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.
Spongites yendoi
On the rocky coasts of South Africa, "Spongites yendoi" is the main algal component of a community of organisms commonly found in the low intertidal zone. A thin layer of this alga tends to cover rock surfaces and seaweeds grow as epiphytes on top. Both the coralline alga and the seaweeds are grazed by the pear limpet and other herbivores. Twice a year, "Spongites yendoi" sloughs off its upper layers but nevertheless seaweeds soon grow again on the exposed surface which is usually kept clean by the feeding activities of the herbivores. Sloughing is probably a means of eliminating old reproductive structures and damaged surface cells, and reducing the risk of surface penetration by burrowing organisms.