Proxies to detect hotspots of invertebrate biodiversity on rhodolith beds across the Southwestern Atlantic.

Rhodolith beds are known worldwide to host high biodiversity to several taxa. Despite their importance, few ecological data explored the influence of rhodolith features and environmental variables on associated biodiversity, a gap that has been hampering the mapping of diversity hotspots and priority areas for conservation. In this study, we investigated large-scale spatial variations of rhodolith beds and their associated fauna, using annelid polychaetes as a biological model. We aimed to identify proxies, based on rhodolith features and environmental variables, to detect biodiversity hotspots across Southwestern Atlantic beds, laying the groundwork for mapping priority areas for conservation. With this goal, we sampled a total of 136 rhodolith nodules across seven sites with beds under distinct latitudes, depths, distances from the mainland coast of Brazil, and rhodolith densities. For each nodule sampled, we measured the volume, diameter, and mass of sediment trapped, as well as the attributes of the associated polychaetes (abundance, richness, diversity, and composition). Our results revealed a complex network of collinearities and synergisms between the rhodolith features and the majority of the polychaetes attributes (i.e., abundance, diversity, and composition). Polychaete richness, in contrast, can be explained by the combination of two proxies: (1) rhodolith nodule diameter and (2) distance of the rhodolith bed from the mainland coast. Nearshore rhodolith beds and larger nodules were associated with higher values of richness. Additionally, rhodoliths with a hollow morphology were also associated with higher values of polychaete richness. These results suggest that nearshore rhodolith beds with large and hollow nodules could be priority areas for conservation. However, further multi-taxa studies using our framework are still needed to explore other regions and scales, delineating more comprehensive proxies for predicting ecological patterns of the rhodoliths associated fauna and to identify priorities for conservation across Southwestern Atlantic beds.

Levelling-up rhodolith-bed science to address global-scale conservation challenges.

Global marine conservation remains fractured by an imbalance in research efforts and policy actions, limiting progression towards sustainability. Rhodolith beds represent a prime example, as they have ecological importance on a global scale, provide a wealth of ecosystem functions and services, including biodiversity provision and potential climate change mitigation, but remain disproportionately understudied, compared to other coastal ecosystems (tropical coral reefs, kelp forests, mangroves, seagrasses). Although rhodolith beds have gained some recognition, as important and sensitive habitats at national/regional levels during the last decade, there is still a notable lack of information and, consequently, specific conservation efforts. We argue that the lack of information about these habitats, and the significant ecosystem services they provide, is hindering the development of effective conservation measures and limiting wider marine conservation success. This is becoming a pressing issue, considering the multiple severe pressures and threats these habitats are exposed to (e.g., pollution, fishing activities, climate change), which may lead to an erosion of their ecological function and ecosystem services. By synthesizing the current knowledge, we provide arguments to highlight the importance and urgency of levelling-up research efforts focused on rhodolith beds, combating rhodolith bed degradation and avoiding the loss of associated biodiversity, thus ensuring the sustainability of future conservation programs.

Habitat use of five sympatric predatory reef fishes at a remote island in the south-western Atlantic.

Density-dependent mechanisms and habitat use are important drivers of marine spatial distribution in complex ecosystems such as coral or rocky reefs. In the last decade, a few studies have assessed habitat use by reef fishes in nearshore and coastal environments along the Brazilian coast. Serranidae (groupers and sea basses) are regarded as excellent models for understanding habitat use patterns due to their diversity, long lifespan, wide distribution, morphological and functional diversity, and behavioural complexity. Their trophic position in the food web, from meso- to top-predators, grants them critical roles as top-down population controllers. Herein, we present the first assessment of habitat use by five sympatric Serranidae in a Brazilian oceanic island, Trindade. The model species selected for this assessment were the coney (Cephalopholis fulva), the rock hind (Epinephelus adscensionis), the greater soapfish (Rypticus saponaceus), the Creole-fish (Paranthias furcifer) and the hybrid between C. fulva and P. furcifer. Our findings revealed that the species showed specific associations with topographic characteristics related to shelter from predation, reproduction and feeding. Habitat use in Trindade was similar to that observed in nearshore coastal environments (where the hybrid is absent). The present work contributes to the knowledge of habitat use and niche partitioning among key species, which is a valuable tool to subsidize effective conservation initiatives such as designing marine protected areas focusing on the behaviour and habitat use of key ecological players.

Machine learning sheds light on physical-chemical and biological parameters leading to Abrolhos coral reef microbialization.

Microbes play a central role in coral reef health. However, the relative importance of physical-chemical and biological processes in the control of microbial biomass are unknown. Here, we applied machine learning to analyze a large dataset of biological, physical, and chemical parameters (N = 665 coral reef seawater samples) to understand the factors that modulate microbial abundance in the water of Abrolhos reefs, the largest and richest coral reefs of the Southwest Atlantic. Random Forest (RF) and Boosted Regression Tree (BRT) models indicated that hydrodynamic forcing, Dissolved Organic Carbon (DOC), and Total Nitrogen (TN) were the most important predictors of microbial abundance. The possible cumulative effects of higher temperatures, longer seawater residence time, higher nutrient concentration, and lower coral and fish biomass observed in coastal reefs resulted in higher microbial abundance, potentially impacting coral resilience against stressors.

Turbidity shapes shallow Southwestern Atlantic benthic reef communities.

Southwestern Atlantic reefs (Brazilian Province) occur along a broad latitudinal range (∼5°N-27°S) and under varied environmental conditions. We combined large-scale benthic cover and environmental data into uni- and multivariate regression tree analyses to identify unique shallow (<30 m) benthic reef communities and their environmental drivers along the Brazilian Province. Turbidity was the leading environmental driver of benthic reef communities, with the occurrence of two main groups: clear-water (dominated by fleshy macroalgae) and turbid (dominated by turf algae). Seven out of 14 scleractinian coral species were more abundant in the turbid group, thus corroborating the photophobic nature of some Brazilian corals. The most abundant scleractinian in Brazil (Montastraea cavernosa), largely dominated (71-93% of total coral cover) both, the shallow turbid and deeper clear-water reefs. Because these habitat types are widely recognized as potential climate refuges, local threats (e.g. pollution, overfishing) should be averted.

Neospongodes atlantica, a potential case of an early biological introduction in the Southwestern Atlantic.

Soft corals (Anthozoa: Octocorallia) are discreet components in the Southwestern Atlantic reef communities. In Brazil, the native octocoral shallow-reef fauna is mostly represented by gorgonians. Consequently, except for the nephtheid Neospongodes atlantica, most of the known soft corals from this region are considered non-indigenous. Hitherto, the monotypic genus Neospongodes, which was proposed in the early 1900s, has been considered to be endemic to the Northeastern Brazilian coast. Herein, based on in situ records, we show that N. atlantica is a substrate generalist that has been probably expanding its distribution by dominating extensive shallow and mesophotic sandy and reef bottoms, generally outcompeting other reef benthic organisms, including Brazilian endemic species. Based on previously unidentified museum specimens, new records, and a broad literature review, we provide the most comprehensive modelling of the potential distribution of this species in the Southwestern Atlantic. Based on molecular inference supported by in-depth morphological analysis, the probable non-indigenous and, therefore, ancient introduction of N. atlantica in Brazilian waters is discussed. Finally, these results support that Neospongodes and the Indo-Pacific Stereonephthya are synonyms, which led us to propose the latter as taxonomically invalid.

Low functional vulnerability of fish assemblages to coral loss in Southwestern Atlantic marginal reefs.

Marginal reefs sustain coral assemblages under conditions considered suboptimal for most corals, resulting in low coral abundance. These reefs are inhabited by numerous fishes with a generally unknown degree of association with corals that might lead to the assumption that corals play minor roles in determining fish occurrence, when corals could be actually sustaining diverse and resilient assemblages. Using site-occupancy models fitted to data of 113 reef fish species of different life stages (adults and juveniles) from 36 reefs distributed across the Southwestern Atlantic (0.87-27.6°S) we first assessed fish assemblage's response to coral and turf algal cover, and identified coral-associated fish. Then, we simulated the loss of coral-associated fishes and contrasted it with random losses, providing inferences on the resilience of fish assemblage's functional trait space to species loss. The entire fish assemblage responded more positively to coral than to turf algae, with 42 (37%) species being identified as coral-associated fish. The simulated loss of coral-associated fish reduced up to 5% the functional trait space and was not different from the random loss. These results reveal that marginal reefs of Southwestern Atlantic reefs host resilient fish assemblages that might preserve fundamental ecological functions and ecosystem services even with coral declines.

Breviolum and Cladocopium Are Dominant Among Symbiodiniaceae of the Coral Holobiont Madracis decactis.

The scleractinian reef building coral Madracis decactis is a cosmopolitan species. Understanding host-symbiont associations is critical for assessing coral's habitat requirements and its response to environmental changes. In this study, we performed a fine grained phylogenetic analyses of Symbiodiniaceae associated with Madracis in two locations in the Southwest Atlantic Ocean (Abrolhos Bank and St. Peter and St. Paul Archipelago). Previous studies have argued that Madracis is a specialist coral, with colonies harboring a single symbiont from the genus Breviolum (formerly clade B). However, these previous studies have not precisely addressed if Madracis is colonized by several types of Symbiodiniaceae simultaneously or whether this coral is a specialist. The hypothesis that Madracis is a generalist coral host was evaluated in the present study. A total of 1.9 million reads of ITS2 nuclear ribosomal DNA were obtained by Illumina MiSeq sequencing. While Symbiodiniaceae ITS2 sequences between two sampling depths were almost entirely (62%) from the genus Breviolum (formerly clade B), shallow (10-15 m) populations in Abrolhos had a greater diversity of ITS2 sequences in comparison to deeper (25-35 m) populations of St. Peter and St. Paul Archipelago. Cladocopium (formerly clade C) and Symbiodinium (formerly clade A) were also found in Abrolhos. A single Madracis colony can host different symbiont types with > 30 Symbiodiniaceae ITS2-type profiles. Abrolhos corals presented a higher photosynthetic potential as a possible result of co-occurrence of multiple Symbiodiniaceae in a single coral colony. Multiple genera/clades of Symbiodiniaceae possibly confer coral hosts with broader environmental tolerance and ability to occupy diverse or changing habitats.

Metals and organic matter baselines in sediments in a cross-shelf gradient at Abrolhos Bank, SW Atlantic.

The present study performed geochemical fractioning of major and minor elements in a cross-shelf gradient of the Abrolhos Bank, where the largest and most diverse coral reefs in the South Atlantic are concentrated. The fractioning was performed using sequential extractions to determine the degree of availability and toxicity of the elements. The mobility pattern of the elements investigated were in the following order: Ca > Mn > Pb > Cr > Zn > Fe > V > Cu > Ba>Al > Ni > Ti. For elements, such as (Ti, Ni, Al, Ba, Cu, V, Fe, Zn, Cr, Pb), the highest concentrations were in the residual phase at some sampling sites. As established by Environment Canada (Threshold Effect Level - TEL and Probable Effect Level - PEL), Ba, Cr, and Ni produced values higher than the limits, associated with higher concentrations of other elements. In addition, significant proportions of these elements were found in mobile phases in the same sites. Thus, more rigorous measures are critical to avoid alarming levels of chronic environmental pollution inside and outside protected areas of the region. To enhance the sustainability of the region, more effective enforcement is crucial to prevent anthropic contamination that may threaten its biodiversity. The results provide the baseline for future studies regarding the potential impacts of the breach of the tailings dam in the region of Mariana, Minas Gerais.

Protecting nursery areas without fisheries management is not enough to conserve the most endangered parrotfish of the Atlantic Ocean.

Marine protected areas (MPAs) are a primary strategy for marine conservation worldwide, having as a common goal the protection of essential habitats to enhance fish population recovery. However, MPAs alone may not be effective because species are not isolated from critical impacts occurring outside their boundaries. We evaluated how protecting critical nursery habitats affect the population of an important fishing target, using a 6-year database to predict juvenile hotspots and estimate population trends of the endemic and endangered parrotfish Scarus trispinosus within a mosaic of MPAs at the Abrolhos Bank, NE Brazil. We found that important nursery habitats are within no-take areas, but both juvenile and adult populations still show a declining trend over time. MPAs failed to ensure population maintenance and recovery likely due to overfishing in adjacent areas and the lack of compliance to management rules within multiple-use and within no-take MPAs. MPAs alone are not enough to protect ecologically important endangered species, but is still one of the only conservation strategies, particularly in developing countries. Our results shed light on the need for a wider adoption of more effective conservation policies in addition to MPAs, both in Brazil and in countries with similar governance contexts.

Fish biodiversity of Saint Peter and Saint Paul's Archipelago, Mid-Atlantic Ridge, Brazil: new records and a species database.

Saint Peter and Saint Paul's Archipelago (SPSPA), one of the smallest and most isolated island groups in the world, is situated on the Mid-Atlantic Ridge, between Brazil and the African continent. SPSPA has low species richness and high endemism; nonetheless, the diversity of fishes from deep habitats (>30 m depth) had not been previously studied in detail. Several expeditions conducted between 2009 and 2018 explored the shallow and deep reefs of SPSPA using scuba, closed-circuit rebreathers, manned submersibles, baited remote underwater stereo-videos (stereo-BRUV) and fishing between 0 and 1050 m depth. These expeditions yielded 41 new records of fishes for SPSPA: 9 in open waters, 9 in shallow waters (0-30 m), 8 in mesophotic ecosystems (30-150 m) and 15 in deeper reefs (>150 m). Combined with literature records of adult pelagic, shallow and deep-reef species, as well as larvae, the database of the fish biodiversity for SPSPA currently comprises 225 species (169 recorded as adult fishes and 79 as larvae, with 23 species found in both stages). Most of them (112) are pelagic, 86 are reef-associated species and 27 are deep-water specialists. Species accumulation curves show that the number of fish species has not yet reached an asymptote. Whereas the number of species recorded in SPSPA is similar to that in other oceanic islands in the Atlantic Ocean, the proportion of shorefishes is relatively lower, and the endemism level is the third highest in the Atlantic. Twenty-nine species are listed as threatened with extinction. Observations confirm the paucity of top predators on shallow rocky reefs of the island, despite the presence of several pelagic shark species around SPSPA. Because all of the endemic species are reef associated, it is argued that the new marine-protected areas created by the Brazilian government do not ensure the protection and recovery of SPSPA's biodiversity because they allow exploitation of the most vulnerable species around the archipelago itself. This study suggests a ban on reef fish exploitation inside an area delimited by the 1000 m isobath around the islands (where all known endemics are concentrated) as the main conservation strategy to be included in the SPSPA management plan being prepared by the Brazilian government.

Genomic and ecological attributes of marine bacteriophages encoding bacterial virulence genes.

BACKGROUND: Bacteriophages encode genes that modify bacterial functions during infection. The acquisition of phage-encoded virulence genes is a major mechanism for the rise of bacterial pathogens. In coral reefs, high bacterial density and lysogeny has been proposed to exacerbate reef decline through the transfer of phage-encoded virulence genes. However, the functions and distribution of these genes in phage virions on the reef remain unknown. RESULTS: Here, over 28,000 assembled viral genomes from the free viral community in Atlantic and Pacific Ocean coral reefs were queried against a curated database of virulence genes. The diversity of virulence genes encoded in the viral genomes was tested for relationships with host taxonomy and bacterial density in the environment. These analyses showed that bacterial density predicted the profile of virulence genes encoded by phages. The Shannon diversity of virulence-encoding phages was negatively related with bacterial density, leading to dominance of fewer genes at high bacterial abundances. A statistical learning analysis showed that reefs with high microbial density were enriched in viruses encoding genes enabling bacterial recognition and invasion of metazoan epithelium. Over 60% of phages could not have their hosts identified due to limitations of host prediction tools; for those which hosts were identified, host taxonomy was not an indicator of the presence of virulence genes. CONCLUSIONS: This study described bacterial virulence factors encoded in the genomes of bacteriophages at the community level. The results showed that the increase in microbial densities that occurs during coral reef degradation is associated with a change in the genomic repertoire of bacteriophages, specifically in the diversity and distribution of bacterial virulence genes. This suggests that phages are implicated in the rise of pathogens in disturbed marine ecosystems.

Mesophotic ecosystems at Fernando de Noronha Archipelago, Brazil (South-western Atlantic), reveal unique ichthyofauna and need for conservation

Abstract Although several studies on the ichthyofauna of the Fernando de Noronha Archipelago have been carried out, its mesophotic fish diversity has never been surveyed before. Here we used SCUBA and technical rebreather diving, baited remote underwater videos and remotely operated vehicle to record shallow (≤ 30 m depth) and mesophotic (31 to 150 m depth) fishes. Nineteen fish species belonging to 14 families are reported here as new records, representing an increase of 8.2% in marine fish richness for the region, which now has a total of 250 species and 77 families. These new records include four potential new species and highlight the importance of surveying mesophotic ecosystems, even in well studied sites. Our results also emphasize the need for protection and attention to the unique ichthyofauna found at mesophotic depths.(AU)

Resumo Apesar de muitos estudos sobre a ictiofauna do Arquipélago de Fernando de Noronha terem sido realizados, sua diversidade de peixes mesofóticos nunca foi estudada antes. Neste estudo utilizamos mergulho autônomo e mergulho técnico, vídeos subaquáticos remotos com isca e veículo operado remotamente para registrar peixes de ecossistemas rasos (≤ 30 m de profundidade) e mesofóticos (31 a 150 m de profundidade). Dezenove espécies de peixes pertencentes a 14 famílias são apresentadas aqui como novos registros, representando um aumento de 8,2% na riqueza de peixes marinhos da região, que agora possui um total de 250 espécies e 77 famílias. Esses novos registros incluem quatro prováveis novas espécies e reforçam a importância de estudos em ecossistemas mesofóticos. Nossos resultados também enfatizam a necessidade de proteção e atenção à essa ictiofauna única encontrada nesses ecossistemas profundos.(AU)

Age, growth, reproduction and management of Southwestern Atlantic's largest and endangered herbivorous reef fish, Scarus trispinosus Valenciennes, 1840.

The Brazilian-endemic greenbeack parrotfish, Scarus trispinosus Valenciennes, 1840, is the largest herbivorous reef fish in the South Atlantic. Following the sharp decline of large carnivorous reef fishes, parrotfishes (Labridae: Scarinae) were progressively targeted by commercial fisheries in Brazil, resulting in a global population decline of 50% for S. trispinosus. Most of its remnant population is concentrated in the Abrolhos Bank, where the present study was conducted. We present novel information on age, growth and the reproductive cycle of S. trispinosus, based on 814 individuals obtained from commercial fisheries' landings and scientific collections, between 2010 and 2013. Sex ratio was biased toward females (1:8), and spawning occurred year-round with discrete peaks in February-March and June-December. Increment analysis indicated annual deposition of growth rings in otoliths, which presented 1-22 rings. The asymptotic length at which growth is zero (L ∞) was estimated from a Bayesian logistic regression at 85.28 cm, growth rate (K) at 0.14 year-1, and the theoretical age at zero size (t 0) at 0.16. Subregional demographic structuring was detected, with predominance of slower-growing individuals in shallower inshore reefs and predominance of faster-growing and older individuals in deeper offshore sites. We demonstrate that S. trispinosus is highly vulnerable to over-exploitation due to its large size, long live and slow-growth, and review the management measures proposed since its Red List assessment in 2012.

Diversity of settlement-stage reef fishes captured by light-trap in a tropical south-west Atlantic Ocean coastal reef system.

This study reports the results of 5 years of monitoring reef fish post-larvae using light traps in the Bay of Tamandaré, north-east Brazil. An annotated checklist of pre-settlement fish species, their frequency of occurrence and taxonomic characteristics are provided. In total, 4,422 post-larval fishes belonging to 36 families, 56 genera and 76 species were captured. The most species-rich families were Carangidae (7), Lutjanidae (6) and Pomacentridae (4), while the families Gerreidae (30.47%), Holocentridae (16.54%), Blenniidae (12.01%), Labrisomidae (8.36%), Lutjanidae (8.29%) and Acanthuridae (5.95%) were the most abundant. This is the first study of the taxonomic diversity and assemblage structure of settlement-stage reef fishes in the tropical south-west Atlantic Ocean. Although a few common species were not captured due to selectivity of light traps, the composition and taxonomic diversity of this first collection suggests that light traps are useful for studies of the early life history of a wide range of pre-settlement reef fishes.

Remote sensing, isotopic composition and metagenomics analyses revealed Doce River ore plume reached the southern Abrolhos Bank Reefs.

On November 5th, 2015, the Fundão dam rupture released >50 million m3 of ore tailings into the Doce River, Minas Gerais State, Brazil. The huge volume of mud spread along the river and reached the sea, 17 days after the disaster, in Regência, Espírito Santo State (ES). In 2018, after three years of the disaster, the impacts of the ore tailings in the marine environment are still unclear. This study aims to investigate possible short-term impacts in marine biodiversity caused by the ore tailings' mud over the reef ecosystems that are closest to the disaster area: i.e. recently discovered reefs in the southern Abrolhos Bank. A remote sensing surveillance including winds, sea surface temperature, total suspended material and watercolor (MODIS Aqua data) indicated that the iron tailings plume reached the southern portion of Abrolhos Bank on June 16th, 2016. Subsequently, to obtain further evidence of the presence of the tailings in the coral reefs, water samples were collected in a gradient spanning from the river estuary to the reefs in southern Abrolhos Bank, we also analyzed the isotopic and microbial composition of the samples, as well as the reef benthic composition. Despite no clues of negative impact on benthic (coral) communities, isotopic analysis confirmed the presence of the plume over the reefs area. This study serves as a baseline for future long-term impact assessments of the health of coral reefs in the Abrolhos Bank.

Long-term effects of competition and environmental drivers on the growth of the endangered coral Mussismilia braziliensis (Verril, 1867).

Most coral reefs have recently experienced acute changes in benthic community structure, generally involving dominance shifts from slow-growing hard corals to fast-growing benthic invertebrates and fleshy photosynthesizers. Besides overfishing, increased nutrification and sedimentation are important drivers of this process, which is well documented at landscape scales in the Caribbean and in the Indo-Pacific. However, small-scale processes that occur at the level of individual organisms remain poorly explored. In addition, the generality of coral reef decline models still needs to be verified on the vast realm of turbid-zone reefs. Here, we documented the outcome of interactions between an endangered Brazilian-endemic coral (Mussismilia braziliensis) and its most abundant contacting organisms (turf, cyanobacteria, corals, crustose coralline algae and foliose macroalgae). Our study was based on a long (2006-2016) series of high resolution data (fixed photoquadrats) acquired along a cross-shelf gradient that includes coastal unprotected reefs and offshore protected sites. The study region (Abrolhos Bank) comprises the largest and richest coralline complex in the South Atlantic, and a foremost example of a turbid-zone reef system with low diversity and expressive coral cover. Coral growth was significantly different between reefs. Coral-algae contacts predominated inshore, while cyanobacteria and turf contacts dominated offshore. An overall trend in positive coral growth was detected from 2009 onward in the inshore reef, whereas retraction in live coral tissue was observed offshore during this period. Turbidity (+) and cyanobacteria (-) were the best predictors of coral growth. Complimentary incubation experiments, in which treatments of Symbiodinium spp. from M. braziliensis colonies were subjected to cyanobacterial exudates, showed a negative effect of the exudate on the symbionts, demonstrating that cyanobacteria play an important role in coral tissue necrosis. Negative effects of cyanobacteria on living coral tissue may remain undetected from percent cover estimates gathered at larger spatial scales, as these ephemeral organisms tend to be rapidly replaced by longer-living macroalgae, or complex turf-like consortia. The cross-shelf trend of decreasing turbidity and macroalgae abundance suggests either a direct positive effect of turbidity on coral growth, or an indirect effect related to the higher inshore cover of foliose macroalgae, constraining cyanobacterial abundance. It is unclear whether the higher inshore macroalgal abundance (10-20% of reef cover) is a stable phase related to a long-standing high turbidity background, or a contemporary response to anthropogenic stress. Our results challenge the idea that high macroalgal cover is always associated with compromised coral health, as the baselines for turbid zone reefs may derive sharply from those of coral-dominated reefs that dwell under oligotrophic conditions.

Bacterial Community Associated with the Reef Coral Mussismilia braziliensis's Momentum Boundary Layer over a Diel Cycle.

Corals display circadian physiological cycles, changing from autotrophy during the day to heterotrophy during the night. Such physiological transition offers distinct environments to the microbial community associated with corals: an oxygen-rich environment during daylight hours and an oxygen-depleted environment during the night. Most studies of coral reef microbes have been performed on samples taken during the day, representing a bias in the understanding of the composition and function of these communities. We hypothesized that coral circadian physiology alters the composition and function of microbial communities in reef boundary layers. Here, we analyzed microbial communities associated with the momentum boundary layer (MBL) of the Brazilian endemic reef coral Mussismilia braziliensis during a diurnal cycle, and compared them to the water column. We determined microbial abundance and nutrient concentration in samples taken within a few centimeters of the coral's surface every 6 h for 48 h, and sequenced microbial metagenomes from a subset of the samples. We found that dominant taxa and functions in the coral MBL community were stable over the time scale of our sampling, with no significant shifts between night and day samples. Interestingly, the two water column metagenomes sampled 1 m above the corals were also very similar to the MBL metagenomes. When all samples were analyzed together, nutrient concentration significantly explained 40% of the taxonomic dissimilarity among dominant genera in the community. Functional profiles were highly homogenous and not significantly predicted by any environmental variables measured. Our data indicated that water flow may overrule the effects of coral physiology in the MBL bacterial community, at the scale of centimeters, and suggested that sampling resolution at the scale of millimeters may be necessary to address diurnal variation in community composition.

Feeding ecology of two sympatric species of large-sized groupers (Perciformes: Epinephelidae) on Southwestern Atlantic coralline reefs

Red and black groupers are large-bodied opportunistic ambush predators commonly found in Southwestern Atlantic tropical reefs. We investigated the diet of both species in order to detail ontogenetic, spatial and temporal trends, and to assess the extent of overlap in resource use between these two sympatric predators on the Abrolhos Bank, Brazil. Decapods and fishes were the main food items of Epinephelus morio while fishes were the main prey of Mycteroperca bonaci. Both diets were significantly influenced by body size and habitat, but only smaller individuals of E. morio feed almost exclusively on crustaceans. While the two groupers rely on many of the same prey types, coexistence may be facilitated by E. morio feeding more heavily on crustaceans, particularly the blackpoint sculling crab Cronius ruber, while black grouper take comparatively few crustaceans but lots of fish prey. Predators like red and black groupers could trigger indirect effects in the community and influence a large range of ecological processes, such as linkages between top and intermediate predators, and intermediate predators and their resources.(AU)

A garoupa e o badejo-verdadeiro são predadores oportunistas de grande porte, com estratégia de emboscada, comumente encontrados em recifes tropicais do Atlântico Sul. A dieta das duas espécies foi investigada, avaliando influências ontogenéticas, espaciais e temporais, assim como a sobreposição no uso de recursos entre estes dois predadores co-orrentes no Banco dos Abrolhos, Brasil. Decápodes e peixes foram os principais itens alimentares de Epinephelus morio, enquanto que os peixes foram as principais presas de Mycteroperca bonaci. Ambas as dietas foram significativamente influenciadas pelo tamanho corporal e habitat, mas apenas indivíduos menores de E. morio alimentaram-se quase que exclusivamente de crustáceos. Como as duas espécies utilizam muitas presas semelhantes, a coexistencia parece ser facilitada pelo fato de E. morio se alimentar principalmente de crustáceos, particularmente do caranguejo Cronius ruber, enquanto que o badejo-verdadeiro consome relativamente poucos crustáceos e grande quantidade de peixes. Predadores como as espécies estudadas podem causar efeitos indiretos na comunidade e influenciar uma grande variedade de processos ecológicos, como conexões entre predadores de topo e intermediários e predadores intermediários e seus recursos.(AU)