Pocillopora Damicornis Research Articles

Coral microbiome changes over the day–night cycle

Coral-associated microbiomes play important roles in host health and metabolism. It is therefore critical to understand the factors that shape microbiome taxonomic composition and function. Little is known about the stability of coral microbiomes over hourly fluctuations in environmental conditions. For parameters such as temperature and pH, the magnitude of day–night fluctuations can exceed those observed in mean values over seasons, especially on shallow reefs. Such short-term heterogeneity can affect longer term trends, possibly by influencing the extent to which corals acclimate to stress and increase resilience. This study examined diel dynamics of microbiomes (Bacteria and Archaea) in three species of stony coral (Porites lutea, Porites cylindrica, and Pocillopora damicornis) from a shallow reef in Mo’orea (French Polynesia). We assessed microbiome composition and relative transcriptional activity by analyzing 16S rRNA gene and transcript sequences from six timepoints over 48 h for each species. Both the composition and transcription of microbiome members changed significantly over the diel cycle. Most changes did not exhibit clear diel periodicity but were instead stochastic, a pattern potentially influenced also by microspatial variation within a coral colony. However, a subset of taxa, notably the dinoflagellate-associated bacterium Porticoccus and bacteria of the ubiquitous coral-associated Endozoicomonas genus, exhibited cyclic changes in relative frequency over the 2 d sampling period in the DNA dataset of Porites lutea. These patterns raise the possibility that ecological functions of the microbiome may vary substantially over hourly timescales, notably between day and night. Further studies are needed to compare temporal change in the coral microbiome with that due to other factors, such as spatial distance within and among colonies.

Low levels of ultra-violet radiation mitigate the deleterious effects of nitrate and thermal stress on coral photosynthesis

Reef ecosystems are under increasing pressure from global and local stressors. Rising seawater temperature and high ultraviolet radiation (UVR) levels are the main drivers of the disruption of the coral-dinoflagellate symbiosis (bleaching). Bleaching can also be exacerbated by nitrate contamination in coastal reefs. However, the underlying physiological mechanisms are still poorly understood. Here, we assessed the physiological and oxidative state of the scleractinian coral Pocillopora damicornis, maintained eight weeks in a crossed-factorial design including two temperatures (26 °C or 30 °C), and two nitrate (0.5 and 3 μM-enriched), and UVR (no UVR and 25/1.5 Wm−2 UVA/B) levels. Nitrate enrichment, and high temperature, significantly impaired coral photosynthesis. However, UVR alleviated the nitrate and temperature-induced decrease in photosynthesis, by increasing the coral's antioxidant capacity. The present study contributes to our understanding of the combined effects of abiotic stressors on coral bleaching susceptibility. Such information is urgently needed to refine reef management strategies.

Structure and spatial variation of the hermatypic coral assemblages of the southern coast of Jalisco, in the Mexican Central Pacific

The hermatypic coral ecosystems of the southern coast of Jalisco, Mexico, present an important species richness and coverage for the Mexican Central Pacific. However, knowledge of these ecosystems of the Jalisco coast is fragmented. Studies have concentrated on few localities, employing a limited number of coral health indicators, and gaps still remain in the knowledge of ecosystem structure and its local and mesoscale variation. This study evaluated spatial variations in the coral assemblage structure in six sites on the southern coast of Jalisco, Mexico, five of which had never been studied before. Sampling was conducted in September 2019, utilizing a total of 35 transects (each of 25 m in length). The cover of each coral species was recorded, as well as other benthic groups and substrate types. Different community attributes, patterns of similarity in coral species and their relationships with the benthic habitat structure were evaluated in each site. The results showed that the observed richness (8 species) represented 83.7% of that expected by chance. Significant spatial variation was found between coral patch sites and coral community sites, in terms of species richness, Shannon diversity and live coral cover, as well as in the structure of the coral assemblage and the benthic habitat. The results evidenced these conditions despite the existence of a considerable dominance of branched corals of the genus Pocillopora. The species that contributed most to the differences between coral patch sites and coral community sites were Pocillopora damicornis, Pocillopora capitata and Pocillopora verrucosa. For their part, the benthic habitat structural elements that favored the differences between site conditions were live coral cover and turf.

Novel methods to establish whole-body primary cell cultures for the cnidarians Nematostella vectensis and Pocillopora damicornis

Cnidarians are emerging model organisms for cell and molecular biology research. However, successful cell culture development has been challenging due to incomplete tissue dissociation and contamination. In this report, we developed and tested several different methodologies to culture primary cells from all tissues of two species of Cnidaria: Nematostella vectensis and Pocillopora damicornis. In over 170 replicated cell cultures, we demonstrate that physical dissociation was the most successful method for viable and diverse N. vectensis cells while antibiotic-assisted dissociation was most successful for viable and diverse P. damicornis cells. We also demonstrate that a rigorous antibiotic pretreatment results in less initial contamination in cell cultures. Primary cultures of both species averaged 12–13 days of viability, showed proliferation, and maintained high cell diversity including cnidocytes, nematosomes, putative gastrodermal, and epidermal cells. Overall, this work will contribute a needed tool for furthering functional cell biology experiments in Cnidaria.

Chronic Exposure to 4-Nonylphenol Alters UDP-Glycosyltransferase and Sulfotransferase Clearance of Steroids in the Hard Coral, Pocillopora damicornis.

The effects of the xenoestrogen 4-nonylphenol (4NP) on endocrine and metabolic homeostasis in the reef building coral, Pocillopora damicornis were investigated. The aim was to understand if ubiquitous nonylphenol ethoxylate contaminants in the marine environment result in altered homeostatic function. Coral colonies were chronically exposed (6 weeks) to a sublethal concentration (1 ppb) of 4NP and sampled over the coral’s lunar reproductive cycle. Although activity of steroidogenic enzymes [cytochrome P450 (CYP) 17, CYP 19, and 3-β-Hydroxysteroid dehydrogenase] and the conjugation enzyme glutathione-S-transferase was not altered, significant increases in the activity of the steroid clearing enzyme UDP-glycosyltransferase (UGT) were observed. The natural fluctuation of UGT activity with the lunar cycle was replaced with consistently high UGT activity throughout the reproductive cycle during 4NP exposure. No effect of 4NP on the reverse reaction, mediated by β-glucuronidase, was observed. Thus, 4NP shifts the UGT:β-glucuronidase ratio toward greater clearance at points in the lunar cycle where retention of compounds is typically favored. Additionally, 4NP reduced activity of the steroid regeneration enzyme steroid sulfatase, further shifting the system toward clearance rather than regeneration. These data imply that environmentally relevant levels of 4NP may be impacting the reproductive health of corals and threatening the persistence of coral reefs.

Transgenerational Effects on the Coral Pocillopora damicornis Microbiome Under Ocean Acidification.

Reef-building corals are inhabited by functionally diverse microorganisms which play important roles in coral health and persistence in the Anthropocene. However, our understanding of the complex associations within coral holobionts is largely limited, particularly transgenerational exposure to environmental stress,like ocean acidification. Here we investigated the microbiome development of an ecologically important coral Pocillopora damicornis following transgenerational exposure to moderate and high pCO2 (partial pressure of CO2) levels, using amplicon sequencing and analysis. Our results showed that the Symbiodiniaceae community structures in adult and juvenile had similar patterns, all of which were dominated by Durusdinium spp., previously known as clade D. Conversely, prokaryotic communities varied between adults and juveniles, possibly driven by the effect of host development. Surprisingly, there were no significant changes in both Symbiodiniaceae and prokaryotic communities with different pCO2 treatments, which was independent of the life history stage. This study shows that ocean acidification has no significant effect on P. damicornis microbiome, and warrants further research to test whether transgenerational acclimation exists in coral holobiont to projected future climate change.

The role of corals on the abundance of a fish ectoparasite in the Great Barrier Reef

Gnathiid isopods, common fish ectoparasites, can affect fish physiology, behaviour and survival. Gnathiid juveniles emerge from the benthos to feed on fish blood. In the Caribbean, gnathiids are positively associated with dead coral and negatively associated with live coral, due to coral predation on gnathiids. However, such interactions were unstudied in the Great Barrier Reef (GBR). Due to recent extreme weather events (two cyclones and one mass warm-water coral bleaching event, 2014–2016), it is now urgent to understand the role of corals on the abundance of these ectoparasites. Here, to understand parasite–coral dynamics at the micro-habitat level, we examined substrate associations of gnathiid isopods on Lizard Island (GBR) using demersal plankton emergence traps. Additionally, we determined whether two abundant hard coral species, Goniopora lobata and Pocillopora damicornis, predate on gnathiids in a laboratory experiment using containers with gnathiids and fragments from each coral species or dead coral as controls. The abundance of gnathiids over natural substrates was higher for dead compared to live hard coral and sand, but not live soft coral. Moreover, we found that free-swimming gnathiids decreased in containers with live coral compared to dead coral controls. This was attributed to predation as we also directly observed a coral ingesting a gnathiid. Our results suggest that dead coral is a suitable microhabitat for gnathiids, but that live coral is not since live corals can predate on gnathiids. We propose that following extreme events, such as cyclones and heat waves, gnathiids might benefit from more dead coral substrate and a decrease in predation by the reduction in coral cover on the reef. We advocate that an increase in the frequency of extreme events may have cascading effects for the fish population through changes in the population of benthos-dependent ectoparasites.

Nanopore long-read RNAseq reveals regulatory mechanisms of thermally variable reef environments promoting heat tolerance of scleractinian coral Pocillopora damicornis

Some scleractinian corals exhibit high thermal adaptability to climate changes, although the mechanism of their adaptation is unclear. This study investigated the adaptability of scleractinian coral Pocillopora damicornis to thermally variable reef environments by applying a nanopore-based RNA sequencing method to characterize different transcription responses that promote heat tolerance of P. damicornis. We identified 1414 novel genes and optimized 6256 mis-annotated loci. Based on full-length transcriptome data, we identified complex alternative polyadenylation and alternative splicing events, which can improve our understanding of the genome annotation and gene structures of P. damicornis. Furthermore, we constructed differentially expressed lncRNA-mRNA co-expression networks, which may play a crucial role in the P. damicornis thermal adaptive response. KEGG function enrichment analysis revealed that P. damicornis from the high-temperature pool had a lower metabolic rate than that from the low-temperature pool. We hypothesize that metabolic readjustment, in the form of a lower metabolic rate, positively correlated with increased heat tolerance in P. damicornis in thermally variable reef environments. Our study provides novel insights into lncRNAs that promote thermally tolerance of scleractinian corals in the thermally variable reef environment, suggesting potential mechanisms for their adaptation to global warming in the future.

Chemotactic response of Vibrio coralliilyticus to mucus from various coral species.

Vibrio coralliilyticus, a prominent pathogenic bacteria, is known to cause tissue damage in the coral Pocillopora damicornis and is attracted towards the coral via chemotaxis. However, the potential of V. coralliilyticus to infect most of the other coral hosts via chemotaxis is unknown. In this study, we used capillary assays to quantify the chemotactic response of V. coralliilyticus to the mucus of four tank-cultivated coral species (Cataphyllia jardine, Mussidae sp., Nemenzophyllia turbida, and Euphyllia ancora), and mucus from three wild coral species (Acropora sp., Porites sp., and Montipora sp.). The bacteria showed a positive chemotactic response to each coral mucus tested, with the highest response recorded to the mucus of Acropora sp. and the lowest response to the mucus of Montipora sp. A microfluidic chip was then used to assess the chemotactic preference of V. coralliilyticus to the mucus of the tank cultivated corals. Here too, the bacterium showed positive response, but with a slightly different ranking order. The strong chemotactic response of V. coralliilyticus towards the mucus tested could indicate a broader host range of V. coralliilyticus, and by extension, indicate a threat to weakened coral reefs worldwide.

Multispecies spawning of scleractinian corals in nonreefal coral communities of northern Taiwan (northwestern Pacific Ocean)

There is a large body of information on sexual reproduction in scleractinian corals, but regional gaps remain, especially in nonreefal coral communities. This study documented the reproductive patterns of 54 coral species in 23 genera and 8 families (41 hermaphroditic spawners, 10 gonochoric spawners, 2 hermaphroditic brooders, and 1 gonochoric brooder) in northern Taiwan by field observations and histological analysis, which indicated that they predominantly spawned in August while fewer spawned in July, September, and October. Based on the field observations, 50 species in 21 genera and 7 families spawned between 20:00 and 22:00 hrs for 5–8 consecutive nights after the full moon in July and August from 2013 to 2016. The spawning patterns varied profoundly in species and colony number from 2014 to 2016: 19 species (42 colonies) in 2014, 6 species (20 colonies) in 2015, and 33 species (120 colonies) in 2016. Most merulinid and lobophyllid corals were observed to spawn consistently over the three years, particularly Favites pentagona, and corals splitly spawned within the colony. Five coral species spawned bimonthly. Three brooding corals (Pocillopora damicornis, Stylophora pistillata, and Porites lichen) also sexually reproduced between summer and early fall. Through this study, we obtained a better understanding of spatial and temporal patterns of the sexual reproduction of corals in nonreefal coral communities. Furthermore, this research may have broader biogeological implications for the northwestern Pacific Ocean region.

Delivering Beneficial Microorganisms for Corals: Rotifers as Carriers of Probiotic Bacteria.

The use of Beneficial Microorganisms for Corals (BMCs) to increase the resistance of corals to environmental stress has proven to be effective in laboratory trials. Because direct inoculation of BMCs in larger tanks or in the field can be challenging, a delivery mechanism is needed for efficient transmission of the BMC consortium. Packaged delivery mechanisms have been successfully used to transmit probiotics to other organisms, including humans, lobsters, and fish. Here, we tested a method for utilizing rotifers of the species Brachionus plicatilis for delivery of BMCs to corals of the species Pocillopora damicornis. Epifluorescence microscopy combined with a live/dead cell staining assay was used to evaluate the viability of the BMCs and monitor their in vivo uptake by the rotifers. The rotifers efficiently ingested BMCs, which accumulated in the digestive system and on the body surface after 10 min of interaction. Scanning electron microscopy confirmed the adherence of BMCs to the rotifer surfaces. BMC-enriched rotifers were actively ingested by P. damicornis corals, indicating that this is a promising technique for administering coral probiotics in situ. Studies to track the delivery of probiotics through carriers such as B. plicatilis, and the provision or establishment of beneficial traits in corals are the next proof-of-concept research priorities.

Heat stress decreases the diversity, abundance and functional potential of coral gas emissions.

Terrestrial ecosystems emit large quantities of biogenic volatile organic compounds (BVOCs), many of which play important roles in abiotic stress responses, pathogen and grazing defences, inter- and intra-species communications, and climate regulation. Conversely, comparatively little is known about the diversity and functional potential of BVOCs produced in the marine environment, especially in highly productive coral reefs. Here we describe the first 'volatilomes' of two common reef-building corals, Acropora intermedia and Pocillopora damicornis, and how the functional potential of their gaseous emissions is altered by heat stress events that are driving rapid deterioration of coral reef ecosystems worldwide. A total of 87 BVOCs were detected from the two species and the chemical richness of both coral volatilomes-particularly the chemical classes of alkanes and carboxylic acids-decreased during heat stress by 41% and 62% in A. intermedia and P. damicornis, respectively. Across both coral species, the abundance of individual compounds changed significantly during heat stress, with the majority (>86%) significantly decreasing compared to control conditions. Additionally, almost 60% of the coral volatilome (or 52 BVOCs) could be assigned to four key functional groups based on their activities in other species or systems, including stress response, chemical signalling, climate regulation and antimicrobial activity. The total number of compounds assigned to these functions decreased significantly under heat stress for both A. intermedia (by 35%) and P. damicornis (by 64%), with most dramatic losses found for climatically active BVOCs in P. damicornis and antimicrobial BVOCs in A. intermedia. Together, our observations suggest that future heat stress events predicted for coral reefs will reduce the diversity, quantity and functional potential of BVOCs emitted by reef-building corals, potentially further compromising the healthy functioning of these ecosystems.

Speciation-by-depth on coral reefs: Sympatric divergence with gene flow or cryptic transient isolation?

The distributions of many sister species in the sea overlap geographically but are partitioned along depth gradients. The genetic changes leading to depth segregation may evolve in geographic isolation as a prerequisite to coexistence or may emerge during primary divergence leading to new species. These alternatives can now be distinguished via the power endowed by the thousands of scorable loci provided by second‐generation sequence data. Here, we revisit the case of two depth‐segregated, genetically isolated ecotypes of the nominal Caribbean candelabrum coral Eunicea flexuosa. Previous analyses based on a handful of markers could not distinguish between models of genetic exchange after a period of isolation (consistent with secondary contact) and divergence with gene flow (consistent with primary divergence). Analyses of the history of isolation, genetic exchange and population size based on 15,640 new SNP markers derived from RNAseq data best support models where divergence began 800K BP and include epochs of divergence with gene flow, but with an intermediate period of transient isolation. Results also supported the previous conclusion that recent exchange between the ecotypes occurs asymmetrically from the Shallow lineage to the Deep. Parallel analyses of data from two other corals with depth‐segregated populations (Agaricia fragilis and Pocillopora damicornis) suggest divergence leading to depth‐segregated populations may begin with a period of symmetric exchange, but that an epoch of population isolation precedes more complete isolation marked by asymmetric introgression. Thus, while divergence‐with‐gene flow may account for much of the differentiation that separates closely related, depth‐segregated species, it remains to be seen whether any critical steps in the speciation process only occur when populations are isolated.

Calcified macroalgae and their bacterial community in relation to larval settlement and metamorphosis of reef-building coral Pocillopora damicornis.

Calcified macroalgae play an important role in the settlement and metamorphosis of invertebrate larvae in coral reef ecosystems. However, little is known about the algal-associated bacterial communities and their effects on larval settlement. In this study, the responses of larvae of the coral Pocillopora damicornis to calcified algae (Porolithon onkodes, Halimeda cylindracea, Halimeda opuntia and Amphiroa fragilissima) were evaluated. The results revealed that Por. onkodes and H. cylindracea significantly enhanced the rates of settlement and metamorphosis, whereas fewer larvae settled on Am. fragilissima and H. opuntia. Amplicon pyrosequencing of the V3-V4 region of 16S rDNA was applied to investigate the relationship between algal bacterial community and larval settlement. Principal coordinates analysis demonstrated that the bacterial community composition of H. opuntia was more similar to that of Am. fragilissima, but clearly distinct from those of H. cylindracea and Por. onkodes. Furthermore, the relative abundances of bacteria were highly diverse among different algae. H. opuntia had higher percentages of Thalassobius, Pelagibius and SM1A02, whereas the abundances of Mycoplasma and Suttonella were significantly higher in H. cylindracea than other algae. Our results showed that larval settlement/metamorphosis was strongly correlated with the bacterial community composition and with the relative abundance of a few operational taxonomic units.

Differential enrichment and physiological impacts of ingested microplastics in scleractinian corals in situ

Microplastics are emerging contaminants and widespread in the ocean, but their impacts on coral reef ecosystems are poorly understood, and in situ study is still lacking. In the present study, the distribution patterns of microplastics in the environment and inhabiting organisms were investigated along the east coast of Hainan Island, South China Sea, and the physiological impacts of the microplastics on scleractinian corals were analyzed. We documented average microplastic concentrations of 14.90 particlesL−1 in seawater, 343.04 particleskg−1 in sediment, 4.97 particlescm−2 in corals, and 0.67–3.12 particlescm−1 in Tridacnidae, Trochidae and fish intestines. Further analysis revealed that the characteristics of microplastics in the organisms were different from those in the environment, indicating preferential enrichment in the organisms. Furthermore, there was an obvious correlation between microplastic concentration and symbiotic density in corals. Furthermore, caspase3 activity was significantly positively correlated with the microplastic content in the small-polyp coral Pocillopora damicornis, but the large-polyp coral Galaxea fascicularis showed higher tolerance to microplastics. Taken together, our results suggest that microplastics are selectively enriched in corals and other reef-dwellers, in which they exact differential stress (apoptotic) effects, with the potential to impact the coral-Symbiodiniaceae symbiosis and alter the coral community structure.

Increased Ammonium Assimilation Activity in the Scleractinian Coral Pocillopora damicornis but Not Its Symbiont After Acute Heat Stress

Ammonium is the main nitrogen resources for scleractinian coral-Symbiodiniaceae symbiotic association, and there is urgent need to investigate the involvement of ammonium assimilation in the heat acclimation of the symbiotic association to heat stress. In the present study, symbiont density and chlorophyll content, as well as redox and ammonium assimilation enzyme activities in two symbiotic partners of the scleractinian coral Pocillopora damicornis were firstly investigated after acute heat stress (32 °C). Symbiont density and chlorophyll content decreased significantly at 24 h (1.81×105 cell cm-2, p < 0.05) and 36 h (23.25 pg cell-1, p < 0.05) after heat stress, respectively. We observed significant activity increases of coral nitric oxide synthase, superoxide dismutase and catalase, and symbiont superoxide dismutase after heat stress, but no alterations in the activities of symbiont nitric oxide synthase and catalase during the whole experiment period. The activities of coral glutamine synthetase and glutamine oxoglutarate aminotransferase began to increase significantly at 24 h, and reached the peak at 36 h after heat stress. As for glutamate dehydrogenase activity, a significant increase was observed only at 36 h after heat stress. The activities of symbiont glutamine synthetase and glutamine oxoglutarate aminotransferase did not change significantly after heat stress. Secondly, symbiont density, chlorophyll content, apoptosis rate, coral total antioxidant capacity, and caspase3 activation level were determined after glufosinate (glutamine synthetase inhibitor) treatment. Symbiont density decreased significantly at 6 h (1.25×106 cell cm-2, p < 0.05) after glufosinate treatment, and symbiont chlorophyll content also decreased significantly during 12-24 h after glufosinate treatment, with the lowest level at 12 h (16.69 pg cell-1, p < 0.05). Furthermore, the coral total antioxidant capacity and caspase3 activation level both increased significantly at 12 h (0.57 U mg-1, 2.08-fold, p < 0.05) after glufosinate treatment, while no significant change was observed for the symbiont apoptosis rate. These results suggest that the ammonium assimilation activity in the coral host P. damicornis, not its symbiont, was induced by acute heat stress, which might contribute to the acclimatization of the symbiotic association to high temperature through regulating coral antioxidant capacity and apoptosis.

Cryptic species and genetic connectivity among populations of the coral Pocillopora damicornis (Scleractinia) in the tropical southwestern Pacific

Studying population genetic connectivity (i.e., identifying gene flow among populations and understanding their impacts on the genetic structure and diversity of populations) is first a matter of knowing what we work on, that is, accurately delimiting evolutionary units. Here, we focused on Pocillopora damicornis sensu stricto (or Pocillopora PSH04 sensu Gelin et al. in Mol Phylogenet Evol 109:430–446. http://dx.doi.org/10.1016/j.ympev.2017.01.018 , 2017). From 458 colonies sampled within the tropical southwestern Pacific [Chesterfield Islands and New Caledonia (Grande Terre and Loyalty Islands)], Bayesian assignments and network analyses were conducted with 11-microsatellite loci to first evaluate the genetic partitioning of the colonies in distinct Secondary Species Hypotheses (SSHs), then in distinct clusters. Population genetic connectivity was then assessed for each cluster separately. Pocillopora PSH04 was partitioned into two highly differentiated SSHs (SSH04a and SSH04b), regularly found in sympatry. Furthermore, SSH04a was subdivided into two clusters (SSH04a-1 and SSH04a-2). This pattern of genetic structuring seems not related to clonality, but rather to the establishment of reproductive barriers. Nevertheless, considering each cluster separately, the populations appeared highly differentiated, suggesting relatively weak gene flow. This low connectivity among populations, coupled with the existence of cryptic species, brings new insights to the connectivity pattern of this understudied Pacific region.

Coral diversity on artificial reef from coconut shells in northern Bali, Indonesia

Artificial reef from natural product bioreeftek is very easy to apply and can be found in many tropical coastal areas namely coconut shells with natural coral recruitment. The purpose of this study was to calculate the percentages of coral cover, ratio and clustering. At the two research sites in North Bali, Pemuteran - Napoleon reef, depth 5-6m-reef slope found 13 species of live coral from 9 bioreeftek: Porites sp 32%, Pocillopora damicornis 13%, Seriatopora sp 10%, Acropora palifera, Acropora sp, Goniastrea sp, Favia sp, Pachyseris sp = 6%; Montipora sp - Echinopora sp - Favites sp - Fungia fungites and Leptoseris sp = 3%. At the Lovina - Adirama Temple, depth of 6m-reef flat was found in 14 species from 14 bioreeftek: Acropora palifera 24%, Pocillopora damicornis 21%, Porites sp 7%, Montipora sp 4% - Acropora sp - Pavona sp = 3%, Platygyra sp 2%, Acropora humilis - Millepora = 1%. Cluster Analysis showed all corals on two sites are correlated in percent cover, characteristics, influences and occurrences. Artificial reefs with natural materials such as coconut shells are necessary developed in addressing the degradation of coral reef ecosystem. The added value of bioreeftek is insertion/inserted method of coral.

Microbial community and transcriptional responses to increased temperatures in coral Pocillopora damicornis holobiont

SummaryA few studies have holistically examined successive changes in coral holobionts in response to increased temperatures. Here, responses of the coral host Pocillopora damicornis, its Symbiodiniaceae symbionts, and associated bacteria to increased water temperatures were investigated. High temperatures induced bleaching, but no coral mortality was observed. Transcriptome analyses showed that P. damicornis responded more quickly to elevated temperatures than its algal symbionts. Numerous genes putatively associated with apoptosis, exocytosis, and autophagy were upregulated in P. damicornis, suggesting that Symbiodiniaceae can be eliminated or expelled through these mechanisms when P. damicornis experiences heat stress. Furthermore, apoptosis in P. damicornis is presumably induced through tumour necrosis factor and p53 signalling and caspase pathways. The relative abundances of several coral disease‐associated bacteria increased at 32°C, which may affect immune responses in heat‐stressed corals and potentially accelerates the loss of algal symbionts. Additionally, consistency of Symbiodiniaceae community structures under heat stress suggests non‐selective loss of Symbiodiniaceae. We propose that heat stress elicits interrelated response mechanisms in all parts of the coral holobiont.

Functional potential of coral assemblages along a typical Eastern Tropical Pacific reef tract

Coral reefs are considered to be valuable ecosystems due to the goods and services that they provide. However, these ecosystem services are highly dependent on the physical structure of the reef, which in turn depends on the species composition of hermatypic corals. In this study, we explored the functional potential of reefs with a new index that takes into account coral cover, the calcification rate, rugosity, and the height of each species. In June 2019, we surveyed 11 reefs from the southern Mexican Pacific (15°40′N, 96°29′W−15°45′N, 96°5′W) to estimate coral cover and collect quantitative morphometric data of ~15 haphazardly selected coral colonies per site (N = 102). We estimated the calcification rates and structural complexity of the species present and then calculated the Reef Functional Index (RFI), which estimates the species-specific functional contribution of the corals in reef systems by integrating their capacity to create complex three-dimensional structures through calcium carbonate precipitation with morphological complexity. We modelled the effects of shifting species compositions through a permutation approach with 6435 possible combinations. We found a mean coral cover of 48.5 ± 18.09% (±SD) dominated by Pocillopora damicornis, Pocillopora verrucosa, and Pocillopora capitata and low abundance of Porites panamensis and Pavona gigantea. The mean RFI was 0.71 ± 0.1. The permutation model showed that the RFI was very close to its maximum potential (96%) when the relative abundance of pocilloporids was ≥60% and decreased as the relative abundance of massive corals increased. At maximum evenness, the RFI value was at 92% of its maximum potential. Our data highlight the importance of pocilloporids to the functioning of reefs in the Eastern Tropical Pacific (ETP) and confirm that P. damicornis is the primary reef builder in the region. Nevertheless, our findings also highlight the vulnerability of these reefs given that branching corals are more susceptible to environmental disturbance than slow-growing massive corals. In a rapidly changing environment, the future of ETP reefs depends not only on the survival of pocilloporids but also on the ability of coral reefs to withstand highly variable oceanographic conditions as complete ecosystems.