Skip to main content
padlock icon - secure page this page is secure

Free Content Fe redox cycling in Iberian continental margin sediments (NE Atlantic)

Download Article:
In this paper, data are presented on the vertical distribution of pore water Fe2+, ferrozine-extractable Fe2+ and solid phase Fe in sediments along four across-slope transects including the Nazarécanyon at the Iberian margin. Sorbed Fe2+ cannot be measured directly and is operationally defined as the fraction that can be extracted with ferrozine. Our objectives were (1) to investigate the potential role of Fe2+ sorption in the Fe redox cycle, (2) to quantify Fe redox cycling and (3) to determine its rate limiting factors, with emphasis on differences between stations across the slope and in the canyon. In all sediments pore water Fe2+ and ferrozine-extractable Fe2+ concentrations increased simultaneously with depth until a maximum was reached and upon which the pore water Fe2+ concentration rapidly declined, presumably due to precipitation as iron-sulfide. The ferrozine-extractable Fe2+ concentration, however, either slowly diminished or remained unchanged when going deeper into the sediment, suggesting ongoing reaction at the sorption surfaces or much slower desorption than adsorption kinetics. Upon Fe reduction, Fe2+ is released into the pore water where it either directly precipitates and/or adsorbs onto available surfaces of the sediment matrix, including organic matter. Through sorption, authigenic ferrous mineral formation is delayed and Fe2+ may be transported deeper into the sediment. There, sorbed Fe2+ can act as a deep source for authigenic ferrous mineral formation. A simple steady-state model was formulated that includes Fe2+ sorption as a first-order kinetic reaction to estimate Fe reaction rates. Fe oxidation and reduction rates were most intense at the shelf, where organic carbon mineralization rates are high, and decreased with water depth. In the canyon, where deposition fluxes were high, Fe reaction rates increased with water depth until a maximum at the foot of the canyon at 3097 m and decreased again to the abyssal at 4280 m. Turnover times estimated for pore water Fe2+, ferrozine-extractable Fe2+ and solid phase Fe both in the oxidized and reduced layer indicated that sediment mixing was the most important rate limiting factor for Fe cycling at all stations of the Iberian margin. The contribution of Fe reduction to organic matter mineralization was 5% at the 104-m and 113-m stations on the main transect and 6% at the 3097-m station at the foot of the canyon. At the other stations Fe reduction contributed less than 4% to the mineralization of organic matter.

45 References.

No Supplementary Data.
No Article Media
No Metrics

Document Type: Research Article

Publication date: November 1, 2002

More about this publication?
  • The Journal of Marine Research, one of the oldest journals in American marine science, publishes peer-reviewed research articles covering a broad array of topics in physical, biological and chemical oceanography. Articles that deal with processes, as well as those that report significant observations, are welcome. Biological studies involving coupling between ecological and physical processes are preferred over those that report systematics. The editors strive always to serve authors and readers in the academic oceanographic community by publishing papers vital to the marine research in the long and rich tradition of the Sears Foundation for Marine Research. We welcome you to the Journal of Marine Research.
  • Editorial Board
  • Information for Authors
  • Subscribe to this Title
  • Purchase The Sea
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more