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Why does Chlamydomonas sometimes make snow appear red?
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Algae
The macroscopic genus of algae known as Acetabularia is commonly called “mermaid's wine glass” because of the distinctive umbrella-like shape of the tips of its stalks.
The phenomenon of red snow is caused by specific algae that thrive in cold environments, known as cryoflora.12
Specifically, the species Chlamydomonas nivalis is responsible for this coloration. These single-celled green algae contain a red pigment called hematochrome. When the algae become abundant in the upper layers of melting snow, this pigment imparts a distinct red hue to the surface. During periods of extreme cold or limited sunlight, these organisms remain dormant, but they bloom when conditions become favorable.2341