Iron and Phosphorus Cycling in a Changing Arctic Watershed

• Main Author: Sutor, Frederick William
• Format: Text
• Language: English
• Published: UVM ScholarWorks 2023
• Subjects: Arctic; Ecology; Iron; Permafrost; Phosphorus; Sorption; Biogeochemistry; Environmental Sciences; Physical Sciences and Mathematics; permafrost; Tundra
• Online Access: https://scholarworks.uvm.edu/graddis/1786; https://scholarworks.uvm.edu/context/graddis/article/2787/viewcontent/Sutor_uvm_0243N_11573.pdf

The Arctic is warming at nearly four times the rate of the global average, with pronounced deleterious effects on the ecosystems that comprise this fragile biome. Permafrost is a definitive feature of the Arctic landscape, but increasing temperatures are now threatening its permanence. As the seasonally thawed active layer deepens, lateral groundwater flows will begin to contact newly exposed soils and increase the delivery of solutes toward adjacent aquatic systems. However, long-term monitoring of the Kuparuk River revealed a significant decrease in phosphorus (P), the limiting nutrient in tundra streams. The prevailing assumption is that tight phosphorus cycling through biotic pathways has restricted interactions with soil minerals, but recent studies have shown that iron(III) oxides may strongly influence phosphorus availability as well. This project seeks to determine how distinct land features in the upper Kuparuk River watershed differ with respect to physicochemical factors that influence iron (Fe) and phosphorus cycling, and their subsequent ability to serve as a geochemical sink for bioavailable phosphorus. We found high concentrations of iron and aluminum (Al) in our soils, but extremely low concentrations of bioavailable phosphorus throughout the watershed. Therefore, the concentrations of potential mineral sorbents that can abiotically sequester phosphate far outweigh the amount of phosphate available in the system at all sites. Furthermore, all study sites had a pronounced ability to rapidly sequester any additional phosphate that we added to the soils in laboratory experiments. Our study shows that abiotic sorption pathways are crucial to phosphorus movement and availability. Sorption processes represent a prominent reactive and retentive mechanism on the landscape, with the potential to buffer any thaw-driven inputs of novel phosphorus and prevent associated ecological impacts. The long-term, significant decline in total dissolved phosphorus concentrations in the upper Kuparuk River watershed may ...