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Front. Microbiol. | doi: 10.3389/fmicb.2018.00236

Benthic bacterial community composition in the oligohaline-marine transition of surface sediments in the Baltic Sea based on rRNA analysis

Julia Klier1,  Olaf Dellwig2, Thomas Leipe2,  Klaus Jürgens1 and  Daniel P. Herlemann1*
  • 1Biological Oceanography, Leibniz Institute for Baltic Sea Research (LG), Germany
  • 2Marine Geology, Leibniz Institute for Baltic Sea Research (LG), Germany

Salinity has a strong impact on bacterial community composition such that freshwater bacterial communities are very different from those in seawater. By contrast, little is known about the composition and diversity of the bacterial community in the sediments (bacteriobenthos) at the freshwater-seawater transition (mesohaline conditions). In this study, partial 16S-rRNA sequences were used to investigate the bacterial community at five stations, representing almost freshwater (oligohaline) to marine conditions, in the Baltic Sea. Samples were obtained from the silty, top-layer (0–2.5 cm) sediments with mostly oxygenated conditions. The long water residence time characteristic of the Baltic Sea, was predicted to enable the development of autochthonous bacteriobenthos at mesohaline conditions. Our results showed that, similar to the water column, salinity is a major factor in structuring the bacteriobenthos and that there is no loss of bacterial richness at intermediate salinities. The bacterial communities of marine, mesohaline, and oligohaline sediments differed in terms of the relative rRNA abundances of the major bacterial phyla/classes. At mesohaline conditions typical marine and oligohaline operational taxonomic units (OTUs) were abundant. Putative unique OTUs in mesohaline sediments were present only at low abundances, suggesting that the mesohaline environment consists mainly of marine and oligohaline bacteria with a broad salinity tolerance. Our study provides a first overview of the diversity patterns and composition of bacteria in the sediments along the Baltic Sea salinity gradient as well as new insights into the bacteriobenthos at mesohaline conditions.

Keywords: Brackish Microbiology, Estuarine ecology, Baltic Sea, Bacteriobenthos, Bacterial diversity and community composition

Received: 28 Sep 2017; Accepted: 31 Jan 2018.

Edited by:

Marcelino T. Suzuki, Université Pierre et Marie Curie, France

Reviewed by:

Andreas Schramm, Aarhus University, Denmark
Valeria Souza, Universidad Nacional Autónoma de México, Mexico  

Copyright: © 2018 Klier, Dellwig, Leipe, Jürgens and Herlemann. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Daniel P. Herlemann, Leibniz Institute for Baltic Sea Research (LG), Biological Oceanography, Warnemünde, Germany, daniel.herlemann@io-warnemuende.de