Dissolved hydrogen and nitrogen fixation in the oligotrophic North Pacific Subtropical Gyre

Authors

  • Samuel T. Wilson,

    Corresponding author
    1. Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
    • Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI, USA
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  • Daniela A. del Valle,

    1. Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI, USA
    2. Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
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  • Julie C. Robidart,

    1. Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
    2. Ocean Sciences Department, University of California, Santa Cruz, CA, USA
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  • Jonathan P. Zehr,

    1. Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
    2. Ocean Sciences Department, University of California, Santa Cruz, CA, USA
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  • David M. Karl

    1. Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI, USA
    2. Center for Microbial Oceanography: Research and Education, University of Hawaii, Honolulu, HI, USA
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Errata

This article is corrected by:

  1. Errata: Dissolved hydrogen and nitrogen fixation in the oligotrophic North Pacific Subtropical Gyre Volume 6, Issue 1, 122, Article first published online: 20 January 2014

For correspondence. E-mail stwilson@hawaii.edu; Tel. 808 956 0565; Fax 808 956 0581.

Summary

The production of hydrogen (H2) is an inherent component of biological dinitrogen (N2) fixation, and there have been several studies quantifying H2 production relative to N2 fixation in cultures of diazotrophs. However, conducting the relevant measurements for a field population is more complex as shown by this study of N2 fixation, H2 consumption and dissolved H2 concentrations in the oligotrophic North Pacific Ocean. Measurements of H2 oxidation revealed microbial consumption of H2 was equivalent to 1–7% of ethylene produced during the acetylene reduction assay and 11–63% of 15N2 assimilation on a molar scale. Varying abundances of Crocosphaera and Trichodesmium as revealed by nifH gene abundances broadly corresponded with diel changes observed in both N2 fixation and H2 oxidation. However, no corresponding changes were observed in the dissolved H2 concentrations which remained consistently supersaturated (147–560%) relative to atmospheric equilibrium. The results from this field study allow the efficiency of H2 cycling by natural populations of diazotrophs to be compared to cultured representatives. The findings indicate that dissolved H2 concentrations may depend not only on the community composition of diazotrophs but also upon relevant environmental parameters such as light intensity or the presence of other H2-metabolizing microorganisms.

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