AbstractOver the past 30 plus years, the Arctic has warmed at a rate of 0.6°C per decade. This has resulted in considerable permafrost thaw and alterations of hydrological and biogeochemical processes. Coincident with these changes, recent studies document increases in annual fluxes of inorganic nutrients in larger Arctic rivers. Changing nutrient fluxes in Arctic rivers have been largely attributed to warming‐induced active layer expansion and newly exposed subsurface source areas. However, the ability of Arctic headwater streams to modulate inorganic nutrient patterns manifested in larger rivers remains unresolved. We evaluated environmental conditions, stream ecosystem metabolism, and nutrient uptake in three headwater streams of the Alaskan Arctic to quantify patterns of retention of inorganic nitrogen (N) and phosphorous (P). We observed elevated ambient nitrate‐N (NO3‐N) concentrations in late summer/early fall in two of three experimental stream reaches. We observed detectable increases in uptake as a result of nutrient addition in 88% of PO4‐P additions (n = 25), 38% of NH4‐N additions (n = 24), and 24% of NO3‐N additions (n = 25). We observed statistically significant relationships between NH4‐N uptake and ecosystem respiration, and PO4‐P uptake and gross primary productivity. Although these headwater streams demonstrate ability to control downstream transport of PO4‐P, we observed little evidence the same holds for dissolved inorganic N. Consequently, our results suggest that continued increases in terrestrial to aquatic N transfer in Arctic headwater landscapes are likely to be evident in larger Arctic rivers, in‐network lakes, and coastal environments.
