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The crab Trapezia bidentata is a conspicuous crustacean characterized as an obligate symbiont with branching corals, such as species of Pocillopora. These crustaceans have been identified as strict corallivores with a feeding dependency on the mucus excreted by adult colonies in the genus Pocillopora. However, like other crustaceans, individuals of T. bidentata have a nutritional plasticity that has not been described. We used an integrative approach, including traditional taxonomy and high‐throughput sequencing of hypervariable region V9 of the 18S rRNA gene, to describe the mouthparts and the diet of individuals of Trapezia bidentata associated with adult colonies of Pocillopora verrucosa. The presence of setae on the ambulatory dactylus and maxillipeds, forming food brushes and combs, was evident. Sequencing and analyses of the intestinal content of the crustaceans found evidence of 18 phyla, mostly represented by Brachiopoda (28.1%), Arthropoda (31.7%), and Cnidaria (21.1%), but also small contributions (≤2%) of other animal groups such as Mollusca, Annelida, and Tunicata. In addition, a few traces (≤0.5%) of algae and fungi were identified. The feeding structures and intestinal content showed that individuals of T. bidentata are omnivorous and behave as suspension feeders and scrapers, obtaining nourishment from tissues transported in the water column and in the mucus and tissue of P. verrucosa. The results provide a clearer characterization of the role of T. bidentata, which is a crucial guard crustacean associated with P. verrucosa. We found both corallivorous and suspension‐feeding habits, which demonstrates feeding plasticity, a positive characteristic for the survival of the species. [ABSTRACT FROM AUTHOR]

The 2014–2017 global coral bleaching event caused mass coral mortality and reshaped benthic communities across the Pacific. Swains Island (11.0° S, 171.1° W), a remote and uninhabited island within American Samoa, was exposed to moderate heat stress (6 °C-weeks) during this event. Temporal patterns in benthic cover and coral demography were monitored across 13 years straddling this heat stress event to assess the impacts across depth and the recovery trajectory. While Swains's reefs retain some of the highest calcifier cover in the US Pacific Islands, successional trajectories across depth following the 2016 heat stress suggest that these reefs are experiencing a more nuanced pattern of resilience to disturbance, with early signs of recovery in shallow reefs (3–6 m), a shift to non-calcifier dominance at mid depth (6–18 m), and stability on deep reefs (18–30 m). Shallow reefs experienced the largest changes with a relative 50% decline in coral cover, which was replaced by CCA between 2015 and 2018. Shifts in shallow coral community composition were strongly driven by the loss of Pocillopora and early recovery seven years after the event evidenced by an increase in small colonies. Mid-depth reefs experienced a 33% loss in coral cover between 2015 and 2023, and corresponding increase in upright macroalgae. The degree to which increasing macroalgae represents a temporary shift or gradual decline in calcifiers remains to be seen. While Swains's recovery bodes well for persistence of shallow reefs, its remoteness from broodstock and dominance of thermally sensitive taxa pose a threat to future climate resilience. [ABSTRACT FROM AUTHOR]

The decline of coral reefs has increased interest in ecological restoration. Due to the scarcity of coral gardening projects in the Eastern Tropical Pacific, improving our understanding of such techniques is key. We report the results of coral gardening using the branching Pocillopora spp. and massive coral species (Pavona gigantea, Pavona clavus and Porites lobata) in an upwelling area in Costa Rica. We examined whether nursery type influenced Pocillopora spp. survival and growth, and how environmental conditions shaped restoration. We monitored the survival and growth of Pocillopora spp. fragments (n = 334) and microfragments of massive species (P. gigantea [n = 148], P. clavus [n = 37], P. lobata [n = 66]) over 11 months. Survival at the end of the gardening period was 51% for Pocillopora spp., 59% for P. clavus, 55% for P. gigantea, and 17% for P. lobata, with a decline after a cease in maintenance caused by the COVID-19 lockdown. Pocillopora spp. fragments in the floating nurseries exhibited higher growth (7.52 ± 1.98 and 6.64 ± 2.91 cm yr-1) than in the A-frame (4.16 ± 2.35 cm yr-1), which suggests the benefits of suspending fragments. For massive microfragments coral growth was 1.92-4.66 cm² yr-1 and were affected by pigmentation loss, causing partial tissue loss and mortality. Our results point towards acclimation to local conditions, and show the need to develop site-specific cost-efficient gardening techniques for massive species, allowing for a multi-species approach to ensure long-term ecosystem recovery. [ABSTRACT FROM AUTHOR]

Coral reef degradation is a worldwide and growing phenomenon triggering habitat transformation from live to dead coral fragments. Macroinvertebrates play key functions in coral reefs, yet research on the size distribution of their community attributes is limited, particularly in the Eastern Tropical Pacific (ETP). We assessed the size distribution of the macroinvertebrate communities in live and dead corals in an ETP coral reef off Colombia. Live coral supported greater macroinvertebrate biomass than dead corals. In live coral, > 90% of total biomass was allocated in the > 8 mm class, which was mostly represented by trapeziid crabs and alpheid shrimps, both obligate symbionts of Pocillopora colonies. No differences were found in macroinvertebrate densities between substrates. Macroinvertebrate communities were dominated by crustaceans, though not in every size class. In live coral, Decapoda dominated in all size classes except 0.5–1 mm, which was the only class where dominance of a single taxon was not observed. In dead corals, the dominance of crustaceans was only observed in the 0.5–1 mm class due to high abundances of tanaidaceans. The remaining size classes were dominated by Polychaeta (1–2 mm, 2–4 mm) and Ophiuroidea (4–8 mm, > 8 mm). Our findings highlight that coral degradation events could lead to macroinvertebrate assemblages with lower biomass contributions, higher proportions of small crustaceans (< 1 mm), and taxonomic shifts. Such transitions from live to dead corals could likely impact food-web interactions between macroinvertebrates and higher trophic levels, potentially altering the ecosystem services offered by coral reefs. [ABSTRACT FROM AUTHOR]

Coral reefs off the coast of the Republic of Sudan are still considered to be among the most pristine reefs in the central Red Sea. The complex coastal fringing reefs, offshore banks, and shoals of Dungonab Bay in the north and Sanganeb atoll situated further to the south, about 23 km off the Sudanese mainland coast, were inscribed on the UNESCO World Heritage List in 2016. Due to their remote location and limited access, monitoring of the status of the reefs has been sporadic. Here, we present the results of a repeated large area photomosaic survey (5 m × 5 m plots) on the Sanganeb atoll, first established and surveyed in 1980, and revisited in 1991 and most recently in 2019. The 2019 survey recovered and reinstated the four original monitoring plots. Evaluation of photographic and video records from one photomosaic plot on the seaward slope of the atoll revealed general continuity of the overall community structure and composition over 39 years. Individual colonies of Echinopora gemmacea and Lobophyllia erythraea were recorded in the exact same positions as in the 1980 and 1991 plots. The genera Acropora and Pocillopora remain dominant, although in altered proportions. Shifts in composition were detected at the species level (e.g., increase in Pocillopora verrucosa, Stylophora pistillata, Acropora hemprichii, Dipsastraea pallida, and Echinopora gemmacea, decrease in Acropora cytherea and A. superba), in addition to changes in the extent of uncolonized substrate (e.g., increase from 43.9% in 1980 to 52.2% in 2019), and other scleractinian, hydrozoan, and soft coral living cover. While the temporal resolution only includes three sampling events over 39 years (1980, 1991, 2019), this study presents one of the longest time series of benthic community surveys available for the entire Red Sea. A semi-quantitative estimate of vertical reef growth in the studied test plot indicates a reduction in net accretion rates of more than 80%, from 2.27 to 2.72 cm/yr between 1980 and 1991 to 0.28–0.42 cm/yr between 1991 and 2019. We carefully conclude that the changes observed in the coral community in the plot in 2019 (Acropora–Pocillopora shift, increase in Montipora and calcareous algae) are representative of impacts at the community level, including rising sea surface temperatures and recent bleaching events. [ABSTRACT FROM AUTHOR]

The decline of coral reefs has increased interest in ecological restoration. Due to the scarcity of coral gardening projects in the Eastern Tropical Pacific, improving our understanding of such techniques is key. We report the results of coral gardening using the branching Pocillopora spp. and massive coral species (Pavona gigantea, Pavona clavus and Porites lobata) in an upwelling area in Costa Rica. We examined whether nursery type influenced Pocillopora spp. survival and growth, and how environmental conditions shaped restoration. We monitored the survival and growth of Pocillopora spp. fragments (n = 334) and microfragments of massive species (P. gigantea [n = 148], P. clavus [n = 37], P. lobata [n = 66]) over 11 months. Survival at the end of the gardening period was 51% for Pocillopora spp., 59% for P. clavus, 55% for P. gigantea, and 17% for P. lobata, with a decline after a cease in maintenance caused by the COVID-19 lockdown. Pocillopora spp. fragments in the floating nurseries exhibited higher growth (7.52 ± 1.98 and 6.64 ± 2.91 cm yr-1) than in the A-frame (4.16 ± 2.35 cm yr-1), which suggests the benefits of suspending fragments. For massive microfragments coral growth was 1.92-4.66 cm2 yr-1 and were affected by pigmentation loss, causing partial tissue loss and mortality. Our results point towards acclimation to local conditions, and show the need to develop site-specific cost-efficient gardening techniques for massive species, allowing for a multi-species approach to ensure long-term ecosystem recovery.

Abstract Marine heatwaves are increasing in frequency and duration, threatening tropical reef ecosystems through intensified coral bleaching events. We examined a strikingly variable spatial pattern of bleaching in Moorea, French Polynesia following a heatwave that lasted from November 2018 to July 2019. In July 2019, four months after the onset of bleaching, we surveyed > 5000 individual colonies of the two dominant coral genera, Pocillopora and Acropora, at 10 m and 17 m water depths, at six forereef sites around the island where temperature was measured. We found severe bleaching increased with colony size for both coral genera, but Acropora bleached more severely than Pocillopora overall. Acropora bleached more at 10 m than 17 m, likely due to higher light availability at 10 m compared to 17 m, or greater daily temperature fluctuation at depth. Bleaching in Pocillopora corals did not differ with depth but instead varied with the interaction of colony size and Accumulated Heat Stress (AHS), in that larger colonies (> 30 cm) were more sensitive to AHS than mid-size (10–29 cm) or small colonies (5–9 cm). Our findings provide insight into complex interactions among coral taxa, colony size, and water depth that produce high spatial variation in bleaching and related coral mortality.

Marine heatwaves are increasing in frequency and duration, threatening tropical reef ecosystems through intensified coral bleaching events. We examined a strikingly variable spatial pattern of bleaching in Moorea, French Polynesia following a heatwave that lasted from November 2018 to July 2019. In July 2019, four months after the onset of bleaching, we surveyed > 5000 individual colonies of the two dominant coral genera, Pocillopora and Acropora, at 10 m and 17 m water depths, at six forereef sites around the island where temperature was measured. We found severe bleaching increased with colony size for both coral genera, but Acropora bleached more severely than Pocillopora overall. Acropora bleached more at 10 m than 17 m, likely due to higher light availability at 10 m compared to 17 m, or greater daily temperature fluctuation at depth. Bleaching in Pocillopora corals did not differ with depth but instead varied with the interaction of colony size and Accumulated Heat Stress (AHS), in that larger colonies (> 30 cm) were more sensitive to AHS than mid-size (10–29 cm) or small colonies (5–9 cm). Our findings provide insight into complex interactions among coral taxa, colony size, and water depth that produce high spatial variation in bleaching and related coral mortality. [ABSTRACT FROM AUTHOR]

Intervention techniques to restore coral communities have become an important management tool to help recover and rehabilitate damaged reefs. The direct transplantation of healthy coral fragments is the most common method; however, there is controversy in the long-term success, as using coral clones may diminish the genetic diversity of the coral population. Genetic recombination can be achieved when the coral colony produces gametes and eventually reproduces; therefore, it is important to provide evidence that restored colonies produce gametes as their naturally recruited counterparts with similar colony size (age). Natural and restored Pocillopora coral colonies of the same size range (between 40 and 50 cm in diameter) were tagged and sampled during the rainy season to determine gamete maturation. Our results show no differences in the reproductive activity among colonies: natural and restored coral colonies matured gametes from June to October, with a peak in sexually active coral colonies in July. Also, gamete malformation was not observed. During the gamete production period, the area’s temperature ranged from 27.9 to 30.02 °C. The results’ evidence that coral colonies formed through active restoration contribute not only to the increase in live coral cover as seen in previous studies but potentially contribute in the medium term (>5 years after out-planting) to the production of larvae and local and subsidiary recruitment, since they exhibit the same reproductive patterns as their naturally formed counterparts and no differences in the reproductive activity among coral colonies. Therefore, long-term coral restoration projects contribute to maintaining the live coral cover and the genetic diversity in the region, eventually rehabilitating the coral community.

Abstract Background The widespread Indo-Pacific coral species Pocillopora acuta Lamarck, 1816 displays varying levels of asexual versus sexual reproduction, with strong repercussions on genetic diversity, connectivity and genetic structuring within and among populations. For many geographic regions, baseline information on genetic diversity is still lacking, particularly in the Andaman Sea. The region suffered a massive heat-induced bleaching event in 2010 with high coral cover loss of branching coral species such as P. acuta. A subsequent bleaching in 2016, however, revealed a mild bleaching response in pocilloporids compared to other coral taxa in the region, suggesting that rare, heat tolerant genotypes had been selected by the 2010 bleaching event. In order to test whether this potential ‘evolutionary rescue’ event has led to a low genetic diversity, we conducted a population genetic survey covering a total of nine different P. acuta populations (336 individuals) along a 50 km coastal stretch around Phuket Island, Thailand. We used six microsatellite markers to assess genotypic diversity and to determine the prevalent mode of reproduction (i.e. sexual or asexual recruitment). Results In contrast to other Indian Ocean P. acuta populations, the majority of corals in this study adopted a sexual reproduction mode (75% across all populations). At the same time, substantial regional gene flow was observed around Phuket Island with strong genetic differentiation as indicated by three genetic clusters that were separated by only a few kilometers. Patterns of isolation by distance over 0.7 – 40 km suggest small-scale genetic barriers, such as changing currents throughout each monsoonal season, potentially contributing to locally restricted dispersal of P. acuta larvae. Conclusions The occurrence of distinct genetic clusters within short coastal stretches suggests that the 2010 bleaching event has not led to extreme genetic impoverishment. While more in-depth genomic analyses are necessary to investigate changes in genetic diversity following extreme bleaching events, our results will help guide conservation efforts to maintain genetic diversity of a coral species that likely will be dominant in future, warmer Andaman Sea reefs.

Intervention techniques to restore coral communities have become an important management tool to help recover and rehabilitate damaged reefs. The direct transplantation of healthy coral fragments is the most common method; however, there is controversy in the long-term success, as using coral clones may diminish the genetic diversity of the coral population. Genetic recombination can be achieved when the coral colony produces gametes and eventually reproduces; therefore, it is important to provide evidence that restored colonies produce gametes as their naturally recruited counterparts with similar colony size (age). Natural and restored Pocillopora coral colonies of the same size range (between 40 and 50 cm in diameter) were tagged and sampled during the rainy season to determine gamete maturation. Our results show no differences in the reproductive activity among colonies: natural and restored coral colonies matured gametes from June to October, with a peak in sexually active coral colonies in July. Also, gamete malformation was not observed. During the gamete production period, the area's temperature ranged from 27.9 to 30.02 °C. The results' evidence that coral colonies formed through active restoration contribute not only to the increase in live coral cover as seen in previous studies but potentially contribute in the medium term (>5 years after out-planting) to the production of larvae and local and subsidiary recruitment, since they exhibit the same reproductive patterns as their naturally formed counterparts and no differences in the reproductive activity among coral colonies. Therefore, long-term coral restoration projects contribute to maintaining the live coral cover and the genetic diversity in the region, eventually rehabilitating the coral community. [ABSTRACT FROM AUTHOR]

Pocillopora damicornis (Linnaeus, 1758), a species complex, consists of several genetic lineages, some of which likely represent reproductively isolated species, including the species Pocillopora acuta Lamarck, 1816. Pocillopora acuta can exhibit similar morphological characteristics as P. damicornis, thus making it difficult to identify species‐level taxonomic units. To determine whether the P. damicornis‐like colonies on the reefs in the Andaman Sea (previously often identified as P. damicornis) consist of different species, we sampled individual colonies at five sites along a 50 km coastal stretch at Phuket Island and four island sites towards Krabi Province, Thailand. We sequenced 210 coral samples for the mitochondrial open reading frame and identified six distinct haplotypes, all belonging to P. acuta according to the literature. Recently, P. acuta was observed to efficiently recolonize heat‐damaged reefs in Thailand as well as globally, making it a potentially important coral species in future reefs. Specifically in the light of global change, this study underscores the importance of high‐resolution molecular species recognition, since taxonomic units are important factors for population genetic studies, and the latter are crucial for management and conservation efforts. [ABSTRACT FROM AUTHOR]

Coral reefs are under threat from cumulative impacts such as cyclones, crown-of-thorns starfish (COTS) outbreaks and climate-driven coral bleaching events. Branching corals are more severely impacted by these events than other coral morphologies due to their sensitivity to heat stress and weaker skeletons and COTS preferred prey. The central Great Barrier Reef experienced unprecedented back-to-back bleaching events in 2016 and 2017. This study commenced in 2017 at the peak of heat stress and examined the impact of the heatwave on the survival and recovery of corals by assessing the growth, health (based on the visual health index) and physiological parameters (chlorophyll a, zooxanthellae density, lipid and protein content) of two species, Acropora millepora and Pocillopora acuta (N = 60 colonies for each species). It was conducted across a gradient of turbidity at three reefs, Pandora, Orpheus and Rib, that experienced in April 2017, degree heating weeks (DHW) of 9, 8 and 7, respectively. Orpheus experienced the worst bleaching, based on visual health score, followed by Rib and Pandora. Rib experienced the greatest mortality (78% by Nov 2017); however, this was attributed to the presence of actively feeding crown-of-thorns starfish. Growth rates of A. millepora were almost twice the rate of P. acuta. Both species showed significant seasonal variation with growth of A. millepora and P. acuta 35–40% and 23–33% significantly greater in the summer, respectively. Differences in growth rates were best explained by indicators of energy acquisition. For example, the most important predictor variable in determining higher growth rates and visual health score in A. millepora was chlorophyll a content. For P. acuta, visual health score was the best predictor variable for higher growth rates. This study highlights the important role that chlorophyll a and associated symbionts play in growth and survival in these corals during and after a heat stress event. [ABSTRACT FROM AUTHOR]

Coral reefs face an uncertain future punctuated by recurring climate-induced disturbances. Understanding how reefs can recover from and reassemble after mass bleaching events is therefore important to predict their responses and persistence in a rapidly changing ocean. On naturally extreme reefs characterized by strong daily temperature variability, coral heat tolerance can vary significantly over small spatial gradients but it remains poorly understood how this impacts bleaching resilience and recovery dynamics, despite their importance as resilience hotspots and potential refugia. In the macrotidal Kimberley region in NW Australia, the 2016 global mass bleaching event had a strong habitat-specific impact on intertidal and subtidal coral communities at our study site: corals in the thermally variable intertidal bleached less severely and recovered within six months, while 68% of corals in the moderately variable subtidal died. We therefore conducted benthic surveys 3.5 years after the bleaching event to determine potential changes in benthic cover and coral community composition. In the subtidal, we documented substantial increases in algal cover and live coral cover had not fully recovered to pre-bleaching levels. Furthermore, the subtidal coral community shifted from being dominated by branching Acropora corals with a competitive life history strategy to opportunistic, weedy Pocillopora corals which likely has implications for the functioning and stress resilience of this novel coral community. In contrast, no shifts in algal and live coral cover or coral community composition occurred in the intertidal. These findings demonstrate that differences in coral heat tolerance across small spatial scales can have large consequences for bleaching resilience and that spatial patchiness in recovery trajectories and community reassembly after bleaching might be a common feature on thermally variable reefs. Our findings further confirm that reefs adapted to high daily temperature variability play a key role as resilience hotspots under current climate conditions, but their ability to do so may be limited under intensifying ocean warming. [ABSTRACT FROM AUTHOR]

Coral reefs are one of the most biodiverse marine ecosystems. Diverse microbes are associated with corals, including zooxanthellae, protists, prokaryotes, and viruses. This study aimed to investigate the genetic diversity of the culturable fungi associated with scleractinian corals in the Gulf of Thailand. Ribosomal DNA sequence analysis and morphological analysis of 130 fungal isolates revealed a high diversity of fungal phylotypes from three coral species: Pavona decussata, Pocillopora damicornis and Porites lutea. Ascomycota was the most abundant fungal phylum. The predominant orders included Eurotiales, Cladosporiales, Hypocreales, Mycosphaerellales, and Diaporthales. There were eight orders of the Basidiomycota dominated by Polyporales, Hymenochaetales, Agaricales, and Wallemiales. A principal component analysis was performed to compare abundance and correlation between the fungal communities, sampling locations and coral species. The results showed that the dissimilarity of fungal communities corresponded to geographic localities. On the other hand, there was a considerable overlap between the fungal communities of different coral species. The results from this research provide information on the diversity and ecology of the fungal communities associated with scleractinian corals in the Gulf of Thailand. [ABSTRACT FROM AUTHOR]

Climate change is driving the poleward redistribution of coral species, but the rate and magnitude of future range extensions within temperate regions are rarely quantified. A better understanding of the likely future distribution of corals is needed to anticipate the resulting social, economic and environmental implications. Here, we project the rate and magnitude of extensions of suitable thermal conditions for hard coral communities along the east Australian coastline, using data on coral community presence, in conjunction with historical and projected ocean temperatures. Our projections indicate that temperatures will be suitable for coral communities dominated by the subtropical coral Pocillopora aliciae, currently found off Sydney, to extend their range poleward by 80 (RCP 2.6) to 450 km (RCP 8.5) by 2100, corresponding to a rate of 0.9–5.0 km year−1. Similarly, thermal conditions will be such that diverse coral communities, such as those currently occurring in the Solitary Islands, may extend their range by 130 (RCP 2.6) to 580 km (RCP 8.5) by 2100, at a rate of 1.4–6.4 km year−1. These projections are similar to those forecast for coral species in other parts of the world. Newly establishing coral communities in temperate regions may provide a range of novel local economic opportunities, particularly for marine tourism. [ABSTRACT FROM AUTHOR]

Climate change is increasing the frequency and magnitude of temperature anomalies that cause coral bleaching, leading to widespread mortality of stony corals that can fundamentally alter reef structure and function. However, bleaching often is spatially variable for a given heat stress event, and drivers of this heterogeneity are not well resolved. While small-scale experiments have shown that excess nitrogen can increase the susceptibility of a coral colony to bleaching, we lack evidence that heterogeneity in nitrogen pollution can shape spatial patterns of coral bleaching across a seascape. Using island-wide surveys of coral bleaching and nitrogen availability within a Bayesian hierarchical modeling framework, we tested the hypothesis that excess nitrogen interacts with temperature anomalies to alter coral bleaching for the two dominant genera of branching corals in Moorea, French Polynesia. For both coral genera, Pocillopora and Acropora, heat stress primarily drove bleaching prevalence (i.e., the proportion of colonies on a reef that bleached). In contrast, the severity of bleaching (i.e., the proportion of an individual colony that bleached) was positively associated with both heat stress and nitrogen availability for both genera. Importantly, nitrogen interacted with heat stress to increase bleaching severity up to twofold when nitrogen was high and heat stress was relatively low. Our finding that excess nitrogen can trigger severe bleaching even under relatively low heat stress implies that mitigating nutrient pollution may enhance the resilience of coral communities in the face of mounting stresses from global climate change.

The flexibility to associate with more than one symbiont may considerably expand a host's niche breadth. Coral animals and dinoflagellate micro-algae represent one of the most functionally integrated and widespread mutualisms between two eukaryotic partners. Symbiont identity greatly affects a coral's ability to cope with extremes in temperature and light. Over its broad distribution across the Eastern Pacific, the ecologically dominant branching coral, Pocillopora grandis, depends on mutualisms with the dinoflagellates Durusdinium glynnii and Cladocopium latusorum. Measurements of skeletal growth, calcification rates, total mass increase, calyx dimensions, reproductive output and response to thermal stress were used to assess the functional performance of these partner combinations. The results show both host–symbiont combinations displayed similar phenotypes; however, significant functional differences emerged when exposed to increased temperatures. Negligible physiological differences in colonies hosting the more thermally tolerant D. glynnii refute the prevailing view that these mutualisms have considerable growth tradeoffs. Well beyond the Eastern Pacific, pocilloporid colonies with D. glynnii are found across the Pacific in warm, environmentally variable, near shore lagoonal habitats. While rising ocean temperatures threaten the persistence of contemporary coral reefs, lessons from the Eastern Pacific indicate that co-evolved thermally tolerant host–symbiont combinations are likely to expand ecologically and spread geographically to dominate reef ecosystems in the future. [ABSTRACT FROM AUTHOR]

ABSTRACT Polyp bail-out constitutes both a stress response and an asexual reproductive strategy that potentially facilitates dispersal of some scleractinian corals, including several dominant reef-building taxa in the family Pocilloporidae. Recent studies have proposed that microorganisms may be involved in onset and progression of polyp bail-out. However, changes in the coral microbiome during polyp bail-out have not been investigated. In this study, we induced polyp bail-out in Pocillopora corals using hypersaline and hyperthermal methods. Bacterial community dynamics during bail-out induction were examined using the V5-V6 region of the 16S-rRNA gene. From 70 16S-rRNA gene libraries constructed from coral tissues, 1,980 OTUs were identified. Gammaproteobacteria and Alphaproteobacteria consistently constituted the dominant bacterial taxa in all coral tissue samples. Onset of polyp bail-out was characterized by increased relative abundance of Alphaproteobacteria and decreased abundance of Gammaproteobacteria in both induction experiments, with the shift being more prominent in response to elevated temperature than to elevated salinity. Four OTUs, affiliated with Thalassospira, Marisediminitalea, Rhodobacteraceae, and Myxococcales, showed concurrent abundance increases at the onset of polyp bail-out in both experiments, suggesting potential microbial causes of this coral stress response. IMPORTANCE Polyp bail-out represents both a stress response and an asexual reproductive strategy with significant implications for reshaping tropical coral reefs in response to global climate change. Although earlier studies have suggested that coral-associated microbiomes likely contribute to initiation of polyp bail-out in scleractinian corals, there have been no studies of coral microbiome shifts during polyp bail-out. In this study, we present the first investigation of changes in bacterial symbionts during two experiments in which polyp bail-out was induced by different environmental stressors. These results provide a background of coral microbiome dynamics during polyp bail-out development. Increases in abundance of Thalassospira, Marisediminitalea, Rhodobacteraceae, and Myxococcales that occurred in both experiments suggest that these bacteria are potential microbial causes of polyp bail-out, shedding light on the proximal triggering mechanism of this coral stress response.

Theories involving niche diversification to explain high levels of tropical diversity propose that species are more likely to co-occur if they partition at least one dimension of their ecological niche space. Yet, numerous species appear to have widely overlapping niches based upon broad categorizations of resource use or functional traits. In particular, the extent to which food partitioning contributes to species coexistence in hyperdiverse tropical ecosystems remains unresolved. Here, we use a molecular approach to investigate inter- and intraspecific dietary partitioning between two species of damselfish (Dascyllus flavicaudus, Chromis viridis) that commonly co-occur in branching corals. Species-level identification of their diverse zooplankton prey revealed significant differences in diet composition between species despite their seemingly similar feeding strategies. Dascyllus exhibited a more diverse diet than Chromis, whereas Chromis tended to select larger prey items. A large calanoid copepod, Labidocera sp., found in low density and higher in the water column during the day, explained more than 19% of the variation in dietary composition between Dascyllus and Chromis. Dascyllus did not significantly shift its diet in the presence of Chromis, which suggests intrinsic differences in feeding behaviour. Finally, prey composition significantly shifted during the ontogeny of both fish species. Our findings show that levels of dietary specialization among coral reef associated species have likely been underestimated, and they underscore the importance of characterizing trophic webs in tropical ecosystems at higher levels of taxonomic resolution. They also suggest that niche redundancy may not be as common as previously thought.

Coral bleaching and mortality can show significant spatial and taxonomic heterogeneity at local scales, highlighting the need to understand the fine-scale drivers and impacts of thermal stress. In this study, we used structure-from-motion photogrammetry to track coral bleaching, mortality, and changes in community composition during the 2019 marine heatwave in Kāneʻohe Bay, Hawaiʻi. We surveyed 30 shallow reef patches every 3 weeks for the duration of the bleaching event (August-December) and one year after, resulting in a total of 210 large-area, high-resolution photomosaics that enabled us to follow the fate of thousands of coral colonies through time. We also measured environmental variables such as temperature, sedimentation, depth, and wave velocity at each of these sites, and extracted estimates of habitat complexity (rugosity R and fractal dimension D) from digital elevation models to better understand their effects on patterns of bleaching and mortality. We found that up to 80% of corals experienced moderate to severe bleaching in this period, with peak bleaching occurring in October when heat stress (Degree Heating Weeks) reached its maximum. Mortality continued to accumulate as bleaching levels dropped, driving large declines in more heat-susceptible species (77% loss of Pocillopora cover) and moderate declines in heat-tolerant species (19% and 23% for Porites compressa and Montipora capitata, respectively). Declines in live coral were accompanied by a rapid increase in algal cover across the survey sites. Spatial differences in bleaching were significantly linked to habitat complexity and coral species composition, with reefs that were dominated by Pocillopora experiencing the most severe bleaching. Mortality was also influenced by species composition, fractal dimension, and site-level differences in thermal stress. Our results show that spatial heterogeneity in the impacts of bleaching are driven by a mix of environmental variation, habitat complexity, and differences in assemblage composition.

Aim: The symbioses between corals and endosymbiotic dinoflagellates have been described as a flexible relationship whose dynamics could serve as a source of resilience for coral reef ecosystems. However, the factors that drive the establishment and maintenance of this co‐evolutionary relationship remain unclear. We examined the environmental and geographical factors structuring dinoflagellate communities in a wide‐ranging Indo‐Pacific coral to begin to address this gap. Location: Djibouti, Oman, Taiwan and French Polynesia. Taxon: Cauliflower corals (Pocillopora spp.), dinoflagellates (family Symbiodiniaceae). Methods: We analysed publicly available amplicon sequence data from the nuclear ribosomal DNA internal transcribed spacer 2, originating from Pocillopora spp. We also compiled environmental data such as sea surface temperature (SST) and time since the last local mass bleaching event. We ran generalized least squares models, PERMANOVAs and indicator species analyses, to understand how thermal regimes and geographical distances impacted Pocillopora spp.'s Symbiodiniaceae community composition. Results: Sea surface temperature was the most important factor driving Symbiodiniaceae community differences, with the largest effect size of the statistically significant factors. When focusing on individual Symbiodiniaceae genera, SST was likewise the most important factor. Our indicator species analyses revealed that specimens that had recently bleached were characterized by roughly equal proportions of Cladocopium spp. and Durusdinium spp., while specimens that had not recently bleached had a similar proportion of Durusdinium spp. as those that had recently bleached, but also showed a reduction in Cladocopium spp., with this deficiency made up by the presence of Symbiodinium spp. Main Conclusions: We provide further support for the hypothesis that coral's Symbiodiniaceae communities could facilitate host resilience to thermal stress. Our work is in direct conversation with a larger body of biogeography literature that highlights how local environmental regimes can impact contemporary population structure, even in marine taxa with widespread distributions. [ABSTRACT FROM AUTHOR]

Climate change is radically altering coral reef ecosystems, mainly through increasingly frequent and severe bleaching events. Yet, some reefs have exhibited higher thermal tolerance after bleaching severely the first time. To understand changes in thermal tolerance in the eastern tropical Pacific (ETP), we compiled four decades of temperature, coral cover, coral bleaching, and mortality data, including three mass bleaching events during the 1982 to 1983, 1997 to 1998 and 2015 to 2016 El Niño heatwaves. Higher heat resistance in later bleaching events was detected in the dominant framework-building genus, Pocillopora, while other coral taxa exhibited similar susceptibility across events. Genetic analyses of Pocillopora spp. colonies and their algal symbionts (2014 to 2016) revealed that one of two Pocillopora lineages present in the region (Pocillopora "type 1") increased its association with thermotolerant algal symbionts (Durusdinium glynnii) during the 2015 to 2016 heat stress event. This lineage experienced lower bleaching and mortality compared with Pocillopora "type 3", which did not acquire D. glynnii. Under projected thermal stress, ETP reefs may be able to preserve high coral cover through the 2060s or later, mainly composed of Pocillopora colonies that associate with D. glynnii. However, although the low-diversity, high-cover reefs of the ETP could illustrate a potential functional state for some future reefs, this state may only be temporary unless global greenhouse gas emissions and resultant global warming are curtailed. [ABSTRACT FROM AUTHOR]

This study assessed different reef zones (lagoon, reef crest, reef slope) in three urban locations around Okinawa Island (Mizugama, Ginowan, Sunabe) and two marine protected areas around nearby Aka Island (Hizushi, Sakubaru) for marine litter pollution and litter interactions with reef organisms. A total reef area of 2250 m2 was surveyed by scuba diving, and 46 marine litter items were recorded. Litter density ranged from 0.01 to 0.05 items/m2, and plastics (76.09 %) and metals (15.22 %) were the most common litter types. The substrates for litter items were live corals (52.17 %), followed by dead corals and algae (26.09 %), sand (13.04 %), and rocks (8.70 %). Litter items on live corals were entangled exclusively with branching Acropora spp. (95.83 %) and Pocillopora spp. (4.17 %). This study highlights the need to protect coral reef ecosystems from the impacts of urbanisation in order to conserve and sustain their ecological and economic benefits. [Display omitted] • Marine litter interactions with benthos in Okinawa urban reefs was assessed. • A total reef area of 2250 m2 was surveyed by scuba diving. • The most common substrate for litter items were live corals (52.2 %). • Litter items on live corals entangled largely with branching Acropora spp. (95.8 %). • Litter management strategies to protect urban reefs are recommended. [ABSTRACT FROM AUTHOR]

Despite being exposed to extreme water temperatures and solar irradiances, Red Sea corals are relatively resistant to bleaching. While their thermal tolerance is well described, little is known about their resistance to ultraviolet-B radiation (UVB). Here, we performed a short-term (2 days) UVB-removal incubation with Stylophora pistillata, and in situ measurements with Pocillopora verrucosa complemented by a long-term (46 days) transplantation and UVB-removal experiment. Using a suite of physiological parameters (effective quantum yield (Fv’/Fm’), oxidative stress (lipid peroxidation, LPO), and primary production), we assessed the impacts of UVB on the physiology and acclimation capacity of Red Sea corals. Shielding S. pistillata from UVB did not change the gross primary production or Fv’/Fm’, and respiration and LPO in the host remained unaffected. In situ, P. verrucosa exhibited less varying and significantly higher Fv’/Fm’ in 8 m depth (0.61 ± 0.04) than in 4 m (0.52 ± 0.06), 2 m (0.51 ± 0.09), and 0.5 m (0.50 ± 0.11), where water temperatures ranged from 30.5–33.4, 30.6–34.0, 30.8–34.5, 30.6–37.3°C and daily UVB exposures averaged 0.9, 2.9, 11.8 and 21.4 kJ m-2, respectively. Fv’/Fm’ correlated the strongest with UVB (-0.57), followed by PAR (-0.54) and temperature (-0.40), suggesting that UVB is a key determinant of photosynthetic efficiency. Fv’/Fm’ of upward transplanted specimens (T 1m) was initially decreased but gradually increased and reached the same values as shallow corals (1 m) after 44 days. UVB removal significantly increased the Fv’/Fm’ of transplanted corals in the first 20 days. Oxidative stress was initially highest in T 1m samples under full sunlight but equalized with 1 m specimens by day 46, whereas oxidative stress was significantly reduced by day 4 in T 1m corals sheltered from UVB. Overall, UVB-removal generally had little impact on the physiology of shallow-water S. pistillata and P. verrucosa but considerably accelerated the acclimation of upward transplanted corals. Our study highlights that UVB is a crucial stressor governing the photoacclimation capacity of these Red Sea coral species.

Introduction: The 1997-98 El Niño event caused massive coral bleaching and mortality in the Central Mexican Pacific (CMP). Punta de Mita alone used to harbor more than 30 % of the coral coverage in this region, with a mono-specific Pocillopora coverage. The 1997-1998 ENSO event caused massive coral mortality reducing live coral coverage to < 5 %. Despite being considered a coral region unlikely to recover, recent restoration efforts have been implemented to rehabilitate the coral community. Objective: To assess coral recovery by analyzing the coral growth and survival rates of branching Pocillopora species at Punta de Mita. Methods: Healthy coral fragments of opportunity were re-attached to the natural substrata using zip ties and measured considering their growth in terms of maximum length and width (cm) to determine their annual extension rates. Results: After 50 weeks, corals duplicated their size, with a mean growth of ~ 4 cm year-1. After 100 weeks (2 years), corals triplicated their size, increasing on average 8-9 cm in each diameter. Conclusions: Successful coral reef restoration activities in the Central Mexican Pacific are the result of Pocillopora's physiological processes, such as fast growth rates, and recent life-history traits, like the ability to cope with thermal anomalies, which enable them to thrive in a dynamic region severely affected by natural and anthropogenic perturbations. Indeed, a region considered unlikely to recover has regained its live coral cover from < 5 % in 1998 up to 15 % in 20 years. This demonstrates the importance of assisting natural coral recovery with restoration efforts, especially in coral locations that, despite environmental perturbations, have proven to be resilient and may become coral refugia areas under the current climate change scenario. [ABSTRACT FROM AUTHOR]

Introduction: Coral-reef communities are considered one of the most biodiverse, but also most threatened, marine ecosystems, and the accelerating loss of habitat over the past decades warrants active intervention. Objective: The present study demonstrates the successful implementation of a low-impact restoration technique in three Central Mexican Pacific degraded coral communities, using a protocol based on natural fragmentation ("fragments of opportunity") of the branching coral Pocillopora spp., considered the most abundant and primary carbonate-producing coral species of the Eastern Tropical Pacific. Methods: The restoration program was implemented in two offshore and one inshore coraline areas. The relationships between seawater temperature and coral survival, growth, and attachment rate were assessed over one year, with 183 fragments monitored each month. Results: The mean coral growth rate was 3.3 ± 0.1 mm mo-1, with annual growth rates in length and width of 39.9 ± 14.2 and 36.5 ± 19.5 mm yr-1, respectively. Self-attachment efficiency was 78 % and the survival rate was high (84 %). The growth rate differed significantly among reefs. Conclusions: Upon monitoring directly fragmented corals over a year, growth rates were deemed high enough to merit active restoration in the region. However, our data show that structural and abiotic differences and seasonal variability must be considered overall in successful long-term coral community restoration initiatives in the eastern Pacific region. [ABSTRACT FROM AUTHOR]

Introduction: Coral reef structures in Zihuatanejo, Guerrero are well-preserved. The coverage of living corals, near 60 % at several locations, makes them comparable to other coral reefs in the states of Oaxaca, Jalisco, and Nayarit and with high potential to promote their conservation. Objective: To present the outcome of 12 years of research in coral communities from Zihuatanejo, Guerrero, as a justifying argument for the current conservation efforts in the area. Methods: We developed a baseline on the conservation status of the reef structures, bioerosion processes and the source of major natural and anthropogenic impacts. We assessed the genetic diversity of the coral zooxanthellae symbionts, the outcome of a technique of coral transplantation to recover the coverage of living corals and the local ecological knowledge to involve local inhabitants to promote conservation. Results: At least five coral reefs remain exposed to a medium-low level of impact by bioerosion and anthropization. Coral transplantation experiments made in the area showed records of transplant survival nearing 90 %. Although the warming of the sea surface temperature that occurred during the El Niño of 2015-2016 caused coral bleaching and mortality in several coral populations in this area, there were no affectations attributed to this phenomenon in other locations. This response was not related to the level of exposure to anthropogenic impacts, and the presence of thermal resistant zooxanthellae was assessed using molecular tools, confirming the existence of zooxanthellae of the genus Durusdinium. The analysis of local ecological knowledge of the inhabitants of Zihuatanejo showed that they keep elaborate knowledge on the ecology of coral reefs. This is complemented with scientific knowledge that will encourage community participation in conservation strategies. Conclusions: A long-term multidisciplinary strategy is required for coral reef conservation that encompasses: 1) assessing the role of the overall holobiont in the thermal resistance of corals from this area and 2) establishing restoration strategies of coral reefs that include the local knowledge about marine ecology, for the establishment of coral reef protection and management schemes put in place by local inhabitants. [ABSTRACT FROM AUTHOR]

As coral reefs continue to degrade at an alarming rate, coral restoration efforts are increasing worldwide in an attempt to keep up with the global challenge of preserving these iconic ecosystems and the many services they provide. Coral gardening, the farming and outplanting of coral fragments, is a commonly applied practice; however, regional validation is required before upscaling can be considered. This study follows up from the successful farming of fragments in mid‐water rope nurseries, by reporting on the successive outplanting of these corals. Specifically, 60 Pocillopora verrucosa colonies were outplanted to a degraded reef at different depths (1–12 m), applying three arrangement patterns (equal, clustered, random). After 1 year, 72% were considered successfully outplanted (alive and still attached), with detachment being the main challenge at wave‐impacted shallow depths, while loose coral rubble caused more partial mortality at depth. Outplanting stress was observed at 1–6 m depth, but had no impact on survival or growth. Drupella sp. predation was most common at 3 m and 79% of colonies hosted mutualistic fauna after 1 year. Outplanting significantly benefitted the reef environment with a higher fish abundance and diversity along with a higher increase in natural coral cover (H = 2.7; 6.2% increase) in comparison with the control sites. These are promising results, considering that the restoration site has shown little natural recovery in the last few years (coral cover <4%). We hope that our findings provide useful initial insights and help to guide effective restoration practices in the Maldives. [ABSTRACT FROM AUTHOR]

Identifying the core microbiome structure of a metaorganism can be used to monitor the impact of a perturbation against it and the changes in its stability (i.e., dysbiosis), resistance, and resilience. The core‐microbiome interaction regulates holobiont health and homeostasis and is an indicator of the resilience of the whole community. This study determined the exclusive and shared core microbiome taxa of two reef‐building coral species (Pocillopora damicornis and P. verrucosa), as well as the surrounding seawater and sediment, in six coral communities along the Northeastern tropical Pacific region. We also analysed the putative metabolic functions of the most abundant OTUs of these core microbiomes and evaluated the influence of anthropogenic stressors (i.e., tourism, fishery, eutrophication, among others) on core microbiome composition. Bacterial diversity was assessed by sequencing the V4 region of the 16S rRNA. The bacterial families Planctomycetaceae, Oceanospirillaceae, and Moraxellaceae presented the highest relative abundances in corals samples, while Flavobacteriaceae and Rhodobacteraceae dominated in seawater samples. In the sediment samples, Pseudoalteromonadaceae, Oxalobacteraceae, Moraxellaceae, and Pseudonocardiaceae had the highest representation. The core microbiomes of the two coral species, seawater, and sediment, shared 571 OTUs. The P. damicornis core microbiome varied between sites with low and moderately‐high anthropogenic stressors. The core microbiomes of both coral species showed an increase in the relative abundance of the families Planctomycetaceae and Pseudomonadaceae in the sites with moderate‐high anthropogenic stressors, associated with higher values of ammonium, chlorophyll a, and extinction coefficient. In contrast, the core microbiome of P. verrucosa, seawater, and sediments did not vary between sites with different anthropogenic stress conditions. Aerobic chemoheterotrophy was the metabolic function with the highest occurrence in all substrates' core microbiomes, followed by ureolysis and photoautotrophy. [ABSTRACT FROM AUTHOR]

Coral restoration initiatives are gaining significant momentum in a global effort to enhance the recovery of degraded coral reefs. However, the implementation and upkeep of coral nurseries are particularly demanding, so that unforeseen breaks in maintenance operations might jeopardize well‐established projects. In the last 2 years, the COVID‐19 pandemic has resulted in a temporary yet prolonged abandonment of several coral gardening infrastructures worldwide, including remote localities. Here we provide a first assessment of the potential impacts of monitoring and maintenance breakdown in a suite of coral restoration projects (based on floating rope nurseries) in Colombia, Seychelles, and Maldives. Our study comprises nine nurseries from six locations, hosting a total of 3,554 fragments belonging to three coral genera, that were left unsupervised for a period spanning from 29 to 61 weeks. Floating nursery structures experienced various levels of damage, and total fragment survival spanned from 40 to 95% among projects, with Pocillopora showing the highest survival rate in all locations present. Overall, our study shows that, under certain conditions, abandoned coral nurseries can remain functional for several months without suffering critical failure from biofouling and hydrodynamism. Still, even where gardening infrastructures were only marginally affected, the unavoidable interruptions in data collection have slowed down ongoing project progress, diminishing previous investments and reducing future funding opportunities. These results highlight the need to increase the resilience and self‐sufficiency of coral restoration projects, so that the next global lockdown will not further shrink the increasing efforts to prevent coral reefs from disappearing. [ABSTRACT FROM AUTHOR]

Coral diseases are an increasing threat to continuously degrading reefs as disease abundance and virulence are expected to increase in the future. Active conservation measures, specifically coral restoration projects, are increasingly being implemented worldwide. Yet little is known about the implications of disease occurrence in a restoration context. This study describes white syndrome pathogenesis in 2 coral genera, farmed in 2 mid-water rope nurseries located in a reef and a lagoon habitat in the Maldives. Over a 112 d monitoring period, disease metrics were obtained from 336 Pocillopora and 96 Acropora fragments to assess the impacts of unmitigated disease progression in coral nurseries. Disease had low prevalence (2.2%) and incidence (0.007) in reef-farmed Pocillopora, but survival (91%) was significantly reduced in comparison with the unaffected lagoon-farmed Pocillopora (99%). In contrast, lagoon-farmed Acropora showed high disease prevalence (78.5%) and incidence (0.064), and a lower survival (79%) than disease-unaffected reef-farmed Acropora (98%). These findings had distinct implications for coral gardening success. While Pocillopora was considered suitable for outplanting, especially since subsequent mitigation interventions were successful, the diseased, lagoon-reared Acropora posed a potential risk to the restoration site and was unsuitable for outplanting following 1 yr of farming effort. Our findings demonstrate that unmitigated diseases can cause major setbacks to restoration success. Coral gardening projects are likely to be particularly susceptible; therefore, disease monitoring and risk management are imperative. Since there is currently a lack of available diagnostic and mitigative tools, this study aims to provide case study data for restoration practitioners.

Correctly delimiting species and populations is a prerequisite for studies of connectivity, adaptation and conservation. Genomic data are particularly useful to test species differentiation for organisms with few informative morphological characters or low discrimination of cytoplasmic markers, as in Scleractinians. Here we applied Restriction site Associated DNA sequencing (RAD-sequencing) to the study of species differentiation and genetic structure in populations of Pocillopora spp. from Oman and French Polynesia, with the objectives to test species hypotheses, and to study the genetic structure among sampling sites within species. We focused here on coral colonies morphologically similar to P. acuta (damicornis type β). We tested the impact of different filtering strategies on the stability of the results. The main genetic differentiation was observed between samples from Oman and French Polynesia. These samples corresponded to different previously defined primary species hypotheses (PSH), i.e., PSHs 12 and 13 in Oman, and PSH 5 in French Polynesia. In Oman, we did not observe any clear differentiation between the two putative species PSH 12 and 13, nor between sampling sites. In French Polynesia, where a single species hypothesis was studied, there was no differentiation between sites. Our analyses allowed the identification of clonal lineages in Oman and French Polynesia. The impact of clonality on genetic diversity is discussed in light of individual-based simulations. [ABSTRACT FROM AUTHOR]

Artificial reefs and, more recently, ecoengineering are frequently advocated as possible tools to counteract the loss of tropical coral reefs worldwide. Despite increasing availability of novel materials, there is limited understanding of how different materials and their physical and chemical properties can influence coral recruitment success and early benthic community development. This study investigated the efficacy of several innovative materials as recruitment substrates for corals and other sessile benthic communities. Stacks of vertically oriented tiles made of eight innovative materials and two common (control) materials were deployed for 6 months during major coral spawning events on the forereef of Mo'orea, French Polynesia. Tiles were separated from their neighbors by 15 mm to mimic cryptic habitats that are sheltered from predation and typically favored by coral recruits. Six innovative materials, including 3D printed concrete, polyvinyl chloride (PVC) with chitosan coating, fiberglass polymer, and flax‐based polylactic acid, produced similar coral recruitment to control materials (Portland concrete and PVC). Two materials (porous concrete and ceramic foam) produced lower recruitment. Porous concrete was characterized by a high abundance of non‐coralline encrusting red algae, which negatively correlated with coral recruitment, while ceramic foam was prone to erosion. The results suggest the structural micro‐complexity and durability of an artificial material and the composition of the benthic communities colonizing it can strongly influence coral recruitment. This study highlights several innovative materials as suitable recruitment substrates for coral restoration and provides a better understanding of the properties of artificial materials that are critical for coral recruitment success. [ABSTRACT FROM AUTHOR]

As sequencing techniques have advanced and become cheaper in recent years, there has been a rapid increase in the number of studies conducted into the role of the microbiome in coral health, physiology, and response to environmental change. However, there is substantial variation in the methodological approaches applied. For example, DNA extraction protocols and the types of tissues sampled from the coral meta-organism are known to influence the downstream analyses of the amplified microbial communities and subsequently the interpretation of the microbiome diversity, stability and role. Studies have generally focused on whole organisms, in which the coral sampling steps homogenize the meta-organism microhabitats, however other studies targeting specific microhabitats have identified sources of variation specific to distinct compartments of the coral’s microbial landscape. Here we present a comparative analysis of methodologies optimized for the generation of coral microbiome data from the coral tissues and whole coral fragments of two commonly studied branching coral genera with distinct tissue structure. We investigate the microbiome of the imperforate Pocillopora, where the coral tissue does not penetrate through the calcium carbonate matrix, and the perforate Acropora, where the coral tissues and skeleton are interwoven throughout the coral branch. Through comparing data generated from different DNA extraction protocols using fixed coral tissues isolated from the coral skeletal structure with fixed whole coral fragments, we identify sources of variation inherent to microbial data generated from different sample types, species, and extraction protocols.

The density and diversity of Symbiodiniaceae associated with corals can be influenced by seasonal changes . This study provided the first annual investigation of Symbiodiniaceae density and diversity associated with Acropora humilis and Pocillopora cf. damicornis corals in the Gulf of Thailand using both zooxanthellae cell count and next-generation sequencing (ITS-1, ITS-2 regions) techniques, respectively. The results from this study indicated that zooxanthellae cell densities in both coral species differ significantly. The number of zooxanthellae was negatively correlated with the physical environment variable (light intensity). The diversity within A. humilis consisted of two genera, Cladocopium (Cspc_C3: 56.39%, C3w: 33.62%, C93type1: 4.42% and Cspf: 3.59%) and a small amount of Durusdinium (D1: 1.03%) whereas P. cf. damicornis was found to be 100% associated with Durusdinium (D1: 95.58%, D6: 1.01% and D10: 2.7%) suggesting that each coral species may select their appropriate genus/species of Symbiodiniaceae in response to local environmental stressors. The results of this study provided some information on the coral-Symbiodiniaceae relationship between seasons, which may be applied to predict the potential adaptation of corals in localized reef environments. [ABSTRACT FROM AUTHOR]

The need for comprehensive and effective coral restoration projects, as part of a broader conservation management strategy, is accelerating in the face of coral reef ecosystem decline. This study aims to expand the currently limited knowledge base for restoration techniques in the Maldives by testing the performance of mid-water rope nurseries in a lagoon and a reef habitat. We examined whether different coral farming habitats impacted fragment survival, health and growth of two coral genera and how the occurrence of mutualistic fauna, predation and disease influenced coral rearing success. Two nurseries were stocked with a total of 448 Pocillopora verrucosa and 96 Acropora spp. fragments, divided into different groups (four Pocillopora groups: lagoon nursery at 5 m; reef nursery at 5, 10 and 15 m; two Acropora groups: lagoon nursery at 5 m and reef nursery at 5 m). Eight fragment replicates from the same donor colony (Pocillopora genets: N -14, Acropora genets N -6) were used in each group and monitored for one year. Our results show that fragment survival was high in both farming habitats (>90%), with P. verrucosa surviving significantly better in the lagoon and Acropora spp. surviving and growing significantly faster in the reef nursery. P. verrucosa growth rates were similar between reef and lagoon habitat. Different rearing depths in the reef nursery had no impact on the survival of P. verrucosa but coral growth decreased considerably with depth, reducing fragments' ecological volume augmentation and growth rates by almost half from 5 to 15mdepth. Further, higher fish predation rates on fragments were recorded on the reef, which did not impact overall nursery performance. Mutualistic fauna, which correlated positively with fragment survival, was more frequently observed in the lagoon nursery. The occurrence of disease was noted in both habitats, even though implications for fragment health were more severe in the lagoon. Overall, our study demonstrates that lagoon and reef nurseries are suitable for rearing large numbers of coral fragments for transplantation. Nevertheless, we recommend considering the specific environmental conditions of the farming habitat, in particular water quality and year-round accessibility, in each case and to adjust the coral farming strategy accordingly. We hope that this novel research encourages the increased application of mid-water rope nurseries for 'coral gardening' to advance coral reef recovery and climate resilience in the Maldives. [ABSTRACT FROM AUTHOR]

Coral reefs are increasingly threatened by heat stress events leading to coral bleaching. In 2016, a mass bleaching event affected large parts of the Great Barrier Reef (GBR). Whilst bleaching severity and coral mortality are usually monitored throughout major bleaching events, other health indicators, such as changes in microbial partners, are rarely assessed. We examined the impact of the 2016 bleaching event on the composition of the microbial communities in the coral Pocillopora acuta at Havannah Island Pandora reef, separated by 12 km on the inshore central GBR. Corals experienced moderate heat stress (3.6 and 5.3 degree heating weeks), inducing major bleaching (30–60%) at the coral community level. Samples were partitioned according to Symbiodiniaceae densities into three bleaching severity categories (mild, moderate, and severe). Whilst Symbiodiniaceae densities were similar at both reef locations, sequencing of the Symbiodiniaceae ITS2 and prokaryotic 16S rRNA genes revealed that microbial communities were significantly different between reefs, but not according to bleaching severity. Symbiodiniaceae composition was dominated by the genus Cladocopium with low abundances of Durusdinium detected in moderately and severely bleached colonies at both sites, despite site-specific ITS2 profiles. Bacterial communities were dominated by Proteobacteria and were almost entirely lacking the common Pocilloporid associate Endozoicomonas regardless of bleaching severity. Strikingly, only 11.2% of the bacterial Amplicon Sequencing Variants (ASVs) were shared between sites. This reef specificity was driven by 165 ASVs, mainly from the family Rhodobacteraceae. Comparison with previous studies suggests that the moderate heat stress experienced on the central GBR in 2016 caused the near-complete absence of Endozoicomonas. Symbiodiniaceae and bacteria (particularly Rhodobacteraceae) can be vertically transmitted in P. acuta, and larval propagation can be spatially restricted for this brooding species. Our results demonstrate that, unlike bleaching severity, location-specific factors and species-specific life history traits might have been paramount in shaping the P. acuta microbiome. [ABSTRACT FROM AUTHOR]

Abstract We investigated the occurrence of intracolonial genetic variability (IGV) in Pocillopora corals in the southwestern Indian Ocean. Ninety‐six colonies were threefold‐sampled from three sites in Reunion Island. Nubbins were genotyped using 13 microsatellite loci, and their multilocus genotypes compared. Over 50% of the colonies presented at least two different genotypes among their three nubbins, and IGV was found abundant in all sites (from 36.7% to 58.1%). To define the threshold distinguishing mosaicism from chimerism, we developed a new method based on different evolution models by computing the number of different alleles for the infinite allele model (IAM) and the Bruvo's distance for the stepwise mutation model (SMM). Colonies were considered as chimeras if their nubbins differed from more than four alleles and if the pairwise Bruvo's distance was higher than 0.12. Thus 80% of the IGV colonies were mosaics and 20% chimeras (representing almost 10% of the total sampling). IGV seems widespread in scleractinians and beyond the disabilities of this phenomenon reported in several studies, it should also bring benefits. Next steps are to identify these benefits and to understand processes leading to IGV, as well as factors influencing them.

The capacity of coral reefs to provide ecosystem services is widely recognized, but this ability depends on continued carbonate production within the coral community. The Islas Marías archipelago (21° 29.5′ N–106° 15′ W) is subject to minimal anthropic pressures. This archipelago serves as a model to study the influence of environmental variables [e.g., sea surface temperature (SST), upwelling periods, El Niño‐Southern Oscillation (ENSO) events, and pH] on the structure of the coral community. The aim of this study was to evaluate the growth parameters, ecological volume, and CaCO3 production of Pocillopora corals, which comprise the dominant genus in the Eastern Tropical Pacific (ETP). During an annual period (2016–2017), 10 colonies were stained with alizarin red and height, major diameter, and minor diameter measurements were recorded. Live coral cover, the annual extension rate (cm/year), skeletal density (g/cm3), the calcification rate (g/cm2 year−1), ecological volume (cm−3), and carbonate production (kg m−2 year−1) were also calculated. The average extension rate (± SD), skeletal density, and the calcification rate were 1.86 ± 0.31 cm/year, 2.28 ± 0.34 g CaCO3 cm−3, and 4.34 ± 1.28 g CaCO3 cm−2 year−1, respectively. The average live coral coverage was 3.19 ± 3.17%, and the relative cover of Pocillopora corals was 65%. Ecological volume increased 140.6 ± 84.28% with respect to the initial volume, and the average production of CaCO3 was 0.46 ± 0.41 kg CaCO3 m−2 year−1. This study shows evidence of low growth rates, low generation of three‐dimensionality, and low CaCO3 production in the study area when compared to other sites in the ETP. These results are relevant because they indicate compromised long‐term maintenance and reef development in Islas Marías, which may result in low reef functionality and compromise the stability of reef‐associated biodiversity and ecosystem services. [ABSTRACT FROM AUTHOR]

To evaluate potential coral adaptive mechanisms, we investigated physiological traits (biomass, lipid, protein, chlorophyll, and isotopic proxies for trophic strategy) in eight Hawaiian corals species along an environmental gradient of significant wave height, sea surface temperature, and seawater chlorophyll a concentration around the island of O'ahu, Hawai'i. We used the amount of physiological variation expressed in corals, and the proportion of this variation that could be explained by environmental variables, to construct hypotheses about the relative capacity for each species to adapt or acclimatize to differing conditions. Genus-level analyses indicated that Montipora and Pocillopora phenotypes are influenced more strongly by the environment than Porites corals. Species-level analyses revealed that Montipora capitata and Pocillopora acuta have the widest physiological niche boundaries, whereas Porites evermanni and Pocillopora meandrina are more physiologically restricted. Correlations between individual traits and the environmental gradient provided insight into potential adaptive mechanisms employed by each species that allow them to persist in reefs such as those within Kāne'ohe Bay, where water flow is lowest, and temperature, acidity, and nutrient concentrations are highest relative to other reefs around O'ahu. Potential adaptive mechanisms included (a) increased surface-area-to-volume ratios to facilitate higher material flux across the diffusive boundary layer and/or to maximize light harvesting (M. capitata and P. acuta), (b) strategic investment of metabolic energy toward energy reserves (Montipora and Pocillopora), (c) changes in protein management likely via differential expression and function (Porites), and d) increased chlorophyll concentration per Symbiodiniaceae cell to maximize photosynthesis (Porites compressa). Comparison of our results with established patterns in the relative abundance of these species around O'ahu suggests that species with wide physiological niche boundaries like M. capitata and M. flabellata might be expected to do better under predicted future ocean conditions and outcompete species such as P. evermanni and P. meandrina, making them potential candidates for coral conservation efforts. [ABSTRACT FROM AUTHOR]

The resistance of corals to a changing climate has been linked to physiological parameters including heterotrophic capacity and energy reserves. Recently, the potential flexibility and diversity of coral-associated microbial communities have also been related to coral health and resistance to environmental stress. This study uses the island of O'ahu in Hawai'i, USA, as a natural laboratory to explore variability in the microbial community composition of four coral species (Porites compressa, Porites lobata, Pocillopora acuta, and Pocillopora meandrina) across a gradient of natural ocean conditions. In addition, we assessed potential relationships between the composition of coral-associated microbial communities with coral physiology. We found that microbial community composition differed among all coral species, as well as among several of the collection sites within species. Microbial community assembly appeared to be governed by a combination of deterministic and stochastic processes, and the composition of these communities was more often related to measurements of coral physiology than environmental parameters among the collection sites. Specifically, coral lipid and protein levels, two components of coral energy reserves, explained significant portions of microbial community composition in Porites lobata and Pocillopora acuta, respectively. Further, microbial community diversity decreased as the proportionate contribution of heterotrophy relative to photoautotrophy in coral tissues increased in Porites compressa and Pocillopora acuta, but the opposite was true for Porites lobata. These findings suggest that if coral heterotrophy increases with warming oceans, it could co-occur with shifts in microbial community diversity in some coral species, possibly from decreased production of photosynthates and/or changes in the nutritional makeup of the mucus layer. Overall, connections with energy reserves and heterotrophy suggest a role for coral resource use in shaping the composition of coral-associated microbial communities across a range of natural ocean conditions, a relationship that may be important as some corals acclimatize to global climate change. [ABSTRACT FROM AUTHOR]

Using the electric field in the biorock method increases the growth and survival rate in a wide variety of coral species. In this regard, we evaluated the effects biorock method on the growth and survival of coral Acropora calthrata and Pocillopora damicornis in Chabahar Bay for four months. Coral pieces were placed on steel structures under a 6V electric field in the biorock process. The mean coral growth of P. damicornis and A. calthrata in the biorock structure was 10.68 ± 0.3(cm) and 12 ± 0.29(cm), respectively, and in the control construct was 5.27 ± 0.2(cm) and 5.25 ± 0.23(cm), respectively. The results showed a significant difference between coral growth in biorock and non-biorock structures (p