Sources of dissolved iron to oxygen minimum zone waters on the Senegalese continental margin in the tropical North Atlantic Ocean: Insights from iron isotopes
Résumé
Oxygen minimum zones (OMZs) cover extensive areas of eastern boundary ocean regions and play an important role in the cycling of the essential micronutrient iron (Fe). The isotopic composition of dissolved Fe (dFe) in shelf and slope waters on the Senegalese margin was determined to investigate the processes leading to enhanced dFe concentrations (up to 2 nM) in this tropical North Atlantic OMZ. Our results show that benthic sources of Fe inputs, characterised by low 56 Fe down to-0.33 and recycled in the water column by remineralisation processes. We show that regeneration of sinking organic material becomes a more important dFe source with distance from the shelf and this remineralised dFe has relatively high 56 Fe Remineralisation plays an important role in in the redistribution of dFe that is mainly supplied by benthic and atmospheric inputs, although dust loading, calculated from dissolved aluminium-2 d-1). As OMZs are expected to expand, our data provide important insights into Fe sources and Fe cycling in the tropical North Atlantic Ocean.
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