Ecological nightmare in Alaska. Dozens of Alaskan rivers have taken a severe Orange color in recent years, because the melting of permafrost – a permanent frozen layer of the Earth’s surface that covers large areas of the Arctic – has released high levels of toxic metals in waterways; reveals a disturbing new study.

River pollution, which is discrete from space, is a potential ecological nightmare – and it is likely to will get even worse in the coming years, the researchers say.

In the new study, published May 20 in the journal Communications Earth & Environment, researchers identified at least 75 orange rivers and streams in an area the size of Texas in Alaska’s Brooks Range. Most of the affected waterways were initially identified by helicopter surveys of the area.

“The more we flew, we started to see more and more orange rivers and streams,” said study lead author John O’Donnell. “There are certain locations that almost look like milky orange juice.”

Chemical analysis of the rivers revealed high levels of zinc, nickel, copper and cadmium, as well as iron, which is largely responsible for the orange hue of the waterways. The researchers also found that the polluted waterways were unusually acidic: Some of the smaller streams had a pH as low as 2.3, which is about the same as lemon juice or vinegar, according to the US Geological Survey.

High metal concentration and water acidity can both be linked to melting permafrost. As the frozen ground melts due to human-induced climate change, the previously sealed minerals are exposed to rain for the first time in thousands of years, allowing the minerals to dissolve into the rocks and surrounding streams, which feed larger rivers.

Affected habitats are not only visually transformed, but high concentrations of minerals are as well extremely toxic to most aquatic organisms. Researchers are particularly concerned about what the toxic meltwater might do to fish reproduction, which could have major negative effects on US fisheries.