Algae; Occurrence

Algae are mostly aquatic organisms. They are present in both fresh and marine water. Algae may also be:
I. Epiphytes: These algae grow on the surface of other plants. (Ulothric)
II. Endophytes: These algae live inside the other plants. (Ulvella leptochaete)
III. Phytoplankton: The free floating algae are phytoplankton. (diatoms)
IV. Sessile: Some algae are attached to the substratum by holdfast. (Chara)
V. Lithophytic: Algae growing on surface of rocks and stones are lithophytic. (Polysiphonia)
VI. Halophytic: Algae growing in water of high concentration of salts as in salt lakes are halophytic algae e.g., Chlamydomonas ehrenbergii, Ulothrix
VII. Thermophytic: The thermophytic algae grow in water of high temperature where other plant forms cannot grow. (Cyanobacteria- Hyperthermae above 70°C)
VIII. Cryophytic: Algae occurring in snow and ice are cryophytic algae.(Chlamydomonas nivalis)
IX. Epizoic: on other animals, e.g., Cladophora crisposa grows on snails
X. Endozoic: Inside the body of animals e.g., Zoochlorellae is found in Hydra.
XI. Parasitic: Some algae can be found as parasites on plants and animals e.g., Cephaleuros is found on leaves of tea, coffee.