Caldera chronicles: Hot springs' pigments vary depending on water temperature, chemistry

Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week’s contribution is from Jeff Havig, a researcher in Earth and Planetary Science, and Plant and Microbial Biology, at the University of Minnesota.

Hot springs are natural laboratories that allow us to explore how life is able to adapt and thrive in what humans consider to be extreme conditions. Heat tolerance, especially, is something that researchers have learned much about over the past 150 years of study in Yellowstone National Park. Members of Bacteria and Archaea (two of the three domains of life) have been found alive and thriving in the hottest vents in Yellowstone, which are literally boiling, while members of the Eukarya (the third domain of life, and to which all fungi, plants and animals belong) can survive up to around 60°C (140°F).

For hot springs with source water that is above the temperature limit for photosynthesis, you can see the point at which the water temperature crosses the photosynthetic limit threshold with the sudden and dramatic appearance of bright pigments (usually greens and yellows) in the outflow channels. For example, the outflow channel of the alkaline (basic pH) Sapphire Pool in Biscuit

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