Diazotroph derived nitrogen supports diatom growth in the South West Pacific: A quantitative study using nanoSIMS - Archive ouverte HAL Access content directly
Journal Articles Limnology and Oceanography Year : 2016

Diazotroph derived nitrogen supports diatom growth in the South West Pacific: A quantitative study using nanoSIMS

Sophie Bonnet
Kendra Turk-Kubo
  • Function : Author
Sarah Fawcett
  • Function : Author
Ilana Berman-Frank
  • Function : Author
Aude Barani
Gérald Grégori
Julien Dekaezemacker
  • Function : Author
Mar Benavides
Douglas G. Capone
  • Function : Author

Abstract

Nitrogen is essential for life but is often a major limiting nutrient for growth in the ocean. Biological dinitrogen fixation is a major source of new nitrogen to surface waters and promotes marine productivity. Yet the fate of diazotroph-derived nitrogen (DDN) in marine ecosystems has been poorly studied, and its transfer to auto- and heterotrophic plankton has not been measured. Here, we use high-resolution nanometer scale secondary ion mass spectrometry (nanoSIMS) coupled with N-15(2) isotopic labelling and flow cytometry cell sorting to examine the DDN transfer to specific groups of natural phytoplankton and bacteria during three diazotroph blooms dominated by the cyanobacterium Trichodesmium spp. in the South West Pacific. During these experiments, 13%+/- 2% to 48%+/- 5% of the fixed N-15(2) was released into the dissolved pool and 6%+/- 1% to 8%+/- 2% of this DDN was transferred to non-diazotrophic plankton after 48 h. The primary beneficiaries of this DDN were diatoms (45%+/- 4% to 61%+/- 38%) and bacteria (22%+/- 27% to 38%+/- 12%), followed by pico-phytoplankton (3%+/- 1% to 21%+/- 14%). The DDN was quickly converted to non-diazotrophic plankton biomass, in particular that of diatoms, which increased in abundance by a factor of 1.4-15 over the course of the three experiments. The single-cell approach we used enabled quantification of the actual transfer of DDN to specific groups of autotrophic and heterotrophic plankton in the surface ocean, revealing a previously unseen level of complexity in the pathways that occur between N-2 fixation and the eventual export of DDN from the photic zone.

Dates and versions

hal-01443231 , version 1 (22-01-2017)

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Sophie Bonnet, Hugo Berthelot, Kendra Turk-Kubo, Veronique Cornet, Sarah Fawcett, et al.. Diazotroph derived nitrogen supports diatom growth in the South West Pacific: A quantitative study using nanoSIMS. Limnology and Oceanography, 2016, 61 (5), pp.1549-1562. ⟨10.1002/lno.10300⟩. ⟨hal-01443231⟩
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