What is the significance of algae in the biosphere?

Some algae are simple, unicellular and microscopic, while others are complex, multicellular and tens of meters in length. Algae can be found in lakes, oceans, hot springs, and boiling springs near volcanoes, desert sands, snow, and ice.

Algae are the main source of food and energy for other organisms in aquatic ecosystems. As a major producer, algae form the backbone of the aquatic food web.

Algae also provide the main source of oxygen for other organisms. During the growing season, algae can absorb and synthesize nutrients and trace metals.