In the French Alps, mountain tops are often covered with pristine snow. But when summer comes, the snow is adorned in some places with orange-red hues. Some have called this phenomenon “the blood of the glaciers”, others preferred the more sober “snow watermelon”. But it seems that the mystery has finally found an explanation.
According to a team of researchers, whose findings were published in the journal Frontiers in Plant Science and relayed by the New York Times, this color is explained by the presence of snow algae. These algae, normally invisible, take on brighter colors in summer. The Sanguina variety, which colors the snow red, however, was only spotted from an altitude of 2000m, which is why you may never have noticed anything in summer if you had not climbed. so high.
Where do these snow algae come from?
In their conclusions, researchers from CNRS, CEA, Météo France, INRAE and the University of Grenoble explained that the red color comes from pigments and other molecules that snow algae use to protect themselves from the rays. ultraviolet, like a kind of sunscreen. Although they do not yet know in what proportions, scientists say that these algae absorb more sunlight, which would melt the snow faster and accelerate the melting of glaciers.
Eric Maréchal, research director at the laboratory of cellular and plant physiology in Grenoble, confirms to the Parisian that “the red color of snow is problematic for the environment”. “It reflects less solar radiation, heats up and melts faster. In areas without glaciers, this shortens the duration of snowfall, with cascading consequences on the supply of dams or agricultural irrigation in the plains. paradoxical: the more microalgae multiply, the more they contribute to the disappearance of their environment. “
“In recent years, alpine habitats have experienced a proliferation of these algae,” notes the New York Times. “And that’s not a good sign,” he concludes. On paper, however, seaweed is very useful. “They produce a large amount of the world’s oxygen,” explains Adeline Stewart, one of the study’s authors and teacher at the University of Grenoble Alpes. “But they can sometimes throw things off balance.”
In the future, the researchers hope to be able to identify all the species of microalgae inhabiting the snow. They also want to understand what causes their proliferation, if it is global warming or other phenomena related to agriculture for example.