Nature's Snow Cone

Call it 'glacier blood' or 'watermelon snow,' researchers still want to find an explanation.

Winter through spring, the French Alps are wrapped in white snow. But as spring turns to summer, some of the snow takes on bright colors : red, orange, pink. Locals call this ''sand de glacier,'' or ''glacier blood.'' Tourists describe it as ''watermelon snow.''

In reality, the source is algae. In recent years, the algae blooms have increased in alpine habitats all over the world., and while they are poorly understood, the increases are probably not a good sign.

Researchers have begun surveying the algae of the Alps to better grasp which species live there, how they survive and what might be pushing them over the edge.

Tiny yet powerful, the bacteria we call algae are ''the basis of all ecosystems,'' said Adeline Stewart, an author of a new study. Thanks to their photosynthetic properties, algae produce a large amount of the world's oxygen and form the foundation of most food webs.

But they sometimes overdo it, multiplying until they throw things out of balance. They can cause toxic red tides, scummy freshwater blooms or glacier blood.

While it's unclear exactly what brings on the blooms, the color - often red, but sometimes green, gray or yellow - comes from pigments, and other molecules the snow algae use to protect themselves from ultraviolet light.

These hues absorb more sunlight, causing the snow to melt more quickly. They can change the dynamics of the local ecosystems and hasten the shrinking of glaciers. [Cara Giaimo]


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