Last updated: June 21, 2024
Article
Metals released from thawing permafrost are rusting Arctic streams
NPS
In recent years, air and ground temperatures have abruptly increased compared to the preceding 30-year record, exceeding the freezing threshold for near-surface permafrost. Thawing permafrost can alter stream chemistry through changes in watershed hydrology and biogeochemical cycling in the Arctic. Altered soil saturation, groundwater flow, and warmer soil temperatures enhance microbial and weathering processes, which can change the chemistry of groundwater inputs to streams. The weathering process releases sulfides that lower pH and drives stream discoloration. High levels of iron, nickel, zinc, cadmium, and copper have been found in the infected waters. Iron is what is likely turning the streams orange.
Arctic rivers provide habitat for subsistence, sport, and commercial fisheries. Climate change is already impacting high-latitude fish species, including Pacific salmon, due to the effects of warming marine and freshwater ecosystems. Adding to these stresses, the mobilization of iron and toxic metals to Arctic streams in northern Alaska is degrading water quality and reducing habitat.
The emergence of orange streams in northern Alaska represents an unexpected threat to subsistence fisheries and rural drinking water supplies. Communities in northwest Alaska are isolated and depend socioeconomically and culturally on subsistence foods such as fish, large ungulates, and marine mammals. Our preliminary data suggest that metal mobilization may increase the vulnerability of important subsistence fish species—such as Dolly Varden, chum salmon, and whitefish—to population decline. The metals transported downstream from headwater streams to higher-order rivers may also impact drinking water supplies to rural communities.
Our initial findings indicate that orange streams are an indicator of impaired water quality and are associated with declines in stream biodiversity and habitat degradation. Understanding the magnitude, spatial extent, persistence, and timing of stream degradation may inform management responses by federal and state agencies and adaptation by rural communities and subsistence users.
Metal mobilization from thawing permafrost to aquatic ecosystems is driving rusting of Arctic streams
Abstract
Climate change in the Arctic is altering watershed hydrologic processes and biogeochemistry. Here, we present an emergent threat to Arctic watersheds based on observations from 75 streams in Alaska’s Brooks Range that recently turned orange, reflecting increased loading of iron and toxic metals. Using remote sensing, we constrain the timing of stream discoloration to the last 10 years, a period of rapid warming and snowfall, suggesting impairment is likely due to permafrost thaw. Thawing permafrost can foster chemical weathering of minerals, microbial reduction of soil iron, and groundwater transport of metals to streams. Compared to clear reference streams, orange streams have lower pH, higher turbidity, and higher sulfate, iron, and trace metal concentrations, supporting sulfide mineral weathering as a primary mobilization process. Stream discoloration was associated with dramatic declines in macroinvertebrate diversity and fish abundance. These findings have considerable implications for drinking water supplies and subsistence fisheries in rural Alaska.
O'Donnell, J. A., M. P. Carey, J. C. Koch, C. Baughman, K. Hill, C. E. Zimmerman, P. F. Sullivan, R. Dial, T. Lyons, D. J. Cooper, and B. A. Poulin. 2024. Metal mobilization from thawing permafrost to aquatic ecosystems is driving rusting of Arctic streams. Communications Earth & Environment 5: 268.