Catherine Rusoff
For years, researchers were perplexed when Alaska’s rivers and streams turned orange, but new research points to climate change as the answer.
Scientists suspect the drastic color change is the result of thawing permafrost — which is essentially frozen ground — releasing minerals into crystal clear water, according to a study. to study published Monday in the journal Nature Earth and Environment. The move could threaten drinking water and fisheries in the area.
“These orange streams can be problematic both in terms of being toxic, but they can also impede the migration of fish to spawning areas,” said lead author Jon O’Donnell, an ecologist with the National Wildlife Service’s Arctic Inventory and Monitoring Network. Parks, in a press release. .
Here’s a closer look at what’s happening to Alaska’s water.
Where are the orange streams and rivers?
The impacted water is on federal lands, including Gates of the Arctic and Kobuk Valley national parks, researchers said. Scientists collected samples of affected water from 75 sites in an area the size of Texas in the Brooks Range of northern Alaska. Some of the areas sampled are so remote that helicopters are one of the only ways to access them.
“The more we flew, we started to notice more and more orange rivers and streams,” O’Donnell said. “There are certain sites that are almost like orange juice and milk.”
NPS/Jon O’Donnell
Some of the stained areas are so large that the orange rivers are visible from space, according to Brett Poulin, assistant professor of environmental toxicology at UC Davis and a researcher on the study.
“They need to be very stained to be removed from space,” Poulin said in a press release.
O’Donnell first noticed a change in the water in 2018, but researchers said satellite images recorded stained waters dating back to 2008.
“The problem is slowly spreading from small headwaters to larger rivers over time,” O’Donnell said. “When emerging issues or threats arise, we need to be able to understand them.”
O National Park Service previously singled out Salmon River as a particular point of concern. The water there was “pristine” before 2019. That summer, the clear water turned orange-green. The discoloration has persisted and orange stains remain on the riverbanks.
What is in orange water?
Scientists believe minerals stored in permafrost were released as the climate warmed. Metallic ores were exposed to water and oxygen, causing them to release acids and metals.
Samples showed high or elevated levels of iron, zinc, nickel, copper and cadmium in the impacted water. Iron is one of the most dominant metals and is believed to be behind the orange coloring.
Josh Koch, US Geological Survey
Some of the water samples had a pH of 2.3, compared to an average pH of 8 for rivers, meaning the impacted water is significantly more acidic.
What are some future concerns?
Researchers are still working to understand what is happening to the colored water and what risks there may be to fish stocks and drinking water. The study noted that “stream bleaching was associated with dramatic declines in macroinvertebrate diversity and fish abundance.”
Alaska’s Arctic rivers support a variety of fish that are “critical to subsistence, sport and commercial fisheries,” the researchers wrote. Iron and other toxic metals in the water can threaten these fish.
Metals in water can also impact drinking water supplies in rural areas. Researchers said they could, at a minimum, affect the taste of water, requiring rural communities to improve their water filtration.
“There are a lot of implications,” O’Donnell said. “As the climate continues to warm, we expect permafrost to continue to thaw, and therefore wherever these types of minerals exist, there is potential for streams to turn orange and degrade in terms of water quality.”
Researchers plan to study whether rivers and streams can recover if cold weather promotes permafrost recovery.
