Contribution of Electroactive Humic Substances to the Iron-Binding Ligands Released During Microbial Remineralization of Sinking Particles

Hannah Whitby, Matthieu Bressac, Géraldine Sarthou, Michael J. Ellwood, Cécile Guieu, Philip W. Boyd

Research output: Contribution to journalLetterpeer-review

Abstract

Iron is a key micronutrient in seawater, but concentrations would be negligible without the presence of organic ligands. The processes influencing the ligand pool composition are poorly constrained, limiting our understanding of the controls on dissolved iron distributions. To address this, the release of iron and iron-binding ligands during the microbial remineralization of sinking particles was investigated by deploying in situ particle interceptor/incubator devices at subsurface sites in the Mediterranean Sea and Subantarctic. Analyses revealed that the pool of released ligands was largely dominated by electroactive humic substances (74 ± 28%). The release of ligands during remineralization ensured that concurrently released iron remained in solution, which is crucial for iron regeneration. This study presents compelling evidence of the key role of humic ligands in the subsurface replenishment of dissolved iron and thus on the wider oceanic dissolved iron inventory, which ultimately controls the magnitude of iron resupplied to the euphotic zone.

Original languageEnglish (US)
Article numbere2019GL086685
JournalGeophysical Research Letters
Volume47
Issue number7
DOIs
StatePublished - Apr 16 2020

Keywords

  • Iron
  • degradation
  • humic
  • ligand
  • particle
  • remineralisation

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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