Climate change changes the face of the Arctic step by step: forests wander north, the permafrost floor thaws, soils lose their stability. Now there is another dramatic episode. In one of the most remote wilderness areas of North America, crystal-clear rivers once have been turning rusty-orange for several years. But what is behind this unusual phenomenon?
The Arctic is considered one of the last untouched regions of the earth, but even here the climate change leaves visible traces. Ice and snow cover withdraw, previously permanently frozen floors thaw, cold-loving animals have to open up new habitats and heat-loving plant species are increasingly penetrating to the north. These changes bring entire ecosystems out of balance. Even remote wilderness areas are not spared from change.
When clear streams become rusty
Researchers around Patrick Sullivan from the University of Alaska have now observed another serious change in arctic ecosystems in Anchorage. In the Brooks range in the north of Alaska, a huge wilderness area without streets, numerous rivers have been turning permanently orange for a few years. This change on the Salmon River is particularly impressive. He was a crystal -clear wild river until 2018, but in summer 2019 it suddenly turned rust. In order to get to the bottom of the causes and ecological consequences of the phenomenon, the researchers took water samples in several places in the river system and examined them for toxins.
The result: In almost all samples, the concentrations of the metals of iron, aluminum and cadmium significantly exceed the limit values set by the US environmental protection authority. Iron fails as a rusty particle in the water and can deposit on the gill surfaces of fish, where it hinders the oxygen exchange and, in the worst case, leads to suffocation. In addition, the iron -containing water reduces the amount of light that reaches the bottom of the river and nips insect larvae – an important source of food for salmon and other fish. Cadmium, on the other hand, gang into tissues and can damage both the organs and the nervous system of the fish. The food chain also gets into the body of other animals such as bears and birds.
The first observations in neighboring tributaries show how serious the consequences of this metal contamination are. In a source of the Akillik catchment area, the biomass of algae broke down drastically after discoloration of the water, the number of invertebral small animals decreased sharply and young fish disappeared completely, report Sullivan and his colleagues.
Threat to entire regions
But where does all the poisonous metal come from? Such harmful mineral releases are often triggered by mining activities, but there are no in the region. Instead, the researchers suspect that the cause lies in the thawing permafrost. Because this gradually releases minerals, which previously stored under the frozen surface for millennium, including sulfide -rich rocks. “If solved oxygen in the groundwater with newly exposed sulfide minerals such as the iron sulfide mineral pyrite interact, sulfuric acid can arise that leaves metals from the starting material,” the researchers write. As a result, iron, cadmium and co end up in the river water and discolour it. Senior author Timothy Lyons from Colorado State University adds: “As soon as this process has started, there is no back. It is another irreversible change caused by the warming of the planet.”
Particularly dramatic: The Salmon River is far from the only river affected in which these dangerous processes take place. In the meantime, at least 75 other waters have been documented in the Brooks range alone, which also turned orange and have a significant cloudy. Even the rest of the Arctic is not immune. Wherever the right type of rock and thawing permafrost, this process can begin, as the researchers emphasize. “Even here, far from cities and highways, the traces of global warming are unmistakable. No place is spared,” sums up Lyons.
Source: University of California – Riverside; Specialist articles: Proceedings of the National Academy of Sciences, DOI: 10.1073/PNAS.2425644122
