title: Microbial community diversity and physical-chemical features of the Southwestern Atlantic Ocean.
abstract: Microbial oceanography studies have demonstrated the central role of microbes in functioning and nutrient cycling of the global ocean. Most of these former studies including at Southwestern Atlantic Ocean (SAO) focused on surface seawater and benthic organisms (e.g., coral reefs and sponges). This is the first metagenomic study of the SAO. The SAO harbors a great microbial diversity and marine life (e.g., coral reefs and rhodolith beds). The aim of this study was to characterize the microbial community diversity of the SAO along the depth continuum and different water masses by means of metagenomic, physical-chemical and biological analyses. The microbial community abundance and diversity appear to be strongly influenced by the temperature, dissolved organic carbon, and depth, and three groups were defined [1. surface waters; 2. sub-superficial chlorophyll maximum (SCM) (48-82 m) and 3. deep waters (236-1,200 m)] according to the microbial composition. The microbial communities of deep water masses [South Atlantic Central water, Antarctic Intermediate water and Upper Circumpolar Deep water] are highly similar. Of the 421,418 predicted genes for SAO metagenomes, 36.7 % had no homologous hits against 17,451,486 sequences from the North Atlantic, South Atlantic, North Pacific, South Pacific and Indian Oceans. From these unique genes from the SAO, only 6.64 % had hits against the NCBI non-redundant protein database. SAO microbial communities share genes with the global ocean in at least 70 cellular functions; however, more than a third of predicted SAO genes represent a unique gene pool in global ocean. This study was the first attempt to characterize the taxonomic and functional community diversity of different water masses at SAO and compare it with the microbial community diversity of the global ocean, and SAO had a significant portion of endemic gene diversity. Microbial communities of deep water masses (236-1,200 m) are highly similar, suggesting that these water masses have very similar microbiological attributes, despite the common knowledge that water masses determine prokaryotic community and are barriers to microbial dispersal. The present study also shows that SCM is a clearly differentiated layer within Tropical waters with higher abundance of phototrophic microbes and microbial diversity.
authors.affiliation: Institute of Biology, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil.
authors.forename: Nelson
authors.initials: N
authors.lastname: Alves Junior
authors.forename: Pedro Milet
authors.initials: PM
authors.lastname: Meirelles
authors.forename: Eidy
authors.initials: E
authors.lastname: de Oliveira Santos
authors.forename: Bas
authors.initials: B
authors.lastname: Dutilh
authors.forename: Genivaldo G Z
authors.initials: GG
authors.lastname: Silva
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Paranhos
authors.forename: Anderson S
authors.initials: AS
authors.lastname: Cabral
authors.forename: Carlos
authors.initials: C
authors.lastname: Rezende
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Iida
authors.forename: Rodrigo L
authors.initials: RL
authors.lastname: de Moura
authors.forename: Ricardo Henrique
authors.initials: RH
authors.lastname: Kruger
authors.forename: Renato C
authors.initials: RC
authors.lastname: Pereira
authors.forename: Rogério
authors.initials: R
authors.lastname: Valle
authors.forename: Tomoo
authors.initials: T
authors.lastname: Sawabe
authors.forename: Cristiane
authors.initials: C
authors.lastname: Thompson
authors.forename: Fabiano
authors.initials: F
authors.lastname: Thompson
mesh_terms: D000864:Antarctic Regions; D001267:Atlantic Ocean; D044822:Biodiversity; D054892:Metagenome / Q000235:genetics*; D064307:Microbiota / Q000235:genetics*; D012623:Seawater / Q000737:chemistry* / Q000382:microbiology*; D013696:Temperature