Coral Fragments Research Articles

Cryophysiology of coral microfragments: effects of chilling and cryoprotectant toxicity.

Coral reefs are being degraded at alarming rates and decisive intervention actions are urgently needed. One such intervention is coral cryopreservation. Although the cryopreservation of coral sperm and larvae has been achieved, preservation of coral fragments including both its tissue and skeleton, has not. The overarching aim of this study was to understand and assess the physiological stressors that might underlie coral fragment cryopreservation, understand the long-term consequences of these exposures to continued growth, and develop a health metrics scale for future research. Therefore, we assessed small fragments (~1 cm2) from the Hawaiian coral, Porites compressa, examining: (1) chill sensitivity; (2) chemical sensitivity to complex cryoprotectants; (3) methods to safely remove algal symbionts of coral for cryopreservation; (4) continued growth over time of coral fragments exposed to chilling and cryoprotectants; and (5) assessment of health and viability of coral fragments post the applied treatments. Corals were able to withstand chilling to 0 °C for 1 min and after 2 weeks were not significantly different from the live controls, whereas, corals exposed to complex cryoprotectants needed 3 weeks of recovery. Most importantly, it appears that once the coral fragments had surpassed this initial recovery, there was no difference in subsequent growth. Technological advances in cryo-technology promise to support successful coral fragment cryopreservation soon, and its success could help secure much of the genetic and biodiversity of reefs in the next decade.

Differential responses in recovery, growth and survival between intertidal and subtidal corals after acute thermal stress

Sea temperature increases may compromise ecological restoration as a tool for recovering degraded coral reefs. A potential solution may lay within using corals with naturally higher thermal resilience, such as intertidal corals. This study aimed at comparing thermal resilience, growth and survival between intertidal and subtidal corals in a reciprocal transplant experiment. Sixty coral nurseries were installed in a shallow coral reef area in Kenya: half were placed in the intertidal zone and half in the subtidal zone. At both zones, intertidal and subtidal Pocillopora cf. damicornis coral fragments were cultured in equal proportions, resulting in 15 replicate nurseries for four treatments. After an initial culture phase of 1 month in situ, six nurseries per treatment were thermally stressed ex situ by exposing corals for 5 days to a temperature of 32 °C (3 °C above summer maximum), after which they were returned in situ to recover. Fragment brightness was measured as the response variable to thermal stress. Intertidal and subtidal corals increased brightness (i.e., bleached) at a similar rate, but during recovery intertidal corals returned quicker to their original brightness in both culture environments. Coral growth was highest for intertidal corals in the intertidal zone during cooler months and was highest for subtidal corals in the subtidal zone during peak temperatures. Intertidal corals transplanted to the subtidal zone registered the lowest survival. Thus, intertidal corals display higher thermal resilience through quicker recovery, but potential trade-offs require further investigation before these corals can be used as a climate-proof broodstock for reef restoration.

Oceanographic‐informed coral out‐planting density for coral reef restoration activities

Out‐planting corals onto coral reefs as a mechanism to increase coral cover on degraded reef systems is an increasing global activity. Current practices typically focus on asexual out‐planting of coral fragments (coral gardening). Newer sexual reproductive approaches are being developed to out‐plant younger corals produced in aquaculture facilities or sea‐based rearing pools to enable assisted evolution or assisted gene flow conservation genetics approaches. Designing out‐planting deployment operations requires decisions to be made on planting density and location in order to maximize future recruitment on both the out‐planted reefs, and on nearby reefs that are connected through oceanographic transport processes. The thinking presented here seeks to unpack how out‐planting density may be influenced, especially by local oceanographic conditions, in order to guide practitioners undertaking restoration projects.

Luminescence dating of rock surfaces in challenging environments: The case of MIS5e gravelly transgressive lag deposit (Southern Sardinia, West Mediterranean Sea)

Determining the age of precise sea level markers such as marine terraces is often difficult because of the inherent limitation of traditional dating methods. A novel method based on Optical Stimulated Luminescence applicable to rock surfaces has been showing great promise in dating boulder and cobble surfaces from various environments. We performed Optically Stimulated Luminescence Rock Surface Dating (OSL RSD) on five cobbles from a basal transgressive lag deposit sealing a marine terrace referred to as the Last Interglacial (Marine Isotopic Stage 5e). We applied a consistent and highly selective 3-step acceptance criteria on five cobbles and obtained that only one was sufficiently well-bleached prior to burial. The resulting ages of 131 ± 8 ka and 127 ± 8 ka (obtained on 22 analyzed aliquots, n = 22) derived from the post-infrared infrared stimulated signal at 225oC (pIRIR225) and the preceding infrared stimulated signal at 50oC (pIR50/225), respectively, are consistent with each other as well as with the conventional luminescence age of ∼135 ka from the same sequence and with the U/Th age of ∼130 ka obtained from coral fragments. This work demonstrates that the RSD is a promising method for dating gravel veneer deposits overlaying marine terraces, enabling new chronologies for similar Quaternary deposits.

Eccentric compression performance of coral concrete-filled aluminum alloy tube (CCFAT) circular short columns

Coral concrete, utilizing coral reef bodies in place of traditional aggregates, shows promising prospects use in island projects. The use of aluminum alloy-reinforced coral concrete columns effectively enhances the load-bearing capacity of these structures. This study aims to investigate the performance of aluminum alloy circular tube-reinforced coral concrete short columns under eccentric compression. The study involved designing fifteen short columns for eccentric compression experiments, focusing on key parameters such as aluminum content (α), eccentricity (e0), and coral concrete strength (fc). The study obtained failure modes, bearing capacities, and load-deformation relationships, and analyzed the impacts of aluminum content, eccentricity, coral concrete strength, and hoop coefficient (ξa) on the columns’ strength, stiffness, and ductility. Subsequently, a finite element parameter expansion analysis using Abaqus was performed. Ultimately, a correction coefficient model was developed, compared with existing international specifications, and used to establish a suitable calculation model for the bearing capacity of CCFAT eccentric short columns. The results indicated that CCFAT eccentric short columns predominantly experienced bending failure. The stresses in the aluminum alloy round tube can reach the conditional yield strength, effectively collaborating with the concrete. The load-deformation relationship did not exhibit an intensification stage, and the lateral deflection curves tended to follow sinusoidal half-wave patterns. During the initial loading stage, adherence to the plane-section assumption was observed, with the hoop effect primarily manifesting in the compression zone. The strength index showed an approximately quadratic relationship with ξa, the stiffness index showed a positive correlation with ξa, and the ductility index demonstrated a strong positive association with ξa. The correction coefficient model, along with AIJ (2001), can be employed for calculating the bearing capacity of CCFAT eccentric short columns. This study introduces the novel concept of aluminum alloy tube-reinforced coral concrete columns as a composite structure for island civil engineering construction. Beyond the benefits of traditional steel tube concrete, these composite columns are expected to reduce engineering costs, shorten construction timelines, and address durability concerns through the incorporation of marine coral stones and fragments as concrete aggregates.

Assisted sexual coral recruits show high thermal tolerance to the 2023 Caribbean mass bleaching event.

Assisted sexual coral propagation, resulting in greater genet diversity via genetic recombination, has been hypothesized to lead to more adaptable and, hence, resilient restored populations compared to more common clonal techniques. Coral restoration efforts have resulted in substantial populations of 'Assisted sexual Recruits' (i.e., juvenile corals derived from assisted sexual reproduction; AR) of multiple species outplanted to reefs or held in in situ nurseries across many locations in the Caribbean. These AR populations provided context to evaluate their relative resilience compared to co-occurring coral populations during the 2023 marine heat wave of unprecedented duration and intensity that affected the entire Caribbean. Populations of six species of AR, most ranging in age from 1-4 years, were surveyed across five regions during the mass bleaching season in 2023 (Aug-Dec), alongside co-occurring groups of corals to compare prevalence of bleaching and related mortality. Comparison groups included conspecific adult colonies as available, but also the extant co-occurring coral assemblages in which conspecifics were rare or lacking, as well as small, propagated coral fragments. Assisted sexual recruits had significantly lower prevalence of bleaching impacts (overall pooled ~ 10%) than conspecific coral populations typically comprised of larger colonies (~ 60-100% depending on species). In addition, small corals derived from fragmentation (rather than sexual propagation) in two regions showed bleaching susceptibility intermediate between AR and wild adults. Overall, AR exhibited high bleaching resistance under heat stress exposure up to and exceeding Degree Heating Weeks of 20°C-weeks. As coral reefs throughout the globe are subject to increasingly frequent and intense marine heatwaves, restoration activities that include sexual reproduction and seeding can make an important contribution to sustain coral populations.

Evaluating the coral microbiome during cryopreservation

Coral reefs are threatened by various local and global stressors, including elevated ocean temperatures due to anthropogenic climate change. Coral cryopreservation could help secure the diversity of threatened corals. Recently, isochoric vitrification was used to demonstrate that coral fragments lived to 24 hr post-thaw; however, in this study, they were stressed post-thaw. The microbial portion of the coral holobiont has been shown to affect host fitness and the impact of cryopreservation treatment on coral microbiomes is unknown. Therefore, we examined the coral-associated bacterial communities pre- and post-cryopreservation treatments, with a view towards informing potential future stress reduction strategies. We characterized the microbiome of the Hawaiian finger coral, Porites compressa in the wild and at seven steps during the isochoric vitrification process. We observed significant changes in microbiome composition, including: 1) the natural wild microbiomes of P. compressa were dominated by Endozoicomonadaceae (76.5 % relative abundance) and consistent between samples, independent of collection location across Kāneʻohe Bay; 2) Endozoicomonadaceae were reduced to <6.9 % in captivity, and further reduced to <0.5 % relative abundance after isochoric vitrification; and 3) Vibrionaceae dominated communities post-thaw (58.5–74.7 % abundance). Thus, the capture and cryopreservation processes, are implicated as possible causal agents of dysbiosis characterized by the loss of putatively beneficial symbionts (Endozoicomonadaceae) and overgrowth of potential pathogens (Vibrionaceae). Offsetting these changes with probiotic restoration treatments may alleviate cryopreservation stress and improve post-thaw husbandry.

Cold-water octocoral interactions with microplastics under laboratory conditions

Microplastic pollution is ubiquitous in the oceans, threatening the health of marine ecosystems. The deep sea is recognized as a sink for microplastics, but there is a paucity of information on how deep-sea organisms are being affected by this stressor. Considering their vulnerability to disturbance, this information is crucial to fully understand the need for conservation actions. Here, we develop a novel methodology to provide a detailed characterisation of the behavioural responses of the cold-water octocoral Viminella flagellum to microplastic exposure under laboratory conditions. Coral fragments were individually exposed to a concentration of 1500 items/L of fluorescent green polyethylene microspheres biofouled for three weeks, for a period of 24 h, and carefully monitored for the entire exposure period using high resolution time-lapse video. After exposure, each fragment was transferred to another tank, free of microplastics, and monitored for further 24 h. The coral fragments were dissected at the end of the experimental period to assess the number of microplastics that remained in the digestive tract of each polyp. Our results showed that during this short-term exposure period, V. flagellum was ingesting microspheres, but most importantly it demonstrated the capacity of egesting all particles within 24 h. These results are especially important when quantifying microplastic contamination in cold-water corals in their natural habitat, as only recently ingested microplastics may be detected, leading to potential underestimations of their exposure. Additionally, our results indicated that microplastics adhered to the coral tissue surface could be discarded through periodic shedding of the mucus. These observations suggest that cold-water octocorals can handle microplastics as they do with other foreign particles, although the cleaning mechanisms may require significant energy expenditures.

Growth and Survival Rate of Pocillopora spp. Fragments on Coral Tree and Coral Table Media in Semut Kecil Island, Anambas Islands

Graphical Abstract Highlight Research Pocillopora spp. coral fragments have been identified and analyzed. Growth of new coral polyp tissue on skeletal media and substrate. The presence of coral bleaching was caused by sedimentation and algal growth that covered the fragments. The effectiveness of the media for transplantation. Abstract Pulau Semut Kecil, Anambas Islands, are located within the coral reef triangle, as one of the largest Marine Protected Areas (MPAs) in Indonesia. Coral reefs possess significant functional attributes within ecosystems, and their condition is progressively deteriorating due to anthropogenic activities. This situation necessitates restoration endeavors, primarily through coral transplantation methodologies. The methods involved the introduction or relocation of donor corals into substrates such as tree transplantation media and tables, exhibiting high success rates. This study was conducted to determine the growth and survival rate of Pocillopora spp. The direct survey approach was used and the different coral transplanting media were statistically analyzed with the ANOVA test and SPSS software. The results of the growth of coral fragments Pocillopora spp. Reported coral tree media and table with an average value of 0.55 cm/month and 0.15 cm/month. The survival rate of Pocillopora spp. coral fragments in tree media and table was 97.3% and 87.0%. The media for dropping coral trees and table did not affect the growth and survival rate. This coral transplantation method can facilitate for the restoration of degraded ecosystem and ecological succession.

Survival rates of branching Acropora morphologies on coral rubble stabilization structures

Compact bushy and expansive branching Acropora survival rates were compared in an experimental restoration setting. Coral fragments were sourced as corals of opportunity (CoPs) or refragmented from CoPs reared on a floating mid‐water rope nursery. Fragments were attached in single‐species and mixed‐species aggregations to modular substrate stabilization structures (reef stars) on degraded, unconsolidated dead coral rubble slopes in Wakatobi Marine National Park, central Indonesia. In total, 1440 Acropora fragments were outplanted to 96 reef stars across five experimental restoration blocks at 14 m depth. Fragment survival was recorded 40–44 months post‐attachment. Survival had a significant relationship with fragment morphology (p &lt; 0.001) and aggregation type (p &lt; 0.01). Sourcing fragments as CoPs or from the nursery did not have a significant relationship with survival. No significant relationships were found with fragment survival for any interactions between morphology, outplanted aggregation, and source. Survival rates for bushy Acropora were 3.44 times and 5.25 times higher than for expansive species for direct CoP outplants and nursery‐reared corals, respectively. The results demonstrate the potential efficacy of returning complex bushy branching Acropora morphologies to mid‐depth reef slopes previously dominated by the genus, using single‐species aggregations interspersed with mixed‐species aggregations. The study also supports using mid‐water nurseries to create a closed or semi‐closed nursery cycle to scale up restoration, and proposes introducing the term “biomass production system” to distinguish this as a process distinct from other coral nursery approaches.

Holocene to present-day coastal landscapes of Bar al Hikman (Oman): Neolithic waypoints on the shores of the Arabian Sea

Dramatic climatic and environmental changes over the last 12,000 years have significantly impacted Arabian coastal stratigraphy and human populations. The Bar Al Hikman peninsula (BAH), the largest low-lying area (1000 km2) along the Arabian Sea coast of Oman is a monsoon storm-dominated carbonate-evaporite system, where late Neolithic artifacts suggest human presence from at least 5.75–5.05 ka before the present (BP). Despite its archaeological significance at the crossroads of important Neolithic coastal sites in Dhofar, Masirah, and Ja'alan coast, paleoenvironmental interpretation, timing, and expression of relative sea level (RSL) changes in this coastal area remain poorly understood. Fortunately, the extensive size and arid climate of the area have preserved carbonate-dominated Mid-Late Holocene coastal geomorphologies exceptionally well, making this area an excellent geological archive to study past coastal environments, thereby understanding how environmental changes at BAH influenced Neolithic human mobility and settlement patterns. This study reconstructs the paleoenvironment of BAH over the last 12,000 years using a combination of field and remote sensing techniques, including satellite imagery, digital elevation models, bathymetric data, GIA modeling, and Sea Level Index Points to trace RSL history. The Holocene transgression began flooding the extensive continental shelf offshore BAH around 10 ka BP, progressively separating Masirah from the mainland through channel formation between 9.5 and 8.0 ka BP. It then inundated the present-day BAH peninsula around 7.7 ka BP, reaching a highstand of 2.5–3.2 m above present sea level by 6.0 ka BP (Mid-Holocene Highstand; MHHS), before gradually declining to the current level. Human presence documented at BAH (5.75–5.05 ka BP) coincides with the end of the mid-Holocene highstand, and the onset of the regression. This relative sea level history is contemporaneous to the aridification of Arabia, a period of transition from mangrove-dominated intertidal settings to coral reef and carbonate coastal barriers. The disappearance of mangrove-like gastropods around 5.4 cal ka BP and the subsequent appearance of significant coral fragments in the sediment indicates a critical change in terms of environmental settings with less nutrients and a warmer sea surface temperature). Comparing the findings at BAH to well-established nearby Neolithic sites on Masirah Island, the scarcity of prehistoric remains at BAH suggests that during the Mid-Holocene Highstand (MHHS), the small, rocky, paleo-low-lying islands at BAH may have served as waypoints and shelters between Masirah and the mainland.

A mathematical model for wound healing in the reef-building coral Pocillopora damicornis

Coral reefs, among the most diverse ecosystems on Earth, currently face major threats from pollution, unsustainable fishing practices , and perturbations in environmental parameters brought on by climate change. Corals also sustain regular wounding from other sea life and human activity. Recent reef restoration practices have even involved intentional wounding by systematically breaking coral fragments and relocating them to revitalize damaged reefs, a practice known as microfragmentation. Despite its importance, very little research has explored the inner mechanisms of wound healing in corals. Some reef-building corals have been observed to initiate an immunological response to wounding similar to that observed in mammalian species. Utilizing prior models of wound healing in mammalian species as the mathematical basis, we formulated a mechanistic model of wound healing, including observations of the immune response and tissue repair in scleractinian corals for the species Pocillopora damicornis. The model consists of four differential equations which track changes in remaining wound debris, number of cells involved in inflammation, number of cells involved in proliferation, and amount of wound closure through re-epithelialization. The model is fit to experimental wound size data from linear and circular shaped wounds on a live coral fragment. Mathematical methods, including numerical simulations and local sensitivity analysis, were used to analyze the resulting model. The parameter space was also explored to investigate drivers of other possible wound outcomes. This model serves as a first step in generating mathematical models for wound healing in corals that will not only aid in the understanding of wound healing as a whole, but also help optimize reef restoration practices and predict recovery behavior after major wounding events.

Morphology and molecular evidence reveal hidden diversity among snapping shrimp of the Alpheus obesomanus group (Decapoda: Alpheidae) with the description of a new species from Brazil

The snapping shrimp family Alpheidae Rafinesque, 1815 includes numerous species, most of which present controversial geographical distributions. The disjunct distribution of Alpheus simus Guérin-Méneville, 1856 in the western Atlantic, from Florida to the south of the Caribbean Sea and then from Rio Grande do Norte to Bahia in Brazil, suggests that Brazilian material may belong to an undescribed species. The examination of specimens previously identified as A. simus revealed the distinct morphology of material from Brazil, resulting in the description of a new species based on morphological and molecular evidence. The specimens were collected from fragments of fire coral at the Parque Municipal Marinho do Recife de Fora, Porto Seguro, Bahia, Brazil. Alpheus coralvivo sp. nov. belongs to the A. obesomanus group and is morphologically similar to A. simus (northwestern Atlantic) and A. saxidomus Holthuis, 1980 (eastern Pacific), differing mainly in the stylocerite and scaphocerite lengths and in the large gap between the cephalothorax and pleuron of the first pleonal segment. Molecular analysis using the mitochondrial cytochrome oxidase subunit I gene support the existence of the new species.

In situ lesion recovery of Scleractinian branching coral wild colonies from asexual coral propagation

As coral reefs worldwide continue to degrade due to natural and anthropogenic threats, coral restoration efforts have been rapidly growing in recent decades to maintain the ecological function of coral reefs. In Malaysia, asexual propagation by fragmenting branches from healthy Acropora wild colonies is becoming the norm, but other coral genera are rarely considered in restoration efforts despite the need to enhance diversity and reef resilience. Additionally, restoration efforts in Malaysia mainly focus on the recovery of coral fragments in nurseries while overlooking the wild coral colonies they were sourced from. Lesion recovery from physical damage should be investigated to maximise restoration success and to ensure the wild coral populations do not degrade due to fragmentation from coral propagation efforts. To address this, we investigated the recuperation capabilities of two branching coral species, Acropora muricata and Echinopora horrida, in a shallow reef (<8 m) of Pulau Rawa, Johor, Malaysia. Coral colonies were induced with physical damage, and lesion recovery was measured via lesion site closure, colour score and relative growth of the broken colonies (n=30) over 129 days. The lesion site of A. muricata closed significantly more at 99.94±0.04SE%, compared to E. horrida with 86.97±3.53SE%. When compared to E. horrida, A. muricata had achieved full colour recovery by day 27 and more than double the value of relative growth (9.7 %). The differences in lesion recovery capabilities between A. muricata and E. horrida are hypothesised to be attributed to their different life adaptive strategies where A. muricata is an r adaptive strategist and E. horrida is a K adaptive strategist. The findings imply that future coral restoration efforts should investigate the recovery capabilities of the wild coral colonies before starting coral propagation efforts to prevent partial mortality of wild colonies and maintain species diversity and ecological functions of the reef.

Habitat Characteristics and Morphology of Chlorophyta (Order Bryopsidales) on the Intertidal of Pandanan Hamlet, West Sekotong

Bryopsidales order macroalgae can be found on various substrates in marine waters. The Bryopsidales order has a morphological form that is shaped like a filament or shaped like a leaf and has pigments like land plants. The study aims to determine the habitat characteristics and morphology of the Bryopsidales order on the coast of Pandanan Hamlet. Sampling was carried out using the line transect method and 1x1 meter quadrant. A total of 5 transect lines were stretched from the shoreline to the point where macroalgae were found. Each transect is placed in quadrants every 20 meters in a zigzag manner. The Bryopsidales order found consisted of 13 species, 3 families and 4 genera growing in habitats with substrates of loamy sand, loam, sand, and sandy loam, rock, dead coral, coral fragments, and live coral. There are 3 types of holdfast were found, namely bulbous, fibrous, and sprawling growers. There are also three blade shapes in this order, namely creeping blades in the Caulerpaceae family, segmented blades in the Halimedaceae family, and blades that are neither creeping nor segmented that resemble sponges in the Codiaceae family.

Experimental Observations And Prediction Of Wave Attenuation Using A Coral Reef Restoration Approach

The large bottom roughness typical of coral reefs can be effective at reducing wave energy incident to coastlines through the dissipation induced by how wave-driven oscillatory flows interact with the roughness to determine hydrodynamic forces (i.e., drag and inertial). A physical understanding of these fluid-structure interaction processes is essential in designing coral reef restoration projects that can enhance coastal protection as well as deliver other beneficial ecosystem services, as a more sustainable alternative over conventional engineered structures (e.g. breakwaters and seawalls). In this study we quantify both wave attenuation and hydrodynamic forces across progressive stages of a coral reef restoration solution developed by Mars Sustainable Solutions. The Mars Assisted Reef Restoration System (MARRS) involves propagating coral fragments onto hexagonal steel structures called Reef Stars, which are connected in tessellating patterns over degraded reef flats (Figure 1).

Density and Distribution Pattern of Lola Snail (Trocus niloticus) in the Coastal Waters of Malaku Village, Central Maluku

The lola snail (Trochus niloticus) is a species of sea snail that has important economic value. This research aims to determine the density and distribution patterns of lola snails in the coastal waters of Malaku Village, Central Maluku. Sampling used a stratified random sampling method with line transects, the research location was divided into 3 stations. Stations I and III have plank coral substrates and dead coral fragments, while station II has rocky substrates and coral flats. The results of the research found that the total number of lola snail individuals found at the research location was 110 individuals spread across 3 research stations. The maximum size of lola snails found was 99.41 mm in diameter and the minimum size found was 47.18 mm in diameter. The highest density of Lola snails at each research station was 0.08 ind/m2 and the lowest was 0.05 ind/m2. The distribution pattern of Lola snails at the research location is a clustered pattern.

Coral mariculture using abandoned abalone farming ponds in northeastern Taiwan

Stony corals are ecologically and economically important marine organisms. Coral aquaculture is essential to provide live coral materials for the marine ornamental trade, reef restoration programs, and environmental education. This study sought to establish coral farms in Taiwan. To culture corals, we adopted an abandoned abalone farming pond built along the northeastern coast of Taiwan, and investigated whether it is possible to propagate corals in this artificial environment. Stainless steel underwater tables were anchored to the pond floor, and fragments of Acropora tumida, Pocillopora damicornis, Stylophora pistillata, Favites pentagona, and Porites lobata were cultured on the tables for one year. Environmental factors in the pond were also monitored. The mean surface temperature was 23.07 °C, ranging from >30 °C in summer to 18 °C in winter. The mean salinity and pH were about 35 ppt and 8.14, respectively. Survivorship of these five species after one year ranged from 100% to 67%, with a 1.37–1.51-fold increase in weight and a 3.22–3.38-fold increase in area, demonstrating that although environmental factors fluctuate depending on the season and weather, long-term and stable asexual propagation of corals is feasible in the pond. For further optimization of culture conditions, the effects of initial fragment size for culture on subsequent survival and growth were investigated. Fragments of 3 sizes (1.5, 3.0, and 4.5 cm) were prepared from parental colonies of A. tumida, P. damicornis, and S. pistillata and cultured for 6 months by hanging them under the table. There were no significant differences in survivorship among these sizes. Differences were observed in biomass (weight) increase. In A. tumida, 3-cm fragments showed significantly more weight gain than other lengths, while 1.5-cm fragments showed a significant weight increase in P. damicornis. In S. pistillata, no significant difference in weight increase was observed among size groups, suggesting the necessity to optimize the initial fragment size for culture for each species before mass culture. Histological analysis showed that mature gametes were formed in some cultured corals, suggesting that sexual propagation may also be possible in the future. The established coral farm, which is culturing >4000 coral fragments now, will be able to support not only basic and applied coral research, but also sustainable reef development and marine ornamental trade.

Restoration of herbivory on Caribbean coral reefs: are fishes, urchins, or crabs the solution?

That coral reefs are in decline worldwide, particularly in the Caribbean, will come as no surprise. This decades-long decline has reached a potential tipping point as the weight of the effects of climate change have come decidedly to bear on the planet’s most diverse marine ecosystem. Whether coral reefs can persist without restorative intervention is debatable, which has prompted a surge in coral reef restoration projects focusing primarily on the cultivation and transplantation of coral fragments onto degraded reefs. But that widespread approach does little to address the underlying causes of coral loss, one of which is the proliferation of macroalgae that are deleterious to corals. An emerging solution to this problem is the enhancement of herbivory on coral reefs through improved management of herbivores, artificial enhancement of herbivore settlement, or their mariculture and subsequent stocking. This review explores the nuances of the biology of well-studied Caribbean coral reef herbivores (fishes, sea urchins, and crabs) as it relates to their mariculture and investigates the promise of herbivore stocking onto coral reefs as a restoration strategy. Fish, urchin, and crab herbivores differ appreciably in life histories, which confers advantages and disadvantages with respect to their mariculture and effectiveness as grazers. Mariculture of herbivorous marine fish for reef restoration is essentially non-existent so the reestablishment of grazing fish abundance on coral reefs focuses primarily on their protection through fishery regulations, but only at a few locations in the Caribbean. Mariculture of herbivorous urchins and crabs for restoration purposes is in its infancy, but promising especially for crabs whose larval rearing is less difficult. Perhaps the biggest challenge for the mariculture of either taxon is “scaling-up” from research settings to large-scale mariculture needed for stocking. Numerous studies extol the benefits of functional redundancy and complementarity for coral reef ecosystem stability, but whether this principal applies to the restoration of grazing function is untested. We identify gaps in our knowledge of best practices for the restoration of grazing function on coral reefs and conclude with some practical guidance on the establishment of targets for macroalgal reduction, along with strategic advice on grazer stocking in a given reef habitat.

Bacterial symbionts of the precious coral Corallium rubrum are differentially distributed across colony-specific compartments and differ among colormorphs.

Corals engage in symbioses with micro-organisms that provide nutrients and protect the host. Where the prokaryotic microbes perform their symbiotic functions within a coral is, however, poorly understood. Here, we studied the tissue-specific microbiota of the coral Corallium rubrum by dissecting its tissues from the skeleton and separating the white polyps from the red-coloured coenenchyme, followed by 16S rRNA gene metabarcoding of the three fractions. Dissection was facilitated by incubating coral fragments in RNAlater, which caused tissues to detach from the skeleton. Our results show compartmentalisation of the microbiota. Specifically, Endozoicomonas, Parcubacteria and a Gammaproteobacteria were primarily located in polyps, whereas Nitrincolaceae and one Spirochaeta phylotype were found mainly in the coenenchyme. The skeleton-associated microbiota was distinct from the microbiota in the tissues. Given the difference in tissue colour and microbiota of the polyps and coenenchyme, we analysed the microbiota of three colormorphs of C. rubrum (red, pink, white), finding that the main difference was a very low abundance of Spirochaeta in white colormorphs. While the functions of C. rubrum's symbionts are unknown, their localisation within the colony suggests that microhabitats exist, and the presence of Spirochaeta appears to be linked to the colour of C. rubrum.