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Redox processes impacting the flux of iron(II) from shelf sediments to the OMZ along the Peruvian shelf

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journal contribution
posted on 2023-05-20, 01:08 authored by Croot, PL, Heller, MI, Kathrin WuttigKathrin Wuttig

Iron (Fe) is a limiting nutrient in many regions of the open ocean and can also play a key role in controlling primary productivity in Eastern Boundary Upwelling Systems (EBUS). In EBUS regions, where intense oxygen minimum zones (OMZs) contact the continental shelf, significant iron inputs can result from the supply of Fe(II) from reducing sediments. How much of this iron makes it to the photic zone depends on physical processes mixing over different time scales (minutes to decades) and the kinetics of redox and complexation processes impacting the biogeochemical cycling of iron. In this work we examine the controls on Fe(II) release from shelf sediments across the Peruvian OMZ by measuring Fe(II) and hydrogen peroxide (H2O2) in the water column and benthic boundary layer (BBL) and applying a simple 1D mixing model, with either 1 or 2 layers, where the flux of Fe(II) to the water column is treated as analogous to radon, that the decay rate is constant within the mixing layer. Our modeling approach then allows us to compare our estimated decay rate against published oxidation rates for specific oxidants of Fe(II) in OMZ waters and check the validity of our approach. Our data indicate that throughout the OMZ, Fe(II) decay rates may be partially influenced by H2O2, but it is most likely that nitrate-dependent anaerobic Fe(II) oxidizing (NDFO) bacteria are the main oxidizers. In the secondary nitrite maxima (SNM), abiotic NO2 or biotic-mediated processes may also be important. This work highlights the importance and uses of redox species in understanding biogeochemical cycles in the ocean.

History

Publication title

ACS Earth and Space Chemistry

Issue

4

Pagination

537-549

ISSN

2472-3452

Department/School

Institute for Marine and Antarctic Studies

Publisher

American Chemical Society

Place of publication

United States

Rights statement

Copyright 2019 American Chemical Society

Repository Status

  • Restricted

Socio-economic Objectives

Oceanic processes (excl. in the Antarctic and Southern Ocean)

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