In a startling turn of events, some of Alaska’s pristine, icy blue waterways have transformed into a striking rust orange hue, a change so intense it can be observed from space. According to environmental toxicologist Brett Poulin from the University of California (UC) Davis, “The stained rivers are so big we can see them from space. These have to be stained a lot to pick them up from space.”
The phenomenon was first observed in 2018 by National Park Service ecologist Jon O’Donnell and his colleagues, who noticed the discoloration during river bank inspections and fly-overs. Using satellite imagery and public reports, the team identified over 75 remote streams across nearly 1,000 kilometers (1,610 miles) of Alaska’s Brooks Range that have recently turned an unusual orange color.
“There are certain sites that look almost like a milky orange juice,” O’Donnell described. “Those orange streams can be problematic both in terms of being toxic but might also prevent migration of fish to spawning areas.”
Samples collected from these waterways between June and September 2022 revealed high concentrations of iron and other toxic metals, such as zinc, copper, nickel, and lead, compared to nearby healthy streams. In some cases, these pollutants increased the water’s acidity from a usual pH of 8 to a highly acidic pH of 2.3. Poulin noted that the results resemble acidic mining runoff, yet no mines are located near these areas.
By examining satellite imagery from 1985 to 2022, O’Donnell, Poulin, and their colleagues determined that this phenomenon has only emerged in the last decade, coinciding with warmer weather and increased snowfall. “Our working hypothesis is that the thawing of permafrost soil is allowing water to infiltrate deeper and interact with minerals that have been locked away for thousands of years,” Poulin explained.
The Arctic is warming about four times faster than the rest of the planet, causing frozen ground to melt, increasing microbial activity, and leading to ‘shrubification’ – with new plant roots further disturbing the soil. These processes expose previously protected minerals to weathering and displace them into watersheds.
“Climate change and associated permafrost thaw appear to be the primary drivers of stream impairment,” the researchers concluded. The discoloration of streams was linked to significant declines in macroinvertebrate diversity and fish abundance, threatening not only wildlife but also local communities that rely on these streams for drinking water and subsistence fishing.
O’Donnell and his team are continuing their investigation to understand the broader ecological impacts on the region and predict when and where the toxic orange taint might occur again. “There’s a lot of implications,” O’Donnell said. “As the climate continues to warm, we would expect permafrost to continue to thaw, and so wherever there are these types of minerals, there’s potential for streams to be turning orange and becoming degraded in terms of water quality.”
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Reference: https://www.sciencealert.com/alaskas-pristine-waterways-are-turning-a-shocking-orange
