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https://doi.org/10.5194/egusphere-2025-1798
https://doi.org/10.5194/egusphere-2025-1798
20 May 2025
 | 20 May 2025

Organic iron-binding ligands mediate dissolved-particulate exchange in hydrothermal vent plumes along the mid-Atlantic Ridge

Travis Mellett, Justine Albers, Alyson Santoro, Pascal Salaun, Joseph Resing, Wenhao Wang, Alistar Lough, Alessandro Tagliabue, Maeve Lohan, Randelle Bundy, and Kristen Buck

Abstract. Hydrothermal vents are important contributors to the dissolved iron inventory in the ocean. Investigating the processes underlying iron behavior in hydrothermal plumes is challenging, but important for constraining deep ocean iron cycling. Field studies suggest that the retention of hydrothermal iron in the deep ocean is primarily supported by two mechanisms: the formation of colloidal nanoparticles and the stabilization of iron by organic ligands. Here we present a novel dataset from shipboard incubation experiments designed to investigate the interplay between these two processes and how they contribute to the stabilization of iron away from ridge axes. Filtered and unfiltered water collected from the hydrothermal plumes of three vent fields along the Mid-Atlantic Ridge as part of GEOTRACES cruise GA13 was incubated in the dark and regularly sampled over time (up to 3 weeks) for concentrations of size-fractionated iron and iron-binding ligands, for dissolved iron isotopic composition, and for microbial community composition. We observed rapid exchange of iron between physiochemical phases that appeared to be mediated in part by organic iron-binding ligands at each stage of plume evolution. Weaker iron-binding ligands sources from the vents were largely lost to the particulate phase with colloidal Fe phases via aggregation early in plume development, similar to the loss of iron and organic matter commonly observed in estuarine systems. Soluble organic ligand production was observed in later stages of all unfiltered incubations followed by mobilization of particulate and colloidal Fe into the soluble phase in the longer incubations, revealing a potentially important mechanism for generating the persistent iron observed in long-range plumes.

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Travis Mellett, Justine Albers, Alyson Santoro, Pascal Salaun, Joseph Resing, Wenhao Wang, Alistar Lough, Alessandro Tagliabue, Maeve Lohan, Randelle Bundy, and Kristen Buck

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-1798', Anonymous Referee #1, 15 Jun 2025
    • AC2: 'Reply on RC1', Travis Mellett, 22 Jul 2025
  • RC2: 'Comment on egusphere-2025-1798', Anonymous Referee #2, 02 Jul 2025
    • AC1: 'Reply on RC2', Travis Mellett, 22 Jul 2025
Travis Mellett, Justine Albers, Alyson Santoro, Pascal Salaun, Joseph Resing, Wenhao Wang, Alistar Lough, Alessandro Tagliabue, Maeve Lohan, Randelle Bundy, and Kristen Buck
Travis Mellett, Justine Albers, Alyson Santoro, Pascal Salaun, Joseph Resing, Wenhao Wang, Alistar Lough, Alessandro Tagliabue, Maeve Lohan, Randelle Bundy, and Kristen Buck

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Short summary
Hydrothermal plumes of iron have been observed to persist in the deep ocean, but the exact mechanisms that contribute to the long-range transport of iron is not well defined. We collected plume waters from three different vent systems along the mid-Atlantic Ridge and monitored the temporal evolution of the physical and chemical forms of iron and its interaction with organic matter over time to learn about the mechanisms that control its dispersion.
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