Algae occur in aquatic
(both marine and fresh water), and terrestrial habitat. They are found in damp
places, water bodies, in conditions of extreme temperatures (ice cold or hot
spring), on the barks of trees, on rocks and woods, on moist surfaces of
various places etc. They are associated with other organisms. For example they
may be present inside the tissues of other plants (endophytes), in lichens (as
symbionts), or as epiphytes or parasites.
Example of  Algae (Occurrence)
Example of Epiphytic algae: Oedognium, Vaucheria, Bulbochaete
Example of Epizoic algae: Chladophora on snail
Example of Endozoic algae: Zoochlorella
Example of Parasitic algae: Cephaleuros virescens, Harveyella
Example of Terrestrial: Fritschiella tuberosa
Example of Cryptophytic: Nostoc
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Example of Marine: Fucus, Laminaria
Example of Halophytic: Chlamydomonas ehrenbergii
Example of Symbiotic: Blue green algae in lichens, Cycas, Anthoceros
Found in mud: Chara
Found at the banks of lakes or ponds: Spirogyra or Rivularia
Found in high temperature: Oscillatoria brewis
Found in very low temperature.In snow, providing different colours to snow are:
a) Red snow is caused by Chlamydomonas nivalis
b) Green snow is caused by Chlamydomonas yellowstonensis