El Niño‐driven oxygenation impacts Peruvian shelf iron supply to the South Pacific Ocean.

Rapp, Insa, Schlosser, Christian , Browning, Thomas J. , Wolf, Fabian, Le Moigne, Frederic A. C. , Gledhill, Martha and Achterberg, Eric P. (2020) El Niño‐driven oxygenation impacts Peruvian shelf iron supply to the South Pacific Ocean. Open Access Geophysical Research Letters, 47 (7). Art.Nr. e2019GL086631. DOI 10.1029/2019GL086631.

2019GL086631.pdf - Published Version
Available under License Creative Commons: Attribution 4.0.

Download (5Mb) | Preview

Supplementary data:


Upwelling ocean currents associated with oxygen minimum zones (OMZs) supply nutrients fuelling intense marine productivity. Perturbations in the extent and intensity of OMZs are projected in the future, but it is currently uncertain how this will impact fluxes of redox‐sensitive trace metal micronutrients to the surface ocean. Here we report seawater concentrations of Fe, Mn, Co, Cd, and Ni alongside the redox indicator iodide/iodate in the Peruvian OMZ during the 2015 El Niño event. The El Niño drove atypical upwelling of oxygen‐enriched water over the Peruvian Shelf, resulting in oxidized iodine and strongly depleted Fe (II), total dissolved Fe, and reactive particulate Fe concentrations relative to non‐El Niño conditions. Observations of Fe were matched by the redox‐sensitive micronutrients Co and Mn, but not by non‐redox‐sensitive Cd and Ni. These observations demonstrate that oxygenation of OMZs significantly reduces water column inventories of redox‐sensitive micronutrients, with potential impacts on ocean productivity.

Plain Language Summary

Some trace metals, including iron, are essential micronutrients for phytoplankton growth. However, the solubility of iron is very low under oxygenated conditions. Consequently, restricted iron availability in oxygen‐rich seawater can limit phytoplankton growth in the ocean, including in the Eastern Tropical South Pacific. Under typical conditions, depleted oxygen on the South American continental shelf is generally thought to enhance iron supply to the ocean, fuelling phytoplankton productivity in overlying waters. However, the impact of changes in oxygenation, which are predicted to occur in the future, are not known. The 2015 El Niño event led to unusually high oxygen on the Peruvian shelf, offering a system‐scale test on how oxygen influences seawater iron concentrations. We show that El Niño‐driven oxygenation resulted in marked decreases in iron and other metals sensitive to oxygen (cobalt and manganese), whilst metals not sensitive to oxygen (cadmium and nickel) were unaffected. The measured reductions in iron may have led to decreased phytoplankton productivity.

Document Type: Article
Keywords: Iron, Trace metals, Oxygen minimum zones, El Niño, Eastern Tropical South Pacific, Shelf source
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > SFB 754
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography > Water column biogeochemistry
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2019GL086631
ISSN: 0094-8276
Related URLs:
Projects: SFB754, Future Ocean, OceanLiNES
Date Deposited: 16 Mar 2020 13:15
Last Modified: 23 Apr 2021 09:52
URI: http://oceanrep.geomar.de/id/eprint/49264

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...