Water covers about 75 percent of the planet and since plants are absent from major water sources like oceans; the survival of virtually all marine life solely relies on algae. Algae form food from water and carbon dioxide via photosynthesis, using the sun´s light and converting it into energy.
Since algae are the predominant photosynthetic organisms in the aquatic ecosystem, they form the base of the aquatic food chain. All other non-photosynthetic marine life depends on the presence of algae.
Algae also have various applications outside the aquatic ecosystem. Different species of algae produce extracts like agar, alginates and carrageenans, which have multiple industrial, cosmetic and pharmaceutical applications.