Algae are rich in carbohydrates, many inorganic and organic compounds, proteins, vitamins, etc. In some of the algae these substances are found in large amounts and are, therefore, used as food.
(1) The following members of Chlorophyceae (green algae) are used as food. Ulva (sea lettuce) is used as a vegetable
after drying and salting. Chlorella has a high percentage of proteins and lipids. Besides this, vitamins A and DD are also found in sufficient amounts. It has a very short life cycle and can be grown quickly. These characteristics make Chlorella a suitable food for future generations. It has also been grown easily in over-head tanks and was considered to be very suitable food for space flights.
(2) Members of Phaeophyceae (brown algae) used as food include Alaria, Laminaria, Sargassum, etc. The food value is due to proteins, fats and carbohydrates. They are rich in iodine and, therefore, goitre does not occur in the countries where these are eaten.
(3) Among Rhodophyceae (red algae) the genera commonly used as food are Chondrus (carrageen or Irish moss), Porphyra, Gigartina, Rhodymenia, etc. In species of Porphyra, vitamins C and B12 are found in sufficient quantities.
(4) A blue-green alga (Cyanophyceae) Nostoc commune is eaten as food in China, Java, etc. Another blue green alga, Spirulina is also used these days being very rich in proteins.