Travel Reference
In-Depth Information
isms that thrive in environments above 176°F (80°C), are found in the hottest water, while
algae grow best where the runoff water has cooled to about 113-122°F (45-50°C). Their
various colors are due to pigments—such as the yellow-green of chlorophyll—in those or-
ganisms that use light as their source of energy, that is, the photosynthetic ones. The bright
green Cyanidiales order of alga living in a prominent runoff channel in Porcelain Basin
at Norris is an example (picture, page 241 ). Carotenoid pigments may contribute red, or-
ange, or yellow. Another common pigment is melanin, which contributes a dark maroon
or brown color to a relatively low-temperature alga (at about 95°F, or 35°C) called Zygo-
gonium.
Non-photosynthetic bacteria live in the hottest water, while algae and photosynthetic
bacteria occupy the cooler water farther from the hot spring source. Archaea use iron and
precipitate it out. There are so many different families and genera of these tiny beings that
scientists have only begun to find them and study their characteristics.
Microorganisms thrive in the runoff of Firehole Spring (described on page 59 ).
As you travel in Yellowstone, you may notice colors around the hot springs other than
the ones mentioned here. Not all the colors are organic; some are due to minerals. For
example, iron-containing minerals are responsible for various shades of yellow and red
around the acidic springs of Norris Geyser Basin. The pinks that stain some geyser cones
are due to manganese-containing minerals. A great deal of manganese oxide in water will
turn it black. Compounds of sulfur, arsenic, and mercury create some of the reds and yel-
lows. In summary, the colors are due both to the pigments in the microbes and to bio-
chemical processes carried out by metabolism within them, such as the oxidation of iron.
Microorganisms are too small to be seen individually with the naked eye, but the colored
mats formed by countless masses of them appear everywhere in the park, sometimes as fil-
amentous streamers, other times as masses of color adhering to the geyserite and travertine
around the hot springs.
 
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