Were there any snow algae on the Cryogenian ‘Snowball Earth’?

• During Cryogenian global glaciations snow algae inhabited inland and shelf glaciers. • Geochemical biomarkers in Proterozoic rocks provide possible links to carotenoids in modern 'red snow. • Present snow algae communities may serve a an analogue to Cryogenian 'Snowball Earth' terrestrial biomes. Unicellular algae have unique adaptation capacities for primary production in different extreme environments. In Neoproterozoic times (1000–542 Ma) a group of green algae developed evolutionary production and survival strategies like those of modern snow algae, and during the Cryogenian Sturtian and Marinoan global glaciations these algae inhabited ice covered shelves. To what extent snow algae existed on inland glaciers and snow-covered terrains is discussed. Evidence supporting a ‘Snowball Earth’ with terrestrial biomes and snow algae are morphological resemblances between aplanospores of modern cryophilic microalgae (Chlamydomonadaceae) found in high mountains in central Norway and Meso- and Neoproterozoic clusters of organic-walled microfossils and sphaeromorphic acritarchs. Geochemical biomarkers in Proterozoic rocks also provide possible links to carotenoids found in modern ‘red snow’. The abundant and diverse communities of present-day continental snow algae on glaciers and snow fields around the world may serve as a modern analogue to the Neoproterozoic ‘Snowball Earth’ glacial terrestrial biomes.