Green Algae Phylum Chlorophyta
Some green algae thrive in snow banks, adding colour to the snow. Species such as Hormidium subtile and Raphidonema nivale form green patches, while grey patches of snow can be caused by the green alga, Mesotaenium berggrenii. Red snow is generally due to the presence of spores of green algal species such as Chlamydomonas nivalis. Green algae also grow attached to ice, adding colour to frozen lakes. Life on snow and ice means that algae must have adaptations to prevent their cells from freezing. Since the free water content in their cells has the highest risk of freezing, algae survive by binding this water to structures within the cell.