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MEPS - Vol. 470 - Feature article
Saharan dust particles entrained in and around a radial colony of Trichodesmium erythraeum filaments. Photo: R. Langlois, J. LaRoche

Langlois RJ, Mills MM, Ridame C,
Croot P, LaRoche J

 

Diazotrophic bacteria respond to Saharan dust additions

 

The distribution of oceanic dinitrogen fixing organisms (diazotrophs), especially cyanobacteria Trichodesmium spp., is correlated with atmospheric mineral dust deposition. Aerosol dust deposition is the major source of iron to open ocean waters. Langlois and co-workers performed bottle experiments with added nutrients and Saharan dust. They found that gene abundances of all diazotrophic groups at least doubled after Saharan dust additions in waters with low iron concentrations. Laboratory experiments with cultures of Trichodesmium erythraeum grown with or without iron and/or Saharan dust demonstrated that dust addition promoted colony formation and the persistence of T. erythraeum biomass relative to cultures without iron. The field and laboratory experiments both indicate that Saharan dust positively affects diazotroph gene abundance and changes T. erythraeum colony morphology.

 

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