Live Coral Research Articles

Improvement of live coral shipping conditions using an illuminated box

The transportation of live coral nubbins is a major constraint of the coral trade. Corals must be transported within a timeframe of <20 hours using concentrated oxygen to avoid high post-transportation mortality. To understand the effects of transportation water quality on coral nubbin growth and post-transportation mortality, a series of transportation simulations were performed on Seriatopora hystrix. Different water volumes (dry method, 125 ml, 190 ml, and 325 ml) and oxygen concentrations in the gas phase (21 %, 40 %, and 85 %) were tested, and a 24 LED Handy Lamp was added to provide light irradiance of >100 µmol m-2 s-1 in the transportation box. During transportation nubbins extracted calcium carbonate for growth reducing water alkalinity and consequently pH to 6.67. Dissolved oxygen concentration also rapidly decreased to 0.19 mg L-1. The concentration of inorganic nitrogen, particularly ammonium ions, increased after 24 hours and reached very high concentrations after 48 hours. Before 48 hours, the larger the water volume and oxygen concentration, the faster the nubbin growth after transportation. Beyond 48 hours, in all cases, reduction in water quality became critical for nubbins and resulted in partial mortality. Illuminating the transportation box improved water quality for 72 hours using normal air.

A biological condition gradient for Caribbean coral reefs: Part II. Numeric rules using sessile benthic organisms.

The Biological Condition Gradient (BCG) is a conceptual model used to describe incremental changes in biological condition along a gradient of increasing anthropogenic stress. As coral reefs collapse globally, scientists and managers are focused on how to sustain the crucial structure and functions, and the benefits that healthy coral reef ecosystems provide for many economies and societies. We developed a numeric (quantitative) BGC model for the coral reefs of Puerto Rico and the US Virgin Islands to transparently facilitate ecologically meaningful management decisions regarding these fragile resources. Here, reef conditions range from natural, undisturbed conditions to severely altered or degraded conditions. Numeric decision rules were developed by an expert panel for scleractinian corals and other benthic assemblages using multiple attributes to apply in shallow-water tropical fore reefs with depths <30 m. The numeric model employed decision rules based on metrics (e.g., % live coral cover, coral species richness, pollution-sensitive coral species, unproductive and sediment substrates, % cover by Orbicella spp.) used to assess coral reef condition. Model confirmation showed the numeric BCG model predicted the panel’s median site ratings for 84% of the sites used to calibrate the model and 89% of independent validation sites. The numeric BCG model is suitable for adaptive management applications and supports bioassessment and criteria development. It is a robust assessment tool that could be used to establish ecosystem condition that would aid resource managers in evaluating and communicating current or changing conditions, protect water and habitat quality in areas of high biological integrity, or develop restoration goals with stakeholders and other public beneficiaries.

Pemetaan sebaran dan kondisi tutupan terumbu karang di Desa Gili Gede Indah, Lombok Nusa Tenggara Barat (studi kasus: Gili Gede, Gili Layar, Gili Asahan)

Coral reefs are one of the potential marine resources in Indonesia, especially on the island of Lombok which needs to be taken into account. So that the mapping of the distribution and extent of coral reefs is needed in developing the potential of marine and coastal resources. One of the small islands that have potential is on the west side of the island of Lombok, namely in Gili Gede Indah Village, Gili Asahan, and Gili Layar. The ecological and economic functions of the coral reef ecosystem will run well if the condition of the coral reef is in a healthy condition. The method used to calculate the distribution is using Sentinel 2A satellite imagery with a spectral resolution of 30 m2 with a supervised method of image data processing using Google Earth Engine (GEE). in situ observational physics parameter data. coral reefs were carried out at a depth of 3.8 – 6 meters. The results of observations and analysis of coral reef cover area on Gili Gede 17.84 km2, Gili Layar 9.72 km2 and Gili Asahan 11.91 km2. Confusion matrix interpretation results are Gili Gede 82%, Gili Layar 70.3%, and Gili Asahan 88.5%. While the percentage of live coral reefs in the three dyke is 9.2 - 26.2%. This percentage shows the criteria and conditions of low to moderate coral reefs. Although the condition of the physicochemical parameters in the three dyke was classified as good, namely DO 8.4 – 8.7 mg/l, salinity 31 – 32 ‰, temperature 29.6 -30.2 0C, sea water clarity to 100%. Coral damage due to fishing and tourism activities.

Comparison of the bleaching susceptibility of coral species by using minimal samples of live corals.

In massive bleaching events (losing symbiotic algae from corals), more sensitive corals are bleached earlier than other corals. To perform a comparison of bleaching susceptibility within and across coral species, a simple quantitative method is required. Accordingly, we present a laboratory-based method for comparing the bleaching susceptibility of various coral species by using a standardized image analysis protocol. Coral fragments were sampled from the colonies of five species selected from Kenting, southern Taiwan, and maintained in the same aquarium tank with circulating seawater; 2 seawater temperature regimes were used (i.e., fast-heating program (FHP), with a heating rate of 1 °C per day; and slow-heating program (SHP), with a heating rate of 1 °C per 3 days). Each coral fragment was photographed periodically, and the colored images were subsequently converted to grayscale images and then digitally analyzed to determine the standardized grayscale values (G0) by comparing with that of standard color strip. The G0 of a sample at each time of photographing during bleaching was divided by the difference of G0 between the acclimating and the same but completely bleached fragment to derive the relative grayscale (RG%) at a particular stage of bleaching; this is done for each coral fragment of a colony. The smaller the RG% of a coral fragment the closer it is approaching completely bleached condition. The level of decrease in RG% within a time series of images in each heating regime was used to establish a bleaching time index (BTI). The lower the BTI, the sooner to reach a defined bleaching level (e.g., 30%), this indicates the coral is more sensitive to thermal bleaching. In the experiment, we compared the bleaching susceptibility of the five species. Based on the proposed BTI, the five species were ranked in terms of bleaching susceptibility, and the rankings were identical between the two temperature regimes; three species in Pocilloporidae had lower BTI, whereas the hydrocoral Millepora species had the highest BTI. Within each heating regime, the BTI of different species were ranked and used to indicate susceptibility. In the FHP, the three Pocilloporidae species could be divided into two groups in terms of bleaching susceptibility. FHP not only displayed a higher differentiating capability on coal bleaching susceptibility than SHP, but also had a faster completion time, thus reducing the likelihood of unforeseen complications during the tank experiments. Our color-based method is easier and less effort-intensive than methods involving the assessment of zooxanthellae densities. Moreover, it requires much fewer replicates and all samples in one large tank (e.g., 300 L) for the studies considering multiple species comparisons. This method opens opportunities for studying the effects of species types, acclimatization (e.g., seasons), and environmental factors other than temperature on coral bleaching.

Destructive outbreaks of the corallivorous starfish Acanthaster cf. solarisspare coral assemblages in the shallowest reef flat areas in New Caledonia

Abstract Outbreaks of the corallivorous starfish Acanthaster cf. solaris (COTS) are not fully understood, especially in the shallowest areas behind the reef crests where limited COTS impacts are often reported. Here, we investigated the outbreak occurrence and compared post-outbreak habitat impacts in reef flats vs. upper fore reefs at 13 sites in New Caledonia. In this Pacific territory so far considered marginally affected by COTS, we documented wide occurrences of aggregations, combining massive population increases (maximum 605 COTS per swim, abundances &amp;gt;100 COTS recorded in 46% of the sites) with limited spatiotemporal boundaries. Abundance levels met the highest values in the literature, but were restricted to relatively small, isolated mid-shelf reefs. Typical residence time was short (&amp;lt; two years), with at least one site where COTS seemingly disappeared within seven months. The spread of COTS population and subsequent impacts appeared self-contained, and never affected the reef flats (0.5–1.5 m). The transition to severely affected fore reefs was abrupt, with live coral cover divided by nine and morphological diversity halved within a very few meters (3–5 m). We suggest that these differential impacts likely result from harsh environmental conditions making shallow, coral-rich areas less suitable for COTS, thereby pushing predation pressure further downwards.

Episcomitra angelesae (Mollusca: Gastropoda: Mitridae), a new species from an exceptional deep habitat in the Alboran Sea

A new species of gastropod, Episcomitra angelesae (Neogastropoda: Mitridae), is described from specimens collected in the upper bathyal level of the Alboran Sea (Seco de los Olivos and Alboran Ridge). The new species is compared with other similar species known from the Atlanto-Mediterranean area, including Episcomitra zonata (Marryat, 1819) and Isara turtoni (Watson, 1890). The habitat of this new species, hard substrate with coral rubble patches at 250-320 m depth on submarine elevations, is very unusual in the Mediterranean Sea and is described based on Remotely Operated Vehicle video footage. The amount of coral rubble on the type locality is disproportionate to the very few live coral colonies found in the vicinity, and is assumed to be relict of former hydrological conditions.

Condition of Coral Reef Cover and Overview of Coral Fish in Pagang Island, South Coast, West Sumatera

This research was conducted in October 2020 in the waters of Pagang Island, Koto XI Tarusan District, South Coast Regency, West Sumatera Province. This study aims to determine the condition of coral reefs and reef fish in coral reef ecosystems which were analyzed based on the coral cover in Pagang Island. The method used in this research is UPT (Underwater Photo Transect) for assessing the live coral coverage and the UVC (Underwater Visual Census) for collecting the reef fishes data. The result shows that the condition of coral reef cover in Pagang Island at all stations is in critical condition. However, the high percentage of coral dying at all stations presumed that these coral reefs were in good condition. Percentage of coral cover in the station I 4.13%, station II 6.2%, station III 1.2%, and station IV 2.07%. A total of 31 fish species belonging to 7 families with a total of 328 individuals were identified in all stations. The average abundance of fish at all stations is 0.328 ind/m2

Holocene sea levels at the Gulf of Aqaba, northern Red Sea

A new relative sea level (RSL) curve is presented for the Holocene Gulf of Aqaba, northern Red Sea. The curve is based on U–Th ages of corals retrieved from leveled fossil reefs comprising the Tur Yam Terrace at the shore of the city of Elat, Israel and the Aqaba reef terraces, Jordan, located respectively east and west of the northern tip of the gulf. Both terrace tops are submerged under high tide and subaerial at low tide. The fossil corals are in growth position between two beachrock units. The corals comprise 100% aragonite, show pristine textures with no secondary aragonite cements and yield initial 234U/238U activity ratios of 1.146 ± 0.004, similar to the values of live corals and modern Gulf of Aqaba (GoA) waters. Sixteen U–Th ages of corals from the Tur Yam Terrace span the time interval of 6.8 to 5.5 ka, and are ordered along the growth direction of the terrace. Detailed mapping of the terrace, the distribution of corals’ genera and the order of their ages on the terrace, suggest that the exposed terrace was the back reef/lagoon zone, a very close to shore environment of a fringing reef. Identification of this reef zone was based on a detailed ecological study that we conducted on the Nature Reserve Reef (NRR), a modern fringing reef located several hundred meters to the south. A morpho-tectonic analysis of the Elat shore indicates that the Tur Yam Terrace lies on top of the footwall of the active Elat Fault and has remained at its original level, with negligible vertical shift. Thus, it appears that during the time interval of formation of the Tur Yam corals, sea level at GoA reached a maximum stand that was 1–2 m above the modern elevation. A similar figure is shown by Mid-Holocene corals from the Aqaba fossil reefs and shore indicators from the Red Sea. The relative sea level (RSL) curve deduced from the Gulf of Aqaba corals and from the Red Sea indicators resembles those of precisely-dated stable reefs off west and east Australia and a few other well dated reefs in the Indo-Pacific. This similarity calls for coeval response of the Indo-Pacific oceans to ice melting during the early to mid- Holocene, and a similar pattern of decline to the present level during the late Holocene. Such a coeval rise of distant parts of the Indo-Pacific oceans is consistent with dominance of melt waters releases over the oceans with minor effects of all other “sea level drivers".

Assessing of coral reef resilience on Lembeh Island, North Sulawesi

Resilience is the ability of a system to reach equilibrium after a temporary disturbance. When an ecosystem is disturbed, then the recovery of the system is very dependent on the diversity of species that are still left. The remaining communities determine the direction of new successional communities formed after the disturbance has passed, including coral, fish, and other biota communities. This study aimed to determine the level of resilience of coral reef ecosystems on Lembeh Island. The observation was carried out from January 16-19, 2019, at a 7-meter depth. Determination of the coral reef index will refer to coral reef resilience index table. It is found that the resilience of coral reefs on Lembeh Island currently has a high potential for recovery (resilience) from natural stressors based on the 16 parameters. Seven parameters have very high resilience values: the proportion of bleaching resistant species, community resistance to bleaching, taxonomic diversity, size/age distribution, the abundance of reef fish on live coral, and the abundance of coral benthos on live coral and coral disease levels. Lembeh Island is dominated by hard corals measuring between 5.1 to 25 cm (size M) by ~46%, then sizes more than 25 cm (size L) by ~37% and juvenile size (size S) by 17%. The coral health index on Lembeh Island has the capacity to recover if the condition of coral cover is minimally maintained or improved and lower fleshy seaweed cover by increasing the abundance and biomass of herbivorous fish.

Crown-of-thorns starfish outbreak at Taiping Island (Itu Aba), Spratlys, South China Sea

Outbreak of crown-of-thorns sea stars, Acanthaster cf. solaris, were documented in coral reefs around Taiping Island, Spratlys for the first time. The outbreak might be thereason for the significant decline in live coral cover in 2021. Comprehensive monitoring through regional collaboration is needed.

Analysis of Water Environment Support for Marine Ecotourism Suitability Category Diving in Ataúro Island

Ataúro Island is one of the islands in Timor-Leste which has a fairly complete coastal and marine ecosystem, (coral reefs, seagrass and a few mangrove). Ataúro Island also has several long white sandy beaches where green sea turtle and Hawksbill Sea turtle are often found laying eggs in certain seasons. Coral reefs on Ataúro Island attract tourists to visit. This study aims to determine the suitability of the environmental carrying capacity of the diving category based on diving marine ecotourism suitability index. Data collection was carried out from September to November. The method used in this study is the intercept photo transects method, and water quality sampling. The results of the analysis of water quality on the island of Ataúro based on the Decree of the Minister of Environment 51 of 2004 concerning that sea water quality standards for marine ecotourism, it can be concluded that the average water quality on the island meets the quality standards. Live coral cover in all study sites had a cover of 54.80% in the 'good' category, analysis of the diving marine ecotourism suitability index for the diving category in Beloi village 75.93% in the appropriate category, Vila-Maumeta village 66.67% suitable, Biqueli 61.11% suitable.

Status of benthic cover in Carbin Reef, Sagay Marine Reserve, Western Visayas, the Philippines

This study determined the status of Carbin Reef benthic cover, Sagay Marine Reserve, Negros Occidental. The underwater benthic assessment was conducted on March 2019 by laying eight 50-meter transect lines at the depths of 6 meters (crest) and 12 meters (slope). Photo-quadrat method was used in obtaining still benthic images for every 1-m across eight 50-meter transect lines. A total of 400 still images were acquired and analyzed using Coral Point Count with Excel Extension (CPCe). The sedimentation rate was also determined by deploying sediment collectors. Results showed that Carbin Reef is characterized by 26.09% live coral cover and 43.25% abiotic structure such as rocks, sand, and coral rubbles. Fifty-five (55) coral species belonging to thirty-three (33) genera were identified, dominated by Porites, Fungia, and Goniastrea. Throughout the area, Porites lobata was the most dominant coral species. The overall hard coral cover seemed to have decreased since 2014. Further analysis showed the prevalence of bleached corals and diseases such as white syndrome, and white band disease. Similarly, two signs of compromised health including sediment damage and competition overgrowth were also present. The sedimentation rate per day was below the maximum tolerable levels by most corals during dry season. Overall, this study presents the first extensive study of coral diversity in Carbin Reef–characterized by a moderately diverse area and considered as a moderately stressed habitat.

Kondisi Terkini Presentase Tutupan Terumbu Pada Masa Pandemi Covid-19 di Gili Air, Taman Wisata Perairan Gili Matra, Nusa Tenggara Barat

Gili Matra Aquatic Tourism Park has two conservation targets, namely biological targets and social, cultural and economic targets. Coral reef ecosystems, apart from being a conservation target, are also an attraction for tourists to visit. This research was conducted to determine the condition of the coral reef ecosystem to be used as the basis for the management of conservation areas. The research was conducted by collecting coral reef data either through surveys or secondary data from the results of previous studies. Coral reef survey using the standard Line Intercept Transect method. The survey results show that the condition of coral reefs in the utilization zone is better than the core zone. Live coral cover in the utilization zone reached 71% so it was categorized as good, while in the core zone it only reached 8% so it was categorized as bad. Coral reefs in the core zone are unable to recover even though the number of tourists has decreased during the Covid-19 pandemic. Therefore, the location of the core zone on Gili Air needs to be evaluated further so that the effectiveness of Gili Matra TWP management can be improved. Key words: coral reefs; Gili Matra; Conservation

Status of Coral Reefs in Lagonoy Gulf, Eastern Bicol, Philippines with Emphasis on Marine Protected Areas

Status of coral reef health of 8 Marine Protected Areas (MPA), 6 adjacent MPA reefs and 5 regular reefs of Lagonoy Gulf were assessed from December 2017 to August 2018 and compared with previous gulf-wide assessment results in 1994 and 2004. Underwater photo transect (UPT) method was utilized to collect benthic lifeform information and coral point count with excel extensions (CPCe) was used to analyzed benthic data. Results showed that present live coral cover in MPAs are low with 26% as compared to adjacent MPA reef areas (30%) and regular reef stations (33%). A downtrend was noted from 1993 – 2004 with 10% decline of MPA reefs while from 2004 to 2018 decrease was almost 20% and from 1993 to 2018 an average fall of 25% was detected. Overall, Lagonoy Gulf reef health is declining and can be attributed to both natural and fisheries activities, as evidenced by almost 20 typhoons affecting the Region per year with a super typhoon at least every 5-10 years and the heavy dependence of fishing communities on reef fishes respectively. However, non-MPA reefs decline was observed to very minimal as compared for both MPA and adjacent MPA reefs ranging from 1% to 6%. With this, MPA management schemes should be revisited and amended to improve and strengthen MPA governance, direction and strategies.

Lessons learned from small‐scale coral outplanting intervention at a restoration site on the Great Barrier Reef

SummaryScientific, tourism and non‐government organisations collaborated to design and undertake a small‐scale coral outplanting intervention at Fitzroy Island, the Great Barrier Reef (GBR), Cairns, Australia. Activities were implemented to assist recovery of a reef showing signs of reduced coral cover after recent coral bleaching and to trial potential for implementation of work of this kind by community members. In December 2017, 240 coral fragments were collected and deployed on mid‐water coral nursery infrastructure. Ten months later, 96 corals (˜15 cm) were outplanted onto bare sections of the surrounding reef rock at depths of 2–8 m. Monitoring was undertaken to measure changes in coral cover at treatment and control locations to determine the potential of using coral outplanting intervention to assist the recovery of degraded reefs. We found no significant difference in live coral cover between controls and treatment over a 12‐month period. Although statistically insignificant, we observed an increase in live coral cover in treatment plots (9.8%) and control plots (2.2%), indicating natural recovery processes occurring across the reef. Total number of fish species and abundance increased significantly over time. Although the outplanting may not have been needed in this case, as a pilot project and the first coral nursery and active reef restoration project in the GBR Marine Park, the research provided valuable lessons associated with project collaboration and planning, site selection, monitoring and natural recovery vs restoration.

Benthic habitat mapping using Object-Based Image Analysis (OBIA) on Tidung Island, Kepulauan Seribu, DKI Jakarta

Tidung Island is one of the islands in Kepulauan Seribu, DKI Jakarta, Indonesia. This island has various benthic that live on the coastal areas, and benthic habitat has various functions both ecologically and economically. Nowadays, remote sensing technology is one way to detect benthic habitats in coastal areas. Mapping benthic habitat is essential for sustainable coastal resource management and to predict the distribution of benthic organisms. This study aims to map the benthic habitats using the object-based image analysis (OBIA) and calculate the accuracy of benthic habitat classification results in Tidung Island, Kepulauan Seribu, DKI Jakarta. The field data were collected on June 2021, and the image data used is satellite Sentinel-2 imagery acquired in June 2021. The result shows that the benthic habitat classification was produced in 4 classes: seagrass, rubble, sand, and live coral. The accuracy test result obtained an overall accuracy (OA) of 74.29% at the optimum value of the MRS segmentation scale 15;0,1;0.7 with the SVM algorithm. The results of benthic habitat classification show that the Seagrass class dominates the shallow water area at the research site with an area of 118.77 ha followed by Life Coral 104.809 ha, Sand 43.352 ha, and the smallest area is the Rubble class of 42.28 Ha.

Pemetaan Habitat Dasar Perairan Dangkal Menggunakan Citra Satelit SPOT-7 di Pulau Nusa Lembongan, Bali

Shallow water habitat is one of the regions that has high dynamics and has an important role are ecologically and economically. The high dynamics of the ideal shallow water habitat is always followed by updating information so that an overview of the area is obtained in accordance with reality. Remote sensing technology is one of the technologies that can be used for mapping natural resource studies such as mapping of shallow water habitats with the satellite imagery. This study aims to map the distribution of shallow water habitats using SPOT-7 satellite imagery on Nusa Lembongan Island, Bali and test the level of accuracy. The method used true color composite and DII (Depth Invariant Index) transformation and uses the maximum likelihood classification. The classification scheme used 6 classes, namely sand, seagrass, macro algae, rubble, live coral, and dead coral. The results of this study indicate the distribution of shallow water habitat on Nusa Lembongan Island, Bali spread equally based on the level of water depth with a total area of shallow water habitat of 453.41 ha. The results of mapping accuracy test showed the overall accuracy of the DII transformation classification results is better than the composite image classification results with an overall accuracy of 75.43% and a kappa coefficient is 0.71. So from these results can be said that used of a water column correction with the DII method can improve image accuracy in mapping shallow water habitats.

About the Cover

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreThe cover image features a crown-of-thorns sea star (Acanthaster sp.) feeding on a branching coral in Australia’s Great Barrier Reef. Crown-of-thorns sea stars are one of the largest and most efficient predators on scleractinian (hard) corals and are capable of killing entire regions of coral reefs. They are notorious for their propensity to periodically undergo population outbreaks, which have contributed to sustained and ongoing declines in live coral cover across the Indo-Pacific. Despite being one of the most ecologically influential and most intensively studied species in the marine environment, key knowledge gaps remain about the biology and ecology of Acanthaster sp.In this issue, a group of crown-of-thorns sea star researchers from all around Australia (Pratchett et al., pp. 330–346) present a list of unresolved questions as a guide for future research efforts to better understand and manage Acanthaster sp. populations. Most of the research questions enumerated by Pratchett et al. are also broadly relevant for the study of sea star species that are keystone predators in other locations and habitats. In their Introduction (pp. 217–218), the editors of the series—Ciemon F. Caballes and Maria Byrne—highlight the importance of these contributions in advancing our knowledge of sea star population dynamics. This special issue brings together contributions examining the demography, life history, feeding ecology, behavior, and physiology of sea stars. This collective body of knowledge on sea stars provides some critical scientific underpinning for the management of irruptive pest species and for the conservation of threatened species.Credits: Photo of crown-of-thorns starfish at Lodestone Reef, central Great Barrier Reef, Australia: Ciemon F. Caballes, ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia. Cover design: Matt Lang, University of Chicago Press. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 241, Number 3December 2021Demography, Ecology, and Management of Sea Star Populations Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/718908 Views: 809Total views on this site © 2021 The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.

Biomass Mapping for an Improved Understanding of the Contribution of Cold-Water Coral Carbonate Mounds to C and N Cycling

This study used a novel approach combining biological, environmental, and ecosystem function data of the Logachev cold-water coral carbonate mound province to predictively map coral framework (bio)mass. A more accurate representation and quantification of cold-water coral reef ecosystem functions such as Carbon and Nitrogen stock and turnover were given by accounting for the spatial heterogeneity. Our results indicate that 45% is covered by dead and only 3% by live coral framework. The remaining 51%, is covered by fine sediments. It is estimated that 75,034–93,534 tons (T) of live coral framework is present in the area, of which ∼10% (7,747–9,316 T) consists of Cinorg and ∼1% (411–1,061 T) of Corg. A much larger amount of 3,485,828–4,357,435 T (60:1 dead:live ratio) dead coral framework contained ∼11% (418,299–522,892 T) Cinorg and &amp;lt;1% (0–16 T) Corg. The nutrient turnover by dead coral framework is the largest, contributing 45–51% (2,596–3,626 T) C year–1 and 30–62% (290–1,989 T) N year–1 to the total turnover in the area. Live coral framework turns over 1,656–2,828 T C year–1 and 53–286 T N year–1. Sediments contribute between 1,216–1,512 T C year–1 and 629–919 T N year–1 to the area’s benthic organic matter mineralization. However, this amount is likely higher as sediments baffled by coral framework might play a much more critical role in reefs CN cycling than previously assumed. Our calculations showed that the area overturns 1–3.4 times the C compared to a soft-sediment area at a similar depth. With only 5–9% of the primary productivity reaching the corals via natural deposition, this study indicated that the supply of food largely depends on local hydrodynamical food supply mechanisms and the reefs ability to retain and recycle nutrients. Climate-induced changes in primary production, local hydrodynamical food supply and the dissolution of particle-baffling coral framework could have severe implications for the survival and functioning of cold-water coral reefs.

Characterizing the spatial distribution of coral reefs in the South-Central Coast region of Viet Nam using Planetscope imagery.

This study aims to understand the spatial distribution of coral reefs in the central region of Viet Nam. We classified live coral cover in Son Tra Peninsula (ST) and Cu Lao Cham Island (CLC) in the South-Central Coast Region of Viet Nam using the Maximum Likelihood Classifier on 3 m Planetscope imagery. Confusion matrices and the accuracy of the classifier were assessed using field data (1,543 and 1,560 photographs in ST and CLC, respectively). The results showed that the reef’s width ranged from 30 to 300 m across the study site, and we were able to detect live coral cover across a depth gradient of 2 to 6 m below the sea surface. The overall accuracies of the classifier (the Kappa coefficient) were 76.78% (0.76) and 78.08% (0.78) for ST and CLC, respectively. We found that 60.25% of coral reefs in ST were unhealthy and the live coral cover was less than 50%, while 25.75% and 11.46% of those in CLC were in good and excellent conditions, respectively. This study demonstrates the feasibility of utilizing Planetscope imagery to monitor shallow coral reefs of small islands at a high spatial resolution of 3 m. The results of this study provide valuable information for coral reef protection and conservation.