Seaweed
"Seaweed" is a colloquial term and lacks a formal definition. A seaweed may belong to one of several groups of multicellular algae: the red algae, green algae, and brown algae. As these three groups do not have a common multicellular ancestor, the seaweed are in a polyphyletic group. In addition, some tuft-forming bluegreen algae (Cyanobacteria) are sometimes considered to be seaweed.
Wildlife of Antarctica
Other algae live in or on the sea ice, often on its underside, or on the seabed in shallow areas. Over 700 seaweed species have been identified, of which 35% are endemic. Outside of the ocean many algae are found in freshwater both on the continent and on the subantarctic islands. Terrestrial algae, such as snow algae, have been found living in soil as far south as 86° 29'. Most are single-celled. In summer algal blooms can cause snow and ice to appear red, green, orange, or grey. These blooms can reach about 10 cells per mL. The dominant group of snow algae is chlamydomonas , a type of green algae.