Algae help us in fixing carbon dioxide. about half of the carbon dioxide on earth is fixed by algae. They increase the amount of oxygen on earth.They are the primary producers of energy rich components which forms the basic of food cycles of all aquatic animals. certain marine brown and red algae produce large amount of hydrocolloids. Agar, one of the commercial product obtained from gelidium and gracileria are used to grow microbes and in preparations of ice-creams and jellies. Chlorella and spirullina are unicellular algae, rich in proteins and are used as food supplements even by space travellers.