organisms that live in thawed areas on the surface of ice or snow and in water filled with sea ice; a drop in the temperature causes cryophiles to become frozen in the ice. These organisms include unicellular algae (which compose the principal mass of cryoplankton) and small animals (several kinds of worms and insects). Mass development of cryophilic algae causes pigmentation of the snow or ice (for example, Chlamydomonas nivalis of the subclass Phytomastigina turns the snow or ice red). The diatomaceous algae that live within the ice in the polar seas color the floes yellow-brown, promoting their thawing and lessening their solidity. Microorganisms that belong to the cryophiles are most often called psychrophilic microorganisms.