The snow algal flora is thought to be dominated by
chlamydomonads, a group of green algae characterised by single
cells with two flagella at their anterior ends. However, species
from other algal groups are also important and the dominant alga
in many of the glaciers around the world is a saccoderm desmid
Mesotaenium berggrenii, an alga that colours the snow grey.Many
of the snow algal species go through a complicated life cycle
involving vegetative and or motile cells which are usually green
in colour and immotile spores or cysts which may be red, orange
or yellow green in colour. The green vegetative cells give rise
to green snow and the red and orange snow are generally caused
by the spore stages of the snow algae although some snow algae
may be red-pigmented in their vegetative state. These pigments
protect the cells from high light and UV radiation damage during
the summer months. The pigments may take the form of iron tannin
compounds, as in M. berggrenii, or orange to red-pigmented
lipids as in the maj