Algae live in bodies of water and damp places and are commonly found in both aquatic and terrestrial environments. Terrestrial algae mostly live in moist, tropical areas. They prefer wet places, because they do not have vascular tissues and the other necessary adaptations to survive on land.
Algae thrive and grow in nearly all habitats across the world. Most unicellular algae dwell in water but some live in moist soil. Other types of algae join with fungi to form lichens. Examples of nonmarine habitats include hot springs, farm dams, bogs, marshes, swamps, lagoons, lakes, mud, sand, ponds, rivers, reservoirs, rocks, snow, sewage, streams and soil. Additionally, they grow on the branches, trunks and shade sides of trees; the surface and inside of leaves; and damp walls.
They also grow on animals like alligators, crustaceans, worms, rotifers, snails, turtles, aquatic ferns and freshwater sponges. They can also live on and inside water plants, including other algae. When there is sufficient available moisture, they grow and flourish.
Algae have the ability to convert sunlight into energy. They have chloroplasts that absorb light and produce oxygen via photosynthesis. Cyanobacteria and photosynthetic algae produce 75 percent or more of the oxygen in the atmosphere and are very useful. However, they can grow in large numbers known as blooms or red tides, which affect the plants and animals in the water.