Coral Species Research Articles

The ecological status and fisheries of Malampaya Sound, northwestern Palawan, Philippines

A review of the state of the marine ecosystem and fisheries of Malampaya Sound, Palawan was undertaken. A total of 30 papers relevant to the topic were selected and reviewed. The results showed that the rich and diverse coastal waters of Malampaya Sound harbor 8 species of seagrasses, 9 species of mangroves, 262 species of fish, and various species of corals and macroinvertebrates including the rare giant clams Tridacna spp. The Sound plays a vital role in the local economy because the local community uses it for subsistence fishing and as a source of livelihood. It is so productive that it was termed the “fishbowl of the country” because it provides a substantial contribution to the country’s fishery sector and economy. However, degradation continuously threatens it, most of which are interrelated anthropogenic issues. The declining environmental condition of the area prompted the government to close it for commercial fishing in the 1970s. Several conservation measures have been undertaken since then to preserve its remaining resources, including its declaration as a protected landscape and seascape in 2000. Despite this, if not for a slight improvement, the condition has worsened. So far, only the mangrove ecosystem has dramatically improved. Seagrass and coral reefs are still in poor to fair condition. A collective effort by the community and government agencies, with the support of the academe and non-government organizations, coupled with strict enforcement of existing laws, income diversification for the locals, monitoring of environmental parameters, and implementation of sustainable fishing practices, is necessary to achieve sustainable use of the area.

Varying effects of climate change on the photosynthesis and calcification of crustose coralline algae: Implications for settlement of coral larvae

Coral recruitment is critical to the maintenance of healthy coral reef ecosystems. Many coral species settle preferentially on certain crustose coralline algae (CCA) (e.g., Hydrolithon boergesenii) over others (e.g., Paragoniolithon solubile). Calcifying organisms like CCA are particularly susceptible to ocean acidification (OA), and settlement behavior of larvae may be compromised as seawater temperatures increase (ocean warming; OW) and pH levels decrease as a result of climate change. Here, we examine the effects of future seawater conditions (OW and OA) on the calcification and photosynthetic efficiency of two CCA species, H. boergesenii and Pa. solubile. We also examine the effects of conditioning CCA in combined OA and OW on the settlement preferences of three coral species, Acropora palmata, A. cervicornis and Porites astreoides. Acropora palmata and Po. astreoides demonstrated a preference for H. boergesenii over Pa. solubile in choice experiments after short-term treatment (7–21 days) and this preference was not affected by future seawater conditions. A. cervicornis did not demonstrate a CCA preference under any treatment. Po. astreoides did not demonstrate a CCA preference in no-choice assays and settlement was unaffected by OW and OA even after the longest exposure (99 days). Both CCA had reduced photosynthetic efficiency after exposure to future seawater conditions. However, net calcification rate was reduced in H. boergesenii but not Pa. solubile after exposure to future seawater conditions. These results demonstrate that while climate change may differentially affect the physiological functioning of various species of CCA, coral settlement preferences are unlikely to be altered.

Scleractinian Corals at Their Subtropical Southwestern Atlantic Limit: Post‐2019 Mass Bleaching Event Analysis

ABSTRACTThermal anomalies caused by climate change have emerged as a major threat to reef ecosystems globally. While the effects of warming oceans have been extensively investigated in tropical reefs, its effects on subtropical reefs, where coral diversity is lower, remain largely unstudied. We analysed the spatial distribution, mean cover and health status of scleractinian corals in the subtropical rocky reefs of the Alcatrazes Archipelago, a no‐take marine protected area located 30 km off the coast of São Paulo state, Brazil (24° S). Data were collected before (2018) and after (2022) the most intense marine heatwave ever recorded in the region, in 2019, using either fixed or random photoquadrats. Five scleractinian corals were recorded as follows: The zooxanthellate massive species Mussismilia hispida and Madracis decactis, the azooxanthellate solitary corals Astrangia spp. and Coenocyathus sebroecki and the invasive sun coral Tubastraea spp. M. hispida and M. decactis were the most abundant species, particularly in the sheltered sites, while Astrangia spp. and C. sebroecki were less abundant and only recorded in the exposed side of the island. In the single site where Tubastraea spp. colonies prevailed, other coral species were nearly absent. Both M. hispida and M. decactis exhibited resilience to the 2019's bleaching event, with their abundance remaining almost the same in 2022. Our findings add evidences to the emerging idea that subtropical reefs in the southwestern Atlantic may serve as refuges during future thermal anomalies, highlighting the importance of monitoring these reefs in the context of changing habitats driven by warming oceans.

Occurrence of priority and emerging organic contaminants in cold-water corals and their habitat: a case study in La Herradura Bay (Spain).

Coastal ecosystems are heavily anthropized areas impacted by discharge of chemical pollutants. We present for the first time the occurrence of a wide number of such chemicals in surface water, sediment, suspended particulate matter, and corals from a protected Mediterranean setting, La Herradura Bay (Spain). A seasonal monitoring sampling campaign was conducted in 2021 (winter and summer). This bay is a marine biodiversity hot spot and home for endangered cold-water corals species (Astroides calycularis and Dendrophyllia ramea). Up to 94 target analytes were present in marine samples, with pharmaceuticals being the predominant compound class (up to 37 ng L-1 in seawater and 775 ng g-1 in sediments), especially during the winter season. Uncontrolled untreated wastewater discharges in combination with hydrodynamics dominating in the area seemed to be the major source of contaminants towards the coral colonies inhabiting the bay, which accumulate pharmaceuticals (up to 154 ng g-1), personal care products (UV filters and synthetic fragrances), polycyclic aromatic hydrocarbons, and organophosphate flame retardants, showing log BAFs up to 6.6. Such values were slightly higher in D. ramea than A. calycularis, but not statistically significant differences were observed (p-value > 0.05). Further research is encouraged to assess possible damage to cold-water coral species exposed to multiple contaminants.

Depth drive shifts in the fish and benthic assemblages of the South American Reef System

The low-latitude habitats of the South American reef system have a high endemism and represent important stepping-stones due to the connectivity with Amazon and Caribbean reefs. We provide the first seabed mapping, and analyze the benthic cover and fish assemblages of these extreme reefs. Fleshy macroalgae (2—66% of cover), algal turfs (0—47%), and sponges (3—25%) are the dominant benthic groups. The main reef builders are crustose coralline algae (2—23%) and only four coral species (0 to 18%), mainly the weedy Siderastrea stellata. Cluster analysis distinguished two groups. The first group includes the shallowest reefs (~ 17 m deep) where fleshy macroalgae are abundant together with higher siltation on the reefs (~ 31% covered by sediments). The second group, by contrast, includes the deeper reefs (22.5—27 m), which have much higher algal turf cover, and the lowest sediment cover (4%). The deeper reefs also have the highest cover of corals (18%) and sponges (25%). We recorded a total of 63 fish species, with the deep reefs being the richest. Analysis indicated that the composition of the benthos was considerably more homogeneous across the study area than the composition of fish assemblages, which had a higher turnover of species among reefs. Moreover, we identified the depth of the reef as a variable structuring the benthic assemblages. The fish assemblage is influenced, in turn, by the benthos. Overall, the seabed mapping revealed the existence of a single reef system with high spatial heterogeneity. Our results provide new insights into the structure of these extreme reefs that have evolved under the influence of sediment resuspension, moderate turbidity, and are warmer than other West Atlantic reefs located at middle- and high-latitudes.

Nuclear eDNA metabarcoding primers for anthozoan coral biodiversity assessment.

The distributions of anthozoan corals are undercharacterized due to their wide bathymetric ranges, occurrences in remote locales, and difficulties of identification from morphology alone. Environmental DNA (eDNA) sequencing promises to be a noninvasive strategy to complement conventional approaches for mapping and monitoring the distribution and biodiversity of coral communities. Primers for eDNA metabarcoding have been designed to amplify nuclear and mitochondrial DNA barcodes in shallow scleractinians and mitochondrial MutS in deep-sea octocorals. However, a comprehensive method for eDNA metabarcoding of all anthozoan corals, including black corals, has not been developed. We leveraged a sequence database of global coral collections, from shallow water to the deep sea, to design new PCR primers for coral eDNA sequencing that target the 28S rRNA gene (28S rDNA). We tested the performance of these primers by amplifying and sequencing eDNA from water samples collected in the Gulf of Mexico near mesophotic and deep-sea corals that were also imaged, sampled, and sequenced. Sequencing libraries produced using the primers were highly enriched in eDNA from octocorals, black corals and scleractinians, with up to 99.9% of the reads originating from these corals. Further, the 28S barcode amplified using the primers distinguished coral genera and species in many cases, like previously developed methods that target eDNA in only octocorals or scleractinians. We recovered amplicon sequencing variants (ASVs) identical to DNA barcodes derived from Sanger sequencing and genome skimming of corals sampled at the same field sites. This new eDNA metabarcoding strategy permits targeted eDNA sequencing of black corals, octocorals, and scleractinians at sites where they co-occur and expands our current toolkit for mapping and monitoring coral communities in shallow coral reefs and the deep sea.

Using underwater mini-ROV for coral eDNA survey: a case study in Okinawan mesophotic ecosystems

AbstractMesophotic coral ecosystems (MCEs) are light-dependent communities occurring at depths of 30–150 m. They have been suggested to serve as refuge against thermal stress during heat waves for some coral species. Recent studies on MCEs have revealed a high diversity of communities, some unique, and that these ecosystems are far from being immune to anthropogenic threats. However, the depths at which these ecosystems are found make their exploration and study challenging. Consequently, most suitable environments for MCEs remain unexplored. To facilitate the detection and characterization of MCEs, we improved the methodology for mesophotic scleractinian survey by environmental DNA (eDNA) metabarcoding analysis using seawater collected by underwater mini-Remote Operated Vehicle (mini-ROV). We tested this improved approach at upper mesophotic sites in Okinawa, Japan, with different corals dominating the communities (i.e., Alveopora-dominated, Seriatopora-dominated, and Acropora-dominated communities). Despite the proximity of the different sites, our eDNA metabarcoding analyses detected the dominant coral genera specific to each site. In addition, this study detected numerous other genera present at these sites, including Acropora, Pachyseris, Galaxea, Lobophyllia, Montipora, Pocillopora, Porites, and others. Therefore, this study might support a new technical gate for comprehensive survey of MCEs using eDNA samples collected by underwater mini-ROV, although further technical improvement is required for quantitative estimation.

High- and low-temperature stress responses of Porites lutea from the relatively high-latitude region of the South China Sea

Global climate change has led to more frequent extreme temperature (extreme heat and cold) events, posing a serious threat to coral reef ecosystems. Higher latitudes are considered potential refuges for reef-building corals, but their response to extreme temperature stress in these regions remain unclear. This study, indoor simulated stress experiments ranging on Porites lutea from Weizhou Island in the northern part of the South China Sea, simulating suitable (26 °C) to extreme high (34 °C) and extreme low (12 °C) temperatures. Physiological, biochemical, and transcriptional responses, were analysed. Results showed P. lutea's tentacles contracted, and symbiotic relationships broke down at both high and low temperatures; leading to oxidative stress, and a higher risk of disease. The coral host's response to temperature stress was positively regulated, mainly through apoptosis and metabolic inhibition pathways, whereas Symbiodiniaceae C15 showed no significant response to either high- or low-temperature stress. The coral host played a dominant role in the holobiont's stress response, using similar mechanisms for both high- and low-temperatures with some differences in the details. This study enhances understanding the temperature response mechanisms of the dominant coral species, P. lutea in the relatively high-latitude regions of the South China Sea.

Evaluating coral reef restoration in marine protected areas using habitat structural complexity and coral communities.

Marine Protected Areas (MPAs) are widely used to protect at-risk ecosystems. This study employed a combined method to quantify the protection performance on coral reef habitats, integrating coral morphology and topographic relief in the rugosity index. In the Weizhou Island reef in the northern South China Sea, after six years of protection, the no-take areas (NTAs) hosted a greater live coral cover (11.7%) compared to the no-protection areas (NPAs, 6.9%), but had a lower rugosity (1.17) than both the NPAs and the habitat protection areas, suggesting that while MPAs enhance coral cover, their benefits for habitat structural complexity may remain insignificant in the short term (six years). In the NTAs, the contribution of live corals to habitat complexity (28.3%) was lower than that of rubbles (34.4%). Moreover, slow-growing massive corals (e.g., Porites lutea), which usually have low rugosity, contributed a larger portion (up to 20%) to habitat complexity. In contrast, fast-growing, structural complex arborescent corals (e.g., Acropora pruinosa) had a limited contribution (2.3%). Foliose corals, which dominated the coral community also have lower rugosity (1.2 ~ 1.3) compared to massive and arborescent corals, presumably due to phenotypic plasticity in response to specific environmental conditions. This study suggests that prioritizing coral species composition, especially corals with high rugosity, is important for effective reef framework reconstruction.

Metabolomic profiles of stony coral species from the Dry Tortugas National Park display inter- and intraspecies variation.

Previous research profiling gene expression, proteins, and metabolites produced during thermal stress have reported the importance of endosymbiont-derived pathways in coral bleaching resistance. However, our understanding of interspecies variation in these pathways among healthy corals and their role in diseases is limited. We surveyed the metabolomes of four species of healthy corals with differing susceptibilities to the devastating stony coral tissue loss disease and applied advanced annotation approaches in untargeted metabolomics to determine the interspecies variation in host and endosymbiont-derived pathways. Using this approach, we propose the survey of immune markers such as vitamin E family compounds, acylcarnitines, and other metabolites to infer their role in resilience to coral diseases. As time-resolved multi-omics datasets are generated for disease-impacted corals, our approach and findings will be valuable in providing insight into the mechanisms of disease resistance.

Bisphenol A leachate from polystyrene microplastics has species-specific impacts on scleractinian corals.

Plastic waste causes pervasive environmental contamination and can result in the release of harmful chemical leachates into marine ecosystems, especially as they fragment to smaller microplastics (<5 mm). The toxicity of commonly found polystyrene (PS) microplastics and associated bisphenol A (BPA) leachate to framework-building corals Pocillopora damicornis and Dipsastraea pallida was assessed through exposure experiments. Intermittent exposure over 14-days to 1) virgin PS, 2) preformulated PS with bound BPA (BPA-PS) and 3) leached BPA-PS (L-BPA-PS; simulating early stages of weathering) showed that microplastics void of leachable BPA had minimal effect on either coral species. However, BPA leachate had negative effects on the maximal photochemical yield (Fv/Fm) and tissue composition of P. damicornis fragments (e.g., decreased chlorophyll and protein compared to controls). Conversely, BPA leachate did not compromise tissues of D. pallida fragments. These results reveal that exposure to chemicals leaching out of microplastics can drive negative effects of microplastic exposure distinct from physical mechanisms due to ingestion alone, and that effects are species specific.

Shallow corals acclimate to mesophotic depths while maintaining their heat tolerance against ongoing climate change

Global warming poses a significant threat to coral reefs. It has been assumed that mesophotic coral ecosystems (MCEs, 30 to 150 m depths) may serve as refugia from ocean warming. This study examined the acclimation capacity and thermal tolerance of two shallow coral species, Porites cylindrica and Turbinaria reniformis, transplanted to mesophotic depths (40 m) for 12 months. Fragments from 5 and 40 m were exposed to control (28 °C), moderate (30 °C), and high (32 °C) temperatures over 14 days. MCE-acclimated fragments showed higher thermal thresholds and survival rates, delayed onset of bleaching, and less decline in photosynthesis efficiency (Fv/Fm) compared to shallow fragments. Both species maintained high thermal tolerance despite prolonged exposure to cooler temperatures of mesophotic depth. These findings suggest that low light intensity in MCEs can act as a modulator of bleaching, supporting the potential of these ecosystems as refugia for shallow corals in a rapidly changing world.

Influence of reef habitat on coral microbial associations.

Corals have complex symbiotic associations that can be influenced by the environment. We compare symbiotic dinoflagellate (family: Symbiodiniaceae) associations and the microbiome of five scleractinian coral species from three different reef habitats in Palau, Micronesia. Although pH and temperature corresponded with specific host-Symbiodiniaceae associations common to the nearshore and offshore habitats, bacterial community dissimilarity analyses indicated minimal influence of these factors on microbial community membership for the corals Coelastrea aspera, Psammocora digitata, and Pachyseris rugosa. However, coral colonies sampled close to human development exhibited greater differences in microbial community diversity compared to the nearshore habitat for the coral species Coelastrea aspera, Montipora foliosa, and Pocillopora acuta, and the offshore habitat for Coelastrea aspera, while also showing less consistency in Symbiodiniaceae associations. These findings indicate the influence that habitat location has on the bacterial and Symbiodiniaceae communities comprising the coral holobiont and provide important considerations for the conservation of coral reef communities, especially for island nations with increasing human populations and development.

Coral performance is comparable when transplanted to disparate reef sites despite divergent histories of reef decline and recovery

As coral reefs degrade worldwide, researchers and managers need to determine whether corals can acclimatize to altered local conditions or whether their fixed phenotypes prevent coral persistence under these new environmental conditions. Fixed phenotypes could produce environmental mismatches that reduce population connectivity and exacerbate decline in the near-term, but a capacity for acclimatization could be harnessed in both passive and proactive coral restoration efforts. Here, we conducted a reciprocal transplant experiment in Mo‘orea, French Polynesia, to test how intraspecific performance of 2 common coral species (Acropora hyacinthus and Pocillopora verrucosa) varied between a neighboring forereef and backreef that differed dramatically in trajectories of coral loss, resilience over decadal time scales, and cover of corals versus competing macroalgae. We also tested how corals responded to 2 common stressors—corallivory and macroalgal competition—and how this varied as a function of transplant location and the area of origin. Growth and survival of both coral species were affected by macroalgal competition, corallivory, transplant location, or some combination thereof, but we found limited evidence that the habitat of origin significantly impacted intraspecific performance. These results suggest that acclimatization capacity may outweigh local adaptation for these common reef-building species and could be leveraged to facilitate coral restoration.

The microbiome of the main deep-water scleractinian reef-framework engineers from the Southwestern Atlantic

Deep waters (>150 m) shelter half of the extant diversity of scleractinian corals, including framework reef-forming species. However, to date, the relationship between microorganisms and corals has focused mainly on their zooxanthellate shallow-water counterparts. Here, using 16S rRNA gene amplicon sequencing, we explore the microbiome of all major Atlantic deep-water scleractinian reef framework engineers (Desmophyllum pertusum, Solenosmilia variabilis, Madrepora oculata, and Enallopsammia rostrata), and correlated them with environmental characteristics. Colony fragments of each coral species used in the present study were sampled from three sedimentary basins off the Southeastern coast of Brazil, including two water masses (Antarctic Intermediate Water and South Atlantic Coastal Water). Although representing distant scleractinian evolutionarily lineages, some evolving apart for more than 300Ma, our results suggest a taxonomic homogeneity in their microbial profile. The species-specific microbial core, as well as the core common to all examined species, were identified. Such cores are composed of bacterial genera that have already been observed in other coral species, including those from zooxanthellate species. Such a pattern suggests an active selection of the microbial community by their hosts, a phenomenon that seems to be fundamental for holobiont fitness, especially in long-lived species, such as corals. Besides the microbial core, for all examined species, part of the determined microbiome was flexible and responded to environmental drivers. This flexibility is most probably related to the host's ability to adapt in ecological time scales. Taken together, these holobiont abilities may be crucial to its success in both ecological and geological timescales.

Insights into the occurrence of phylosymbiosis and co-phylogeny in the holobionts of octocorals from the Mediterranean Sea and Red Sea

BackgroundCorals are the foundational species of coral reefs and coralligenous ecosystems. Their success has been linked to symbioses with microorganisms, and a coral host and its symbionts are therefore considered a single entity, called the holobiont. This suggests that there may be evolutionary links between corals and their microbiomes. While there is evidence of phylosymbiosis in scleractinian hexacorals, little is known about the holobionts of Alcyonacean octocorals.Results16S rRNA gene amplicon sequencing revealed differences in the diversity and composition of bacterial communities associated with octocorals collected from the mesophotic zones of the Mediterranean and Red Seas. The low diversity and consistent dominance of Endozoicomonadaceae and/or Spirochaetaceae in the bacterial communities of Mediterranean octocorals suggest that these corals may have a shared evolutionary history with their microbiota. Phylosymbiotic signals were indeed detected and cophylogeny in associations between several bacterial strains, particularly those belonging to Endozoicomonadaceae or Spirochaetaceae, and coral species were identified. Conversely, phylosymbiotic patterns were not evident in Red Sea octocorals, likely due to the high bacterial taxonomic diversity in their microbiota, but cophylogeny in associations between certain coral and bacterial species was observed. Noteworthy were the associations with Endozoicomonadaceae, suggesting a plausible evolutionary link that warrants further investigations to uncover potential underlying patterns.ConclusionsOverall, our findings emphasize the importance of Endozoicomonadaceae and Spirochaetaceae in coral symbiosis and the significance of exploring host-microbiome interactions in mesophotic ecosystems for a comprehensive understanding of coral-microbiome evolutionary history.

Assessment of coral diseases in the shallow reefs of Aka-jima Marine Reserve (AMR), with a brief geographic perspective of disease occurrence throughout the larger Kerama-Shoto Marine National Park (KMNP), Okinawa, Japan

This study reports on the observation of coral diseases within the shallow/intertidal water habitat of the Akajima Marine Reserve (AMR), located within the Keramashoto Marine National Park (KMNP) of Japan. Major coral genera and species assessed during the survey included Montipora spp., Porites spp., Isopora palifera, Acropora spp., as well as others. Observed diseases and health conditions included Black Band Disease (BBD) in Montipora as well as in Goniopora, Skeletal Growth Anomalies (GAs) in Acropora, Montipora, Porites, Isopora and Astreopora, Terpios hoshinota covering Acropora, Montipora and Seriatopora, as well as bleaching, discoloration, and other compromised health signs. This field study recorded the presence of GAs in the genus Leptastrea for the first time within the Japanese Archipelago. The novelty in this study is reporting unreported genera to be infested with certain disease conditions, further this study demonstrates how surveys in previously poorly studied areas or habitats can reveal important information pertaining to coral diseases, thus helping to fill existing knowledge gaps. Another important aspect of this study is, we provide a review of the distribution of coral diseases within the KMNP based on our results and previous reports. Being a rapid survey, the dynamics of these diseases were not assessed, while the major cause(s) of the diseases remains to be identified. In general, climate change-related aspects including rises in sea surface temperature, as well as other factors such as host density may be responsible for disease prevalences in the region.

Contrasting Patterns of Population Genomic Structure Between Broadcast‐Spawning and Brooding Corals in Southeast Asia

ABSTRACTAimAs climate change increasingly threatens the world's coral reefs, enhancing their resilience by improving population connectivity for key reef species is crucial for ensuring their persistence. Here, we evaluate the population genomic structure of two common coral species, Pocillopora acuta and Porites sp., chosen due to their divergent life histories. Thousands of single‐nucleotide polymorphisms (SNPs) were sequenced and analysed to infer regional connectivity patterns in Southeast Asia, a region that harbours a tremendous diversity of marine life.LocationCoasts of the Malay Peninsula and northern Borneo, covering ~1 million km2.MethodNextRAD genotyping‐by‐sequencing of 185 Porites sp. and 221 Pocillopora acuta colonies. Libraries were prepared and sequenced on Illumina NovaSeq 6000. Genotyping involved initial quality controls, allele frequency filtering and checks for contamination. Genetic structure was assessed with Bayesian clustering, and relationships between genetic variation and environmental factors were studied through redundancy analysis. Contemporary gene flow was estimated using BayesAss.ResultsWe observed panmixia among the broadcasting Porites sp. populations, while for the brooding Pocillopora acuta, the Malay Peninsula acts a strong barrier to dispersal between the Malacca Strait and the southern South China Sea. Moreover, its genomic structure seems to follow current marine ecoregion delineation. By analysing contemporary migrant movement, we can prioritise reef localities for conservation. In particular, localities at the Andaman Coral Coast are contemporarily isolated from the other localities, and Tioman is identified as a major larval source for both species.Main ConclusionOur analyses highlight contrasting population differentiation patterns between the two species that can be explained by the disparity in their reproductive strategies. These findings are important for biodiversity managers in Southeast Asia; incorporation of regional connectivity considerations into conservation planning can help safeguard ecosystem resilience and persistence.

Desert dust improves the photophysiology of heat-stressed corals beyond iron

Desert dust is an important source of essential metals for marine primary productivity, especially in oligotrophic systems surrounded by deserts, such as the Red Sea. However, there are very few studies on the effects of dust on reef-building corals and none on the response of corals to heat stress. We therefore supplied dust to two coral species (Stylophora pistillata and Turbinaria reniformis) kept under control conditions (26 °C) or heat stress (32 °C). Since dust releases large amounts of iron (Fe) in seawater, among other metals, the direct effect of different forms of Fe enrichment on coral photosynthesis was also tested. First, our results show that the desert dust altered the coral metallome by increasing the content of metals that are important for coral physiology (e.g. lithium (up to 5-fold), manganese (up to 4-fold in S. pistillata), iron (up to 3-fold in S. pistillata), magnesium (up to 1.3-fold), molybdenum (up to 1.5-fold in S. pistillata)). Overall, metal enrichment improved the photosynthetic performance of corals, especially under thermal stress (e.g. Pgross (up to 2-fold), Pnet (up to 10-fold), chlorophyll (up to 1.5-fold), symbionts (up to 1.6-fold)). However, Fe exposure (ferric chloride or ferric citrate) did not directly improve photosynthesis, suggesting that it is the combination of metals released by the dust, the so-called “metal cocktail effect”, that has a positive impact on coral photophysiology. Dust also led to a decrease in Ni uptake (up to 1.4-fold in the symbionts), likely related to the nitrogen metabolism. Finally, we found that the isotopic signature of metals such as iron, zinc and copper is a good indicator of heat stress and dust exposure in corals. In conclusion, desert dust can increase coral resistance to bleaching by supplying corals with essential metals.

Acclimation and size influence predation, growth, and survival of sexually produced Diploria labyrinthiformis used in restoration

Stony coral tissue loss disease (SCTLD) has swept through Florida reefs and caused mass mortality of numerous coral species. In the wake of these losses, efforts are underway to propagate coral species impacted by SCTLD and promote population recovery. However, numerous knowledge gaps must be addressed to effectively grow, outplant, and restore populations of the slower growing, massive species that were lost. Here, we used sexual recruits of Diploria labyrinthiformis spawned in captivity to understand how conditioning, coral size, and nutritional status at outplanting affect coral survivorship, growth, and susceptibility to predation. We found that ex situ conditioning with supplemental feeding increased coral growth rates, resulting in larger sized corals at the time of outplanting. In turn, these corals had higher growth rates in the field and a lower probability of being removed by predators than outplants that were conditioned in in situ nurseries. Additionally, we found that coral size was an important predictor of survivorship, suggesting that hastening the speed at which young corals grow and outplanting larger juveniles can improve restoration outcomes. Taken together, our results suggest that providing supplemental food to corals at ex situ facilities confers benefits that could help restore populations of massive coral species impacted by SCTLD.