Dataset Information

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.

SUBMITTER: Franco DC

PROVIDER: S-EPMC5288382 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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High Prevalence of Gammaproteobacteria in the Sediments of Admiralty Bay and North Bransfield Basin, Northwestern Antarctic Peninsula.

Franco Diego C DC Signori Camila N CN Duarte Rubens T D RT Nakayama Cristina R CR Campos Lúcia S LS Pellizari Vivian H VH

Frontiers in microbiology 20170202

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 depos ...[more]

PMID: 28210255

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Project description:Although crucial for the addition of new nitrogen in marine ecosystems, dinitrogen (N2) fixation remains an understudied process, especially under dark conditions and in polar coastal areas, such as the West Antarctic Peninsula (WAP). New measurements of light and dark N2 fixation rates in parallel with carbon (C) fixation rates, as well as analysis of the genetic marker nifH for diazotrophic organisms, were conducted during the late summer in the coastal waters of Chile Bay, South Shetland Islands, WAP. During six late summers (February 2013 to 2019), Chile Bay was characterized by high NO3- concentrations (~20 µM) and an NH4+ content that remained stable near 0.5 µM. The N:P ratio was approximately 14.1, thus close to that of the Redfield ratio (16:1). The presence of Cluster I and Cluster III nifH gene sequences closely related to Alpha-, Delta- and, to a lesser extent, Gammaproteobacteria, suggests that chemosynthetic and heterotrophic bacteria are primarily responsible for N2 fixation in the bay. Photosynthetic carbon assimilation ranged from 51.18 to 1471 nmol C L-1 d-1, while dark chemosynthesis ranged from 9.24 to 805 nmol C L-1 d-1. N2 fixation rates were higher under dark conditions (up to 45.40 nmol N L-1 d-1) than under light conditions (up to 7.70 nmol N L-1 d-1), possibly contributing more than 37% to new nitrogen-based production (≥2.5 g N m-2 y-1). Of all the environmental factors measured, only PO43- exhibited a significant correlation with C and N2 rates, being negatively correlated (p < 0.05) with dark chemosynthesis and N2 fixation under the light condition, revealing the importance of the N:P ratio for these processes in Chile Bay. This significant contribution of N2 fixation expands the ubiquity and biological potential of these marine chemosynthetic diazotrophs. As such, this process should be considered along with the entire N cycle when further reviewing highly productive Antarctic coastal waters and the diazotrophic potential of the global marine ecosystem.

Dataset Information

High Prevalence of Gammaproteobacteria in the Sediments of Admiralty Bay and North Bransfield Basin, Northwestern Antarctic Peninsula.

Publications

High Prevalence of Gammaproteobacteria in the Sediments of Admiralty Bay and North Bransfield Basin, Northwestern Antarctic Peninsula.

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