Basin-wide N2 fixation in the deep waters of the Mediterranean Sea - Archive ouverte HAL Access content directly
Journal Articles Global Biogeochemical Cycles Year : 2016

Basin-wide N2 fixation in the deep waters of the Mediterranean Sea

Mar Benavides
Sophie Bonnet
Nauzet Hernández
  • Function : Author
Alba María Martínez-Pérez
  • Function : Author
Mar Nieto-Cid
  • Function : Author
Xosé Antón Álvarez-Salgado
  • Function : Author
Isabel Baños
  • Function : Author
María Montero
  • Function : Author
Ignacio P Mazuecos
  • Function : Author
Josep M Gasol
Helena Osterholz
  • Function : Author
Thorsten Dittmar
  • Function : Author
Ilana Berman-Frank
  • Function : Author
Javier Arístegui

Abstract

Recent findings indicate that N 2 fixation is significant in aphotic waters, presumably due to heterotrophic diazotrophs depending on organic matter for their nutrition. However, the relationship between organic matter and heterotrophic N 2 fixation remains unknown. Here we explore N 2 fixation in the deep chlorophyll maximum and underneath deep waters across the whole Mediterranean Sea and relate it to organic matter composition, characterized by optical and molecular methods. Our N 2 fixation rates were in the range of those previously reported for the euphotic zone of the Mediterranean Sea (up to 0.43 nmol N L À1 d À1) and were significantly correlated to the presence of relatively labile organic matter with fluorescence and molecular formula properties representative for peptides and unsaturated aliphatics and associated with the presence of more oxygenated ventilated water masses. Finally, and despite that the aphotic N 2 fixation contributes largely to total water column diazotrophic activity (>50%), its contribution to overall nitrogen inputs to the basin is negligible (<0.5%).
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hal-02458925 , version 1 (15-05-2021)

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Mar Benavides, Sophie Bonnet, Nauzet Hernández, Alba María Martínez-Pérez, Mar Nieto-Cid, et al.. Basin-wide N2 fixation in the deep waters of the Mediterranean Sea. Global Biogeochemical Cycles, 2016, ⟨10.1002/2015GB005326⟩. ⟨hal-02458925⟩
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