The Influence of Glacial Cover on Riverine Silicon and Iron Exports in Chilean Patagonia

Helena V Pryer*, Jon R Hawkings, Jemma L Wadham, Laura F Robinson, Katharine R Hendry, Jade E Hatton, Anne M Kellerman, Sebastien Bertrand, Beatriz Gill Olivas, Matthew G Marshall, Richard A Brooker, Giovanni Daneri

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

Abstract

Glaciers are recognised as important sources of bioavailable nutrients, with meltwaters potentially influencing productivity in downstream ecosystems. However, uncertainties about how glacial cover affects riverine nutrient concentrations make it challenging to accurately predict how terrestrial fluxes will change with continued glacial retreat. Using 40 rivers in Chilean Patagonia as a unique natural laboratory, we investigate how glacial cover influences riverine Si and Fe concentrations and infer how exports of these nutrients may change in the future. Dissolved Si (as silicic acid) and soluble Fe (< 0.02 µm size-fraction) concentrations were relatively low in glacier-fed rivers, whereas concentrations of colloidal-nanoparticulate (0.02 – 0.45 µm) Si and Fe increased significantly as a function of glacial cover. These colloidal-nanoparticulate phases were predominately composed of aluminosilicates and Fe-oxyhydroxides, highlighting the need for size32 fractionated analyses and further research to quantify the lability of colloidal-nanoparticulate species. We also demonstrate the importance of reactive particulate (> 0.45 µm) phases of both Si and Fe, which are not typically accounted for in terrestrial nutrient budgets but can dominate riverine exports. Dissolved Si and soluble Fe yield estimates showed no trend with glacial cover, suggesting no significant change in total exports with continued glacial retreat. However, yields of colloidal-nanoparticulate and reactive sediment-bound Si and Fe were an order of magnitude greater in highly glaciated catchments and showed significant positive correlations with glacial cover. As such, regional-scale exports of these phases are likely to decrease as glacial cover disappears across Chilean Patagonia, with potential implications for productivity in downstream ecosystems.
Original languageEnglish
JournalGlobal Biogeochemical Cycles
Publication statusAccepted/In press - 12 Nov 2020

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