BACTERIAL DIVERSITY IN COASTAL TROPICAL ECOSYSTEMS FROM ILHA GRANDE, BRAZIL

Cynthia Barbosa da Silveira (UFRJ); Ricardo Pilz Vieira (UFRJ); Alexander Machado Cardoso (UEZO); Vivian Alves Monteiro (UFRJ); Aline da Silva Turque (UFRJ); Alessandra Morilla Gonzalez (UFRJ); Rodolfo Paranhos (UFRJ); Welington Inácio de Almeida (INPI); Rodolpho Mattos Albano (UERJ); Orlando Bonifácio Martins (UFRJ)

Bacterioplanckton is recognized as an important agent of biogeochemical processes in all aquatic ecosystems, however the taxa that make up these communities are poorly known. The aim of this study was to investigate bacterial assemblages in aquatic ecosystems in Ilha Grande, Rio de Janeiro, a preserved environment of the Atlantic rain forest. We performed analysis of environmental chemistry, microbiological parameters and the construction of bacterial 16S rRNA gene libraries of six sites: tree marine and tree freshwater. All the samples had abiotic profiles expected for pristine coastal tropical areas. The microbial productivity was high when compared to similar environments studied before, like Guanabara bay, Sepetiba bay and Araruama lagoon. A total of 836 sequences were analyzed by DOTUR program, and 474 operational taxonomic units (OTUs) grouped at 97% stringency were obtained, 248 from freshwater and 226 from marine water. Richness and Diversity indexes show freshwater environments as the most diverse samples, especially a water spring. In these samples, the main bacterial group was Betaproteobacteria (43,5%), while Cyanobacteria (30,5%), Alphaproteobacteria (25,5%) and Gammaproteobacteria (26,3%) dominated marine environments. The Bacteroidetes groups was also well represented. Clone libraries were examined with LIBSHUFF statistics and even though the libraries differs significantly from each other,  DC values show that water spring and the river downwards are slightly similar, as well as the tree marine samples. Comparison between freshwater (river) and marine samples reached high values of DC, reflecting the remarkable abiotic differences between these environments. Our results provide a reasonable interpretation of the close relationship between bacterial diversity and environmental variables. It improves the comprehension of microbial dynamics in tropical waters from Atlantic rain forest.