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Yellowstone National Park (Wyoming, USA)
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Yellowstone National Park (Wyoming, USA) contains over 10,000 geothermal features which are evidence of one of the world's largest active volcanoes. Its last major eruption approximately 630,000 years ago created a caldera which spans a large portion of the central area of the Park. Within this caldera, ground water is heated by subsurface molten rock is forced to the surface, and emerges as geysers, fumaroles, hot springs, bubbling mud and similar phenomena. Some of these features have been colonized by a wide variety of thermotolerant and thermophilic organisms and are under investigation by the Thermal Biology Institute at Montana State University, Bozeman, MT. The image above is of Nymph Creek, a thermal (60 degrees C at the source), acidic (pH 2.7) creek, which flows for about 150 meters through a lodge-pole pine forest gradually cooling to about 27 degrees C before it empties into Nymph Lake. Nymph Lake is itself the site of many other small thermal activities. The most striking feature of Nymph Creek is a luxuriant green algal mat along much of the streambed. Near its source, this thermal / acidophilic algal community is primarily composed of Cyanidium caldarium, the most thermotolerant eukaryotic alga known. White streamers of Hydrogenobacter spp. and associated sulphur deposits are found in the hottest regions. Thermal gradients create stable environments for other community members such as Zygogonium sp., a filamentous green alga which can survive temperatures of about 35 degrees C. Diatom blooms are found in the coolest regions of the stream and lake. Samples were collected and images were taken of the community members during August, 2001. Samples were also collected from the Chloroflexus / Synechococcus mats at Mushroom Spring (supplied by Michael Ferris and Dave Ward). This is a thermal, slightly alkaline (pH ~8) pool located in the lower geyser basin of Yellowstone National Park. It has a single effluent channel. The temperature along the effluent channel as it exits the pool is about 69 degrees C and cools to ambient temperatures downstream. At temperatures above about 55 degrees C the spring is dominated by a cyanobacterial mat that is dominated by unicellular, Synechococcus-like cyanobacteria. Bacterial cultures from Dragon Spring (pH 3.1) isolated by Jessie Christiansen were also photographed. This study was conducted in conjunction with the research programs underway at the Thermal Biology Institute. All images are from Nymph Creek unless indicated otherwise. Image of Nymph Creek by D. J. Patterson. Image copyright: D. J. Patterson, used under license to MBL (micro*scope).
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