Acropora Formosa Research Articles

Structural and hydrodynamic modelling of the probability of breakage of branching and plate coral colonies

Climate change is amplifying the intensity of severe weather events, with coastal regions such as coral reefs facing heightened vulnerability to cyclonic wave forces. Structural models to predict bending stress and breakage of corals have been developed for coral colonies to enhance comprehension and prediction of the effects of hydrodynamic disturbances on coral reefs. However, there is scope for improving these predictions by evolving the methodology for quantifying complicated and variable coral morphologies. This study aims to predict breakage thresholds for two of the most prevalent coral morphologies: branching and plate corals (using Acropora muricata and Acropora hyacinthus as study species). Laboratory and field measurements were taken to assess coral morphologies and material characteristics. Morphological features of 47 branching colonies and 100 plate colonies were surveyed at the study site (Heron Reef, southern GBR) and the tensile strength of 80 coral samples was obtained by in situ and laboratory testing. Three-dimensional structural models of branching and plate coral colonies were developed, encompassing multiple coral colonies with varying morphological patterns from relatively shallow (5-7 m) to deep (9-12 m) zones. Model results were calibrated and verified with existing data, revealing that velocity thresholds of 1.7 m/s and 5.0 m/s would destroy 90% of the simulated branching coral structures growing in the deep and shallow parts of the forereef zone, respectively. In contrast, the plate corals have sufficient margins of safety even in extreme flow conditions (7 m/s). Additionally, skeletal strength and structural performance were adjusted based on varying degrees of bioerosion inside the coral skeleton. A higher probability of breakage was observed as the extent of bioerosion increased. The laboratory experiments of hydrodynamic loads on coral colony show that the sheltering effect due to one or two neighbouring colonies in the upwave direction is negligible. These models can be easily adjusted to provide predictions for other coral species, shapes, levels of bioerosion, and locations (e.g., sheltered or exposed areas). Comprehensive predictions about the level of expected damage and rubble generation in different areas can be used in reef management planning and restoration prioritization.

Enhancing coral restoration practices in Seychelles: benefits and limitations of fishing lines and rope as coral stocking methods

Coral restoration plays a pivotal role in mitigating the decline of coral reefs, increasing the need for implementing effective techniques and methodologies. This study investigates the efficacy of stocking Acropora muricata and Pocillopora grandis using fishing line versus rope in mid‐water floating nurseries, offering valuable insights for coral restoration practitioners. Over 1 year, survival, tissue cover, growth, cleaning time, cost, preparation, and stocking timing for both methods were evaluated. Fishing line reduced contact with fouling organisms, contributing to enhanced coral tissue cover and growth rates for P. grandis compared to rope, but no significant effect was detected for A. muricata. Survival differed among species, with higher rates for P. grandis compared to A. muricata, indicating no impact due to stocking methods but species‐specific differences. Challenges like nursery collapses and amphipod outbreaks may have impacted survival, emphasizing the importance of consistent maintenance and accessibility of project sites. Furthermore, the fishing line method reduced cleaning effort. However, cost considerations and preparation complexities for fishing line warrant careful evaluation, particularly with regards to project budgets. The study underscores the necessity for further research, incorporating diverse genotypes, species, and initial fragment sizes to refine restoration strategies. In summary, this study provides important guidance for coral restoration practitioners, aiding informed decisions on stocking methods for different projects and species while considering the balance between coral health benefits and operational feasibility.

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.

Algal symbiont diversity in Acropora muricata from the extreme reef of Bouraké associated with resistance to coral bleaching.

Widespread coral bleaching has generally been linked to high water temperatures at larger geographic scales. However, the bleaching response can be highly variable among individual of the same species, between different species, and across localities; what causes this variability remains unresolved. Here, we tracked bleached and non-bleached colonies of Acropora muricata to see if they recovered or died following a stress event inside the semi-enclosed lagoon of Bouraké (New Caledonia), where corals are long-term acclimatized to extreme conditions of temperature, pH and dissolved oxygen, and at a nearby control reef where conditions are more benign. We describe Symbiodiniaceae community changes based on next-generation sequencing of the ITS2 marker, metabolic responses, and energetic reserve measures (12 physiological traits evaluated) during the La Niña warm and rainy summer in 2021. Widespread coral bleaching (score 1 and 2 on the coral colour health chart) was observed only in Bouraké, likely due to the combination of the high temperatures (up to 32°C) and heavy rain. All colonies (i.e., Bouraké and reference site) associated predominantly with Symbiodinaceae from the genera Cladocopium. Unbleached colonies in Bouraké had a specific ITS2-type profile (proxies for Symbiodiniaceae genotypes), while the bleached colonies in Bouraké had the same ITS2-type profile of the reef control colonies during the stress event. After four months, the few bleached colonies that survived in Bouraké (B2) acquired the same ITS2 type profiles of the unbleached colonies in Bouraké. In terms of physiological performances, all bleached corals showed metabolic depression (e.g., Pgross and Rdark). In contrast, unbleached colonies in Bouraké maintained higher metabolic rates and energetic reserves compared to control corals. Our study suggests that Acropora muricata enhanced their resistance to bleaching thanks to specific Symbiodiniaceae associations, while energetic reserves may increase their resilience after stress.

Nematosit pada Tiga Spesies Karang Scleractinia, Acropora formosa, Seriatopora sp, dan Pocillopora damicornis Di Pantai Nirwana Sumatera Barat

This research was carried out in July - August 2022. The location of coral sampling is in the coral reefs of the Nirwana coast, West Sumatra. The objective by conducting this study is to determine the type of nematocysts in the body tissues of corals scleractinia, Acropora formosa, Seriatopora sp, and Pocillopora damicornis. Method to know the types of nematocysts from A. formosa, Seriatopora sp, and P. damicornis were carried out using an Olympus, microscope with x100 objective lens magnification at the Marine Biology Laboratory, Faculty of Fisheries and Marine Science, University of Riau. Of the 25 major types of nematocysts known in the phylum Cnidarian, two types are found in these three species. The results showed that there were two main types of nematocysts, namely holotrichous isorhizas (HI) and micro basic p-mastigophore (MpM). The three coral species, A. formosa, Seriatopora sp, and P. damicornis, of the holotrichous isorhizas (HI) nematocysts type and the micro basic p-mastigophore (MpM) nematocyst, were found in the coral species A. formosa and P. damicornis. The type of nematocyst is thought to be used to attack and kill prey.

Biodiversity of Coral Reefs and Reef Fishes in Pasir Putih Situbondo

Biodiversity index assessment is an analytical method to determine the stability of an ecosystem. Coral reefs are the primary productivity for fish resources and other supporting organisms. Along with the increasing threats and needs for utilization, it has resulted in a decrease in cover followed by a decrease in reef fish biota. Therefore, it is necessary to identify and monitor the condition of coral reef biodiversity and reef fish. The purpose of this study was to analyze the condition of coral reef biodiversity and reef fish in Pasir Putih Situbondo. The results showed poor (22.06%) to good (59.16%) status coral cover conditions, the main constituents of 3 families namely Poritidae, Acroporidae and Fungiidae. Poritidae family dominated by Porites rus (CS), Acroporidae dominated by Acropora muricata (ACB) and Fungiidae dominated by Fungia (CMR). The average value of H' was 2.39; E was 0.80 and D was 0.15. The main fish category is dominated by the family Pomacentridae species Pomacentrus brachialis at 539 ind/m2, family Caesionidae species Pterocaesio tessellata at 1,179 ind/m2 and family Chaetodontidae species Chaetodon octofasciatus at 45 ind/m2. The average value of H' index was 2.74; E was 0.69 and D was 0.13.

Integrated metagenomic and metaproteomic analyses reveal bacterial micro-ecological mechanisms in coral bleaching.

Coral reefs worldwide are facing rapid decline due to coral bleaching. However, knowledge of the physiological characteristics and molecular mechanisms of coral symbionts respond to stress is scarce. Here, metagenomic and metaproteomic approaches were utilized to shed light on the changes in the composition and functions of coral symbiotic bacteria during coral bleaching. The results demonstrated that coral bleaching significantly affected the composition of symbionts, with bacterial communities dominating in bleached corals. Through differential analyses of gene and protein expression, it becomes evident that symbionts experience functional disturbances in response to heat stress. These disturbances result in abnormal energy metabolism, which could potentially compromise the health and resilience of the symbionts. Furthermore, our findings highlighted the highly diverse microbial communities of coral symbionts, with beneficial bacteria providing critical services to corals in stress responses and pathogenic bacteria driving coral bleaching. This study provides comprehensive insights into the complex response mechanisms of coral symbionts under heat stress from the micro-ecological perspective and offers fundamental data for future monitoring of coral health.

Photoacclimation dynamics in coral holobionts responding to thermal and irradiance changes correlate with photon pressure per symbiont

AbstractPhotoacclimation is a key homeostatic process that enables photosymbiotic reef corals to flourish within highly variable light environments. However, the temporal dynamics of photoacclimation remain poorly characterized. We studied photoacclimation at several time points over 24 d in two scleractinian coral taxa (mounding Porites spp. and branching Acropora muricata). Coral specimens preacclimated at 24°C and 171 μmol quanta m−2 s−1 were exposed to three light levels (−32%, +27%, and +65% relative to that of the acclimation period) at two temperatures (control, 24°C; mildly stressful, 29°C). Intra‐tissue light environment—specifically, photon pressure per symbiont—increased dramatically with each additional light dose and again with increasing temperature in Porites spp.; net photosynthesis (Pnet) rates continued to change for at least 2 weeks following light increase but not light reduction, and vice versa for symbiont densities. Intra‐tissue light environments were substantially dimmer and more homogeneous among all light treatments in A. muricata, which continued to increase its light‐use efficiency and Pnet through time in most or all treatments. Consequently, prolonged change in Fv/Fm at elevated temperature in Porites spp. but not A. muricata may have been caused by differing photodamage loads. Moderation of light levels by conditions within the coral tissue seems to affect the temporal dynamics of the photoacclimation response, and this finding emphasizes new avenues for photoacclimation research.

Comparative analysis of eukaryotic microbial communities associated with Acropora formosa, sediment, and seawater in a coral reef ecosystem of Whale island, Nha Trang bay, Vietnam

In this study, eukaryotic microbial communities associated with coral Acropora formosa and its natural surroundings, sediment and seawater, in a coral reef ecosystem of Whale Island, Nha Trang Bay, Vietnam were investigated. First, genetic material was taken from Acropora formosa’s surface mucus layer (SML) as well as the sediment underneath and seawater above the colonies from four different sampling locations in a coral reef ecosystem. Subsequently, the data were sequenced using 18S rRNA gene amplicon sequencing method. Sequences (reads) were then analyzed in Rstudio version 4.2.0. Bioinfomatic tools such as DADA2 pipeline clustered the sequences into amplicon sequence variants (ASVs), to which the taxonomy was assigned using SILVA 132 database. The majority of the sequences was categorized at the kingdom and phylum levels, but fewer sequences were identified at genus and species level. The visualization of the results revealed changes in abundance and composition of the eukaryotic communities in all samples. The results demonstrated that phylum Dinoflagellata had the highest relative abundance in coral samples. Meanwhile, Ochrophyta was the most prevalent phylum in seawater samples. Notably, after filtering out the sequences with abundance less than 2%, only genus Symbiodinium appeared significantly in coral samples. The composition of samples from coral sampling sites was more consistent. The same was true for samples of seawater, whereas the composition of sediment samples varied more. Alpha and beta diversity indices confirmed that there were significant differences (p &lt; 0.05) in abundance and composition of eukaryotic communities among three different habitats. These findings come as the first effort to explore the diversity of eukaryotic communities in different habitats and could be valuable for further study in functional profiling or metabolic functions of microbial communities in the coral ecosystem.

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.

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

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

Diplosoma simile (Ascidiacea: Didemnidae) distribution and its photosynthetic thermal stress responses from Mauritius: Implications for invasive or opportunistic behavior

Abstract. Fai ALY, Kaullysing D, Jeetun S, Soondur M, Bhagooli R. 2023. Diplosoma simile (Ascidiacea: Didemnidae) distribution and its photosynthetic thermal stress responses from Mauritius: Implications for invasive or opportunistic behavior. Indo Pac J Ocean Life 7: 16-26. This study aimed to investigate the morphological identity of the ascidian Diplosoma, its distribution, experimental thermal stress responses, and its characteristics of being potentially invasive or opportunistic in Mauritian waters. The Diplosoma species were anesthetized in menthol, fixed, and preserved in a formalin-seawater solution. Isolated zooids and embryos were examined under a microscope for distinct morphological characteristics, which revealed their identity as D. simile (Sluiter, 1909). The D. simile percentage cover studied at seven sites in 2019 around Mauritius tended to be high at the near-reef zone, with a high percentage of dead coral cover per 0.5 m2. At Flic en Flac, long-term observations in 2008, 2010, 2016, and 2019 indicated a significant decrease and increased from 61.25±3.31 to 6.15±0.60 % and 0.08±0.05 to 2.50±090% for the percentage covers of live coral and D. simile, respectively. The D. simile was recorded on five coral species, and its percentage occurrence increased from 2008 to 2019 in Acropora muricata, A. cytherea, Pocillopora damicornis, and Montipora aequituberculata with the highest levels occurring in Acropora while Porites lutea was not found to be covered by D. simile during the study. Visual observations from the thermal exposures at 27ºC, 30ºC, and 33ºC during 19 hrs revealed that D. simile was more affected by increasing temperature and exposure time. Using four observed conditions of normal, bleached/paled, tissue sloughing, and mortality, D. simile suffered from only bleaching/paling at 33ºC at 19 hrs exposure. Variable visual responses were noted for corals, with P. lutea appearing normal at all trials while A. cytherea was suffering from mortality both at 30ºC and 33ºC at 19 hrs exposure. The effective quantum yield (?PSII), measured using a Diving-PAM, declined significantly at 33ºC treatments at 6 and 19 hrs of exposure. D. simile generally tended to be more thermally tolerant than corals like P. lutea, P. damicornis, M. aequituberculata, A. muricata, A, cytherea, though the ?PSII thermal responses were variable among the tested corals. When considering the reported behavioral characteristics of D. simile, namely the lack of broad dispersal range and wide environmental tolerance, it is tempting to deduce that the species is potentially invasive. However, in this study, D. simile’s significant distribution on dead corals, its presence in zones of high anthropogenic activities, and its relatively more robust thermal stress responses than corals colonized suggest an opportunistic behavior.

Photo-physiology of healthy-looking and diseased/health-compromised hard corals from Mauritius Island, Western Indian Ocean

Abstract. Jogee SY, Jeetun S, Ricot M, Taleb-Hossenkhan N, Mattan-Moorgawa S, Kaullysing D, Riemann P, Blanc L, Casareto BE, Suzuki Y, Bhagooli R. 2023. Photo-physiology of healthy-looking and diseased/health-compromised hard corals from Mauritius Island, Western Indian Ocean. Indo Pac J Ocean Life 7: 27-37. The spatial photo-physiological responses of in hospite zooxanthellae in hard corals, including coenosarc and polyps, healthy-looking and affected parts in four coral diseases, namely Brown Band, Black Band, Skeletal Eroding Band and White Band on the coral Acropora muricata, and two health-compromised conditions such as the Pink Pigmentation Response and its differentiated morphology, the Pink Line Syndrome, on the coral Porites were investigated using the Imaging-PAM fluorometry. A significantly lower Fv/Fm was observed in case of Black Band, White Band, Brown Band and Pink Pigmentation Response affected parts compared to the healthy-looking parts. The Fv/Fm had the highest decline in Brown Band disease. Both the polyps and coenosarc had significantly lower Fv/Fm in White Band and Brown Band diseased parts compared to their healthy-looking parts. The rETRmax did not change significantly between diseased/health-comprised parts and healthy-looking parts. NPQmax declined significantly in White Band, Black Band and Pink Pigmentation Response cases. ? and ? generally did not tend to be affected in diseased/health-compromised conditions. The photo-physiology of in hospite zooxanthellae was least affected in Pink Line Syndrome. These findings suggest that diseased/health-compromised parts of corals behave differently in terms of their photo-physiology in different diseased and health-compromised coral conditions in important reef-building corals species such as A. muricata and Porites species, with important implications for the productivity and thus adaptive management of coral reefs in a globally warming ocean.

Diversity and Biogeography of Coral Mucus-Associated Bacterial Communities: The Case of Acropora formosa

The role of microorganisms in coral health, disease, and nutrition has been demonstrated in various studies. Environmental factors including pH, temperature, and dissolved oxygen also play crucial roles in maintaining sustainable coral ecosystems. However, how geographical and environmental factors influence bacterial diversity and community composition is unclear. Here, bacterial communities associated with Acropora formosa coral were sampled from four different locations—Phu Quoc Islands (Vietnam), Nha Trang (Vietnam), Ujung Gelam (Indonesia), and Bourake (New Caledonia)—and compared using tagged 16S rRNA sequencing. We identified 24 bacterial phyla, 47 classes, 114 orders, and 495 genera from 18 samples. Overall, Proteobacteria (1039 distant amplicon sequence variants [ASVs]) and Firmicutes (589 ASVs) were predominant, while Verrucomicrobiota (75 ASVs) and Planctomycetota (46 ASVs) were minor taxa. Alpha diversity analyses revealed that the bacterial community associated with Acropora formosa from Ujung Gelam had the highest indexes (Observed and Chao1), while the figures for Bourake were the lowest. Non-metric multidimensional scaling analysis (NMDS) showed significant differences in bacterial communities among locations (ADONIS, p = 1 × 10−4). Temperature was strongly correlated with the distribution of bacterial communities in Bourake, whereas pH and dissolved oxygen were significantly correlated with the presence of coral-associated bacterial communities in Phu Quoc and Nha Trang. Across all samples, 28 potential biological markers and 95 core ASVs were found, revealing significant differences in coral-associated bacterial communities. Collectively, these findings provide a comprehensive understanding of bacterial communities living in coral reefs across different geographic sites, which could be useful springboards for further studies.

Prokaryotic and eukaryotic microbial communities associated with coral species have high host specificity in the South China Sea

Reef-building corals are well known for their obligate association with Symbiodiniaceae, and an array of other microbes, including bacteria, fungi, and symbiotic algae (i.e., total microbiome), which together form the coral holobiont. The total microbiome plays an intricate part in maintaining the homeostasis of the coral holobiont and is closely associated with host health. However, the composition of the coral associated microbiome and interaction between its different members remains elusive because few analyses have bridged taxonomically disparate groups. This research gaps have prevented a holistic understanding of the total microbiome. Thus, to simultaneously characterize the bacterial, fungal and symbiotic algal communities associated with different coral species, and explore the relationship between these symbionts and coral health, healthy and bleached tissues from four coral species, Acropora muricata, Galaxea fascicularis, Platygyra daedalea, and Pavona explanulata, were collected from the Xisha Islands of the South China Sea. Using high throughput sequencing, a high degree of host-specificity was observed among bacterial, fungal, and algal groups across coral species. There were no obvious changes in the microbial community structure of apparently healthy and bleached corals, but host bleaching allowed colonization of the holobionts by diverse opportunistic microbes, resulting in a significant elevation in the α-diversity of microbial communities. In addition, co-occurrence analysis of the coral microbiota also identified more complex microbial interactions in bleached corals than in healthy ones. In summary, this study characterized the structure of coral-associated microbiomes across four coral species, and systematically studied microbiome differences between healthy and bleached corals. The findings improve our understanding of the heterogeneity of symbiotic microorganisms and the impact of coral's physiological status on its associated microbial communities composition.

Utilizing an artificial intelligence system to build the digital structural proteome of reef-building corals.

Reef-building corals play an important role in the marine ecosystem, and analyzing their proteomes from a structural perspective will exert positive effects on exploring their biology. Here we integrated mass spectrometry with newly published ColabFold to obtain digital structural proteomes of dominant reef-building corals. Of the 8,382 homologous proteins in Acropora muricata, Montipora foliosa, and Pocillopora verrucosa identified, 8,166 received predicted structures after about 4,060 GPU hours of computation. The resulting dataset covers 83.6% of residues with a confident prediction, while 25.9% have very high confidence. Our work provides insight-worthy predictions for coral research, confirms the reliability of ColabFold in practice, and is expected to be a reference case in the impending high-throughput era of structural proteomics.

Parasitic pathways and evaluation of non-specific parasitism of ciliate infected captive corals

Coral disease is a serious challenge for thesurvival of both wild and farmed corals. Ciliate infection causes severe damage on the coral health. The present study is the first report on the non-specific infection potential of ciliate parasites on four kinds of corals. The ciliates were isolated from an infected coral, Euphyllia glabrescens and re-infected to various coral species (Acropora muricata, Goniopora columna, Lemnalia fiava, Heteroxenia pinnata). This study aims to bring insights on ciliate infection rate, specific characteristics of infections, and infection pathway of ciliate in corals. In addition, the study also assessed the nature of parasitization in multiple corals, which could be helpful for a significant risk assessment on large-scale coral aquaculture. The 18S rRNA ciliate gene identification results showed about 99% sequence similarity with the Philaster lucinda found in Acropora coral. The purified ciliate was fed with 5 × 106 cell mL−1 of zooxanthellae and could achieve good proliferation. The specific growth rate of the ciliates was increased after 18 h of infection in the E. glabrescens, reaching 828.33 ± 26.10 cell mL−1. Subsequently, the atrophy of coral polyps was observed after 12 h. After 24 h of infection, the coral began to die as the amount/number of zooxanthellae and chlorophyll a were significantly decreased. The coral suffered with 100% mortality within 72 h of infection. The histological study revealed that ciliate parasitized to coral's endoderm while entering the coral coelenteron via its mouth. Tests of ciliate infection revealed that four types of cultured corals were infected by this ciliate and rapidly rot and die, which suggests its non-specific parasitism potential. Furthermore, this study confirmed their onset of infection on different corals simultaneously, which is an important aspect for future coral research, ensuring coral disease management and designing drugs for ciliate prevention.

Reef-Building Corals Do Not Develop Adaptive Mechanisms to Better Cope With Microplastics

Microplastics are omnipresent in the oceans and threaten marine animals through physical contact or ingestion. Short-term studies have already shown that reef-building stony corals respond differently to microplastics than natural food. However, it remains unknown whether corals exhibit acclimation mechanisms to combat the effects of microplastic exposure. Specifically, the long-term effects of microplastics on the feeding and defense behavior of reef-building corals remain unexplored. Therefore, the goal of this study was to infer potential acclimation mechanisms in the behavior of the corals. For this, four reef-building species (Acropora muricata, Porites lutea, Pocillopora verrucosa, and Heliopora coerulea) were exposed in a long-term experiment to microplastics for 15 months. Subsequently, coral feeding rates on microplastics and natural food (Artemia sp. cysts), feeding discrimination, and reactions to both were assessed in a 24 h pulse exposure experiment. The results showed that corals’ feeding rates did not decrease after long-term exposure to microplastics. Similarly, the feeding discrimination (i.e., ratio of feeding on microplastics and natural food) did not differ after long-term exposure to microplastics. Moreover, corals showed no changes in defense behavior (i.e., mucus production or extrusion of mesenterial filaments) against microplastics. These findings suggest that symbiotic, reef-building corals do not develop mechanisms to adapt to long-term microplastic exposure. Thus, microplastic pollution might constitute a constant stressor for coral organisms, likely leading to sustained energy expenditures and impaired health.

Fluctuation of associated microbial with building reef corals \(\textit{Acropora}\) sp. from Hang Rai, Ninh Thuan

El Niño and the prolonged warm sea surface temperature significantly impacted coral reefs and caused coral bleaching in some parts of the world. This study evaluated the density of symbiotic algae and bacteria associated with the three coral species, namely Acropora hyacinthus, Acropora muricata, and Acropora robusta, collected in Hang Rai, Ninh Thuan in May, June, August 2016, and June 2017. The number of zooxanthellae with each coral species was statistically significant and correlated with several environmental factors, suggesting that symbiotic algae could play a key role in coral health. The number of associated microbial with the three coral species was significantly different; they tended to depend on sampling time rather than coral species-specific. At the time of ENSO (2016), the difference in the total associated bacteria with all three coral species was statistically significant. While the total number of related bacteria with all three species of coral collected in 2017 did not differ from the total of bacteria in ambient water. In conclusion, symbiotic algae tend to be species-specific, whereas bacteria fluctuate significantly over sampling time. Studying the molecular issues of microalgae, the presence, the role of some groups of bacteria involved in the N, C, P, and S cycles, and the influence of environmental parameters should also be encouraged to understand the relationship of coral holobiont better.

Colonies of Acropora formosa with greater survival potential have reduced calcification rates.

Coral reefs are facing increasingly devasting impacts from ocean warming and acidification due to anthropogenic climate change. In addition to reducing greenhouse gas emissions, potential solutions have focused either on reducing light stress during heating, or on the potential for identifying or engineering “super corals”. A large subset of these studies, however, have tended to focus primarily on the bleaching response of corals, and assume erroneously that corals that bleach earlier in a thermal event die first. Here, we explore how survival, observable bleaching, coral skeletal growth (as branch extension and densification), and coral tissue growth (protein and lipid concentrations) varies for conspecifics collected from distinctive reef zones at Heron Island on the Southern Great Barrier Reef. A reciprocal transplantation experiment was undertaken using the dominant reef building coral (Acropora formosa) between the highly variable reef flat and the less variable reef slope environments. Coral colonies originating from the reef flat had higher rates of survival and amassed greater protein densities but calcified at reduced rates compared to conspecifics originating from the reef slope. The energetics of both populations however potentially benefited from greater light intensity present in the shallows. Reef flat origin corals moved to the lower light intensity of the reef slope reduced protein density and calcification rates. For A. formosa, genetic differences, or long-term entrainment to a highly variable environment, appeared to promote coral survival at the expense of calcification. The response decouples coral survival from carbonate coral reef resilience, a response that was further exacerbated by reductions in irradiance. As we begin to discuss interventions necessitated by the CO2 that has already been released into the atmosphere, we need to prioritise our focus on the properties that maintain valuable carbonate ecosystems. Rapid and dense calcification by corals such as branching Acropora is essential to the ability of carbonate coral reefs to rebound following disturbance events and maintain 3D structure but may be the first property that is sacrificed to enable coral genet survival under stress.