Seaweeds are any of a large number of marine plants and protists in the category of benthic algae. They are macroscopic and multicellular, in contrast with most other algae. Seaweeds are often found in the seashore biome. Taxonomy Seaweeds consist of several groups of multicellular algae: the red algae, green algae, and brown algae. As these three groups are not thought to have a common multicellular ancestor, the seaweeds are a paraphyletic group. In addition, tuft-forming bluegreen algae (C… (More on Seaweed)