Preprints
https://doi.org/10.5194/egusphere-2024-1706
https://doi.org/10.5194/egusphere-2024-1706
10 Jun 2024
 | 10 Jun 2024
Status: this preprint is open for discussion.

Dissolved Mn(III) is a key redox intermediate in sediments of a seasonally euxinic coastal basin

Robin Klomp, Olga M. Żygadłowska, Mike S. M. Jetten, Véronique E. Oldham, Niels A. G. M. van Helmond, Caroline P. Slomp, and Wytze K. Lenstra

Abstract. Manganese (Mn) is an essential micronutrient and key redox intermediate in marine systems. The role of organically complexed dissolved Mn(III) (dMn(III)-L) as an electron acceptor and donor in marine environments is still incompletely understood. Here, we use geochemical depth profiles and a reactive transport model to reconstruct the seasonality in sedimentary dMn(III)-L dynamics and benthic Mn release in a eutrophic, seasonally euxinic coastal basin (Lake Grevelingen, the Netherlands). We find that dMn(III)-L is a major component of the dissolved Mn pool throughout the year. Our model indicates that, when O2 is present in the bottom water, there are three major sources of pore water dMn(III)-L, namely reduction of Mn oxides coupled to the oxidation of Fe(II), reduction of Mn oxides coupled to organic matter degradation and oxidation of Mn(II) with O2. Removal of pore water dMn(III)-L primarily takes place through reduction by dissolved Fe(II). When bottom waters are euxinic in summer, rates of sedimentary Mn cycling decrease strongly, because of a lower supply of Mn oxides. The dMn(III)-L transformations in summer mostly involve reactions with Fe(II) and organic matter. Benthic release of Mn mainly occurs as dMn(III)-L when bottom waters are oxic, as Mn(II) upon initial bottom water euxinia and as both Mn(II) and dMn(III)-L when the euxinia becomes persistent. Our findings highlight strong interactions between the sedimentary Fe and Mn cycles. Dissolved Mn(III)-L is a relatively stable and mobile Mn species, when compared to Mn(II), and is therefore more easily transported laterally throughout the coastal zone and possibly also to open marine waters.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Robin Klomp, Olga M. Żygadłowska, Mike S. M. Jetten, Véronique E. Oldham, Niels A. G. M. van Helmond, Caroline P. Slomp, and Wytze K. Lenstra

Status: open (until 22 Jul 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
Robin Klomp, Olga M. Żygadłowska, Mike S. M. Jetten, Véronique E. Oldham, Niels A. G. M. van Helmond, Caroline P. Slomp, and Wytze K. Lenstra
Robin Klomp, Olga M. Żygadłowska, Mike S. M. Jetten, Véronique E. Oldham, Niels A. G. M. van Helmond, Caroline P. Slomp, and Wytze K. Lenstra

Viewed

Total article views: 83 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
65 16 2 83 6 0 0
  • HTML: 65
  • PDF: 16
  • XML: 2
  • Total: 83
  • Supplement: 6
  • BibTeX: 0
  • EndNote: 0
Views and downloads (calculated since 10 Jun 2024)
Cumulative views and downloads (calculated since 10 Jun 2024)

Viewed (geographical distribution)

Total article views: 79 (including HTML, PDF, and XML) Thereof 79 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 12 Jun 2024
Download
Short summary
In marine sediments, dissolved Mn is present as either Mn(III) or Mn(II). We apply a reactive transport model to geochemical data for a seasonally anoxic and sulfidic coastal basin to determine the pathways of formation and removal of dissolved Mn(III) in the sediment. We demonstrate a critical role for reactions with Fe(II) and show evidence for substantial benthic release of dissolved Mn(III). Given the mobility of Mn(III), these findings have important implications for marine Mn cycling.