Coral Tissue Research Articles

Adult corals are uniquely more sensitive to manganese than coral early-life stages.

Manganese is an essential element and generally considered to be one of the least toxic metals to aquatic organisms, with chronic effects rarely seen at concentrations below 1000 µg/L. Anthropogenic activities lead to elevated concentrations of manganese in tropical marine waters. Limited data suggests that manganese is more acutely toxic to adult than to early life-stages of scleractinian corals in static renewal tests. However, to enable the inclusion of sufficient sensitive coral data in species sensitivity distributions to derive water quality guideline values (GVs) for manganese, we determined the acute toxicity of manganese to the adult scleractinian coral, Acropora muricata, in flow-through exposures. The 48-h EC50 was 824 µg Mn/L (based on time-weighted average, measured, dissolved manganese). The endpoint was tissue sloughing, a lethal process by which coral tissue detaches from the coral skeleton. Tissue sloughing was unrelated to superoxidase dismutase activity in coral tissue, and occurred in the absence of bleaching, i.e., toxic effects were observed for the coral host, but not for algal symbionts. We confirm that adult scleractinian corals are uniquely sensitive to manganese in acute exposures at concentrations 10 to 340 times lower than those reported to cause acute or chronic toxicity to coral early life stages, challenging the traditional notion that early life stages are more sensitive than mature organisms. This article is protected by copyright. All rights reserved. Environ Toxicol Chem 2023;00:0-0. © 2023 SETAC.

Nursery-reared coral outplanting success in an upwelling-influenced area in Costa Rica

Introduction: Environmental and intrinsic factors such as seawater temperature, salinity, nutrient concentration, upwelling, species, and life history can influence coral outplant survival and growth, and in consequence, the effectiveness of restoration. Thus, it is key to understand how these factors can shape coral outplant performance to ensure the long-term success of a restoration program. 
 Objective: To establish the survival and growth rate of outplanted coral nursery-reared colonies of branching Pocillopora spp. and massive corals Pavona gigantea, Pavona clavus, and Porites lobata in Bahía Culebra, North Pacific of Costa Rica, and to determine whether the site of origin of the coral fragment and the presence of seasonal upwelling affected the growth of Pocillopora outplants. 
 Methods: From September 2020 to September 2021, we monitored the survival, health, and growth of 30 Pocillopora spp. colonies from six donor sites, and 31 fragments of massive species (P. gigantea [n = 18], P. clavus [n = 8], P. lobata [n = 5]) that were outplanted to a degraded reef. We recorded in situ seawater temperature, salinity, and nutrient concentration. 
 Results: By the end of the year, 100 % of the Pocillopora spp. outplants survived. Survival was 71.4 % for P. clavus, 47.5 % for P. gigantea, and 20 % for P. lobata. Coral tissue loss and predation marks were observed at least once in 71 % of massive outplants. Pocillopora spp. colonies increased their initial area in 333.1 %, at a rate of 9.98 ± 1.69 cm yr-1. The site of origin of the outplant influenced growth rate, but not the presence of seasonal upwelling. Massive species fragments grew at a rate of 1.35 ± 0.24 cm yr-1 for P. clavus, 1.48 ± 0.21 cm yr-1 for P. gigantea, and 0.61 cm yr-1 for P. lobata, with no differences among them. 
 Conclusions: Environmental conditions at site level allow for high survival and growth of Pocillopora spp. outplants, previously considered as sensitive to stressors, and point towards acclimation to seasonal upwelling. Although survival of massive species was lower, developing a multi-species approach is key to enhance restoration success.

PRELIMINARY OBSERVATIONS OF THE DEVELOPMENT OF GONAD PIGMENTATION AS A REPRODUCTIVE PATTERNS OF FAVIIDAE IN SPERMONDE ARCHIPHELAGO, INDONESIA

Coral spawning occurs throughout the year in Indonesia due to tropical climate conditions that influence coral development and spawning. As representative data on coral gonad development in the Spermonde Archipelago, observations on the development of the Faviidae gonads were conducted on Barrang Lompo, Kodingareng Keke, Samalona, and Bonetambung Island. Environmental elements are measured in the form of surface water temperature and rainfall. Based on the abundance of this type of gigantic coral at the study site, coral tissue sampling was concentrated on the Faviidae. The pigmentation of the gonads of Faviidae has been studied visually in nature. The samples were carved on the coral before being photographed. To make it easier to detect the level of pigmentation in each species, coral gonadal tissue was imaged. If there is an orange, yellow, or blue tint, it indicates that the coral has colored gonads and is mature gonads, indicating that coral spawning will occur soon. A water lever logger was used to measure the temperature of the water. The results of water temperature measurements vary and can be linked to the development of coral pigmentation as well as observations from November to March when the third phase (pigmented) process in Faviidae was considered to have happened in large numbers. It is possible that Faviidae can breed during this sensitive period. Rainfall data was gathered from Makassar City's Paotere Maritime Meteorological Station.

Coral persistence despite marginal conditions in the Port of Miami

Coral cover has declined worldwide due to anthropogenic stressors that manifest on both global and local scales. Coral communities that exist in extreme conditions can provide information on how these stressors influence ecosystem structure, with implications for their persistence under future conditions. The Port of Miami is located within an urbanized environment, with active coastal development, as well as commercial shipping and recreational boating activity. Monitoring of sites throughout the Port since 2018 has revealed periodic extremes in temperature, seawater pH, and salinity, far in excess of what have been measured in most coral reef environments. Despite conditions that would kill many reef species, we have documented diverse coral communities growing on artificial substrates at these sites—reflecting remarkable tolerance to environmental stressors. Furthermore, many of the more prevalent species within these communities are now conspicuously absent or in low abundance on nearby reefs, owing to their susceptibility and exposure to stony coral tissue loss disease. Natural reef frameworks, however, are largely absent at the urban sites and while diverse fish communities are documented, it is unlikely that these communities provide the same goods and services as natural reef habitats. Regardless, the existence of these communities indicates unlikely persistence and highlights the potential for coexistence of threatened species in anthropogenic environments, provided that suitable stewardship strategies are in place.

Evaluation of Forsythia suspensa extract for drug therapy of ciliate infection in coral (Goniopora columna)

Coral aquaculture is an emerging aquaculture industry. In recent years, ciliate infestation has become a serious hazard to wild and captive corals. Our previous research found that infected corals can fester or die within 72 h, posing a serious threat to large-scale coral aquaculture. Little research has been done on the treatment of coral ciliate disease. Therefore, drugs that seek effective treatment and avoid stress responses to corals will be applied to large-scale coral aquaculture. Forsythia suspensa is a common traditional Chinese medicine with anti-inflammatory, anticancer, antibacterial, antiviral, and insecticidal functions. In this study, the F. suspensa extract at concentrations of 0.5%, 1%, 1.25%, 1.75%, 2.25%, and 2.75% was used to conduct a virulence test on ciliates and evaluate the therapeutic effect on Goniopora columna. The uninfected ciliates are the N-group, and the infected ciliates without drug treatment, the control group, are the C-group. After the experiment, the effects of the F. suspensa extract on the ciliate stress response of corals were evaluated by using the virulence test and calculating damage to histopathology, zooxanthellae, chlorophyll a, and three antioxidant enzymes, namely, superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA). The results showed that the LC50 value of the F. suspensa extract was approximately 1.52%, and when the concentration was increased to 1.75%, the ciliates could be completely killed within 10 min of medicated bathing. The SOD, CAT, and MDA of G. columna under the 1.75% treatment were lower than those of the other treatment groups and higher than only those of the N-group. The zooxanthellae, chlorophyll a, and survival rate were not significantly different from those in the N-group. Upon histological examination, no ciliates or vacuum were found in coral tissue 72 h after treatment. In conclusion, 1.75% Forsythia suspensa extract is effective in the treatment of G. columna ciliate infection without causing a strong stress response in corals. Forsythia suspensa can be effectively applied in the prevention of ciliate diseases in large-scale coral aquaculture.

On the Fate of Butyl Methoxydibenzoylmethane (Avobenzone) in Coral Tissue and Its Effect on Coral Metabolome.

The intensive use of sunscreen products has raised concerns regarding their environmental toxicity and the adverse impacts of ultraviolet (UV) filters on ecologically important coral communities. Prior metabolomic analyses on symbiotic coral Pocillopora damicornis exposed to the UV filter butyl methoxydibenzoylmethane (BM, avobenzone) revealed unidentified ions in the holobiont metabolome. In the present study, follow-up differential metabolomic analyses in BM-exposed P. damicornis detected 57 ions with significantly different relative concentrations in exposed corals. The results showed an accumulation of 17 BM derivatives produced through BM reduction and esterification. The major derivative identified C16:0-dihydroBM, which was synthesized and used as a standard to quantify BM derivatives in coral extracts. The results indicated that relative amounts of BM derivatives made up to 95% of the total BM (w/w) absorbed in coral tissue after 7 days of exposure. Among the remaining metabolites annotated, seven compounds significantly affected by BM exposure could be attributed to the coral dinoflagellate symbiont, indicating that BM exposure might impair the photosynthetic capacity of the holobiont. The present results suggest that the potential role of BM in coral bleaching in anthropogenic areas should be investigated and that BM derivatives should be considered in future assessments on the fate and effects of BM in the environment.

Chemical and genomic characterization of a potential probiotic treatment for stony coral tissue loss disease

Considered one of the most devastating coral disease outbreaks in history, stony coral tissue loss disease (SCTLD) is currently spreading throughout Florida’s coral reefs and the greater Caribbean. SCTLD affects at least two dozen different coral species and has been implicated in extensive losses of coral cover. Here we show Pseudoalteromonas sp. strain McH1-7 has broad-spectrum antibacterial activity against SCTLD-associated bacterial isolates. Chemical analyses indicated McH1-7 produces at least two potential antibacterials, korormicin and tetrabromopyrrole, while genomic analysis identified the genes potentially encoding an L-amino acid oxidase and multiple antibacterial metalloproteases (pseudoalterins). During laboratory trials, McH1-7 arrested or slowed disease progression on 68.2% of diseased Montastraea cavernosa fragments treated (n = 22), and it prevented disease transmission by 100% (n = 12). McH1-7 is the most chemically characterized coral probiotic that is an effective prophylactic and direct treatment for the destructive SCTLD as well as a potential alternative to antibiotic use.

Effects of polypropylene nanofibers on soft corals

Current information regarding the effects of both micro- and nano-plastic debris on coral reefs is limited; especially the toxicity onto corals from nano-plastics originating from secondary sources such as fibers from synthetic fabrics. Within this study, we exposed the alcyonacean coral Pinnigorgia flava to different concentrations of polypropylene secondary nanofibers (0.001, 0.1, 1.0 and 10 mg/L) and then assayed mortality, mucus production, polyps retraction, coral tissue bleaching, and swelling. The assay materials were obtained by artificially weathering non-woven fabrics retrieved from commercially available personal protective equipment. Specifically, polypropylene (PP) nanofibers displaying a hydrodynamic size of 114.7 ± 8.1 nm and a polydispersity index (PDI) of 0.431 were obtained after 180 h exposition in a UV light aging chamber (340 nm at 0.76 Wˑm−2ˑnm−1). After 72 h of PP exposure no mortality was observed but there were evident stress responses from the corals tested. Specifically, the application of nanofibers at different concentrations caused significant differences in mucus production, polyps retraction and coral tissue swelling (ANOVA, p < 0.001, p = 0.015 and p = 0.015, respectively). NOEC (No Observed Effect Concentration) and LOEC (Lowest Observed Effect concentration) at 72 h resulted 0.1 mg/L and 1 mg/L, respectively. Overall, the study indicates that PP secondary nanofibers can cause adverse effects on corals and could potentially act as a stress factor in coral reefs. The generality of the method of producing and assaying the toxicity of secondary nanofibers from synthetic textiles is also discussed.

Rapid prototyping for quantifying belief weights of competing hypotheses about emergent diseases

Emerging diseases can have devastating consequences for wildlife and require a rapid response. A critical first step towards developing appropriate management is identifying the etiology of the disease, which can be difficult to determine, particularly early in emergence. Gathering and synthesizing existing information about potential disease causes, by leveraging expert knowledge or relevant existing studies, provides a principled approach to quickly inform decision-making and management efforts. Additionally, updating the current state of knowledge as more information becomes available over time can reduce scientific uncertainty and lead to substantial improvement in the decision-making process and the application of management actions that incorporate and adapt to newly acquired scientific understanding. Here we present a rapid prototyping method for quantifying belief weights for competing hypotheses about the etiology of disease using a combination of formal expert elicitation and Bayesian hierarchical modeling. We illustrate the application of this approach for investigating the etiology of stony coral tissue loss disease (SCTLD) and discuss the opportunities and challenges of this approach for addressing emergent diseases. Lastly, we detail how our work may apply to other pressing management or conservation problems that require quick responses. We found the rapid prototyping methods to be an efficient and rapid means to narrow down the number of potential hypotheses, synthesize current understanding, and help prioritize future studies and experiments. This approach is rapid by providing a snapshot assessment of the current state of knowledge. It can also be updated periodically (e.g., annually) to assess changes in belief weights over time as scientific understanding increases. Synthesis and applications: The rapid prototyping approaches demonstrated here can be used to combine knowledge from multiple experts and/or studies to help with fast decision-making needed for urgent conservation issues including emerging diseases and other management problems that require rapid responses. These approaches can also be used to adjust belief weights over time as studies and expert knowledge accumulate and can be a helpful tool for adapting management decisions.

High-frequency imagery to capture coral tissue (Montipora capricornis) response to environmental stress, a pilot study.

Environment stress is a major threat to the existence of coral reefs and has generated a lot of interest in the coral research community. Under the environmental stress, corals can experience tissue loss and/or the breakdown of symbiosis between the cnidarian host and its symbiotic algae causing the coral tissue to appear white as the skeleton can be seen by transparency. Image analysis is a common method used to assess tissue response under the environmental stress. However, the traditional approach is limited by the dynamic nature of the coral-algae symbiosis. Here, we observed coral tissue response in the scleractinian coral, Montipora capricornis, using high frequency image analysis throughout the experiment, as opposed to the typical start/end point assessment method. Color analysis reveals that the process can be divided into five stages with two critical stages according to coral tissue morphology and color ratio. We further explore changes to the morphology of individual polyps by means of the Pearson correlation coefficient and recurrence plots, where the quasi-periodic and nonstationary dynamics can be identified. The recurrence quantification analysis also allows the comparison between the different polyps. Our research provides a detailed visual and mathematical analysis of coral tissue response to environmental stress, which potentially shows universal applicability. Moreover, our approach provides a robust quantitative advancement for improving our insight into a suite of biotic responses in the perspective of coral health evaluation and fate prediction.

An Underwater Pandemic Is Wiping Out Caribbean Corals

In many parts of the Caribbean, diving underwater will transport you to a colorful world of fish, sponges, mammals, and more. This dazzling undersea rainforest is created by rock-like animals called corals. But just like humans, corals can get sick—and right now a disease is spreading throughout the Caribbean, infecting and killing some of the world’s oldest and largest animals at an alarming speed. The deadly disease is called stony coral tissue loss disease (SCTLD). This article explains what we know about SCTLD and how to spot it in the ocean, how far the disease has spread, what kinds of corals are getting sick, and how we can work together to stop it. We need everyone’s help to save the corals and in turn save the homes of an incredible amount of sea life.

A meta-analysis of the stony coral tissue loss disease microbiome finds key bacteria in unaffected and lesion tissue in diseased colonies

Stony coral tissue loss disease (SCTLD) has been causing significant whole colony mortality on reefs in Florida and the Caribbean. The cause of SCTLD remains unknown, with the limited concurrence of SCTLD-associated bacteria among studies. We conducted a meta-analysis of 16S ribosomal RNA gene datasets generated by 16 field and laboratory SCTLD studies to find consistent bacteria associated with SCTLD across disease zones (vulnerable, endemic, and epidemic), coral species, coral compartments (mucus, tissue, and skeleton), and colony health states (apparently healthy colony tissue (AH), and unaffected (DU) and lesion (DL) tissue from diseased colonies). We also evaluated bacteria in seawater and sediment, which may be sources of SCTLD transmission. Although AH colonies in endemic and epidemic zones harbor bacteria associated with SCTLD lesions, and aquaria and field samples had distinct microbial compositions, there were still clear differences in the microbial composition among AH, DU, and DL in the combined dataset. Alpha-diversity between AH and DL was not different; however, DU showed increased alpha-diversity compared to AH, indicating that, prior to lesion formation, corals may undergo a disturbance to the microbiome. This disturbance may be driven by Flavobacteriales, which were especially enriched in DU. In DL, Rhodobacterales and Peptostreptococcales–Tissierellales were prominent in structuring microbial interactions. We also predict an enrichment of an alpha-toxin in DL samples which is typically found in Clostridia. We provide a consensus of SCTLD-associated bacteria prior to and during lesion formation and identify how these taxa vary across studies, coral species, coral compartments, seawater, and sediment.

Developing recommendations for coral disease management in Puerto Rico using key informant interviews and participatory mapping

Coral diseases pose one of the greatest threats to sustained coral reef health in Puerto Rico. The Puerto Rico Department of Natural and Environmental Resources oversees government-led coral reef conservation initiatives in the archipelago and made coral disease management a priority following the outbreak of stony coral tissue loss disease. This highly virulent and contagious coral disease arrived in Puerto Rico in 2019 and has caused unparalleled coral cover losses. The goal of this study was to use expert local knowledge for the development of coral disease management recommendations. Semi-structured interviews were conducted with 36 key informants representing 23 institutions throughout Puerto Rico. Participants were additionally guided through a participatory mapping exercise to identify coral disease field observations and recommend priority monitoring and intervention sites. Interview inductive coding analysis led to the identification of 10 coral disease management recommendations, each of which contain corresponding actions and strategies under four themes: monitoring, intervention, research, and education. Commonly occurring themes amongst interviewee recommendations included collaboration, communication, organization, and local capacity building. Participatory mapping exercises resulted in 193 disease sighting entries containing 778 disease observations, as well as 149 recommendations for priority coral disease monitoring and/or intervention efforts. The most frequently selected criteria for determining priority sites for coral disease intervention and monitoring were ecological importance, chance of recovery, logistical convenience, and high prior monitoring. An integrated assessment based on priority site selection criteria and interviews was used to identify 14 priority locations for monitoring and intervention and 7 priority locations for targeted citizen science outreach. The results of this study are currently being used to inform coral disease management decision making in a way that uses local knowledge, engages diverse partners, and encourages interagency and cross-regional collaborations. This study can be used as a guide for other localities seeking to develop comprehensive and localized marine ecosystem management plans.

Systematic Review on the Drivers of Coral Bleaching in India

Most of the papers on coral bleaching dealt with some basic knowledges which summarises as corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae living in their tissues, causing them to turn completely white is called Coral bleaching. Depending on extent of bleaching, this may be categorised as healthy coral, stressed coral, bleached coral etc. Coral and algae depend on each other to survive. Corals have a symbiotic relationship with microscopic algae called zooxanthellae that live in their tissues. These algae are the coral’s primary food source and give them their colour Stressed Coral: If stressed, algae leaves the coral. When, the symbiotic relationship becomes stressed due to increased ocean temperature or pollution, the algae leave the coral's tissue. Bleached Coral: Coral is left bleached and vulnerable. Without the algae, the coral loses its major source of food, turns white or very pale, and is more susceptible to disease. Warmer water temperatures can result in coral bleaching. When water is too warm, corals will expel the algae (zooxanthellae) living in their tissues causing the coral to turn completely white. This is called coral bleaching. When a coral bleaches, it is not dead. Corals can survive a bleaching event, but they are under more stress and are subject to mortality. A cold water temperature causes a coral bleaching event that resulted in coral death. There are several causes of coral bleaching, depending on the location. In this project we have to search the papers where the causes of coral bleaching in that particular location. The extent of bleaching may be concluded on the water Quality index of other global factors. Depending on the nature of finding coral reef in geographical location researchers can conclude the causes of bleaching and vice versa. Depending on the nature of finding coral reef in a oceanic location they can conclude the causes of bleaching and vice versa. Nature of water quality, temperature, fish content etc. of the oceanic water etc. may be also predicted as primary findings without secondary testing. The research work has been carried out at least 10 to 15 arbitrarily chosen oceanic coastal areas in India where coral reefs are generally found in the most of the research papers.

Coral Gardens Reef, Belize: An Acropora spp. refugium under threat in a warming world.

Live coral cover has declined precipitously on Caribbean reefs in recent decades. Acropora cervicornis coral has been particularly decimated, and few Western Atlantic Acropora spp. refugia remain. Coral Gardens, Belize, was identified in 2020 as a long-term refugium for this species. This study assesses changes in live A. cervicornis coral abundance over time at Coral Gardens to monitor the stability of A. cervicornis corals, and to explore potential threats to this important refugium. Live coral cover was documented annually from 2012-2019 along five permanent transects. In situ sea-surface temperature data were collected at Coral Gardens throughout the study period and compared with calibrated satellite data to calculate Maximum Monthly Mean (MMM) temperatures and Degree Heating Weeks (DHW). Data on bathymetry, sediment, substrate, herbivore abundance, and macroalgal abundance were collected in 2014 and 2019 to assess potential threats to Coral Gardens. Live coral cover declined at all five transect sites over the study period. The greatest loss of live coral occurred between 2016 and 2017, coincident with the earliest and highest maximum average temperatures recorded at the study site, and the passage of a hurricane in 2016. Structural storm damage was not observed at Coral Gardens, though live coral cover declined after the passage of the storm. Uranium-thorium (230Th) dating of 26 dead in situ fragments of A. cervicornis collected in 2015 from Coral Gardens revealed no correlation between coral mortality and tropical storms and hurricanes in the recent past. Our data suggest that several other common drivers for coral decline (i.e. herbivory, predation, sedimentation, pH) may likely be ruled out for Coral Gardens. At the end of the study period, Coral Gardens satisfied most criteria for refugium status. However, the early onset, higher mean, and longer duration of above-average temperatures, as well as intermittent temperature anomalies likely played a critical role in the stability of this refugium. We suggest that temperature stress in 2016 and perhaps 2015 may have increased coral tissue vulnerability at Coral Gardens to a passing hurricane, threatening the status of this unique refugium.

Testing hypotheses on the calcification in scleractinian corals using a spatio-temporal model that shows a high degree of robustness

Calcification in photosynthetic scleractinian corals is a complicated process that involves many different biological, chemical, and physical sub-processes that happen within and around the coral tissue. Identifying and quantifying the role of separate processes in vivo or in vitro is difficult or not possible. A computational model can facilitate this research by simulating the sub-processes independently. This study presents a spatio-temporal model of the calcification physiology, which is based on processes that are considered essential for calcification: respiration, photosynthesis, Ca2＋-ATPase, carbonic anhydrase. The model is used to test different hypotheses considering ion transport across the calicoblastic cells and Light Enhanced Calcification (LEC). It is also used to quantify the effect of ocean acidification (OA) on the Extracellular Calcifying Medium (ECM) and ATP-consumption of Ca2＋-ATPase. It was able to reproduce the experimental data of three separate studies and finds that paracellular transport plays a minor role compared to transcellular transport. In the model, LEC results from increased Ca2＋-ATPase activity in combination with increased metabolism. Implementing OA increases the concentration of CO2 throughout the entire tissue, thereby increasing the availability of CO3− in the ECM. As a result, the model finds that calcification becomes more energy-demanding and the calcification rate increases.

Bacterial diversity associated with Millepora alcicornis and Phyllogorgia dilatata corals and prospection for genes encoding bioactive molecules

Coral reefs are marine environments with notable biodiversity, considered rich in organisms that produce active molecules. The microorganisms present in coral tissue play different roles that are not yet fully understood. The study of the microbiota can explain how microorganisms influence the health of corals and their participation in defense mechanisms. In this study, the cultivable bacterial communities of Millepora alcicornis and Phyllogorgia dilatata corals were analyzed following the steps of isolation, morphological characterization, and molecular identification by amplification of the gene encoding 16S rRNA. Of the 135 bacterial isolates, 121 of which were from M. alcicornis and 14 from P. dilatata, most belonged to the phyla Proteobacteria and Firmicutes, with the majority from the genera Vibrio and Bacillus. Coral metagenomic DNA was extracted and the gene encoding 16S rRNA was analyzed. The isolates were evaluated, in vitro, for antimicrobial activity against ATCC strains of Escherichia coli and Staphylococcus aureus, and 29 isolates from M. alcicornis showed activity against at least one of the bacteria evaluated. Using specific pairs of primers, 27 isolates showed amplification for at least one pair of primers designed for amplification of genes involved in the synthesis of non-ribosomal peptides (NRPs) and polyketides (PKs). However, only in some cases was a relationship detected between the isolates that showed antimicrobial activity in vitro and the isolates where amplification of genes involved in the synthesis of NRPs and PKs was observed.

Trophic ecology of crustacean endoparasites Petrarca and Baccalaureus (Ascothoracida, Thecostraca) in scleractinian and zoantharian corals

Coral reefs house a great variety of symbiotic associations, including parasitic ones. One of the crucial issues in host-symbiont interactions is the mode of parasite feeding. Most of the parasitism in scleractinian and zoantharian corals is endosymbiotic (endoparasitic). Their trophic interactions are difficult to identify since they only occur in intact associations. Petrarca and Baccaulareus are endosymbiotic crustaceans. In scleractinian corals, Petrarca forms galls in the coral skeleton. Baccaulareus lives inside zoantharians’ gastric cavities. δ13C and δ15N stable isotope analysis (SIA) of Petrarca and its host (holobiont tissue) Turbinaria revealed similar isotopic signatures of the parasite and host (δ13C, -11.77 to -12.69‰; δ15N, 3.66 to 5.52‰), indicating that Petrarca feeds on its host coral. Petrarca has developed mandibles with a row of sharp and dense teeth to cut coral (holobiont) tissue, while maxillules with compound teeth and massive maxillae are involved in further chewing the food. SIA of Baccaulaureus and its host (holobiont) Palythoa revealed that the parasite and its host differ by &gt;12‰ in δ13C, indicating that Baccalaureus does not feed on its host. The analyzed specimens of Baccalaureus revealed 2 groups with different δ15N values; these specimens may obtain food from different trophic levels. The mouth parts of Baccalaureus have reduced mandibles and maxillules with weak armament. Baccalaureus seems to be an opportunist feeder that steals food directly from the host gastric cavity, resulting in significant variations in δ13C and δ15N values.

Decadal-scale variation in coral calcification on coral-depleted Caribbean reefs

Over recent decades, many Caribbean reefs have transitioned to states where stony corals are no longer spatially dominant. The community dynamics culminating in this outcome are well known, but its functional implications remain incompletely understood. Here we used annual surveys from 1992 to 2019 to describe coral communities at 6 sites off St. John, US Virgin Islands, and explored how their ecological dynamics interact with their capacity to sustain estimated coral community calcification (G, kg CaCO3 m-2 yr-1). These communities had low coral cover (≤4.4%), but they changed through small and incremental events that summed to a slight decline in coral cover and changes in species assemblages favoring biotic homogenization and weedy species. Estimated coral G remained low, between 0.3 and 1.3 kg CaCO3 m-2 yr-1 (8.2-35.6 mmol CaCO3 m-2 d-1), but it differed among sites and years. The dominant contributors to G were Siderastrea siderea (1 site), Porites astreoides (1 site), and Orbicella spp. (4 sites), but higher G only occurred where Orbicella spp. remained relatively common; G dramatically declined at 1 site when the abundance of this genus decreased. These results suggest that some coral-depleted reefs may maintain low G that could be sufficient to avoid transitions into net negative budget states, provided that biological and physical erosion and dissolution of CaCO3 (not recorded here) are minimal. Further mortalities of the few coral species remaining on these reefs through disturbances like stony coral tissue loss disease would compromise this delicate production-erosion balance, and likely see transitions of such reefs into negative carbonate budget states.

Dynamics of the Benthic Communities of Pigeon Islets (Guadeloupe Island, Lesser Antilles) from 2012 to 2021 Monitored by a Photo-Quadrats Technique

Since 2012, the benthic communities of the Pigeon Islets (Guadeloupe Island, Lesser Antilles) have been monitored biannually by the National Park of Guadeloupe using photo—quadrats. This monitoring was carried out at 12 coral reef stations distributed around the islets. The data collected from 2012 to 2021 highlight the significant events that disrupted the coral communities of Guadeloupe. Among these remarkable phenomena, an episode of coral bleaching occurred in 2019, followed by the appearance of a new coral disease, Stony Coral Tissue Loss Disease (SCTLD), in 2020. As a result of these threats, a drop of 54% of coral cover was observed in the monitored sites, accompanied by a rise of 16% of the surface occupied by macroalgae. The protocol set up by the National Park of Guadeloupe was found to be efficient to follow the temporal dynamics of benthic reef communities.