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Bacterial abundance and composition in marine sediments beneath the R oss I ce S helf, A ntarctica
Author(s) -
Carr S. A.,
Vogel S. W.,
Dunbar R. B.,
Brandes J.,
Spear J. R.,
Levy R.,
Naish T. R.,
Powell R. D.,
Wakeham S. G.,
Mandernack K. W.
Publication year - 2013
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/gbi.12042
Subject(s) - microbial population biology , heterotroph , environmental chemistry , total organic carbon , pyrosequencing , mineralization (soil science) , biology , sediment , chemistry , alteromonas , organic matter , food science , bacteria , ecology , biochemistry , gene , paleontology , genetics , soil water
Marine sediments of the R oss S ea, A ntarctica, harbor microbial communities that play a significant role in the decomposition, mineralization, and recycling of organic carbon ( OC ). In this study, the cell densities within a 153‐cm sediment core from the R oss S ea were estimated based on microbial phospholipid fatty acid ( PLFA ) concentrations and acridine orange direct cell counts. The resulting densities were as high as 1.7 × 10 7  cells mL −1 in the top ten centimeters of sediments. These densities are lower than those calculated for most near‐shore sites but consistent with deep‐sea locations with comparable sedimentation rates. The δ 13 C measurements of PLFA s and sedimentary and dissolved carbon sources, in combination with ribosomal RNA ( SSU r RNA ) gene pyrosequencing, were used to infer microbial metabolic pathways. The δ 13 C values of dissolved inorganic carbon ( DIC ) in porewaters ranged downcore from −2.5‰ to −3.7‰, while δ 13 C values for the corresponding sedimentary particulate OC ( POC ) varied from −26.2‰ to −23.1‰. The δ 13 C values of PLFA s ranged between −29‰ and −35‰ throughout the sediment core, consistent with a microbial community dominated by heterotrophs. The SSU r RNA gene pyrosequencing revealed that members of this microbial community were dominated by β‐, δ‐, and γ‐ P roteobacteria, A ctinobacteria, C hloroflexi and B acteroidetes. Among the sequenced organisms, many appear to be related to known heterotrophs that utilize OC sources such as amino acids, oligosaccharides, and lactose, consistent with our interpretation from δ 13 C PLFA analysis. Integrating phospholipids analyses with porewater chemistry, δ 13 C DIC and δ 13 C POC values and SSU r RNA gene sequences provides a more comprehensive understanding of microbial communities and carbon cycling in marine sediments, including those of this unique ice shelf environment.

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