Whirligig geyser, Yellowstone National Park. This geyser is situated in Norris Geyser Basin, the hottest geyser basin in Yellowstone. Water emerging here is rich in iron and thus acidic. It flows along a surface channel that is inhabited by specific thermophilic organisms. Chemotrophic bacteria inhabit regions where the temperature is between 50 and 60 degrees celsius. They obtain their energy from iron. In doing so they become coated in rust, which is why these regions are brown. The green areas are thermophilic algae such as Cyandium sp. They live in a temperature range from 38 to 56 degrees celsius.