What ‘Glacier Blood’ on the French Alps Tells Scientists About Climate Change at High Elevations

The red hue is produced by snow algae blooms. The color most likely shields the algae from damaging ultraviolet rays

A photo of a scientists taking a sample of pink colored snow to later analyze
The snow’s red hue may also create a ‘snowball’ effect that harms ecosystems because red-tinged snow does not reflect as effectively as white snow and will melt faster. Jean-Gabriel VALAY/JARDIN DU LAUTARET/UGA/CNRS

In recent years, the French Alps have seen a surge in snow algae blooms. The crescent-shaped mountain range spanning from the coastline of southern France to the edge of the Adriatic Sea is covered in a blanket of snow from winter to spring. In late spring, when the snowfall thaws, the mountain’s snow changes from a colorless hue to alarming shades of deep, rusty red.

Dubbed "glacier blood," the phenomenon occurs when algae rapidly overgrow, and researchers suspect it can reveal how climate change affects high elevation environments like the Alps, reports Dharna Noor for Gizmodo. The study was published in Frontiers in Plant Science.

Algae are a crucial part of the world’s ecosystems. Through photosynthesis, the organism produces 50 percent of the world’s oxygen, reports Cara Giaimo for the New York Times. However, when algae multiply excessively, they can release toxins that poison drinking water, disrupt ecosystems, and cause illness in animals and humans.

Similar to how climate change and pollution fuel algal blooms in the ocean, nutrient-rich pollution delivered to mountains tops via snow or rainfall can cause algae blooms in mountainous regions. Different types of algae can produce various hues of red, purple, and orange. Rising levels of carbon dioxide can also start the algae’s growth, and in turn, intensify the effects of climate change on the surrounding ecosystem, reports Nicoletta Lanese for Live Science.

Researchers suspect that the increasing presence of the "glacier blood" on the Alps is a marker of climate change. As carbon dioxide levels rise during the climate crisis, more blooms may occur, reports Gizmodo. The snow’s red hue may also create a snowball effect that exacerbates global warming because red-tinged snow does not reflect as effectively as white snow and will melt faster, Live Science reports.

However, what causes the blooms is not fully understood. To better understand what species of algae causes the blooms, researchers surveyed five sites in the French Alps for microalgae species in 2016. The elevations of each site varied from 3,280 to 9,842 feet above sea level, reports Live Science. The team took a total of 158 soil samples from the sites, and through DNA analysis, they found that specific kinds of algae thrived at certain elevations.

The algae responsible for causing red snow belongs to the genus Sanguina, which was found at elevations 6,560 feet above sea level. The red hue most likely shields the algae from damaging ultraviolet rays at higher elevations. In comparison, other geneses of algae such as Desmococcus and Symbiochloris were found at lower altitudes under 4,920 feet, reports Live Science.

From the data, the team created a database called AlpAlga on the microalgae’s distributions and species as the mountain’s elevation changes. While the researchers still do not know what may be fueling the overgrowth of algae, the team says their findings are a starting point in identifying the algae's cycle and how the blooms might affect glaciers and snow melt, reports Live Science.

The team plans on tracking algal blooms through various seasons and analyzing the varying gradients between the snow’s changing colors to further explore how the Alps ecosystem may vary due to climate change and track how species distributions change over time, reports the New York Times.

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