Marine Heatwave Caused Differentiated Dysbiosis in Photosymbiont Assemblages of Corals and Hydrocorals During El Niño 2015/2016.

Reef corals have been threatened by climate change, with more frequent and intense bleaching events leading to extensive coral mortality and loss of coral cover worldwide. In the face of this, the corals' photosymbiont assemblages have received special attention as a key to better understand the bleaching process and its recovery. To assess the effects of thermal anomalies, the coral Mussismilia harttii and the hydrocoral Millepora alcicornis were monitored through the El Niño 2015/2016 at a Southwestern Atlantic (SWA) coral reef. A severe bleaching event (57% of colonies bleached) was documented, triggered by a < 3 °C-week heatwave, but no mortality was detected. The hydrocoral was more susceptible than the scleractinian, displaying bleaching symptoms earlier and experiencing a longer and more intense bleaching event. The composition of photosymbionts in the M. alcicornis population was affected only at the rare biosphere level (< 5% relative abundance), with the emergence of new symbionts after bleaching. Conversely, a temporary dysbiosis was observed in the M. harttii population, with one of the dominant symbiodiniaceans decreasing in relative abundance at the peak of the bleaching, which negatively affected the total ß-diversity. After colonies' complete recovery, symbiodiniaceans' dominances returned to normal levels in both hosts. These results highlight critical differences in how the two coral species cope with bleaching and contribute to the understanding of the role of photosymbionts throughout the bleaching-recovery process.

Transcriptomic differences between bleached and unbleached hydrozoan Millepora complanata following the 2015-2016 ENSO in the Mexican Caribbean.

The 2015-2016 El Niño-southern oscillation or "ENSO" caused many M. complanata colonies that live in the Mexican Caribbean to experience extensive bleaching. The purpose of this work was to analyze the effect of bleaching on the cellular response of M. complanata, employing a transcriptomic approach with RNA-seq. As expected, bleached specimens contained a significantly lower chlorophyll content than unbleached hydrocorals. The presence of algae of the genera Durusdinium and Cladocopium was only found in tissues of unbleached M. complanata, which could be associated to the greater resistance that these colonies exhibited during bleaching. We found that 299 genes were differentially expressed in M. complanata bleached colonies following the 2015-2016 ENSO in the Mexican Caribbean. The differential expression analysis of bleached M. complanata specimens evidenced enriched terms for functional categories, such as ribosome, RNA polymerase and basal transcription factors, chaperone, oxidoreductase, among others. Our results suggest that the heat-shock response mechanisms displayed by M. complanata include: an up-regulation of endogenous antioxidant defenses; a higher expression of heat stress response genes; up-regulation of transcription-related genes, higher expression of genes associated to transport processes, inter alia. This study constitutes the first differential gene expression analysis of the molecular response of a reef-forming hydrozoan during bleaching.

Shifts in predator behaviour following climate induced disturbance on coral reefs.

Coral reefs are increasingly ecologically destabilized across the globe due to climate change. Behavioural plasticity in corallivore behaviour and short-term trophic ecology in response to bleaching events may influence the extent and severity of coral bleaching and subsequent recovery potential, yet our understanding of these interactions in situ remains unclear. Here, we investigated interactions between corallivory and coral bleaching during a severe high thermal event (10.3-degree heating weeks) in Belize. We found that parrotfish changed their grazing behaviour in response to bleaching by selectively avoiding bleached Orbicella spp. colonies regardless of bleaching severity or coral size. For bleached corals, we hypothesize that this short-term respite from corallivory may temporarily buffer coral energy budgets by not redirecting energetic resources to wound healing, and may therefore enable compensatory nutrient acquisition. However, colonies that had previously been heavily grazed were also more susceptible to bleaching, which is likely to increase mortality risk. Thus, short-term respite from corallivory during bleaching may not be sufficient to functionally rescue corals during prolonged bleaching. Such pairwise interactions and behavioural shifts in response to disturbance may appear small scale and short term, but have the potential to fundamentally alter ecological outcomes, especially in already-degraded ecosystems that are vulnerable and sensitive to change.

Recent dynamics on turbid-water corals reefs following the 2010 mass bleaching event in Tobago.

We detail the benthic compositon of the turbid-water coral reefs of Tobago in 2016 and examine the influence of mass coral bleaching and hydro-geomorphic setting (sheltereted vs. wave-exposed) on benthic community dynamics against the 2007 baseline. In the current assessment mean hard coral cover was 14.83% ± 0.85, which ranged from 2% to 37% with few sites exceeding 20%. Mean macroalgal cover was low (6.04% ± 0.61) with most sites experiencing less than 8% macroalgal cover. Differences in benthic cover between sheltered and wave-exposed settings were mainly driven by contrasts in proportions of sponge, macroalgae and Orbicella faveolata corals. Linear mixed-effects modelling suggests stability in hard coral cover and decline in macroalgal cover across sites against the 2007 baseline. Significant spatio-temporal interactions were observed for soft coral and CTB (crustose coralline algae, turf algae and bare substrate). Overall, hard coral cover appears to have declined at some sites and macroalgal cover to have increased at other, but there is no evidence of widespread regime shift. While the hydro-geomorphic setting had a significant but weak effect (R > 0.3) on observed spatial and temporal patterns, our findings suggest that sheltered settings were less predisposed to macroalgal overgrowth compared to wave-exposed areas. In the era of climate change, targeted management should focus on strategies that mitigate macroalgal overgrowth, promote hard coral stability (or resilience) while preventing further loss.

Drivers of coral bleaching in a Marine Protected Area of the Southern Gulf of Mexico during the 2015 event.

Here we report the bleached coral cover and its drivers observed at Alacranes Reef in 2015. Our results show that 2015 was an unprecedented heat stress event. However, we observed low coral bleaching, with the most substantial impact on sites with a 10-20% of coral cover with bleaching. Depth was the most relevant variable related to coral bleaching and the bleaching severity index, with deeper reefs being most affected. Further, our results show that reefs with higher structural complexity based on species composition were among the most affected. We identified that accumulated heat stress and thermal variation in the last 28 days were relevant drivers of coral bleaching. This work highlights the importance of multidimensional frameworks in assessing the spatial variation of coral bleaching, demonstrating the importance of structural habitat variables such as depth in high heat stress events and at a reef scale.

Elevated Temperature and Exposure to Copper Leads to Changes in the Antioxidant Defense System of the Reef-Building Coral Mussismilia harttii.

The frequency and severity of coral bleaching events have increased in recent years. Global warming and contamination are primarily responsible for triggering these responses in corals. Thus, the objective of this study was to evaluate the isolated and combined effects of elevated temperature and exposure to copper (Cu) on responses of the antioxidant defense system of coral Mussismilia harttii. In a marine mesocosm, fragments of the coral were exposed to three temperatures (25.0, 26.6, and 27.3°C) and three concentrations of Cu (2.9, 5.4, and 8.6 µg/L) for up to 12 days. Levels of reduced glutathione (GSH) and the activity of enzymes, such as superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and glutamate cysteine ligase (GCL), were evaluated on the corals and symbionts. The short exposure to isolated and combined stressors caused a reduction in GSH levels and inhibition of the activity of antioxidant enzymes. After prolonged exposure, the combination of stressors continued to reduce GSH levels and SOD, CAT, and GCL activity in symbionts and GST activity in host corals. GCL activity was the parameter most affected by stressors, remaining inhibited after 12-days exposure. Interesting that long-term exposure to stressors stimulated antioxidant defense proteins in M. harttii, demonstrating a counteracting response that may beneficiate the oxidative state. These results, combined with other studies already published suggest that the antioxidant system should be further studied in order to understand the mechanisms of tolerance of South Atlantic reefs.

Histopatological effects of bleaching and disease on the coral Siderastrea stellata from coastal reefs of Brazil / Efeitos histopatológicos dos eventos de branqueamento e doenças no coral Siderastrea stellata dos recifes costeiros do Brasil

Histological analysis of bleached samples of Siderastrea stellata Verrill, 1868, with white plague disease and with alteration in the color pattern, revealed drastic tissue and cellular disturbances, such as lysis of the external epithelium, hyperplasia of gastrodermis, apoptosis of epithelial cells and zooxanthellae, and degradation of mesenteric filaments and reproductive cells. Fungal hyphae, diatoms, and cyanobacteria were present in diseased samples and colonies with alteration in the color pattern. Furthermore, bleached and diseased samples showed significant reductions in the number of zooxanthellae per 100 µm2 of gastrodermis and significant reductions in the diameters and volumes of stage V oocytes. We found that bleaching events, diseases, and colonies with alteration in the color pattern promoted degradation of reproductive cells, resulting in the consequent interruption of the reproduction of the coral S. stellata, which is one of the most common Brazilian coral species. The implications of these indirect effects of bleaching, disease, and changes in coral color patterns in the population dynamics of Brazilian reefs are discussed.(AU)

Análises histológicas de amostras de Siderastrea stellata Verrill, 1868 branqueadas, doentes e com alteração no padrão de cloração, revelaram drásticas perturbações teciduais e celulares, como lise do epitélio externo, hiperplasia da mesogleia, apoptose das células epiteliais e das zooxantelas, e degradação dos filamentos mesentéricos e das células reprodutivas. Hifas fúngicas, diatomáceas e cianobactérias estavam presentes em amostras doentes e em tecidos de colônias com alteração no padrão de coloração. Além disso, amostras branqueadas e doentes apresentavam reduções significativas no número de zooxantelas por 100 µm2 da gastrodermis e, reduções significativas nos diâmetros e volumes dos oócitos de estágio V. Constatamos que eventos de branqueamento, doenças e colônias com alteração no padrão de cloração, promoveram degradação das células reprodutivas, resultando na consequente interrupção da reprodução do coral S. stellata, que é uma das espécies de corais brasileiro mais comuns. As implicações desses efeitos indiretos do branqueamento, doenças e das mudanças nos padrões de coloração dos corais na dinâmica populacional dos recifes brasileiros são discutidas.(AU)

Histopatological effects of bleaching and disease on the coral Siderastrea stellata from coastal reefs of Brazil / Efeitos histopatológicos dos eventos de branqueamento e doenças no coral Siderastrea stellata dos recifes costeiros do Brasil

Histological analysis of bleached samples of Siderastrea stellata Verrill, 1868, with white plague disease and with alteration in the color pattern, revealed drastic tissue and cellular disturbances, such as lysis of the external epithelium, hyperplasia of gastrodermis, apoptosis of epithelial cells and zooxanthellae, and degradation of mesenteric filaments and reproductive cells. Fungal hyphae, diatoms, and cyanobacteria were present in diseased samples and colonies with alteration in the color pattern. Furthermore, bleached and diseased samples showed significant reductions in the number of zooxanthellae per 100 µm2 of gastrodermis and significant reductions in the diameters and volumes of stage V oocytes. We found that bleaching events, diseases, and colonies with alteration in the color pattern promoted degradation of reproductive cells, resulting in the consequent interruption of the reproduction of the coral S. stellata, which is one of the most common Brazilian coral species. The implications of these indirect effects of bleaching, disease, and changes in coral color patterns in the population dynamics of Brazilian reefs are discussed.

Análises histológicas de amostras de Siderastrea stellata Verrill, 1868 branqueadas, doentes e com alteração no padrão de cloração, revelaram drásticas perturbações teciduais e celulares, como lise do epitélio externo, hiperplasia da mesogleia, apoptose das células epiteliais e das zooxantelas, e degradação dos filamentos mesentéricos e das células reprodutivas. Hifas fúngicas, diatomáceas e cianobactérias estavam presentes em amostras doentes e em tecidos de colônias com alteração no padrão de coloração. Além disso, amostras branqueadas e doentes apresentavam reduções significativas no número de zooxantelas por 100 µm2 da gastrodermis e, reduções significativas nos diâmetros e volumes dos oócitos de estágio V. Constatamos que eventos de branqueamento, doenças e colônias com alteração no padrão de cloração, promoveram degradação das células reprodutivas, resultando na consequente interrupção da reprodução do coral S. stellata, que é uma das espécies de corais brasileiro mais comuns. As implicações desses efeitos indiretos do branqueamento, doenças e das mudanças nos padrões de coloração dos corais na dinâmica populacional dos recifes brasileiros são discutidas.

Histopatological effects of bleaching and disease on the coral Siderastrea stellata from coastal reefs of Brazil

ABSTRACT Histological analysis of bleached samples of Siderastrea stellata Verrill, 1868, with white plague disease and with alteration in the color pattern, revealed drastic tissue and cellular disturbances, such as lysis of the external epithelium, hyperplasia of gastrodermis, apoptosis of epithelial cells and zooxanthellae, and degradation of mesenteric filaments and reproductive cells. Fungal hyphae, diatoms, and cyanobacteria were present in diseased samples and colonies with alteration in the color pattern. Furthermore, bleached and diseased samples showed significant reductions in the number of zooxanthellae per 100 µm2 of gastrodermis and significant reductions in the diameters and volumes of stage V oocytes. We found that bleaching events, diseases, and colonies with alteration in the color pattern promoted degradation of reproductive cells, resulting in the consequent interruption of the reproduction of the coral S. stellata, which is one of the most common Brazilian coral species. The implications of these indirect effects of bleaching, disease, and changes in coral color patterns in the population dynamics of Brazilian reefs are discussed.

RESUMO Análises histológicas de amostras de Siderastrea stellata Verrill, 1868 branqueadas, doentes e com alteração no padrão de cloração, revelaram drásticas perturbações teciduais e celulares, como lise do epitélio externo, hiperplasia da mesogleia, apoptose das células epiteliais e das zooxantelas, e degradação dos filamentos mesentéricos e das células reprodutivas. Hifas fúngicas, diatomáceas e cianobactérias estavam presentes em amostras doentes e em tecidos de colônias com alteração no padrão de coloração. Além disso, amostras branqueadas e doentes apresentavam reduções significativas no número de zooxantelas por 100 µm2 da gastrodermis e, reduções significativas nos diâmetros e volumes dos oócitos de estágio V. Constatamos que eventos de branqueamento, doenças e colônias com alteração no padrão de cloração, promoveram degradação das células reprodutivas, resultando na consequente interrupção da reprodução do coral S. stellata, que é uma das espécies de corais brasileiro mais comuns. As implicações desses efeitos indiretos do branqueamento, doenças e das mudanças nos padrões de coloração dos corais na dinâmica populacional dos recifes brasileiros são discutidas.

Robust natural ultraviolet filters from marine ecosystems for the formulation of environmental friendlier bio-sunscreens.

Ultraviolet radiation (UVR) has detrimental effects on human health. It induces oxidative stress, deregulates signaling mechanisms, and produces DNA mutations, factors that ultimately can lead to the development of skin cancer. Therefore, reducing exposure to UVR is of major importance. Among available measures to diminish exposure is the use of sunscreens. However, recent studies indicate that several of the currently used filters have adverse effects on marine ecosystems and human health. This situation leads to the search for new photoprotective compounds that, apart from offering protection, are environmentally friendly. The answer may lie in the same marine ecosystems since molecules such as mycosporine-like amino acids (MAAs) and scytonemin can serve as the defense system of some marine organisms against UVR. This review will discuss the harmful effects of UVR and the mechanisms that microalgae have developed to cope with it. Then it will focus on the biological distribution, characteristics, extraction, and purification methods of MAAs and scytonemin molecules to finally assess its potential as new filters for sunscreen formulation.

Comparative Analysis of the Soluble Proteome and the Cytolytic Activity of Unbleached and Bleached Millepora complanata ("Fire Coral") from the Mexican Caribbean.

Coral bleaching caused by global warming has resulted in massive damage to coral reefs worldwide. Studies addressing the consequences of elevated temperature have focused on organisms of the class Anthozoa, and up to now, there is little information regarding the mechanisms by which reef forming Hydrozoans face thermal stress. In this study, we carried out a comparative analysis of the soluble proteome and the cytolytic activity of unbleached and bleached Millepora complanata ("fire coral") that inhabited reef colonies exposed to the 2015-2016 El Niño-Southern Oscillation in the Mexican Caribbean. A differential proteomic response involving proteins implicated in key cellular processes, such as glycolysis, DNA repair, stress response, calcium homeostasis, exocytosis, and cytoskeleton organization was found in bleached hydrocorals. Four of the proteins, whose levels increased in bleached specimens, displayed sequence similarity to a phospholipase A2, an astacin-like metalloprotease, and two pore forming toxins. However, a protein, which displayed sequence similarity to a calcium-independent phospholipase A2, showed lower levels in bleached cnidarians. Accordingly, the hemolytic effect of the soluble proteome of bleached hydrocorals was significantly higher, whereas the phospholipase A2 activity was significantly reduced. Our results suggest that bleached M. complanata is capable of increasing its toxins production in order to balance the lack of nutrients supplied by its symbionts.

Heritable variation in bleaching responses and its functional genomic basis in reef-building corals (Orbicella faveolata).

Reef-building corals are highly sensitive to rising ocean temperatures, and substantial adaptation will be required for corals and the ecosystems they support to persist in changing ocean conditions. Genetic variation that might support adaptive responses has been measured in larval stages of some corals, but these estimates remain unavailable for adult corals and the functional basis of this variation remains unclear. In this study, we focused on the potential for adaptation in Orbicella faveolata, a dominant reef-builder in the Caribbean. We conducted thermal stress experiments using corals collected from natural populations in Bocas del Toro, Panama, and used multilocus SNP genotypes to estimate genetic relatedness among samples. This allowed us to estimate narrow-sense heritability of variation in bleaching responses, revealing that variation in these responses was highly heritable (h2  = 0.58). This suggests substantial potential for adaptive responses to warming by natural populations of O. faveolata in this region. We further investigated the functional basis for this variation using genomic and transcriptomic approaches. We used a publicly available genetic linkage map and genome assembly to map markers associated with bleaching responses, identifying twelve markers associated with variation in bleaching responses. We also profiled gene expression in corals with contrasting bleaching phenotypes, uncovering substantial differences in transcriptional stress responses between heat-tolerant and heat-susceptible corals. Together, our findings contribute to the growing body of evidence that natural populations of corals possess genetic variation in thermal stress responses that may potentially support adaptive responses to rising ocean temperatures.

Tropical dead zones and mass mortalities on coral reefs.

Degradation of coastal water quality in the form of low dissolved oxygen levels (hypoxia) can harm biodiversity, ecosystem function, and human wellbeing. Extreme hypoxic conditions along the coast, leading to what are often referred to as "dead zones," are known primarily from temperate regions. However, little is known about the potential threat of hypoxia in the tropics, even though the known risk factors, including eutrophication and elevated temperatures, are common. Here we document an unprecedented hypoxic event on the Caribbean coast of Panama and assess the risk of dead zones to coral reefs worldwide. The event caused coral bleaching and massive mortality of corals and other reef-associated organisms, but observed shifts in community structure combined with laboratory experiments revealed that not all coral species are equally sensitive to hypoxia. Analyses of global databases showed that coral reefs are associated with more than half of the known tropical dead zones worldwide, with >10% of all coral reefs at elevated risk for hypoxia based on local and global risk factors. Hypoxic events in the tropics and associated mortality events have likely been underreported, perhaps by an order of magnitude, because of the lack of local scientific capacity for their detection. Monitoring and management plans for coral reef resilience should incorporate the growing threat of coastal hypoxia and include support for increased detection and research capacity.

Coral reef health response to chronic and acute changes in water quality in St. Thomas, United States Virgin Islands.

It is suspected that land cover alteration on the southern coast of St. Thomas, USVI has increased runoff, degrading nearshore water quality and coral reef health. Chronic and acute changes in water quality, sediment deposition, and coral health metrics were assessed in three zones based upon perceived degree of human influence. Chlorophyll (p<0.0001) and turbidity (p=0.0113) were significantly higher in nearshore zones and in the high impact zone during heavy precipitation. Net sediment deposition and terrigenous content increased in nearshore zones during periods of greater precipitation and port activity. Macroalgae overgrowth significantly increased along a gradient of decreasing water quality (p<0.0001). Coral bleaching in all zones peaked in November with a regional thermal stress event (p<0.0001). However, mean bleaching prevalence was significantly greater in the most impacted zone compared to the offshore zone (p=0.0396), suggesting a link between declining water quality and bleaching severity.

Transient turbid water mass reduces temperature-induced coral bleaching and mortality in Barbados.

Global warming is seen as one of the greatest threats to the world's coral reefs and, with the continued rise in sea surface temperature predicted into the future, there is a great need for further understanding of how to prevent and address the damaging impacts. This is particularly so for countries whose economies depend heavily on healthy reefs, such as those of the eastern Caribbean. Here, we compare the severity of bleaching and mortality for five dominant coral species at six representative reef sites in Barbados during the two most significant warm-water events ever recorded in the eastern Caribbean, i.e., 2005 and 2010, and describe prevailing island-scale sea water conditions during both events. In so doing, we demonstrate that coral bleaching and subsequent mortality were considerably lower in 2010 than in 2005 for all species, irrespective of site, even though the anomalously warm water temperature profiles were very similar between years. We also show that during the 2010 event, Barbados was engulfed by a transient dark green turbid water mass of riverine origin coming from South America. We suggest that reduced exposure to high solar radiation associated with this transient water mass was the primary contributing factor to the lower bleaching and mortality observed in all corals. We conclude that monitoring these episodic mesoscale oceanographic features might improve risk assessments of southeastern Caribbean reefs to warm-water events in the future.

Proteomic analysis of bleached and unbleached Acropora palmata, a threatened coral species of the Caribbean.

There has been an increase in the scale and frequency of coral bleaching around the world due mainly to changes in sea temperature. This may occur at large scales, often resulting in significant decline in coral coverage. In order to understand the molecular and cellular basis of the ever-increasing incidence of coral bleaching, we have undertaken a comparative proteomic approach with the endangered Caribbean coral Acropora palmata. Using a proteomic tandem mass spectrometry approach, we identified 285 and 321 expressed protein signatures in bleached and unbleached A. palmata colonies, respectively, in southwestern Puerto Rico. Overall the expression level of 38 key proteins was significantly different between bleached and unbleached corals. A wide range of proteins was detected and categorized, including transcription factors involved mainly in heat stress/UV responses, immunity, apoptosis, biomineralization, the cytoskeleton, and endo-exophagocytosis. The results suggest that for bleached A. palmata, there was an induced differential protein expression response compared with those colonies that did not bleach under the same environmental conditions.

A study on the recovery of Tobago's coral reefs following the 2010 mass bleaching event.

In 2010, severe coral bleaching was observed across the southeastern Caribbean, including the island of Tobago, where coral reefs are subject to sedimentation and high nutrient levels from terrestrial runoff. Here we examine changes in corals' colony size distributions over time (2010-2013), juvenile abundances and sedimentation rates for sites across Tobago following the 2010 bleaching event. The results indicated that since pre-bleaching coral cover was already low due to local factors and past disturbance, the 2010 event affected only particular susceptible species' population size structure and increased the proportion of small sized colonies. The low density of juveniles (mean of 5.4±6.3 juveniles/m(-2)) suggests that Tobago's reefs already experienced limited recruitment, especially of large broadcasting species. The juvenile distribution and the response of individual species to the bleaching event support the notion that Caribbean reefs are becoming dominated by weedy non-framework building taxa which are more resilient to disturbances.

Decadal-scale rates of reef erosion following El Niño-related mass coral mortality.

As the frequency and intensity of coral mortality events increase under climate change, understanding how declines in coral cover may affect the bioerosion of reef frameworks is of increasing importance. Here, we explore decadal-scale rates of bioerosion of the framework building coral Orbicella annularis by grazing parrotfish following the 1997/1998 El Niño-related mass mortality event at Long Cay, Belize. Using high-precision U-Th dating and CT scan analysis, we quantified in situ rates of external bioerosion over a 13-year period (1998-2011). Based upon the error-weighted average U-Th age of dead O. annularis skeletons, we estimate the average external bioerosion between 1998 and 2011 as 0.92 ± 0.55 cm depth. Empirical observations of herbivore foraging, and a nonlinear numerical response of parrotfish to an increase in food availability, were used to create a model of external bioerosion at Long Cay. Model estimates of external bioerosion were in close agreement with U-Th estimates (0.85 ± 0.09 cm). The model was then used to quantify how rates of external bioerosion changed across a gradient of coral mortality (i.e., from few corals experiencing mortality following coral bleaching to complete mortality). Our results indicate that external bioerosion is remarkably robust to declines in coral cover, with no significant relationship predicted between the rate of external bioerosion and the proportion of O. annularis that died in the 1998 bleaching event. The outcome was robust because the reduction in grazing intensity that follows coral mortality was compensated for by a positive numerical response of parrotfish to an increase in food availability. Our model estimates further indicate that for an O. annularis-dominated reef to maintain a positive state of reef accretion, a necessity for sustained ecosystem function, live cover of O. annularis must not drop below a ~5-10% threshold of cover.

Photobacterium sanctipauli sp. nov. isolated from bleached Madracis decactis (Scleractinia) in the St Peter & St Paul Archipelago, Mid-Atlantic Ridge, Brazil.

Five novel strains of Photobacterium (A-394T, A-373, A-379, A-397 and A-398) were isolated from bleached coral Madracis decactis (scleractinian) in the remote St Peter & St Archipelago (SPSPA), Mid-Atlantic Ridge, Brazil. Healthy M. decactis specimens were also surveyed, but no strains were related to them. The novel isolates formed a distinct lineage based on the 16S rRNA, recA, and rpoA gene sequences analysis. Their closest phylogenetic neighbours were Photobacterium rosenbergii, P. gaetbulicola, and P. lutimaris, sharing 96.6 to 95.8% 16S rRNA gene sequence similarity. The novel species can be differentiated from the closest neighbours by several phenotypic and chemotaxonomic markers. It grows at pH 11, produces tryptophane deaminase, presents the fatty acid C18:0, but lacks C16:0 iso. The whole cell protein profile, based in MALDI-TOF MS, distinguished the strains of the novel species among each other and from the closest neighbors. In addition, we are releasing the whole genome sequence of the type strain. The name Photobacterium sanctipauli sp. nov. is proposed for this taxon. The G + C content of the type strain A-394(T) (= LMG27910(T) = CAIM1892(T)) is 48.2 mol%.

Unrecognized coral species diversity masks differences in functional ecology.

Porites corals are foundation species on Pacific reefs but a confused taxonomy hinders understanding of their ecosystem function and responses to climate change. Here, we show that what has been considered a single species in the eastern tropical Pacific, Porites lobata, includes a morphologically similar yet ecologically distinct species, Porites evermanni. While P. lobata reproduces mainly sexually, P. evermanni dominates in areas where triggerfish prey on bioeroding mussels living within the coral skeleton, thereby generating asexual coral fragments. These fragments proliferate in marginal habitat not colonized by P. lobata. The two Porites species also show a differential bleaching response despite hosting the same dominant symbiont subclade. Thus, hidden diversity within these reef-builders has until now obscured differences in trophic interactions, reproductive dynamics and bleaching susceptibility, indicative of differential responses when confronted with future climate change.