Potential loss of salmonid spawning habitat in the Arctic due to rusting rivers

Permafrost thaw is a disturbance impacting high-altitude and high-latitude environments. In northern Alaska, permafrost thaw is driving the mobilization of metals from soils and degrading the water quality of Arctic rivers. Due to the weathering of sulfide mineral deposits, river reaches can appear orange due to iron oxides either suspended in the water or deposited on the substrate creating the appearance of rusting rivers. A primary concern about rusting rivers is the negative effect on spawning habitat due to increasing metal concentrations above toxicity thresholds in surface waters or altering hyporheic flow. We examined the spatial overlap between spawning habitat of Dolly Varden ( Salvelinus malma) and rusting river degradation in northwest Alaska using a time-series of satellite imagery. Annual overlap between total Dolly Varden spawning area and degraded habitat ranged from 0% to 21% from 1986 to 2024. Spatial overlap of degraded water and spawning habitat varied temporally amongst watersheds. Spatial and temporal variability in the overlap of degraded water and spawning habitat indicates a complex interaction between rusting rivers, fish, and aquatic food webs.