Thermophilic Eukarya

Dark green algal mats growing in runoff water.
Eukarya, like these waving streamers of Zygogonium live in the extreme environments of Yellowstone.



Plants, animals, and mushrooms are the eukarya most of us know. Millions of unseen, microscopic members of this kingdom exist throughout our world, including in the extreme environments of Yellowstone.

Norris Geyser Basin is one of the best places to see thermophilic algae. Bright green Cyanidioschyzon grows on top of orange-red iron deposits around Whirligig and Echinus geysers and their runoff channels. Waving streamers of Zygogonium are especially easy to see in Porcelain Basin, where their dark colors contrast with the white surface.

From the boardwalk crossing Porcelain Basin, you can also see larger eukarya, such as ephydrid flies. They live among the thermophilic mats and streamers, and eat, among other things, algae. The species that lives in the waters of Geyser Hill, in the Upper Geyser Basin, lays its eggs in pink-orange mounds, sometimes on the firm surfaces of the mats. Part of the thermophilic food chain, ephydrid flies become prey for spiders, beetles, and birds.

A fly rests near a clump of eggs
Ephydrid flies lay eggs in pink-orange mounds, sometimes on the firm surfaces of the mats.



Some microscopic eukarya consume other thermophiles. A predatory protozoan, called Vorticella, thrives in the warm, acidic waters of Obsidian Creek, which flows north toward Mammoth Hot Springs, where it consumes thermophilic bacteria.

Thermophilic eukarya include one form that is dangerous to humans: Naegleria, a type of amoeba, that can cause disease and death in humans if inhaled through the nose.

Although they aren't visible like mushrooms, several thermophilic fungi thrive in Yellowstone. Curvularia protuberata lives in the roots of hot springs panic grass. This association helps both survive higher temperatures than when alone. In addition, researchers have recently discovered a virus inside the fungus that is also essential to the grass's ability to grow on hot ground.

Of all the thousands (if not millions) of thermophilic species thriving in Yellowstone's extreme environments, the eukarya are the group that bridges the world of thermophilic microbes with the larger life forms—such as geese, elk, and bison—that thrive in ecological communities beyond the hot springs.

Green vegetation with sharp, purple points
The fungi Curvularia proturberata lives in the roots of hot springs panic grass.

Thermal Biology Institute, Montana State University


Thermophilic Eukarya in Yellowstone National Park

Name Type pH Temperature Notes Location
Cyanidioschyzon Red algae 0–4 40–55°C (104–131°F) Bright green, photosynthetic metabolism, forms a coating on top of formations or grows in mats Norris Geyser Basin, Lemonade Creek, Nymph Creek
Zygogonium Green algae 0–4 32–55°C (90–131°F) Appears black or dark purple in sunlight, photosynthetic metabolism, grows in filaments and mats --
Naegleria Protozoa (amoeba) Alkaline Warm Predator; can infect humans when ingested through nose Huckleberry Hot Springs, Boiling River
Vorticella Protozoa (ciliate) -- -- Consumer; single-celled ciliate (feathery appendages swirl water, bringing prey) Obsidian Creek
Mutablis Euglenids 1–2 <43°C (109°F) Single-celled, photosynthetic metabolism, moves by waving one or two strands called flagella --
Curvularia protuberata Fungi -- ≤65°C (149°F) with panic grass, <55°C (131°F) without Grows in roots of hot springs panic grass (Dichanthelium lanuginosum), enabling both to survive high temperatures; the plant also produces sugars that the fungus feeds on --
Ephydra sp. Ephydrid fly >2 <43°C (109°F) Nonbiting insect that eats microscopic algae as larvae and adult; prey for spiders, beetles, dragonflies, killdeer Norris (especially Porcelain Basin), Upper Geyser Basin (especially Geyser Hill), Mammoth Hot Springs
Agrostis rossiae Ross’s bentgrass -- 38°C (100°F) One of Yellowstone’s three endemic plant species; may bloom in winter; dries out in summer’s hot air temperatures Banks of Firehole River, Near Shoshone Lake
Warm springs spike rush, with some Tweedy’s rush Rush plant Acidic Warm Forms thick floating mats, which also provide habitat for thermophilic algae and other thermophiles Obsidian Creek
Archaea are found in place like the mudpots of Mud Volcano.

Thermophilic Archaea

Archaea are the most extreme of all extremophiles.

Traverine terraces of Mammoth Hot Springs host thermophilic bacteria.

Thermophilic Bacteria

Almost all hot springs and geysers host thermophilic bacteria.

Blue waters of Congress Pool are host to thermophilic viruses

Thermophilic Viruses

Viruses, a logical part of thermophilic ecosystems, have been found in some pools in Yellowstone.

Orange-colered bacterial column growing in geyser runoff water.

Thermophilic Communities

Thermophilic communities are very diverse, depending on the microbes living there, the pH, and the water temperature.

View of the

Thermophiles in Time & Space

Yellowstone's hydrothermal features and thermophilic communities are studied by scientists searching for evidence of life on other planets.

A dark blue hot spring with a white crested edge rimmed by orange water

Life in Extreme Heat

Hydrothermal features are habitats for microscopic organisms called thermophiles: "thermo" for heat, "phile" for lover.

Last updated: August 23, 2017

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