further field observation and experimental studies (i.e., whether the presence/absence of colonial anemones affects the behavior and survival of the hermit crabs).

Dark fermentative hydrogen production in packed-bed bioreactor using the Persian Gulf dead coral, ceramic saddle, and ceramic ball as support matrixes

Dark fermentative hydrogen production by Enterobacter aerogenes in a packed bed bioreactor using three immobilization supports was studied. The effects of glucose concentrations (20, 10, 5, 2.5, and 1.5 g/L) and support matrixes (Persian Gulf dead coral, ceramic saddle, and ceramic ball) on the hydrogen yield (HY) and hydrogen production rate (HPR) at low hydraulic retention time (HRT) were investigated. According to the achieved results, glucose concentration, porosity and shape support, and bed voidage affected hydrogen production. The HYs were increased with decreasing glucose concentration and at 2.5 g/L glucose concentration, the maximum HYs of 3.11, 2.86 and 2.79 mol hydrogen/mol glucose were obtained for dead coral, ceramic ball, and ceramic saddle, respectively. The results indicated that at the HRT of 0.6 h, the bioreactor packed with dead coral resulted in higher HY (3.11 mol H2/mol glucose) and HPR (173 mL/L.h) representing 8–11%, and 8–15%, enhancement compared to the bioreactor packed with ceramic supports. Besides, based on the acquired results, the HY and HPR of the ceramic ball were higher than the ceramic saddle.

Species composition and distribution of mollusca on dead coral from Central to North Vietnam

A study on Mollusks’ species composition and distribution on dead coral from Quang Ngai to Cat Ba was conducted during the field survey between Vietnam and Russia on the AKADEMIC OPARIN RC vessel in 2021 at 39 reef stations in 14 study areas. By comparative morphology method, the authors have identified 135 taxa of Mollusca belonging to 48 families, 4 classes on coral reefs. The species composition of Mollusca was slightly different between study areas.

Analysis of Coral Reef Coverage Condition in The Waters of Central Bangka Regency

This research aims to discover the percentage of coral reef coverage and the condition of the coral reef ecosystem in small islands in Central Bangka regency waters. The research was conducted on May 2022 on six small islands: Panjang Island, Semujur Island, Ketawai Island, Ketugas Island, Gusung Asam Island, and Bebuar Island. The method used was underwater photo transect (UPT) and then analyzed using Coral Point Count with Excel extension software (CPCe). The result shows that of 6 small islands, only Semujur Island is populated. Coral reefs in small islands in Central Bangka regency were a type of fringing reef dan patch reefs with 3,0 - 8,8 meter depth. Standard damage criteria show that the damage was Moderate (44,60%) to Excellent (87,00%). The details were Moderate category on Ketugar Island, Good category was in Panjang Island, Gusung Asam Island, and Bebuar Island, while the coral reefs in Excellent category were in Semujur Island and Ketawai Island. 24 lifeform types were found with a dominant percentage value of approximately 18,47 - 46,87%. Lifeform was dominated by Coral Foliose (CF), Acropora Tabulate (ACT), dan Dead Coral with algae (DCA). Live coral reefs closer were dominated by healthy lifeforms, with most of the close being Dead Coral with algae. It showed that coral reefs might get disturbed by algae occurrence and triggers massive algae expansion. Fish in Coral reefs primarily targeted fish. It prefers the lifeform type to dead coral with algae lifeform.

Coral density level in the context of ecological resilience and its effect on sustainable tourism in Pari Island, DKI Jakarta

Social changes in the context of climate change include the character of capitalism and the relationship between nature and culture that encourages people to respond to climate change and adapt their livelihoods. The purpose of this study is to calculate coral density in the context of ecological resilience and its effect on sustainable tourism in Pari Island, DKI Jakarta. The research method uses a survey with the Line Intercept Transect method. Sampling was carried out at a depth of 5 and 7 meters, depending on the presence of coral. The length of transect used is 50 meters and is placed parallel to the shoreline of the island. The results showed: First, most of the coral reefs in Pari Island are still in good and healthy condition. Of the 15 sample points observed, only 2 showed coral mortality due to internal and external factors in the sea. From the results of the analysis it was concluded that the condition of healthy coral reefs in the waters of Pari Island had a high density. Meanwhile, stressed or dead coral reefs have a low density. This condition indicates that coral reefs are still effective in supporting tourism activities.

Dynamics of Herbivorous Fish and Its Role in Controlling Algal Coverage in Coral Reef Restoration Area Affected by the Bleaching Phenomenon in 2016

Coral reefs in the waters of Liukangloe Island were reported to have experienced a bleaching phenomenon in May 2016 and rehabilitation efforts were carried out in 2019. This study aimed to analyze the structure of the herbivorous fish community and its role in controlling algal cover in the rehabilitation area. Observations of herbivorous fish were carried out using visual census techniques on an area of ​​4m2 and observation of algae in 0.5x0.5 m2 transects on several coral attachment media from dead coral substrates. The results showed that the proportion of herbivorous fish species in the transplant area ranged from 15.81-58.67% and the proportion of individuals ranged from 12.51-34.62%. The dynamics of the number of species and abundance of herbivorous reef fish did not show significant differences between substrates and had the same dynamic pattern in all substrates uses but varied temporally according to the time of observation. The exception is the rubble area which continues to increase until the end of the observation. A high number of herbivorous fish species richness was observed in the branching and natural coral substrates and low in the rubble substrate. The abundance of herbivorous reef fish showed a significant and negative relationship to algal cover and confirmed that the presence of herbivorous reef fish could control or reduce the value of algal cover.

The paleo-community of the Sciacca red coral

The sub-fossil red coral deposits of Sciacca (Sicily Channel) have attracted scientific attention for nearly 150 years. Their origin and formation have been long questioned and investigated, given the fact that they represent one of the most intriguing geobiological events ever to occur in the Mediterranean basin. Less attention was given to the paleo-community associated with the sub-fossil coral. Radiocarbon age determinations, in particular, were provided only for red coral, neglecting the possibility of understanding which species were simultaneously present in the coralline paleo-community and which was their role. The study of cemented coral rubble pieces revealed that Corallium rubrum covered the largest time interval (more than 3000 years) and was contemporary to many secondary epibionts over two millennia and to Madrepora oculata for about 500 years; this last finding suggested that an uncommon co-dominance between the two structuring species occurred in the nearby living communities. The lack of Fe–Mg deposits on the cemented coral rubbles coupled with the low bioerosion rate of the red coral skeletons by the demosponge Siphonodictyon coralliirubri (assessed through the analysis of the erosive paleo-scars) suggested that the deposits met with a rapid sediment cover-up. Moreover, for the first time, the analysis of a piece of cemented coral rubble of sub-fossil red coral coming from Sardinian waters confirmed that, albeit to a lesser extent, the conditions favouring the preservation of dead corals can occur also in different localities far from Sciacca.

Three-dimensional (3D) modelling to determine the weight of massive corals in Gili Labak Island, Sumenep, Madura, East Java, Indonesia

ABSTRACT This study aimed to non-destructively measure the weight of massive (live) corals through three-dimensional (3D) modelling. The 3D models were constructed using the volumes and weight of massive (dead) corals. The study was conducted through photographs, 3D analysis, and weighing 32 massive (dead) coral samples. Volume and weight were modelled using linear and non-linear regressions, and their accuracy was tested using root mean square error (RMSE) and mean absolute percentage error (MAPE). This study showed that the weight of massive (live) corals could be measured using a 3D model of the massive (dead) coral’s volume and the weight mainly through regression, polynomial, and geometric equations. The power/geometric equation is a more suitable approach for determining the actual value of coral weight. Linear regression obtained an average weight of 6.13 kg per plot. Three-dimensional modelling can be widely applied to measure the massive corals in the deep sea.

New Cretaceous (Aptian/Albian) boxer shrimp (Crustacea, Decapoda, Stenopodidea) from the Araripe Sedimentary Basin, NE, Brazil.

Stenopodidean shrimps are mostly cryptic in their habitats and are typically related with coral rubble or dead coral heads, rocks and crevices, and in association with other marine invertebrate such as sponges, crinoids and corals. Here, we describe a new stenopodidean shrimp, Dubiostenopus parvus n. gen. n. sp., from the Romualdo Formation (Aptian/Albian), Araripe Sedimentary Basin. The specimen studied here was collected in the municipality of Trindade, Pernambuco State, Brazil. The specimen is the imprint of a small shrimp approximately 10 mm in length, with a robust cephalothorax, a well-developed cheliped in the third pereiopod, and a second pleura not overlapping the first. This is the first stenopodidean shrimp described from the Romualdo Formation and the first described from South America. Comparisons with other Brazilian shrimp-like fossils are made, as well as comparisons with all other fossil stenopodideans.

Contrasting Impacts of Different Disturbance Types on Coral Reefs: Wave Disturbance vs. Coral Bleaching

Photo 1. Coral reef environments on the island of Moorea, French Polynesia following two different types of major disturbance events: (left) a large wave disturbance and (right) a coral bleaching event. The reef affected by the wave disturbance has relatively little structural complexity remaining on the reef, while the reef affected by bleaching retained high structural complexity in the form of dead coral skeletons. The center triangle depicts an undisturbed reef characterized by high cover of living coral. Photo credit: Kai L. Kopecky (left panel), Andrew Thurber (right and central panels). These photographs illustrate the article “Material legacies can degrade resilience: Structure-retaining disturbances promote regime shifts on coral reefs” by Kai L. Kopecky, Adrian C. Stier, Russell J. Schmitt, Sally J. Holbrook, Holly V. Moeller published in Ecology. https://doi.org/10.1002/ecy.4006

THE CHANGES OF COASTAL ECOSYSTEM IN EAST SERAM DISTRICT, MALUKU PROVINCE, INDONESIA AND ITS IMPACT ON THE JULUNG-JULUNG FISH (Hemirhamphus sp) RESOURCES

"The sub-district of East Seram (SBT) is the oldest district in the East Seram Regency, Maluku Province, Indonesia. Ninety percent of this area is covered by the sea with 3 unique tropical coastal ecosystems, namely mangroves, seagrass, and coral reefs. This high productivity ecosystem provides various goods and environmental services in fisheries, tourism, and other industries. One of them is coastal resources such as Julung julung fish (Half-beak, Hemirhamphus spp) that use this ecosystem for their primary habitat. Unfortunately, little is known about the interaction between Julung-julung and their habitat. This paper aims to assess the changes of the coastal ecosystem of the SBT and their impact on Julung-julung resources. Two satellite images of Landsat-7 ETM+ (2001) and Sentinel-2A (2018) were analyzed to monitor the condition changes of mangrove and seagrass. Six habitat classes of sea, land vegetation, mangrove, dense, medium, and sparse seagrass were classified using isocluster analysis, validated using ground truth data collected during intensive field survey, and then the areas of each habitat class were calculated. From the period of 2001 to 2018, the areas of mangrove and seagrass have decreased from 1401.5 to 1118.8 ha, and from 3183.8 to 2509.4 ha, respectively. The decrease of mangroves was due to mangrove cutting for firewood that use to smoke Julung-julung, one of the famous fish products from the SBT, while mining dead coral for building materials in seagrass beds decreased their areas. Interview with experienced SBT’s fishers in catching Julung-julung showed that the population of this fish has decreased by about 30-50% within 20 years, which was most likely due to the impact of their habitat degradation. In contrast, the decrease of Julung-julung stocks in other province was mostly due to overfishing. Thus, maintaining, conserving, and revitalizing the mangrove and seagrass ecosystems in the SBT as the important habitat for the early life history of Julungjulung is inevitable, as well as it is necessary to immediately conduct in-depth study on biological and population dynamics of this fish, whose data is still lacking, so that the Julungjulung stocks can manage sustainably."