Algae is a primitive eukaryotic autotroph that uses nutrients and sunlight to survive. Algal species do not differentiate between leaves roots and stems like land plants and they have no true vascular conduction system. Most commonly you might think of algae as a green or brown film found in a lake or pond. However, contrary to common belief, algae can grow in fresh water and in brackish or salt water. In the ocean, one can find both microalgae, on a singular cellular level, like phytoplankton, or macroalgae, on a multicellular level, like seaweed. Algae exists in multiple forms as free living (planktonic), benthic, epiphytic, endophytic and sometimes even parasitic.