In a geothermal area water and steam deposit chemicals such as sulfur on the surface. These minerals can provide food for bacteria and algae that can


In a geothermal area water and steam deposit chemicals such as sulfur on the surface. These minerals can provide food for bacteria and algae that can tolerate heat and acidity. This thermal spring, (bottom left) has been colonised by mats of Cyanidium, a red acidophile thermophilic algae. The streamers, consisting of filaments of Cyanidium cells, are covered in minerals giving it a grey colour. They wave in the current of the runoff water at 47 C near its source. These remarkable organisms are probably some of the earliest life forms on earth with fossil evidence from 3500 million YAG and there are many species that vary in form and colour, tolerance to heat and chemicals in the water. Photographed in Krysuvik, Seltun, Iceland.


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Photo credit: © MARTYN F. CHILLMAID/SCIENCE PHOTO LIBRARY / Alamy / Afripics
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