Influence of salinity on bacterioplankton communities from the Brazilian rain forest to the coastal Atlantic Ocean |
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Authors: | Silveira Cynthia B Vieira Ricardo P Cardoso Alexander M Paranhos Rodolfo Albano Rodolpho M Martins Orlando B |
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Institution: | Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. |
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Abstract: | BackgroundPlanktonic bacteria are recognized as important drivers 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 communities in aquatic ecosystems at Ilha Grande, Rio de Janeiro,
Brazil, a preserved insular environment of the Atlantic rain forest and how
they correlate with a salinity gradient going from terrestrial aquatic
habitats to the coastal Atlantic Ocean.Methodology/Principal FindingsWe analyzed chemical and microbiological parameters of water samples and
constructed 16S rRNA gene libraries of free living bacteria obtained at
three marine (two coastal and one offshore) and three freshwater (water
spring, river, and mangrove) environments. A total of 836 sequences were
analyzed by MOTHUR, yielding 269 freshwater and 219 marine operational
taxonomic units (OTUs) grouped at 97% stringency. Richness and
diversity indexes indicated that freshwater environments were the most
diverse, especially the water spring. The main bacterial group in freshwater
environments was Betaproteobacteria (43.5%), whereas
Cyanobacteria (30.5%),
Alphaproteobacteria (25.5%), and
Gammaproteobacteria (26.3%) dominated the marine
ones. Venn diagram showed no overlap between marine and freshwater OTUs at
97% stringency. LIBSHUFF statistics and PCA analysis revealed marked
differences between the freshwater and marine libraries suggesting the
importance of salinity as a driver of community composition in this habitat.
The phylogenetic analysis of marine and freshwater libraries showed that the
differences in community composition are consistent.Conclusions/SignificanceOur data supports the notion that a divergent evolutionary scenario is
driving community composition in the studied habitats. This work also
improves the comprehension of microbial community dynamics in tropical
waters and how they are structured in relation to physicochemical
parameters. Furthermore, this paper reveals for the first time the pristine
bacterioplankton communities in a tropical island at the South Atlantic
Ocean. |
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