title: Physiologic and metagenomic attributes of the rhodoliths forming the largest CaCO3 bed in the South Atlantic Ocean.
abstract: 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 ∼21,000 km(2)) and has one of the largest marine CaCO3 deposits (producing 25 megatons of CaCO3 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 ammonia-oxidizing 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 μmol carbon m(-2 )s(-1)), allowing the entire Abrolhos rhodolith bed to produce 5.65 × 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.
authors.affiliation: Institute of Biology, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
authors.forename: Giselle S
authors.initials: GS
authors.lastname: Cavalcanti
authors.affiliation: Institute of Biology, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
authors.forename: Gustavo B
authors.initials: GB
authors.lastname: Gregoracci
authors.affiliation: Institute of Biology, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
authors.forename: Eidy O
authors.initials: EO
authors.lastname: dos Santos
authors.affiliation: Institute of Biology, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
authors.forename: Cynthia B
authors.initials: CB
authors.lastname: Silveira
authors.affiliation: Institute of Biology, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
authors.forename: Pedro M
authors.initials: PM
authors.lastname: Meirelles
authors.affiliation: Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Leila
authors.initials: L
authors.lastname: Longo
authors.affiliation: Laboratory of Genomic Research on Pathogenic Bacteria, International Research Center for Infectious Diseases, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Gotoh
authors.affiliation: Laboratory of Genomic Research on Pathogenic Bacteria, International Research Center for Infectious Diseases, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Laboratory of Genomic Research on Pathogenic Bacteria, International Research Center for Infectious Diseases, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Iida
authors.affiliation: Laboratory of Microbiology, Hokkaido University, Sapporo, Japan.
authors.forename: Tomoo
authors.initials: T
authors.lastname: Sawabe
authors.affiliation: Environmental Science Laboratory, Campos dos Goytacazes, UENF, Rio de Janeiro, Brazil.
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Rezende
authors.affiliation: Department of Engineering and Environment, Federal University of Paraíba, Paraíba, Brazil.
authors.forename: Ronaldo B
authors.initials: RB
authors.lastname: Francini-Filho
authors.affiliation: Institute of Biology, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
authors.forename: Rodrigo L
authors.initials: RL
authors.lastname: Moura
authors.affiliation: Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Gilberto M
authors.initials: GM
authors.lastname: Amado-Filho
authors.affiliation: Institute of Biology, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
authors.forename: Fabiano L
authors.initials: FL
authors.lastname: Thompson
mesh_terms: D000818:Animals; D001105:Archaea / Q000145:classification / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001267:Atlantic Ocean; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism; D018407:Bacterial Physiological Phenomena; D044822:Biodiversity; D001938:Brazil; D002119:Calcium Carbonate / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism; D017753:Ecosystem; D007448:Invertebrates / Q000502:physiology; D054892:Metagenome / Q000235:genetics*; D010788:Photosynthesis / Q000235:genetics; D000461:Rhodophyta / Q000382:microbiology*
chemical_list: D002244:Carbon; D002119:Calcium Carbonate