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Benthic iron flux influenced by climate‐sensitive interplay between organic carbon availability and sedimentation rate in Arctic fjords
Author(s) -
Herbert Lisa C.,
Zhu Qingzhi,
Michaud Alexander B.,
LauferMeiser Katja,
Jones Christopher K.,
Riedinger Natascha,
Stooksbury Zachery S.,
Aller Robert C.,
Jørgensen Bo Barker,
Wehrmann Laura M.
Publication year - 2021
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.11885
Subject(s) - fjord , benthic zone , oceanography , arctic , environmental science , total organic carbon , sediment , bottom water , glacial period , sedimentation , biogeochemical cycle , geology , environmental chemistry , chemistry , geomorphology
Benthic iron (Fe) fluxes from continental shelf sediments are an important source of Fe to the global ocean, yet the magnitude of these fluxes is not well constrained. Processing of Fe in sediments is of particular importance in the Arctic Ocean, which has a large shelf area and Fe limitation of primary productivity. In the Arctic fjords of Svalbard, glacial weathering delivers high volumes of Fe‐rich sediment to the fjord benthos. Benthic redox cycling of Fe proceeds through multiple pathways of reduction (i.e., dissimilatory iron reduction and reduction by hydrogen sulfide) and re‐oxidation. There are few estimates of the magnitude and controlling factors of the benthic Fe flux in Arctic fjords. We collected cores from two Svalbard fjords (Kongsfjorden and Lilliehöökfjorden), measured dissolved Fe 2+ concentrations using a two‐dimensional sensor, and analyzed iron, manganese, carbon, and sulfur species to study benthic Fe fluxes. Benthic fluxes of Fe 2+ vary throughout the fjords, with a “sweet spot” mid‐fjord controlled by the availability of organic carbon linked to sedimentation rates. The flux is also impacted by fjord circulation and sea ice cover, which influence overall mineralization rates in the sediment. Due to ongoing Arctic warming, we predict an increase in the benthic Fe 2+ flux with reduced sea ice cover in some fjords and a decrease in the Fe 2+ flux with the retreat of tidewater glaciers in other regions. Decreasing benthic Fe 2+ fluxes in fjords may exacerbate Fe limitation of primary productivity in the Arctic Ocean.