In spring, névés (large areas of melting snow) are frequently dotted with bright red patches. This phenomenon, familiar to hikers, is often confused with the ochre coloration caused by sands carried by Saharan winds. In fact, it’s the manifestation of a microscopic living world, mainly made up of microalgae, which populates the snowdrifts, proliferating to the point of changing the color of the snow. This ‘blood of the glaciers’ has been described since Antiquity. The microalgae that dominate this microbial ecosystem were first observed under the microscope by Horace Bénédict de Saussure, from a sample collected in 1760 on Mont Brévent. Although red snows have been documented for centuries, the species that inhabit them are only just beginning to be studied in depth.

As part of CREA Mont-Blanc’s #ScienceSandwich, Eric Maréchal describes how the ALPALGA consortium, which brings together biologists, ecologists, physicists and snow experts from Grenoble University, is tackling this phenomenon. Studies now reveal the existence of a little-known world from mountain peaks to the polar regions. It’s possible to begin to understand what it means to ‘live in a wasteland’. The snow forms a complete ecosystem, probably inherited from the last ice ages, which we are just beginning to decipher, even though it has been weakened in many regions by climate change.

Science Sandwich at CREA Mont-Blanc
at Espace Animation des Houches (27 place de la Mairie 74310 Les Houches)