Greek kryos - cold, frost, ice and biontos - living.
Cryobionts - organisms (cryoplankton, some worms, insects, unicellular algae) living on the ice surface, in its cracks, in snow. Permanent inhabitants of very cold places (on or in snow and ice). They include snow chlamydomonads, etc.
Organisms that can exist only at relatively low temperatures are now recognized as a special ecological group and are called cryobionts. Snow protozoa are almost all cryobionts.