In what experts are calling a marker of the escalating climate change, scarlet streaks that look like blood have appeared on the French Alps glaciers, turning kilometres of snow into murder scenes.

According to a new study published in Frontiers in Plant Science, the phenomenon known as “glacier blood” is formed by microalgae reacting with impurities and climate change pollutants, resulting in crimson stains.

To better understand alpine algae that creates red snow, a group of scientists in Grenoble, France, conducted the AlpAlga study in the Alps, 3,280 to 9,842 feet above sea level.

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Snow-borne microalgae, like the microalgae that live in seas, lakes, and rivers, help build the foundation of an alpine ecosystem’s food web and are expected to react to pollution and climate change in a similar way, according to Eric Maréchal, a coordinator of the AlpAlga project. Mr Maréchal is also the head of the Laboratory of Cellular and Plant Physiology at Grenoble, France, where he conducts research.

“The algae are probably markers of climate change,” Mr Marechal told LiveScience that the microalgae proliferation is a reflection of increasing carbon dioxide levels and related environmental changes.

“I’ve seen, in my lifetime, the disappearance of ecosystems on a scale not of 100 years, but decades,” study author Mr Maréchal, was quoted by Live Science as saying. “This ecosystem is super fragile.”

According to him, the algae that turn snow red are actually green algae. As the name indicates, green algae are green, but warmer weather causes them to develop an orange or red pigment that functions as an antioxidant — a sunscreen that shields them from the harmful effects of bright light and UV radiation.

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Scientists are familiar with the occurrence of snow coloration since colourful coats have been seen in freezing climates before, while select parts continue to get warmer. However, the questions surrounding these microbes have yet to be solved.

Researchers are currently studying the creatures as part of the AlpaAlga project to see whether they may be used as a biomarker for climate change.