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Where do algae commonly live?

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Microbiology Photomicrograph of *Streptococcus pyogenes*, a bacterium that can cause scarlet fever. (Magnified about 900×.)

Algae are nearly ubiquitous, inhabiting a vast array of environments across the globe. Their distribution is primarily categorized by their specific ecological habitats.1

Aquatic and Terrestrial Habitats

Water: Planktonic algae grow suspended in water, while neustonic algae reside on the water's surface.1
Extreme Environments: Some species are cryophilic, living in snow and ice, while thermophilic algae thrive in hot springs. Certain algae, such as Cyanidium caldarium, can even survive in highly acidic conditions like hot sulfuric acid.12
Soil: Edaphic algae live on or within soil.1

Associations with Other Organisms

Algae frequently live in association with other life forms:
* Surface Growth: Algae can be epizoic (growing on animals like turtles or sloths), epiphytic (on fungi or plants), or corticolous (on tree bark).1
* Rock Surfaces: They may be epilithic (on rocks), endolithic (in porous rocks or coral), or chasmolithic (in rock fissures).1
* Endosymbionts: Many algae live inside other organisms, including sponges, protozoa, and various animals.13