The red algae are nonmotile, which means they do not move on their own. Found all over the world in mostly marine but also freshwater habitats, red algae depend upon the movement of the water in which they dwell.
Red algae, also known as rhodophyta, which means "red plant", have from 5,000 to 10,000 species, some of which are seaweeds. They derive their red color from a number of pigments, the most important of which is phycoerythrin. They obtain their energy through photosynthesis. Because the red pigmentation is able to absorb blue light waves, they can survive deeper in the ocean than other forms of algae. Some red algae, called coralline algae, contribute to the formation of coral reef structures by secreting calcium carbonate. Red algae reproduce sexually. Water currents carry male gametes to female sex organs, called carpogonium, where they become attached.
Red algae are consumed not only by fish, crustaceans and other marine animals, but also by humans. They are rich in vitamins and protein and easy to cultivate. The Japanese call them nori and use them to wrap sushi. In Britain they are known as laver and are eaten cold as a salad, baked into bread, fried or mixed with oatmeal. Red algae called Irish Moss are used in puddings, ice cream, preserves, and even beer and wine.