Longitudinal variability of diazotroph abundances in the subtropical North Atlantic Ocean - Archive ouverte HAL Access content directly
Journal Articles Journal of Plankton Research Year : 2016

Longitudinal variability of diazotroph abundances in the subtropical North Atlantic Ocean

Mar Benavides
Pia H. Moisander
  • Function : Author
Meaghan C. Daley
  • Function : Author
Antonio Bode
  • Function : Author
Javier Aristegui
  • Function : Author

Abstract

Diazotrophy-related studies in the North Atlantic have largely focused on its western tropical area, leaving the subtropics and the east undersampled. We studied the longitudinal distribution of Trichodesmium, UCYN-A, UCYN-B, the putative Gammaproteobacterium g-24774A11 and Richelia (Het1) along 24.5 degrees N, using quantitative polymerase chain reaction on different size fractions (10, 10-3 and 3-0.2 mm) and additional filament counts for Trichodesmium. Trichodesmium was the most abundant phylotype, followed by UCYN-A, gamma-24774A11 and Het1, with maximum abundances of 8.8 x 10(5), 2.0 x 10(5), 3.3 x 10(3) and 3.4 x 10(2) nifH copies L-1, respectively, whereas UCYN-B was mostly undetected. A clear shift in the diazotroph community was observed at similar to 30 degrees W, coinciding with the transition between the North Atlantic Subtropical Gyre boundary and inner core. This transition zone divided the transect into an eastern half dominated by UCYN-A and western half dominated by Trichodesmium and gamma-24774A11. gamma-24774A11 was only detected in the 10-3 mu m fraction, suggesting their association with larger microbes or aggregates. Our results indicate that typical size fractionation by 10 mu m is not optimal for reconciling diazotroph phylotypes to N-2 fixation rates and that non-cyanobacterial diazotrophs may contribute importantly to bulk diazotrophic activity in the western subtropical North Atlantic.

Dates and versions

hal-01443608 , version 1 (23-01-2017)

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Mar Benavides, Pia H. Moisander, Meaghan C. Daley, Antonio Bode, Javier Aristegui. Longitudinal variability of diazotroph abundances in the subtropical North Atlantic Ocean. Journal of Plankton Research, 2016, 38 (3), pp.662-672. ⟨10.1093/plankt/fbv121⟩. ⟨hal-01443608⟩
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