Environmental Controls on the Cycling of Fe and Mn in Patagonian Fjord Systems
Piret, L.; Hawkings, J.R.; Hopf, L.; McCabe, D. (2025). Environmental Controls on the Cycling of Fe and Mn in Patagonian Fjord Systems. JGR: Biogeosciences 131(1): e2025JG009378. https://dx.doi.org/10.1029/2025JG009378
In: Journal of Geophysical Research-Biogeosciences. AMER GEOPHYSICAL UNION: Washington. ISSN 2169-8953; e-ISSN 2169-8961, more
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| Author keywords |
biogeochemistry;fjord;Patagonia;sediment;fe;Mn;organic-matter;surface sediments;proglacial lakes;glacial erosion;iron;transport;manganese;kinetics;river |
| Authors | | Top |
- Piret, L., more
- Hawkings, J.R.
- Hopf, L.
- McCabe, D.
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| Abstract |
Fjord sediments are important reservoirs and conduits of potentially bioavailable iron (Fe) and manganese (Mn). Both elements are critical to life, serving as key reactants in metabolic pathways, and play an important role in the reactivity and burial of organic carbon. Once deposited in marine sediments, these micronutrients undergo cycling through abiotic and microbially driven redox reactions. Here, we investigate the primary controls on the distribution, partitioning, and cycling of extractable Fe and Mn within fjord sediments from Chilean Patagonia. Sequential chemical extractions of samples from sediment cores covering a range of environmental variables reveal that active redox cycling in Patagonian fjord sediments leads to Fe and Mn enrichment in surface sediments comparable to or exceeding those in Arctic fjords. The main factors controlling Fe and Mn distributions were: grain size; sedimentation rate; bedrock lithology; local oceanography. Mobility indices reveal a decoupling in the behavior of Mn and Fe. Mn shows greater mobility, particularly in the most labile phase, which is attributed to faster reaction kinetics and much slower oxidation compared to Fe. While diagenesis is thought to obscure paleo-signatures, we identify the preservation of seemingly intact Fe and Mn phases beneath instantaneous deposits. Our findings suggest that integrating sedimentological analyses offers new insights into benthic fjord sediment diagenesis and may help infer past redox conditions. Ultimately, by connecting biogeochemical patterns to glacially-driven controls on sedimentation in marine systems, our work provides a framework to better predict how benthic micronutrient cycling and carbon burial will respond to future climate change. |
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