Thermophilic Algae and Bacteria

The water shown is very hot and is run-off from the hot spring in the Norris Geyser Basin in Yellowstone National Park. The colors are of thermophilic (heat-loving) algae and bacteria that live in the hot water. Water at temperatures of 167 degrees Fahrenheit and above contain thermophiles that allow the water to retain its blue color. Below 167 degrees that thermophiles are bright yellow or orange and as the water cools to 120-130 degrees (still too hot to touch - a hot tub is around 100 degrees) the colors change to green and brown. These thermophiles can also live in water that is very acidic and must be able to do so when the thermal features produce sulfuric acid (the rotten-egg smell in the geyser basins is the sulfur).