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Coral reefs are known to be one of the most diverse marine ecosystems on earth. However, these important ecosystems are heavily stressed by natural and anthropogenic activities. Environmental DNA (eDNA) metabarcoding is an innovative approach that can provide a greater diversity of taxonomic detections, non-invasive sampling, and a lower field component cost than traditional biomonitoring methods. Taiping Island (Itu Aba Island) is one of the major coral reef islands situated in the South China Sea where underwater visual surveys documented an outbreak of Crown-of-Thorns starfish (COTS) in 2021. In our study, we used eDNA metabarcoding to investigate whether there were shifts in coral communities by comparing pre- and post-COTS outbreak communities. One metabarcoding assay targeting the 18S gene and two assays targeting the ITS2 region (one of these assays specifically targeting Acroporid corals) were applied to 42 seawater samples collected in 2019 and 2021 from 12 sites around Taiping Island. Based on these three metabarcoding assays, 52 unique hard coral species were identified, corresponding to a total of 51 species in 2019 and 26 species in 2021. Our results indicated a significant decline in coral diversity but an increase in sponge diversity from the phylum porifera at Taiping Island in 2021. We suggest that these faunal shifts may be due to active feeding and disturbance of COTS at outbreak proportions that result in habitat changes. Our findings also suggest that eDNA can continue to serve as a promising tool to monitor the change in coral as well as reef-associated taxa during devastating outbreak events. [ABSTRACT FROM AUTHOR]

The capacity for natural coral reef recovery and the effectiveness of active restoration efforts are often contingent upon uncertain and understudied background variables, such as chronic predation for example. In the Maldives, small coral colonies (< 10 cm), primarily from the genera Pocillopora and Acropora (often found recolonising degraded reefs) are frequently predated on by the spiny cushion sea-star (Culcita schmideliana). Incidentally, these same corals (especially Acroporids) are often prioritised in active reef restoration practices. However, the level of risk these corallivores pose on restoration success has not yet been assessed. Here, we aimed to initially document the population densities of C. schmideliana on a degraded reef system in the Maldives (Kunfunadhoo, Baa Atoll). We then assessed their associated predatory effects on coral recruits and transplants, and explored the benefits of C. schmideliana removal on the survival of these corals. Population densities ranged between 1.2 and 3.3 individuals per 100 m2, which resulted in high predation rates on coral recruits (4 – 20%) and transplants (11 – 43%). Culcita schmideliana predation accounted for the majority of the documented mortality (85%). Where C. schmideliana were removed, a significant increase in survival for recruits (9% higher) and transplants (24% higher) was shown. Further observations linked a cessation of C. schmideliana removal to a significant rise in predation instances for previously protected corals (up to 52%). Our study therefore highlights the severe impacts of C. schmideliana predation and shows Culcita spp. population management as a viable passive solution for effective reef restoration. [ABSTRACT FROM AUTHOR]

In the face of rising global temperatures, coral reefs experience coral mass bleaching and mortality. Subtropical and mesophotic environments may represent refugia for reef corals under climate change, where they can survive and eventually recolonize degraded areas. Using a comprehensive database of fossil reefs, we empirically assess the efficacy of subtropical, deeper, and turbid mesophotic environments to restore coral reefs after past global warming events. We focus on tropical coral reefs over the last 275 million years and four rapid climate warming events, which coincided with global reef crises in the geological record. In the aftermath of such hyperthermal events, we observed an increase in the proportions of reefs occurring in deeper (blue) mesophotic environments. Additionally, we found a trend of reef distributions and coral shifting towards higher latitudes. The number of coral occurrences in turbid (brown mesophotic) environments also increased after hyperthermal events. Our results suggest that subtropical, blue, and brown mesophotic environments may have served as immediate refugia for shallow-water coral species escaping warming seawater. While the patterns of reef range shifts and the establishment of blue and brown mesophotic refugia following ancient hyperthermal events provide some hope for coral reefs under current climate change, re-establishement of background reef conditions took most times millions of years. Ante el incremento de temperatura global, los arrecifes coralinos están experimentando eventos masivos de blanqueamiento y mortalidad. Los ambientes subtropicales y mesofóticos pueden representar refugios para los corales arrecifales, en los cuales pueden escapar de los efectos del cambio climático, sobrevivir y desde allí recolonizar áreas previamente degradadas. Mediante el uso de una exhaustiva base de datos en arrecifes coralinos, en este estudio se evaluó empíricamente la eficacia de los ambientes subtropicales y mesofóticos, tanto de aguas turbias someras (marrones) como de aguas claras profundas (azules), en la recuperación de arrecifes coralinos después de eventos hipertermales en el pasado. Nuestro enfoque estuvo en los arrecifes coralinos tropicales durante los últimos 275 millones de años y cuatro eventos de calentamiento climático rápido, los cuales coinciden con crisis globales en la ocurrencia de arrecifes en el registro fósil. Como consecuencia de dichos eventos hipertermales, observamos un aumento del número de arrecifes en ambientes mesofóticos de aguas profundas (azules). Además, encontramos una tendencia en la distribución de arrecifes y corales que se desplazan hacia latitudes más altas. También se observó un aumento en el número de corales que estuvieron presentes en ambientes de aguas turbias (marrones) después de dichos eventos hipertermales. Nuestros resultados sugieren que, en el pasado, los ambientes subtropicales, mesofóticos azules y mesofóticos marrones pudieron haber servido como refugios inmediatos para las especies de coral de aguas someras, en los cuales encuentran condiciones atenuantes ante el calentamiento oceánico. Si bien los patrones de desplazamiento de los arrecifes en el rango latitudinal y el establecimiento de refugios mesofóticos de aguas marrones y azules posteriores a eventos hipertermales brindan una luz de esperanza para el futuro de los arrecifes coralinos de cara al cambio climático actual, nuestros resultados evidencian que el restablecimiento de los arrecifes puede tomar millones de años. [ABSTRACT FROM AUTHOR]

Investigating coral recruitment is critical to better understand replenishment and resilience capacities of coral reef ecosystems and to improve their conservation. Here, we examined the spatio‐temporal patterns of coral recruitment and the influence of confamilial adult coral cover in the region of Toliara, southwest Madagascar. Terracotta tiles were immersed from October to late January over a 3‐year period (2018–2021) at 10 stations located on major reef habitats. Overall recruitment rates were relatively high compared to those of other reefs in the Southwestern Indian Ocean, ranging from 219.20 recruits.m−2 in 2018–2019 to 156.30 recruits.m−2 in 2020–2021. Recruit assemblages were dominated by Acroporidae (45.5%) and Pocilloporidae (45.0%), whereas Poritidae (1.9%) and "other" recruits (3.6%) were rarely recorded. Recruitment patterns varied among stations and habitats, with higher rates in patch reef (187.06 recruits.m−2) and outer slope stations (156.99 recruits.m−2) compared to inner slope stations (108.04 recruits.m−2). With the exception of "other" recruits, recruitment rates decreased between 2018 and 2019 and 2019 and 2020, followed by an increase in 2020–2021 that reached or even exceeded initial values at some stations. The abundance of Pocilloporidae recruits was positively correlated with the cover of confamilial adult corals, highlighting potential stock–recruitment or recruitment–limitation relationships, or an aggregative settlement of young stages near the established adult colonies, whereas no such relationships were recorded for other coral family categories. This study identified sites on the outer slope and patch reefs to consider prioritizing for protection as recruitment hotspots, as well as degraded inner slope sites that could benefit from restoration, with the important caveat that any measures should be accompanied by alternative income‐generating activities through local involvement that suits the Malagasy context, such as locally marine managed areas. [ABSTRACT FROM AUTHOR]

Reef-building corals (Scleractinia, Anthozoa, Cnidaria) are the keystone organisms of coral reefs, which constitute the most diverse marine ecosystems. Since the first decoded coral genome reported in 2011, about 40 reference genomes are registered as of 2023. Comparative genomic analyses of coral genomes have revealed genomic characters that may underlie unique biological characteristics and coral diversification. These include existence of genes for biosynthesis of mycosporine-like amino acids, loss of an enzyme necessary for cysteine biosynthesis in family Acroporidae, and lineage-specific gene expansions of DMSP lyase-like genes in the genus Acropora. While symbiosis with endosymbiotic photosynthetic dinoflagellates is a common biological feature among reef-building corals, genes associated with the intricate symbiotic relationship encompass not only those shared by many coral species, but also genes that were uniquely duplicated in each coral lineage, suggesting diversified molecular mechanisms of coral-algal symbiosis. Coral genomic data have also enabled detection of hidden, complex population structures of corals, indicating the need for species-specific, local-scale, carefully considered conservation policies for effective maintenance of corals. Consequently, accumulating coral genomic data from a wide range of taxa and from individuals of a species not only promotes deeper understanding of coral reef biodiversity, but also promotes appropriate and effective coral reef conservation. Considering the diverse biological traits of different coral species and accurately understanding population structure and genetic diversity revealed by coral genomic analyses during coral reef restoration planning could enable us to "archive" coral reef environments that are nearly identical to natural coral reefs. [ABSTRACT FROM AUTHOR]

Efforts to restore coral reefs usually involve transplanting asexually propagated fast-growing corals. However, this approach can lead to outplanted populations with low genotypic diversity, composed of taxa susceptible to stressors such as marine heatwaves. Sexual coral propagation leads to greater genotypic diversity, and using slow-growing, stress-tolerant taxa may provide a longer-term return on restoration efforts due to higher outplant survival. However, there have been no reports to date detailing the full cycle of rearing stress-tolerant, slow-growing corals from eggs until sexual maturity. Here, we sexually propagated and transplanted two massive slow-growing coral species to examine long-term success as part of reef restoration efforts. Coral spat were settled on artificial substrates and reared in nurseries for approximately two years, before being outplanted and monitored for survivorship and growth for a further four years. More than half of initially settled substrates supported a living coral following nursery rearing, and survivorship was also high following outplantation with yields declining by just 10 to 14% over four years. At 6-years post-fertilisation over 90% of outplanted corals were reproductively mature, demonstrating the feasibility of restoring populations of sexually mature massive corals in under a decade. Although use of slower growing, stress tolerant corals for reef restoration may provide a longer-term return on investment due to high post-transplantation survival rates, considerable time is required to achieve even modest gains in coral cover due to their relatively slow rates of growth. This highlights the need to use a mix of species with a range of life-history traits in reef restoration and to improve survivorship of susceptible fast-growing taxa that can generate rapid increases in coral cover. [ABSTRACT FROM AUTHOR]

Petrarca is an ascothoracidan endoparasite in scleratinian dendrophyllid corals. Petrarca can stimulate coral growth, forming a gall chamber to house itself inside the coral skeleton. The diversity, molecular phylogeny and feeding ecology of Petrarca are understudied. This is the first study of Petrarca to be based on light and scanning electron microscopy to document the fine-scale external and functional morphology of its trophi and other structures. A combined molecular and morphological approach revealed at least four closely related species of Petrarca , P. goanna , P. morula , Petrarca nozawai sp. nov. and Petrarca rubus sp. nov. in Turbinaria and Astreopora corals in Asia. Carapace shape and fine morphology, ultrastructure of the antennular aesthetasc, morphological characteristics of the trophi and the shape and size of the penis rami are diagnostic characters. Several morphological characters, which are all probably synapomorphies, have been proposed to distinguish the genus Petrarca from other Ascothoracida. Mouthparts morphology of Petrarca are developed for cutting and chewing, rather than for piercing and sucking as in many other Ascothoracida. The external surface of the carapace of Petrarca is ornamented with densely packed secretory papillae used putatively for the chemical dissolution of the substrate necessary for the formation of the gall chamber. [ABSTRACT FROM AUTHOR]

The invasive sun corals Tubastraea spp. were introduced to Brazil in the late 1980s. The invasion prompted rapid changes in seascapes and local biological communities by excluding native species, particularly sessile ones. However, little is known about the impact on the mobile invertebrates. Using an experimental approach this study investigated the effects of living and dead sun corals and coral cover (50 vs. 100% covered areas) on the taxonomic composition, diversity (H') and abundance of reptant and natant macro-crustaceans and tanaids at the species level. Experimental units consisted of 60 tiles measuring 400 cm2, half and fully covered with living or dead corals which were deployed between 3 and 5 m for 12 months on concrete blocks. A total of 1346 specimens of decapods were obtained (27 native and 1 invasive species). 1059 specimens of the tanaid Chondrochelia dubia were sampled. The overall taxonomic composition was neither affected by coral condition (live or dead) nor by coral cover area. The diversity of reptant and natant species responded differently to coral condition and coral cover. The combination of dead corals and full cover accounted for the highest abundance of reptants. Natant abundance was influenced by coral cover area, irrespective of coral condition. The positive relationship between body size and abundance was statistically significant. Abundance of the obligate tube builder C. dubia was favoured by the greater availability of space on blocks half covered by corals. No signs were found of invasion meltdown in the mobile crustacean fauna. [ABSTRACT FROM AUTHOR]

Middle Jurassic reefs are known and studied from a wide range of palaeolatitudes, yet southern Tethyan reefs have been relatively understudied. The high abundance of stromatoporoids in southern Tethyan reefs was suggested to indicate a tolerance to oligotrophic and overheated waters. Recent studies affirmed the longtime hypothesis of a warm equable climate in low palaeolatitudes during the Jurassic, which could account for the documented low diversities of low-latitudinal coral reefs during this time interval. We present a case study showing possible evidence for the suggested connection between heat stress, low coral diversity and the success of stromatoporoids in the southern Tethys. The study focuses on the unique erosional depression of Makhtesh Gadol, southern Israel, which preserves a continuous section of the Callovian (Middle Jurassic). It is rich in fossils of benthic macrofauna, especially patch reefs of corals and stromatoporoids. Our quantitative analysis shows, for the first time: (1) a variation between a low- and high-diversity of coral patch reefs; and (2) a major shift from coral-dominated patch reefs in the lower part of the section to dominating stromatoporoids in the upper part. The faunal assemblage is used to reconstruct the depositional environment, indicating a shallowing upwards and increasing warmer waters. Patch reef beds showing low coral diversity are correlated with isotopic reconstructions from the same section, providing evidence for elevated water temperatures. The faunal transition from corals to stromatoporoids is correlated with a similar shift in Saudi Arabia, improving the regional correlation to the Arabian Carbonate Platform. [ABSTRACT FROM AUTHOR]

Sexually produced juvenile scleractinian corals play a key role in the adaptation process of coral reefs, as they are considered to possess an innate plasticity and thus can adjust to changing environmental parameters within a certain range. In this study we investigated in detail the early life stages of the brooding species Leptastrea purpurea to identify, categorize and visualize the critical steps of the complex transformation process from a swimming coral larva to a sessile coral recruit and later to a coral colony. For that, we performed settlement experiments using previously known cues: cycloprodigiosin (CYPRO) and crustose coralline algae (CCA) as well as novel cues: crude extracts of Pseudoalteromonas espejiana and P. piscicida to identify a general, cue-independent settlement pathway. We monitored the development of L. purpurea over 12 months using bright field and fluorescence microscopy. Also we identified the fluorescence signals of L. purpurea with confocal microscopy at four crucial development steps: (A) swimming larva, (B) metamorphosing larva, (C) coral recruit and (D) adult coral. Our methodological approach allowed us to observe an ontogenetic shift of fluorescence signals which provokes the hypothesis that certain fluorescence patterns might be connected to distinct sequential functions in the early life cycle of scleractinian corals. Our observations showed great similarities to the early development of other brooding and spawning corals, making L. purpurea a prospective candidate to be used as a model organism for coral research. Furthermore, our in-depth picture series provides a robust monitoring reference for coral nurseries or field applications and demonstrates the potential of fluorescence as an indicator to instantly determine the growth stage of a developing coral recruit.

Introduction: One of the main bottlenecks in restoration projects based on sexual reproduction is post-settlement survival, mainly due to competition for substrate with fleshy algae and predation. Therefore, substrates of different shapes and materials have been created and tested, seeking to optimize these processes with attractive surfaces for the larvae and structures where the recruits are protected from predation, and competition is reduced. Objective: To improve settlement and post-settlement survival of two important Caribbean reef-building corals, using different coatings on substrates. Methods: To determine whether substrate coatings properties are favourable to larval settlement in Orbicella annularis, and O. faveolata, collected in Puerto Morelos, Mexican Caribbean, we evaluated their settlement for three weeks on six coatings with a combination of properties. Each coating was designed to provide a combination of two out of three properties: 1) water repellence (hydrophobicity), 2) phosphorescence-based colour, and 3) mineral-enriched surface chemistry. In a separate experiment larvae settlement was tested using coatings with a single property. Finally, we determined the post-settlement survival of O. annularis and O. faveolata on the different coatings for seven weeks. Results: The combination of high hydrophobicity and light blue phosphorescent microparticles and high hydrophobicity and red-orange phosphorescent microparticles resulted in a higher settlement of O. annularis and O. faveolata when compared with other coatings (30.8 - 66.7 % higher). No significant differences were found in the number of larval settled when the water-repellence and the phosphorescence-based were evaluated independently. Post-settlement survival time on substrates was low, with a maximum of 34 days after settlement for O. annularis and 42 days for O. faveolata. Conclusions: In terms of the larval settlement, the combination of the coatings properties appears to play an essential role in the choice of microhabitat for both O. annularis and O. faveolata. But individually these properties did not generate an advantage in the larval settlement. Moreover, some chemical components associated with the coatings may be counterproductive to the survival of the polyps over time. [ABSTRACT FROM AUTHOR]

Accurate identification of scleractinian coral species is fundamental for proper biodiversity estimates, for aiding in efforts of reef monitoring, conservation, restoration, and for the management of coral reefs. Here, we provide the first DNA barcoding reference library for coral species in Eilat, Red Sea, based on the mitochondrial gene cytochrome c oxidase subunit I (COI), targeting the identification of stony coral species from shallow (0–12 m) reefs. A total of 191 specimens were collected, depicting 14 families, 39 genera, and 94 species (all are new full species records to the BOLD system). Three species (Sclerophyllia margariticola, Cyphastrea magna, and Psammocora profundacella) are first records for Eilat's coral reef. The results presented here strengthen the claim that COI is not universally informative for delimitation of stony coral species, a notion reinforced by the constructed maximum likelihood phylogenetic tree. This library is the first step in a long journey towards elucidating coral biodiversity in the coral reef at Eilat and for improving future management and monitoring efforts. [ABSTRACT FROM AUTHOR]

The abundance and health of scleractinian coral communities of Hormuz Island were investigated. For this purpose, we employed 20 m line intercept transects—12 in the intertidal zone and 15 subtidally to evaluate coral cover and community composition. The estimated dead coral coverage was 6.21%±0.81%, while live coral coverage was 16.93%±1.81%, considered as very poor. Totally, 12 genera were recorded, of which Porites with 11.9%±1.4% live cover was the dominant, while Goniopora had the least cover (0.07%±0.08%). Based on Mann-Whitney U-test, live coral coverage, dead coral coverage, algal coverage, cover of other benthic organisms and abiotic components showed significant univariate differences between zones (p<0.05). The Spearman correlation test between the abundance of biotic and abiotic components indicated significant negative correlation of live coral and sand with zoantharian and significant positive correlation of algae and other benthic organisms with rubble. The reef health indices used for the corals indicated that, in general, the environmental conditions were not suitable, which could be attributed to both natural and anthropogenic factors, the most important of which was zoantharian' overgrowth on the scleractinian corals in this region. [ABSTRACT FROM AUTHOR]

Microbes play a key role in reef dynamics, mediating the competition between scleractinian corals and benthic algae; however, major shifts in bacterial communities among coral species in response to increases in the abundance of algae are not well understood. We investigated the taxonomic composition of coral-associated microbial communities under algae-overgrowth conditions using 16S rRNA gene sequencing. The results showed that non-algal (i.e., healthy) tissue (HH) had lower bacterial abundance and diversity than tissue collected from the coral–algae interface boundary (HA) and areas of algae growth (AA). Specifically, the HA and AA samples had higher relative abundances of Saprospiraceae, Rhodobacteraceae, and Alteromonadaceae. Compared with Platygyra sp. and Montipora sp., the physiological response of Pocillopora sp. was more intense under algae-induced stress based on microbial gene function prediction. Our results indicate that algal pressure can significantly alter the microbial community structure and function of coral ecosystems. Our data thus provide new insight into the relationship between corals and their microbiome under environmental stress. [ABSTRACT FROM AUTHOR]

Sea cucumbers are important ecological engineers in marine ecosystems. However, the fishery demand of some species, especially large-epifaunal and commercially used (LEC) sea cucumbers, has risen drastically, resulting in serious depletion of local populations for many species. Despite this problem, basic ecological data on sea cucumbers, such as population densities and preferred habitats, are often still insufficient. Here, we report on the population densities of multiple LEC sea cucumber species, and their ambient benthic communities at eight sites around Okinawa Islands. Further, we discuss the correspondence between sea cucumber densities and the surrounding coral communities. Our results show two sites within national or quasi-national parks, Aka and Manza, where stricter rules have been placed on fisheries and land reclamation compared to other areas, had the highest and third highest sea cucumber population densities among sites, respectively. Holothuria atra was observed at all survey sites and made up the majority of sea cucumber populations at all sites except for Chatan and Sesoko, where Holothuria leucospilota and Stichopus chloronotus were most abundant, respectively. Regarding the relationships between benthic composition and LEC sea cucumber species, S. chloronotus was significantly correlated with dead corals, scleractinian corals, and coralline algae. As well, H. leucospilota had significant correlations with rubble. Although there were no significant correlations between any specific scleractinian coral genus and sea cucumber densities, S. chloronotus was marginally insignificant with Platygyra and Psammocora. Notably, medium- to highly valued species were sparse in our surveys, and most of them appeared at only one site. Additionally, at one site (Odo), only three LEC sea cucumber individuals were observed. Combining these facts with relatively low population densities around the Okinawa Islands compared to densities reported in previous research from the Indo-West Pacific Ocean region, we conclude that Okinawan LEC sea cucumber populations have been and are being impacted by high levels of direct (e.g., overexploitation, as well as coastal development) and indirect anthropogenic pressure (e.g., decreasing water quality). To address the current situation, repeated monitoring and more detailed investigations to reveal the drivers that determine LEC sea cucumber species aggregations and population densities are urgently needed, along with more robust management of remaining LEC sea cucumber populations. [ABSTRACT FROM AUTHOR]

Using a standardized SNP array, we identified two populations of Acropora cervicornis and one population of A. palmata in the Caribbean coast of Colombia. San Andrés was the most genetically differentiated location for both species. An average pairwise FST value of 0.131 and 0.050 between San Andrés and neighboring collection sites was estimated, for A. cervicornis and A. palmata, respectively. Based on population patterns of both acroporid species, we inferred that Magdalena River is not a barrier of genetic connectivity among Colombian populations. Genetic comparisons between the Colombian coast of Caribbean with other Caribbean locations agree with previous studies for both species, where four populations were identified in A. cervicornis and three in A. palmata. Our results support published bio-physical model predictions and highlight the Panama-Colombia gyre as a possible isolating mechanism within the western Caribbean. However, the genetic diversity in both species was about half (mean HE per siteD0.321 in A. palmata and 0.369 in A. cervicornis) than previous estimates in acroporid populations in the Caribbean. The lower genetic diversity as well their relative isolation and high levels of reef degradation may be of particular conservation concern that may require species-specific management coupled with science-based restoration efforts. [ABSTRACT FROM AUTHOR]

Members of the ammonium transporter family occur in all domains of life. However, they have been characterized, at the molecular level, mainly in bacteria and plants, whereas in animals their molecular characterization is limited to a few species. In marine invertebrates, recent studies have reported a multitude of physiological functions in which ammonium could take part. Among them, calcification is one for which very few data are available. In scleractinian corals, it has been reported that external sources of ammonium and/or ammonium containing compounds enhance calcification. However, despite these physiological insights, the underlying transport mechanisms are still unknown at the molecular level. In this study, we performed a first molecular characterization of ammonium transporters in the scleractinian coral Stylophora pistillata. By performing differential gene expression analysis, through quantitative real-time PCR, we show that S. pistillata ammonium transporters possess different tissue specificities. Most notably, one ammonium transporter, spiAMT1d, is specifically expressed in the coral tissue containing the calcifying cells. Furthermore, we determined spiAMT1d subcellular localization by immunostaining S. pistillata histological cross-sections and show that it localizes on the apical side of the calcifying cells and in their intracellular compartments. Taken together our results strongly suggest a role of ammonium transporters in coral calcification and lay the groundwork for many future studies aiming to better elucidate the potential role of ammonium in calcification. [ABSTRACT FROM AUTHOR]

Using a standardized SNP array, we identified two populations of Acropora cervicornis and one population of A. palmata in the Caribbean coast of Colombia. San Andrés was the most genetically differentiated location for both species. An average pairwise FST value of 0.131 and 0.050 between San Andrés and neighboring collection sites was estimated, for A. cervicornis and A. palmata, respectively. Based on population patterns of both acroporid species, we inferred that Magdalena River is not a barrier of genetic connectivity among Colombian populations. Genetic comparisons between the Colombian coast of Caribbean with other Caribbean locations agree with previous studies for both species, where four populations were identified in A. cervicornis and three in A. palmata. Our results support published bio-physical model predictions and highlight the Panama-Colombia gyre as a possible isolating mechanism within the western Caribbean. However, the genetic diversity in both species was about half (mean HE per site = 0.321 in A. palmata and 0.369 in A. cervicornis) than previous estimates in acroporid populations in the Caribbean. The lower genetic diversity as well their relative isolation and high levels of reef degradation may be of particular conservation concern that may require species-specific management coupled with science-based restoration efforts.

Abstract Corals have evolved a variety of stress responses to changing conditions, many of which have been the subject of scientific research. However, polyp bailout has not received widespread scientific attention, despite being described more than 80 years ago. Polyp bailout is a drastic response to acute stress in which coral colonies break down, with individual and patches of polyps detaching from the colony and the calcareous skeleton Polyps retain their symbiotic partners, have dispersal ability, and may undergo secondary settlement and calcification. Polyp bailout has been described worldwide in a variety of anthozoan species, especially in Scleractinia. It can be induced by multiple natural stressors, but also artificially. Little is known about the evolutionary and ecological potential and consequences of breaking down modularity, the dispersal ability, and reattachment of polyps resulting from polyp bailout. It has been shown that polyp bailout can be used as a model system, with promise for implementation in various research topics. To date, there has been no compilation of knowledge on polyp bailout, which prompted us to review this interesting stress response and provide a basis to discuss research topics and priorities for the future.

Ocean acidification (OA) poses a major threat to calcifying organisms such as reef-building corals, typically leading to reduced calcification rates. Mechanisms to compensate the effects of OA on coral growth may, however, involve processes other than calcification. Yet, the physiological patterns mediating coral growth under OA are not fully understood, despite an extensive body of literature characterizing physiological changes in corals under OA. Therefore, we conducted a three-month laboratory experiment with six scleractinian coral species (Acropora humilis, Acropora millepora, Pocillopora damicornis, Pocillopora verrucosa, Porites cylindrica, and Porites lutea) to assess physiological parameters that potentially characterize growth (calcification, volume, and surface area), maintenance (tissue biomass, and lipid and protein content), and cellular stress (apoptotic activity) response under ambient (pH 7.9) and low pH (pH 7.7). We identified genus- and species-specific physiological parameters potentially mediating the observed growth responses to low pH. We found no significant changes in calcification but species showed decreasing growth in volume and surface area, which occurred alongside changes in maintenance and cellular stress parameters that differed between genera and species. Acropora spp. showed elevated cellular stress and Pocillopora spp. showed changes in maintenance-associated parameters, while both genera largely maintained growth under low pH. Conversely, Porites spp. experienced the largest decreases in volume growth but showed no major changes in parameters related to maintenance or cellular stress. Our findings indicate that growth- and calcification-related responses alone may not fully reflect coral susceptibility to OA. They may also contribute to a better understanding of the complex physiological processes leading to differential growth changes of reef-building corals in response to low pH conditions.

The article presents data indicating the relationship of the bathymetric distribution of solitary endemic scleractinian corals inhabiting the Antarctic continental shelf and upper continental slope with the vertical density of the Antarctic Circumpolar Current. The study is based on materials collected by expeditions of the Shirshov Institute of Oceanology (IO RAS) and the literature data. The results show that endemic species that appeared in the Late Neogene and Pleistocene were unable to propagate across other oceans due to the existing horizontal and vertical density of the Arctic Circumpolar Current during that period. [ABSTRACT FROM AUTHOR]

Skeletons of contemporary reef‐building scleractinian corals are formed of aragonite, a polymorph of the calcium carbonate (CaCO3), notwithstanding calcite being a more stable phase under the condition of coral habitats. Circumstances developing aragonite in coral calcification have been addressed currently. Considering that the symbiotic relationship between the coral host and dinoflagellate algae (zooxanthellae) is perhaps relevant to coral calcification, we studied the impact of these symbiotic relationships on CaCO3 polymorph selection. Juvenile scleractinian corals (Acropora tenuis and Acropora digitifera) absent symbionts were cultured in seawaters with varied Mg/Ca molar ratios (mMg/Ca), and the mineral phases of the skeletons were detected employing X‐ray diffraction. The findings revealed that diminutive quantities of calcite precipitated as coral skeleton in Acropora digitifera surprisingly in pseudo‐present seawater (mMg/Ca∼5). Additionally, coral developed skeletons from only calcite in seawater with an mMg/Ca < 1. The evidence gathered in this investigation suggests that the symbiotic relationship affects the establishment of aragonite skeletons in the course of coral calcification. Plain Language Summary: Skeletons of contemporary reef‐building corals are made of calcium carbonate. The calcium carbonates have polymorphs: calcite, aragonite, and vaterite. Aragonite is a component of coral skeletons, but calcite can thermodynamically precipitate more easily than aragonite in the living conditions of corals. Circumstances resulting in aragonite precipitation in coral calcification have been addressed recently. Considering that the symbiotic relationship between the coral host and dinoflagellate algae is perhaps relevant to coral calcification, we studied the impact of these symbiotic relationships on aragonite precipitation. Juvenile scleractinian corals without symbionts were cultured in seawater with varied Mg/Ca molar ratios to evaluate the effects of mineral component differences resulting from Mg/Ca molar ratio on calcium carbonate polymorphs. The mineral phases of the skeletons were identified using an X‐ray diffraction. The findings revealed that small quantities of calcite precipitated as coral skeleton in pseudo‐present seawater (Mg/Ca molar ratio of ∼5). Additionally, coral developed skeletons from only calcite in seawater with an Mg/Ca molar ratio of <1. The evidence gathered in this investigation suggests that the symbiotic relationship affects the establishment of aragonite skeletons in the course of coral calcification. Key Points: Reef‐building corals build their skeletons using calcium carbonate in aragonite form, which is thermodynamically less stable than calciteCorals build entirely calcitc skeletons in artificial seawater with low Mg/Ca ratio without a symbiotic relationship with zooxthantellaeA symbiotic relationship involves CaCO3 polymorph selection in coral calcification [ABSTRACT FROM AUTHOR]

Abstract Background Sexual reproduction of scleractinians has captured the attention of researchers and the general public for decades. Although extensive ecological data has been acquired, underlying molecular and cellular mechanisms remain largely unknown. In this study, to better understand mechanisms underlying gametogenesis, we isolated ovaries and testes at different developmental phases from a gonochoric coral, Euphyllia ancora, and adopted a transcriptomic approach to reveal sex- and phase-specific gene expression profiles. In particular, we explored genes associated with oocyte development and maturation, spermiogenesis, sperm motility / capacitation, and fertilization. Results 1.6 billion raw reads were obtained from 24 gonadal samples. De novo assembly of trimmed reads, and elimination of contigs derived from symbiotic dinoflagellates (Symbiodiniaceae) and other organisms yielded a reference E. ancora gonadal transcriptome of 35,802 contigs. Analysis of 4 developmental phases identified 2023 genes that were differentially expressed during oogenesis and 678 during spermatogenesis. In premature/mature ovaries, 631 genes were specifically upregulated, with 538 in mature testes. Upregulated genes included those involved in gametogenesis, gamete maturation, sperm motility / capacitation, and fertilization in other metazoans, including humans. Meanwhile, a large number of genes without homology to sequences in the SWISS-PROT database were also observed among upregulated genes in premature / mature ovaries and mature testes. Conclusions Our findings show that scleractinian gametogenesis shares many molecular characteristics with that of other metazoans, but it also possesses unique characteristics developed during cnidarian and/or scleractinian evolution. To the best of our knowledge, this study is the first to create a gonadal transcriptome assembly from any scleractinian. This study and associated datasets provide a foundation for future studies regarding gametogenesis and differences between male and female colonies from molecular and cellular perspectives. Furthermore, our transcriptome assembly will be a useful reference for future development of sex-specific and/or stage-specific germ cell markers that can be used in coral aquaculture and ecological studies.

This study reports the first attempt to quantitatively describe a Dendrophyllia ramea population on the Apollo bank (Ionian Sea), revealed in summer 2021 through a remotely operated vehicle (ROV) survey. The habitat description, bathymetric distribution, population density, and structure of the species were assessed by image analysis. A well-developed population of D. ramea, located on boulders on a sedimentary plateau at 70–80 m depth, was observed. The density ranged on average between 0.17 ± 0.04 and 0.8 ± 2.4 colonies m–2 with dense patches up to 8 colonies m–2. The population consisted primarily of many isolated single corallites and colonies of various sizes, some of which reached a maximum height of more than 40 cm. Deepwater fishing activities, primarily longline fishing, negatively affected this species. The newly collected data add knowledge about this vulnerable scleractinian coral. The documented negative effect of fishing activities on vulnerable marine ecosystem (VME) species further highlights the need for urgent conservation measures.

In the North Patagonian fjord region, the cold-water coral (CWC) Desmophyllum dianthus occurs in high densities, in spite of low pH and aragonite saturation. If and how these conditions affect the energy demand of the corals is so far unknown. In a laboratory experiment, we investigated the carbon and nitrogen (C, N) budget of D. dianthus from Comau Fjord under three feeding scenarios: (1) live fjord zooplankton (100-2,300 µm), (2) live fjord zooplankton plus krill (>7 mm), and (3) four-day food deprivation. In closed incubations, C and N budgets were derived from the difference between C and N uptake during feeding and subsequent C and N loss through respiration, ammonium excretion, release of particulate organic carbon and nitrogen (POC, PON). Additional feeding with krill significantly increased coral respiration (35%), excretion (131%), and POC release (67%) compared to feeding on zooplankton only. Nevertheless, the higher C and N losses were overcompensated by the threefold higher C and N uptake, indicating a high assimilation and growth efficiency for the krill plus zooplankton diet. In contrast, short food deprivation caused a substantial reduction in respiration (59%), excretion (54%), release of POC (73%) and PON (87%) compared to feeding on zooplankton, suggesting a high potential to acclimatize to food scarcity (e.g., in winter). Notwithstanding, unfed corals 'lost' 2% of their tissue-C and 1.2% of their tissue-N per day in terms of metabolism and released particulate organic matter (likely mucus). To balance the C (N) losses, each D. dianthus polyp has to consume around 700 (400) zooplankters per day. The capture of a single, large krill individual, however, provides enough C and N to compensate daily C and N losses and grow tissue reserves, suggesting that krill plays an important nutritional role for the fjord corals. Efficient krill and zooplankton capture, as well as dietary and metabolic flexibility, may enable D. dianthus to thrive under adverse environmental conditions in its fjord habitat; however, it is not known how combined anthropogenic warming, acidification and eutrophication jeopardize the energy balance of this important habitat-building species. [ABSTRACT FROM AUTHOR]

The structural complexity of coral reefs provides important ecosystem functions, such as wave attenuation for coastal protection, surfaces for coral growth, and habitat for other organisms. Corals build much of this structure, but an understanding of how colonies of different species and sizes contribute to complexity is lacking. We quantified three interdependent descriptors of complexity—rugosity, fractal dimension, and height range—for reef patches as well as the corals growing upon them in Kāne'ohe Bay (O'ahu, Hawai'i). Despite similar levels of reef-scale complexity throughout the bay, we found marked differences in how species contribute to this complexity. Variation in complexity among species was closely tied to colony morphology, but not to colony size. Together, our results show that no one species is sufficient to generate the full spectrum of habitat complexities we see on coral reefs, which has direct implications for reef recovery and restoration. [ABSTRACT FROM AUTHOR]

In the North Patagonian fjord region, the cold-water coral (CWC) Desmophyllum dianthus occurs in high densities, in spite of low pH and aragonite saturation. If and how these conditions affect the energy demand of the corals is so far unknown. In a laboratory experiment, we investigated the carbon and nitrogen (C, N) budget of D. dianthus from Comau Fjord under three feeding scenarios: (1) live fjord zooplankton (100–2,300 µm), (2) live fjord zooplankton plus krill (>7 mm), and (3) four-day food deprivation. In closed incubations, C and N budgets were derived from the difference between C and N uptake during feeding and subsequent C and N loss through respiration, ammonium excretion, release of particulate organic carbon and nitrogen (POC, PON). Additional feeding with krill significantly increased coral respiration (35%), excretion (131%), and POC release (67%) compared to feeding on zooplankton only. Nevertheless, the higher C and N losses were overcompensated by the threefold higher C and N uptake, indicating a high assimilation and growth efficiency for the krill plus zooplankton diet. In contrast, short food deprivation caused a substantial reduction in respiration (59%), excretion (54%), release of POC (73%) and PON (87%) compared to feeding on zooplankton, suggesting a high potential to acclimatize to food scarcity (e.g., in winter). Notwithstanding, unfed corals ‘lost’ 2% of their tissue-C and 1.2% of their tissue-N per day in terms of metabolism and released particulate organic matter (likely mucus). To balance the C (N) losses, each D. dianthus polyp has to consume around 700 (400) zooplankters per day. The capture of a single, large krill individual, however, provides enough C and N to compensate daily C and N losses and grow tissue reserves, suggesting that krill plays an important nutritional role for the fjord corals. Efficient krill and zooplankton capture, as well as dietary and metabolic flexibility, may enable D. dianthus to thrive under adverse environmental conditions in its fjord habitat; however, it is not known how combined anthropogenic warming, acidification and eutrophication jeopardize the energy balance of this important habitat-building species.

Accurate identification of scleractinian coral species is fundamental for proper biodiversity estimates, for aiding in efforts of reef monitoring, conservation, restoration, and for the management of coral reefs. Here, we provide the first DNA barcoding reference library for coral species in Eilat, Red Sea, based on the mitochondrial gene cytochrome c oxidase subunit I (COI), targeting the identification of stony coral species from shallow (0–12 m) reefs. A total of 191 specimens were collected, depicting 14 families, 39 genera, and 94 species (all are new full species records to the BOLD system). Three species (Sclerophyllia margariticola, Cyphastrea magna, and Psammocora profundacella) are first records for Eilat’s coral reef. The results presented here strengthen the claim that COI is not universally informative for delimitation of stony coral species, a notion reinforced by the constructed maximum likelihood phylogenetic tree. This library is the first step in a long journey towards elucidating coral biodiversity in the coral reef at Eilat and for improving future management and monitoring efforts.

Microbes play a key role in reef dynamics, mediating the competition between scleractinian corals and benthic algae; however, major shifts in bacterial communities among coral species in response to increases in the abundance of algae are not well understood. We investigated the taxonomic composition of coral-associated microbial communities under algae-overgrowth conditions using 16S rRNA gene sequencing. The results showed that non-algal (i.e., healthy) tissue (HH) had lower bacterial abundance and diversity than tissue collected from the coral–algae interface boundary (HA) and areas of algae growth (AA). Specifically, the HA and AA samples had higher relative abundances of Saprospiraceae, Rhodobacteraceae, and Alteromonadaceae. Compared with Platygyra sp. and Montipora sp., the physiological response of Pocillopora sp. was more intense under algae-induced stress based on microbial gene function prediction. Our results indicate that algal pressure can significantly alter the microbial community structure and function of coral ecosystems. Our data thus provide new insight into the relationship between corals and their microbiome under environmental stress.

Ocean warming is altering the biogeographical distribution of marine organisms. In the tropics, rising sea surface temperatures are restructuring coral reef communities with sensitive species being lost. At the biogeographical divide between temperate and tropical communities, warming is causing macroalgal forest loss and the spread of tropical corals, fishes and other species, termed "tropicalization". A lack of field research into the combined effects of warming and ocean acidification means there is a gap in our ability to understand and plan for changes in coastal ecosystems. Here, we focus on the tropicalization trajectory of temperate marine ecosystems becoming coral‐dominated systems. We conducted field surveys and in situ transplants at natural analogues for present and future conditions under (i) ocean warming and (ii) both ocean warming and acidification at a transition zone between kelp and coral‐dominated ecosystems. We show that increased herbivory by warm‐water fishes exacerbates kelp forest loss and that ocean acidification negates any benefits of warming for range extending tropical corals growth and physiology at temperate latitudes. Our data show that, as the combined effects of ocean acidification and warming ratchet up, marine coastal ecosystems lose kelp forests but do not gain scleractinian corals. Ocean acidification plus warming leads to overall habitat loss and a shift to simple turf‐dominated ecosystems, rather than the complex coral‐dominated tropicalized systems often seen with warming alone. Simplification of marine habitats by increased CO2 levels cascades through the ecosystem and could have severe consequences for the provision of goods and services. [ABSTRACT FROM AUTHOR]

This work provides a comprehensive description of the Scleractinian family Merulinidae (Verrill, 1865) of the Red Sea at species level based on skeletal structure for helping in evaluating and estimation of actual species diversity, as well as predicting their response to environmental changes. The present study is a first attempt to describe and illustrate the coral species of the family Merulinidae in the Farasan Islands (Saudi Arabian Coast). Moreover, coral reef terraces are investigated around El Quseir‐Marsa Alam area on the Egyptian Red Sea Coast. Overall, 42 scleractinian coral species from the family Merulinidae (Verrill, 1865) have been identified. They belong to 14 genera: Dipsastraea, Favites, Echinopora, Goniastrea, Coelastrea, Paragoniastrea, Paramontastraea, Astrea, Cyphastrea, Erythrastrea, Merulina, Platygyra, Leptoria, and Hydnophora. About 37 species are recorded for the first time from the Farasan Islands and 26 species from El Quseir‐Marsa Alam area, among them three species are recognized as new records. Two species are added to coral communities of the Red Sea (Goniastrea favulus and Paragoniastrea deformis), and six species were added to the fossil record of the Red Sea. The terminology, systematic classification, and the criteria of identification for all studied coral taxa are generally updated according to recent results. The known age and all recorded stratigraphic range of these species are illustrated and discussed. From the results, most of the corals are still living in the present Red Sea except for three species: Favites micropentagonus, Goniastrea favulus, and Paragoniastrea deformis. All species are extended down to the Pleistocene and a few to the Pliocene and Miocene. [ABSTRACT FROM AUTHOR]

Reef-building corals generally thrive in nutrient-poor tropical waters, where among other elements, nitrogen (N) availability often limits primary productivity. In addition to their close association with endosymbiotic dinoflagellates of the family Symbiodiniaceae, enabling an effective use and retention of dissolved inorganic nitrogen (DIN), scleractinian corals have developed strategies to acquire new N: (1) They can ingest N-rich sediment particles and preys (from picoplankton to macro-zooplankton) via heterotrophy, including diazotrophs [plankton fixing dinitrogen (N2) and releasing part of this nitrogen—Diazotroph-Derived N (DDN)—in seawater], a pathway called “heterotrophic nutrition on diazotrophs”; (2) Symbiotic diazotrophs located in the coral holobiont have the molecular machinery to fix N2, a pathway called “symbiotic N2 fixation”. Here we used the 15N2 isotopic labeling in a series of incubations to investigate the relative contribution of each of these DDN transfer pathways in three worldwide distributed coral species: Acropora muricata, Galaxea fascicularis, and Pocillopora damicornis. We show that N provision via “symbiotic N2 fixation” is negligible compared to that obtained via “heterotrophic nutrition on diazotrophs,” with DDN assimilation rates about a thousand times lower for P. damicornis and G. fascicularis, or assimilation rates via “symbiotic N2 fixation” almost nil for A. muricata. Through heterotrophic feeding on planktonic diazotrophs, only G. fascicularis and P. damicornis can successfully obtain N and fulfill a large part of their N requirements (DDN asimilation rates: 0.111 ± 0.056 and 0.517 ± 0.070 μg N cm–2 h–1 in their Symbiodiniaceae, respectively). Whereas this contribution is again negligible for A. muricata. They also largely consume the picoplankton that likely benefit from this DDN (Prochlorococcus and Synechococcus cells; respectively, 2.56 ± 1.57 104 and 2.70 ± 1.66 104 cell h–1 cm–2 for G. fascicularis; 3.02 ± 0.19 105 and 1.14 ± 0.79 104 cell h–1 cm–2 for P. damicornis). The present study confirms the different dependencies of the three tested species regarding heterotrophy, with P. damicornis and G. fascicularis appearing highly efficient at capturing plankton, while A. muricata, considered as mainly autotroph, does not rely on these food resources to meet its N and energy needs.

Corals have evolved a variety of stress responses to changing conditions, many of which have been the subject of scientific research. However, polyp bailout has not received widespread scientific attention, despite being described more than 80 years ago. Polyp bailout is a drastic response to acute stress in which coral colonies break down, with individual and patches of polyps detaching from the colony and the calcareous skeleton Polyps retain their symbiotic partners, have dispersal ability, and may undergo secondary settlement and calcification. Polyp bailout has been described worldwide in a variety of anthozoan species, especially in Scleractinia. It can be induced by multiple natural stressors, but also artificially. Little is known about the evolutionary and ecological potential and consequences of breaking down modularity, the dispersal ability, and reattachment of polyps resulting from polyp bailout. It has been shown that polyp bailout can be used as a model system, with promise for implementation in various research topics. To date, there has been no compilation of knowledge on polyp bailout, which prompted us to review this interesting stress response and provide a basis to discuss research topics and priorities for the future. [ABSTRACT FROM AUTHOR]

With coral reefs declining globally, resilience of these ecosystems hinges on successful coral recruitment. However, knowledge of the acclimatory and/or adaptive potential in response to environmental challenges such as ocean acidification (OA) in earliest life stages is limited. Our combination of physiological measurements, microscopy, computed tomography techniques and gene expression analysis allowed us to thoroughly elucidate the mechanisms underlying the response of early-life stages of corals, together with their algal partners, to the projected decline in oceanic pH. We observed extensive physiological, morphological and transcriptional changes in surviving recruits, and the transition to a less-skeleton/more-tissue phenotype. We found that decreased pH conditions stimulate photosynthesis and endosymbiont growth, and gene expression potentially linked to photosynthates translocation. Our unique holistic study discloses the previously unseen intricate net of interacting mechanisms that regulate the performance of these organisms in response to OA. [ABSTRACT FROM AUTHOR]

Scleractinian corals exhibit a dual trophic pattern of autotrophic photosynthesis and heterotrophic predation. However, whether corals can adjust their trophic status under contrasting environmental conditions remains unclear. In our study, 70 scleractinian corals (Favia palauensis) were collected from Sanya and the Xisha and Nansha Islands in the South China Sea. We measured the zooxanthellae density (ZD) and δ13C of zooxanthellae (δ13Cz) and host tissue (δ13Ch) and analyzed the difference between δ13Ch and δ13Cz (i.e., Δh−z 13C). The relatively high ZD and δ13Cz values in the samples from Sanya indicate that these corals might have higher photosynthetic rates and autotrophic abilities than those from Xisha and Nansha. In contrast, the relatively low δ13Ch and Δh−z 13C values in the samples from Xisha and Nansha suggest that these corals might have a higher heterotrophic ability than those from Sanya. In addition, we tested the coral tissue biomass and skeletal δ13C (δ13Cs) in the samples from Sanya and examined their correlations with Δh−z 13C. The results showed a negative correlation, indicating that the more the organic material produced by the coral, the stronger its heterotrophic ability. Our results show that corals can adjust their trophic status under different environmental and physiological conditions, which is essential for increasing their adaptability to different environmental conditions. [ABSTRACT FROM AUTHOR]

The detection and control of invasive alien species in marine ecosystems is especially challenging because it is difficult to visualize the full extension of an invasion, while control options are often limited. The invasive scleractinian coral Tubastraea coccinea have spread over 8000 km of the Atlantic coastline, from Florida in the USA to southern Brazil, mainly in association with oil and gas platforms. This invasive coral threatens endemic species, reduces native coral recruitment, and modifies communities and trophic interactions, posing a relevant threat to shallow Atlantic reefs. The main aim of our study was to assess the effectiveness of an ongoing T. coccinea control program by analyzing the results of control interventions on population structure and cover of the target species in its southern Atlantic limit of distribution. We also describe the reproductive effort of T. coccinea in a 12-month time span. Between 2012 and 2019, almost 14,000 colonies were removed, most of them of small size (< 5 polyps). The highest reproductive effort was observed in September. Changes in T. coccinea cover, population structure and potential local propagule supply were observed. Control activities led to a reduction in up to half the cover of the invaded area, maintained the majority of the population in non-reproductive sizes, and consequently lowered the potential local propagule supply. Our paper highlights the fundamental role of control in preventing the local spread of T. coccinea. Recommendations on management frequency and timing are also discussed in order to contribute to the improvement of management efficiency. [ABSTRACT FROM AUTHOR]

Habitat structure increases richness and abundance of species in many environments by providing easy access to resources and refuge from predators. In coral reefs, corals are habitat for many organisms and differences in their morphologies may act as variation in habitat structure for associated fauna. In the present study, we investigate whether there are differences in the richness and abundance of molluscs associated with three species of Mussismilia corals exhibiting different growth morphologies, in two different reef areas of the Bahia state. Mussismilia harttii has a meandroid pattern, M. hispida is a massive coral, M. braziliensis also has a massive growth pattern with crevices at the corallum base. Coral characteristics were measured in the laboratory. Significant differences were identified for richness among coral species – higher values were reported in colonies of M. harttii and no significant statistical differences were observed between M. braziliensis and M. hispida. Considering the density of associated molluscs, the same pattern was found. The results are in accordance with previous studies and indicate the importance of M. harttii as a key habitat to maintain a richer and more abundant associated fauna. The internal volume of interpolypal space is an important factor influencing the richness and density of associated species. [ABSTRACT FROM AUTHOR]

Coral-based reconstructions of sea surface temperatures (SSTs) using Sr/Ca, U/Ca and δ18O are important tools for quantitative analysis of past climate variabilities. However, post-depositional alteration of coral aragonite, particularly early diagenesis, restrict the accuracy of calibrated proxies even on young corals. Considering the diagenetic effects, we present new Mid to Late Holocene SST reconstructions on well-dated (U/Th: ∼70 yr to 5.4 ka) fossil Porites sp. collected from the Society Islands, French Polynesia. For few corals, quality pre-screening routines revealed the presence of secondary aragonite needles inside primary pore space, resulting in a mean increase in Sr/Ca ratios between 5-30%, in contrast to the massive skeletal parts. Characterized by a Sr/Ca above 10 mmol/mol, we interpret this value as the threshold between diagenetically altered and unaltered coral material. At a high-resolution, observed intra-skeletal variability of 5.4 to 9.9 mmol/mol probably reflects the physiological control of corals over their trace metal uptake, and individual variations controlled by CaCO3– precipitation rates. Overall, the Sr/Ca, U/Ca and δ18O trends are well correlated, but we observed a significant offset up to ± 7°C among the proxies on derived palaeo-SST estimates. It appears that the related alteration process tends to amplify temperature extremes, resulting in increased SST-U/Ca and SST-Sr/Ca gradients, and consequently their apparent temperature sensitivities. A relative SST reconstruction is still feasible by normalizing our records to their individual mean value defined as ΔSST. This approach shows that ΔSST records derived from different proxies agree with an amplitudinal variability of up to ± 2°C with respect to their Holocene mean value. Higher ΔSST values than the mean SSTs (Holocene warm periods) were recorded from ∼1.8 to ∼2.8 ka (Interval I), ∼3.7 to 4.0 ka (Interval III) and before ∼5 ka, while lower ΔSST values (Holocene cold periods, Interval II and IV) were recorded in between. The ensuing SST periodicity of ∼1.5 ka in the Society Islands record is in line with the solar activity reconstructed from 10Be and 14C production (Vonmoos et al., 2006), emphasizing the role of solar activity on climate variability during the Late Holocene.