Numerous algal species occur in nature. They are commonly found in water (Fresh, marine or brackish). They may either be suspended (Planktonic) or attached and living at the bottom (Benthic). Plankton consists of free-floating microscopic aquatic organisms. Phytoplankton is made up of algae and small plants while zooplankton consists of animal organisms. Some algae grow on damp soil, moist rocks, wood and on tree bark. Algae also exist as endosymbionts in various plants and protozoa. Algae associate with fungi to form Lichens.