Distribution

Although most algae are found in bodies of water, many microscopic species, which require only a thin film of moisture, can exist on or in the soil, on damp rocks, and on trees. Some microscopic algae are found on aquatic animals and plants. A few species of algae that lack chlorophyll live in the digestive tracts of animals (including humans) or inside plants.

Most multicelled algae grow at the bottom of bodies of waterusually near the shore. However, multicelled marine algae have been collected from depths as great as 884 feet (269 m). Multicelled algae also grow attached to various submerged objects, such as twigs and rocks. A few species of multi-celled algae are free-floating; for example, those found in the Sargasso Sea.

Most single-celled algae are free-floating. Some species, however, grow attached to rocks or trees along the shoreline, or on submerged objects.

Algae are found in a variety of temperature ranges. Some grow on ice and snow; others thrive in hot springs where the water temperature exceeds 180 F. (82 C.). Some algae are adapted to live in turbulent waters, while others live in the intertidal zone (the area between the high-tide line and the low-tide line) of seacoasts, where they are exposed to dry conditions for at least a few hours each day. A few species of algae live in close association with organisms called fungi, forming lichens. (S