Nitrogen fixation within the water column associated with two hypoxic basins in the Southern California Bight

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Author(s) Hamersley, M. Robert, Turk, K.A., Leinweber, A., Gruber, N., Zehr, J.P., Gunderson, T., Capone, D.G.
Publication Type Journal Items, Publication Status: Published
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Title Nitrogen fixation within the water column associated with two hypoxic basins in the Southern California Bight
Author(s) Hamersley, M. Robert
Turk, K.A.
Leinweber, A.
Gruber, N.
Zehr, J.P.
Gunderson, T.
Capone, D.G.
Journal or Series Title Aquatic microbial ecology
Volume Number 63
Issue Number 2
Start Page 193
End Page 205
ISSN 0948-3055
Publisher Inter-Research
Publication Place Oldendorf/Luhe
Publication Date 2011-04
Keyword(s) Nitrogen fixation
Southern California Bight
Hypoxic basin
Abstract We measured pelagic dinitrogen (N-2) fixation by incorporation of N-15(2) during regular cruises over 4 yr to deep hypoxic basins in the Southern California Bight, USA. N-2 fixation in the photic zone was dominated (80%) by nanoplankton (< 10 mu m). N-2 fixation rates in surface waters were near the upper range measured for nanoplankton in tropical waters, averaging 5.8 mu mol m(-3) d(-1) at the San Pedro Ocean Time Series (SPOTS) station, and 2.4 mu mol m(-3) d(-1) at the Santa Monica Bay Observatory (SMBO) station, with a maximum at SPOTS of 35 mu mol m(-3) d(-1). Quantitative polymerase chain reaction (qPCR) assays and nested PCR-based clone libraries targeting the nitrogenase gene nifH indicate that the uncultivated unicellular cyanobacterial group A (UCYN-A) is an abundant diazotroph in the photic zone. Although N-2 fixation rates were highest at the surface, mean N-2 fixation averaged 0.07 mu mol m(-3) d(-1) at depths of 500 and 885 m within hypoxic basin waters (< 10% O-2 saturation). When integrated over the aphotic water column, this deep N2 fixation may account for as much as one-third of the total areal N-2 fixation, estimated at 150 mu mol N m(-2) d(-1). These deep hypoxic N-2 fixers were an assemblage of heterotrophic bacteria, including Alpha-and Gammaproteobacteria and putative sulfate-reducing bacteria. Our results suggest that N-2 fixation could play a role in other hypoxic, high-nitrate waters.
DOI 10.3354/ame01494
Additional Notes Submitted 10 June 2010, Accepted 13 January 2011
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03731
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NEBIS System Number 001442878
Source Database ID WOS-000289577600009
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  author = "Hamersley, M. Robert and Turk, K.A. and Leinweber, A. and Gruber, N. and Zehr, J.P. and Gunderson, T. and Capone, D.G.",
  title = "{N}itrogen fixation within the water column associated with two hypoxic basins in the {S}outhern {C}alifornia {B}ight",
  journal = "Aquatic microbial ecology",
  year = 2011,
  volume = "63",
  number = "2",
  pages = "193--205",
  month = apr,

E-Citations record created: Mon, 09 May 2011, 06:55:57 CET