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Shifts in coastal sediment oxygenation cause pronounced changes in microbial community composition and associated metabolism

Author:
  • Elias Broman
  • Johanna Sjöstedt
  • Jarone Pinhassi
  • Mark Dopson
Publishing year: 2017-08-09
Language: English
Pages:
Publication/Series: Microbiome
Volume: 5
Document type: Journal article
Publisher: BioMed Central (BMC)

Abstract english

BACKGROUND: A key characteristic of eutrophication in coastal seas is the expansion of hypoxic bottom waters, often referred to as 'dead zones'. One proposed remediation strategy for coastal dead zones in the Baltic Sea is to mix the water column using pump stations, circulating oxygenated water to the sea bottom. Although microbial metabolism in the sediment surface is recognized as key in regulating bulk chemical fluxes, it remains unknown how the microbial community and its metabolic processes are influenced by shifts in oxygen availability. Here, coastal Baltic Sea sediments sampled from oxic and anoxic sites, plus an intermediate area subjected to episodic oxygenation, were experimentally exposed to oxygen shifts. Chemical, 16S rRNA gene, metagenomic, and metatranscriptomic analyses were conducted to investigate changes in chemistry fluxes, microbial community structure, and metabolic functions in the sediment surface.

RESULTS: Compared to anoxic controls, oxygenation of anoxic sediment resulted in a proliferation of bacterial populations in the facultative anaerobic genus Sulfurovum that are capable of oxidizing toxic sulfide. Furthermore, the oxygenated sediment had higher amounts of RNA transcripts annotated as sqr, fccB, and dsrA involved in sulfide oxidation. In addition, the importance of cryptic sulfur cycling was highlighted by the oxidative genes listed above as well as dsvA, ttrB, dmsA, and ddhAB that encode reductive processes being identified in anoxic and intermediate sediments turned oxic. In particular, the intermediate site sediments responded differently upon oxygenation compared to the anoxic and oxic site sediments. This included a microbial community composition with more habitat generalists, lower amounts of RNA transcripts attributed to methane oxidation, and a reduced rate of organic matter degradation.

CONCLUSIONS: These novel data emphasize that genetic expression analyses has the power to identify key molecular mechanisms that regulate microbial community responses upon oxygenation of dead zones. Moreover, these results highlight that microbial responses, and therefore ultimately remediation efforts, depend largely on the oxygenation history of sites. Furthermore, it was shown that re-oxygenation efforts to remediate dead zones could ultimately be facilitated by in situ microbial molecular mechanisms involved in removal of toxic H2S and the potent greenhouse gas methane.

Keywords

  • Bacteria/classification
  • Bacterial Physiological Phenomena/genetics
  • Baltic States
  • Gene Expression Profiling
  • Geologic Sediments/chemistry
  • Hydrogen Sulfide/metabolism
  • Metagenomics
  • Methane/metabolism
  • Microbial Consortia/genetics
  • Oceans and Seas
  • Oxidation-Reduction
  • Oxygen/metabolism
  • Phylogeny
  • RNA, Ribosomal, 16S/genetics

Other

Published
  • ISSN: 2049-2618
Portrait of Johanna Sjöstedt
E-mail: johanna [dot] sjostedt [at] biol [dot] lu [dot] se

Postdoctoral fellow

Division aquatic ecology

+46 46 222 84 38

+46 73 913 31 19

E-C111

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Researcher

Aquatic Ecology

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Research group

Aquatic Ecology

Projects

 

Postdoc host

  • Emma Kritzberg
  • Eva Lindström, Uppsala University
  • Silke Langenheder, Uppsala University

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Raw data for the artikel Effect of repeated disturbances on resistance and resilience in aquatic bacterioplankton communities (Zip; 2 MB)