Active nitrogen fixing heterotrophic bacteria at and below the chemocline of the central Baltic Sea

Hanna Farnelid, Mikkel Bentzon-Tilia, Anders F. Andersson, Stefan Bertilsson, Günter Jost, Matthias Labrenz, Klaus Jürgens, Lasse Riemann

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The Baltic Sea receives large nitrogen inputs by diazotrophic (N2-fixing) heterocystous cyanobacteria but the significance of heterotrophic N2 fixation has not been studied. Here, the diversity, abundance and transcription of the nifH fragment of the nitrogenase enzyme in two basins of the Baltic Sea proper was examined. N2 fixation was measured at the surface (5 m) and in anoxic water (200 m). Vertical sampling profiles of >10 and <10 μm size fractions were collected in 2007, 2008 and 2011 at the Gotland Deep and in 2011 in the Bornholm Basin. Both of these stations are characterized by permanently anoxic bottom water. The 454-pyrosequencing nifH analysis revealed a diverse assemblage of nifH genes related to alpha-, beta- and gammaproteobacteria (nifH cluster I) and anaerobic bacteria (nifH cluster III) at and below the chemocline. Abundances of genes and transcripts of seven diazotrophic phylotypes were investigated using quantitative polymerase chain reaction revealing abundances of heterotrophic nifH phylotypes of up to 2.1 × 107 nifH copies l−1. Abundant nifH transcripts (up to 3.2 × 104 transcripts l−1) within nifH cluster III and co-occurring N2 fixation (0.44±0.26 nmol l−1 day−1) in deep water suggests that heterotrophic diazotrophs are fixing N2 in anoxic ammonium-rich waters. Our results reveal that N2 fixation in the Baltic Sea is not limited to illuminated N-deplete surface waters and suggest that N2 fixation could also be of importance in other suboxic regions of the world’s oceans.
Original languageEnglish
JournalI S M E Journal
Volume7
Pages (from-to)1413-1423
Number of pages11
ISSN1751-7362
DOIs
Publication statusPublished - 2013
Externally publishedYes

Keywords

  • Baltic Sea
  • Chemocline
  • nifH
  • Nitrogen
  • Fixation
  • Oxic-anoxic interface
  • Pyrosequencing

Cite this

Farnelid, Hanna ; Bentzon-Tilia, Mikkel ; Andersson, Anders F. ; Bertilsson, Stefan ; Jost, Günter ; Labrenz, Matthias ; Jürgens, Klaus ; Riemann, Lasse. / Active nitrogen fixing heterotrophic bacteria at and below the chemocline of the central Baltic Sea. In: I S M E Journal. 2013 ; Vol. 7. pp. 1413-1423.
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abstract = "The Baltic Sea receives large nitrogen inputs by diazotrophic (N2-fixing) heterocystous cyanobacteria but the significance of heterotrophic N2 fixation has not been studied. Here, the diversity, abundance and transcription of the nifH fragment of the nitrogenase enzyme in two basins of the Baltic Sea proper was examined. N2 fixation was measured at the surface (5 m) and in anoxic water (200 m). Vertical sampling profiles of >10 and <10 μm size fractions were collected in 2007, 2008 and 2011 at the Gotland Deep and in 2011 in the Bornholm Basin. Both of these stations are characterized by permanently anoxic bottom water. The 454-pyrosequencing nifH analysis revealed a diverse assemblage of nifH genes related to alpha-, beta- and gammaproteobacteria (nifH cluster I) and anaerobic bacteria (nifH cluster III) at and below the chemocline. Abundances of genes and transcripts of seven diazotrophic phylotypes were investigated using quantitative polymerase chain reaction revealing abundances of heterotrophic nifH phylotypes of up to 2.1 × 107 nifH copies l−1. Abundant nifH transcripts (up to 3.2 × 104 transcripts l−1) within nifH cluster III and co-occurring N2 fixation (0.44±0.26 nmol l−1 day−1) in deep water suggests that heterotrophic diazotrophs are fixing N2 in anoxic ammonium-rich waters. Our results reveal that N2 fixation in the Baltic Sea is not limited to illuminated N-deplete surface waters and suggest that N2 fixation could also be of importance in other suboxic regions of the world’s oceans.",
keywords = "Baltic Sea, Chemocline, nifH, Nitrogen, Fixation, Oxic-anoxic interface, Pyrosequencing",
author = "Hanna Farnelid and Mikkel Bentzon-Tilia and Andersson, {Anders F.} and Stefan Bertilsson and G{\"u}nter Jost and Matthias Labrenz and Klaus J{\"u}rgens and Lasse Riemann",
year = "2013",
doi = "10.1038/ismej.2013.26",
language = "English",
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journal = "I S M E Journal",
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Farnelid, H, Bentzon-Tilia, M, Andersson, AF, Bertilsson, S, Jost, G, Labrenz, M, Jürgens, K & Riemann, L 2013, 'Active nitrogen fixing heterotrophic bacteria at and below the chemocline of the central Baltic Sea', I S M E Journal, vol. 7, pp. 1413-1423. https://doi.org/10.1038/ismej.2013.26

Active nitrogen fixing heterotrophic bacteria at and below the chemocline of the central Baltic Sea. / Farnelid, Hanna; Bentzon-Tilia, Mikkel; Andersson, Anders F.; Bertilsson, Stefan; Jost, Günter; Labrenz, Matthias; Jürgens, Klaus; Riemann, Lasse.

In: I S M E Journal, Vol. 7, 2013, p. 1413-1423.

Research output: Contribution to journalJournal articleResearchpeer-review

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T1 - Active nitrogen fixing heterotrophic bacteria at and below the chemocline of the central Baltic Sea

AU - Farnelid, Hanna

AU - Bentzon-Tilia, Mikkel

AU - Andersson, Anders F.

AU - Bertilsson, Stefan

AU - Jost, Günter

AU - Labrenz, Matthias

AU - Jürgens, Klaus

AU - Riemann, Lasse

PY - 2013

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AB - The Baltic Sea receives large nitrogen inputs by diazotrophic (N2-fixing) heterocystous cyanobacteria but the significance of heterotrophic N2 fixation has not been studied. Here, the diversity, abundance and transcription of the nifH fragment of the nitrogenase enzyme in two basins of the Baltic Sea proper was examined. N2 fixation was measured at the surface (5 m) and in anoxic water (200 m). Vertical sampling profiles of >10 and <10 μm size fractions were collected in 2007, 2008 and 2011 at the Gotland Deep and in 2011 in the Bornholm Basin. Both of these stations are characterized by permanently anoxic bottom water. The 454-pyrosequencing nifH analysis revealed a diverse assemblage of nifH genes related to alpha-, beta- and gammaproteobacteria (nifH cluster I) and anaerobic bacteria (nifH cluster III) at and below the chemocline. Abundances of genes and transcripts of seven diazotrophic phylotypes were investigated using quantitative polymerase chain reaction revealing abundances of heterotrophic nifH phylotypes of up to 2.1 × 107 nifH copies l−1. Abundant nifH transcripts (up to 3.2 × 104 transcripts l−1) within nifH cluster III and co-occurring N2 fixation (0.44±0.26 nmol l−1 day−1) in deep water suggests that heterotrophic diazotrophs are fixing N2 in anoxic ammonium-rich waters. Our results reveal that N2 fixation in the Baltic Sea is not limited to illuminated N-deplete surface waters and suggest that N2 fixation could also be of importance in other suboxic regions of the world’s oceans.

KW - Baltic Sea

KW - Chemocline

KW - nifH

KW - Nitrogen

KW - Fixation

KW - Oxic-anoxic interface

KW - Pyrosequencing

U2 - 10.1038/ismej.2013.26

DO - 10.1038/ismej.2013.26

M3 - Journal article

VL - 7

SP - 1413

EP - 1423

JO - I S M E Journal

JF - I S M E Journal

SN - 1751-7362

ER -