A novel Amazonian reef biome was discovered, encompassing large rhodolith and sponge beds under low light, low oxygen, and high POC.

Aim To present an updated database of fish species recorded on south‐western Atlantic reef environments and to explore the ecological drivers of the structure, the latitudinal gradient of biodiversity and the centre of endemism in this peripheral province. Location South‐western Atlantic (SWA): Brazilian and Argentinian Provinces. Methods A database composed of 733 fish species along 23 locations in the SWA (00°55′ N to 43°00′ S) was compiled based on primary data, literature and museum records. Cluster and beta diversity analyses were carried out to evaluate faunal overlaps among locations and subprovinces. “Target‐area‐distance effect” and “stepping stones dispersal” hypotheses for assemblage composition were tested through Mantel tests. Relationships between the distribution patterns and ecological traits of reef fish species were investigated through generalized linear mixed‐effect models. Results Out of the 733 fish species, 405 are SWA resident reef fishes, of which 111 (27%) are endemics and 78 are threatened with extinction. Cluster analysis detected six subprovinces in the SWA structured following the target‐area‐distance model, and with no evidence for a latitudinal gradient in diversity. The greatest overall richness and endemic species richness were found in the east–south‐eastern region. Depth range, habitat use and body size were the main drivers of SWA reef fish assemblage structure. Main conclusions The Brazilian and Argentinian coasts constitute different provinces structured by oceanographic barriers and environmental filters. Similarities among oceanic islands indicate connectivity driven by stochastic and ecological factors. Species richness and endemism indicate that peripheral provinces may also bear centres of origin and biodiversity, patterns driven by parapatric/ecological speciation and the overlap between tropical and subtropical reef fish species. Ecological drivers of reef fish distribution, such as habitat specialization and body size, support hypotheses of speciation in the periphery. New approaches for spatial planning, marine protected areas and off‐reserve marine management are essential for the conservation and sustainability of SWA reef fishes.

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Despite a strong increase in research on seamounts and oceanic islands ecology and biogeography, many basic aspects of their biodiversity are still unknown. In the southwestern Atlantic, the Vitória-Trindade Seamount Chain (VTC) extends ca. 1,200 km offshore the Brazilian continental shelf, from the Vitória seamount to the oceanic islands of Trindade and Martin Vaz. For a long time, most of the biological information available regarded its islands. Our study presents and analyzes an extensive database on the VTC fish biodiversity, built on data compiled from literature and recent scientific expeditions that assessed both shallow to mesophotic environments. A total of 273 species were recorded, 211 of which occur on seamounts and 173 at the islands. New records for seamounts or islands include 191 reef fish species and 64 depth range extensions. The structure of fish assemblages was similar between islands and seamounts, not differing in species geographic distribution, trophic composition, or spawning strategies. Main differences were related to endemism, higher at the islands, and to the number of endangered species, higher at the seamounts. Since unregulated fishing activities are common in the region, and mining activities are expected to drastically increase in the near future (carbonates on seamount summits and metals on slopes), this unique biodiversity needs urgent attention and management.

Here we provide a broad overview of the Great Amazon Reef System (GARS) based on the first-ever video surveys of the region. This footage supports four major hypotheses: (1) the GARS area may be six times larger than previously suggested (up to 56,000 km 2 ); (2) the GARS may extend deeper than previously suggested (up to 220 m); (3) the GARS is composed of a greater complexity and diversity of habitats than previously recognized (e.g., reef platforms, reef walls, rhodolith beds, and sponge bottoms); and (4) the GARS represents a useful system to test whether a deep corridor connects the Caribbean Sea to the Southwest Atlantic Ocean. We also call attention to the urgent need to adopt precautionary conservation measures to protect the region in the face of increasing threats from extractive oil and gas practices. With less than 5% of the potential area of the GARS surveyed so far, more research will be required to inform a systematic conservation planning approach and determine how best to establish a network of marine protected areas. Such planning will be required to reconcile extractive activities with effective biodiversity conservation in the GARS.

Mass coral bleaching has increased in intensity and frequency and has severely impacted shallow tropical reefs worldwide. Although extensive investigation has been conducted on the resistance and resilience of coral reefs in the Indo-Pacific and Caribbean, the unique reefs of the South Atlantic remain largely unassessed. Here we compiled primary and literature data for reefs from three biogeographical regions: Indo-Pacific, Caribbean and South Atlantic and performed comparative analyses to investigate whether the latter may be more resistant to bleaching. Our findings show that South Atlantic corals display critical features that make them less susceptible to mass coral bleaching: (i) deeper bathymetric distribution, as species have a mean maximum depth of occurrence of 70 m; (ii) higher tolerance to turbidity, as nearly 60% of species are found in turbid conditions; (iii) higher tolerance to nutrient enrichment, as nitrate concentration in the South Atlantic is naturally elevated; (iv) higher morphological resistance, as massive growth forms are dominant and comprise two thirds of species; and (v) more flexible symbiotic associations, as 75% of corals and 60% of symbiont phylotypes are generalists. Such features were associated with occurrence of fewer bleaching episodes with coral mortality in the South Atlantic, approximately 60% less than the Indo-Pacific and 50% less than the Caribbean. In addition, no mass coral mortality episodes associated with the three global mass bleaching events have been reported for the South Atlantic, which suffered considerably less bleaching. These results show that South Atlantic reefs display several remarkable features for withstanding thermal stress. Together with a historic experience of lower heat stress, our findings may explain why climate change impacts in this region have been less intense. Given the large extension and latitudinal distribution of South Atlantic coral reefs and communities, the region may be recognized as a major refugium and likely to resist climate change impacts more effectively than Indo-Pacific and Caribbean reefs.

Mesophotic reeffish assemblages (30-90 m depth) of the small and remote St. Peter and St. Paul's Archipelago (SPSPA), Mid-Atlantic Ridge, Brazil, were characterized using remotely operated vehicles. Ordination analyses identified distinct fish assemblages in the upper (30-50 m) and lower (50-90 m) mesophotic zones, the former characterized by high abundances of species that are also abundant at euphotic reefs (Caranx lugubris, Melichthys niger, Stegastes sanctipauli and Chromis multilineata) and the latter dominated by two mesophotic specialists (Prognathodes obliquus and Chromis enchrysura). Planktivores dominated fish assemblages, particularly in the upper mesophotic zone, possibly due to a greater availability of zooplankton coming from the colder Equatorial Undercurrent in mesophotic depths of the SPSPA. Turf algae, fleshy macroalgae and scleractinian corals dominated benthic assemblages between 30 and 40 m depth, while bryozoans, black corals and sponges dominated between 40 and 90 m depth. Canonical correspondence analysis explained 74 % of the relationship between environmental characteristics (depth, benthic cover and complexity) and structure of fish assemblages, with depth as the most important independent variable. Juveniles of Bodianus insularis and adults of P. obliquus and C. enchrysura were clearly associated with branching black corals (Tanacetipathes spp.), suggesting that black corals play key ecological roles in lower mesophotic reefs

Rhodoliths are free-living coralline algae (Rhodophyta, Corallinales) that are ecologically important for the functioning of marine environments. They form extensive beds distributed worldwide, providing a habitat and nursery for benthic organisms and space for fisheries, and are an important source of calcium carbonate. The Abrolhos Bank, off eastern Brazil, harbors the world's largest continuous rhodolith bed (of B21 000 km 2 ) and has one of the largest marine CaCO 3 deposits (producing 25 megatons of CaCO 3 per year). Nevertheless, there is a lack of information about the microbial diversity, photosynthetic potential and ecological interactions within the rhodolith holobiont. Herein, we performed an ecophysiologic and metagenomic analysis of the Abrolhos rhodoliths to understand their microbial composition and functional components. Rhodoliths contained a specific microbiome that displayed a significant enrichment in aerobic ammoniaoxidizing betaproteobacteria and dissimilative sulfate-reducing deltaproteobacteria. We also observed a significant contribution of bacterial guilds (that is, photolithoautotrophs, anaerobic heterotrophs, sulfide oxidizers, anoxygenic phototrophs and methanogens) in the rhodolith metagenome, suggested to have important roles in biomineralization. The increased hits in aromatic compounds, fatty acid and secondary metabolism subsystems hint at an important chemically mediated interaction in which a functional job partition among eukaryal, archaeal and bacterial groups allows the rhodolith holobiont to thrive in the global ocean. High rates of photosynthesis were measured for Abrolhos rhodoliths (52.16 lmol carbon m À 2 s À 1 ), allowing the entire Abrolhos rhodolith bed to produce 5.65 Â 10 5 tons C per day. This estimate illustrates the great importance of the Abrolhos rhodolith beds for dissolved carbon production in the South Atlantic Ocean.