title: High Prevalence of Gammaproteobacteria in the Sediments of Admiralty Bay and North Bransfield Basin, Northwestern Antarctic Peninsula.
abstract: Microorganisms dominate most Antarctic marine ecosystems, in terms of biomass and taxonomic diversity, and play crucial role in ecosystem functioning due to their high metabolic plasticity. Admiralty Bay is the largest bay on King George Island (South Shetland Islands, Antarctic Peninsula) and a combination of hydro-oceanographic characteristics (bathymetry, sea ice and glacier melting, seasonal entrance of water masses, turbidity, vertical fluxes) create conditions favoring organic carbon deposition on the seafloor and microbial activities. We sampled surface sediments from 15 sites across Admiralty Bay (100-502 m total depth) and the adjacent North Bransfield Basin (693-1147 m), and used the amplicon 454-sequencing of 16S rRNA gene tags to compare the bacterial composition, diversity, and microbial community structure across environmental parameters (sediment grain size, pigments and organic nutrients) between the two areas. Marine sediments had a high abundance of heterotrophic Gammaproteobacteria (92.4% and 83.8% inside and outside the bay, respectively), followed by Alphaproteobacteria (2.5 and 5.5%), Firmicutes (1.5 and 1.6%), Bacteroidetes (1.1 and 1.7%), Deltaproteobacteria (0.8 and 2.5%) and Actinobacteria (0.7 and 1.3%). Differences in alpha-diversity and bacterial community structure were found between the two areas, reflecting the physical and chemical differences in the sediments, and the organic matter input.
authors.affiliation: Departamento de Oceanografia Biológica, Instituto Oceanográfico, Universidade de São Paulo São Paulo, Brazil.
authors.forename: Diego C
authors.initials: DC
authors.lastname: Franco
authors.affiliation: Departamento de Oceanografia Biológica, Instituto Oceanográfico, Universidade de São Paulo São Paulo, Brazil.
authors.forename: Camila N
authors.initials: CN
authors.lastname: Signori
authors.affiliation: Centro de Ciências Biológicas, Universidade Federal de Santa Catarina Florianópolis, Brazil.
authors.forename: Rubens T D
authors.initials: RT
authors.lastname: Duarte
authors.affiliation: Departamento de Ciências Ambientais, Instituto de Ciências Ambientais, Químicas e Farmacêuticas, Universidade Federal de São Paulo Diadema, Brazil.
authors.forename: Cristina R
authors.initials: CR
authors.lastname: Nakayama
authors.affiliation: Departamento de Zoologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro Rio de Janeiro, Brazil.
authors.forename: Lúcia S
authors.initials: LS
authors.lastname: Campos
authors.affiliation: Departamento de Oceanografia Biológica, Instituto Oceanográfico, Universidade de São Paulo São Paulo, Brazil.
authors.forename: Vivian H
authors.initials: VH
authors.lastname: Pellizari
keywords: Antarctica; bacterial community structure; marine sediments; microbial diversity; polar microbiology