An ecosystem is defined as a community of organisms and their environment, interacting physically, chemically, and in regard to energy. The Yellowstone ecosystem includes living animals from bison and grizzly bears to microscopic thermophiles and a physical environment that includes a giant live volcano over a huge reservoir of molten rock, mountain ranges, high plateaus, lakes, rivers and river valleys covering over 18 million acres of Wyoming, Montana and Idaho, forming an area roughly the size of West Virginia. It is one of the largest wild temperate zone ecosystems on the planet.
Some thermophiles thrive not only in extreme heat but also in highly acidic or alkaline conditions, or in solutions of chemicals such as sulfur. The bacteria are thought related to the cyanobacteria, the earliest bacteria to inhabit the planet, and the organismsm responsible for making our atmosphere oxygen-rich. Archeae predate even the cyanobacteria. Both encourage speculation about life forms that might be able to inhabit planets with conditions our species considers severe.The smallest living things in Yellowstone are the most recently discovered. In 1966 Dr. Thomas Brock discovered a bacterium in the Lower Geyser Basin of Yellowstone Park, near Great Fountain Geyser and White Dome Geyser. Three years later they were to name it Thermus Aquaticus, meaning an organism that can live in extremely hot water. Since its discovery, other thermophiles, meaning heat loving, and thermotolerant species of bacteria and archaea, another type of microorganism, have been discovered in Yellowstone’s hot springs, geysers, fumaroles and mudpots. Some form streamers and others live in mats, which may include thermophilic fungi as well, and the varied colors of mudpots are due to thermophiles’ pigments, such as chlorophyll and carotenoids. The latter is similar to the vitamin A that gives carrots their orange color. Species of thermophiles can be identified in the various thermal features by their colors. They can be pink, yellow, black, green, orange or white.
At one time it was thought that all life on Earth depended upon photosynthesis in one way or another, but T. aquaticus and some of the other thermophiles are exceptions to this rule, relying upon processing chemicals to get energy. Some thermophiles change hydrogen or sulfur into forms other thermophiles can use.
Some thermophiles, on the other hand, do photosynthesize, providing oxygen for other thermophiles. Cyanobacteria and non-sulfur green bacteria are among the photosynthesizers.
Around the thermal features of Yellowstone, diatoms are found in the soil. Diatoms make the soil unique, since in other parts of the world they are found only in water environments. Thermophilic fungi and bacteria also inhabit the hot soil around hot springs and other heated water.
In at least one thermal vent at the bottom of Yellowstone Lake, shrimp and worms live in an oasis of moss. The tiny ecosystem was discovered in October of 2010.
A wide variety of lichens and mosses inhabit Yellowstone’s meadows and forests. Lichens colonize rhyolite, a rock formed from magma, and granite, which they gradually break down into soil. Mosses grow on soil, trees, and cracks in rocks, also helping to break down rocks.
Soil bacteria serve to break down waste products from bison and elks, making nitrogen available for growing plants. Grasses are part of the native prairie, and are a favorite food of bison and elk. When mammals graze on the tops of grass plants, the roots become food for soil bacteria, which in turn cause decomposition, making the soil rich for grass and other plants. When the animals eat the grass, carbon is released into the soil, stimulating the growth of microorganisms, giving bison the nickname of engineers of the Yellowstone ecosystem.
Conifers, or pine-producing trees, include whitebark, limber and lodgepole pines, Douglas and subalpine fir, Rocky Mountain and common juniper, and Engleman and blue spruce.There are over 1700 native plants in Yellowstone, and over 170 plant invaders. Deciduous trees and sagebrush inhabit the lower river valleys. Pine forests are found in the middle altitudes and tundra plants live in the alpine zone. Sparse, low-growing tundra plants, grasses, and mosses provide food for mountain goats. Sedges, wildflowers and shrubs provide sustenance for pronghorns, elk and muledeer in the meadows. All the green plants take energy from the sun and convert it to sugar, giving the sun’s energy to the animals of Yellowstone.
Flowering plants provide pollen and nectar that is gathered by the bees and when the plants die they become natural compost for new plants. Plant roots help to prevent soil erosion. When trees die the fungi break them down by decomposition, and a kind of wildflower called a coralroot lives on the fungi.
Whitebark pine nuts provide an important source of protein for grizzly bears, especially for females who can find pines at high elevations where they do not have to compete with male grizzlies and wild boars. Beetles killing whitebark pines could prove a problem for grizzly bears, who might have to rely more upon killing bison to provide the calories and protein they need.
Lodgepole pines form a major part of the coniferous forests, and rely upon fires for reproduction. Their cones are held together with a resin, which must melt at high temperatures to release the pine nuts. Fires can be caused by humans or lightning.
Deciduous trees include cottonwood and aspen, which provide food for the ungulates that are in turn eaten by bears.
Hydrothermal features of Yellowstone can have a devastating effect upon plant life, as illustrated by petrified trees. The trees took in hot water from the soil and were cooked from the inside.
This diverse ecosystem includes two kinds of cactus, one of which is the plains prickly pear, which is most abundant in the Mammoth area.
Beetles, ants, bees, wasps, and grasshoppers are plentiful in Yellowstone. Terrestrial insects sometimes fall into the lakes and streams and become food for fish. They also provide protein in the diets of black bears and grizzly bears.
Species of fish in Yellowstone’s lakes and streams include the native arctic grayling, westslope cutthroat trout and Yellowstone cutthroat trout. Nonnative species include the brook trout, brown trout, lake trout and rainbow trout, and a hybrid fish with cutthroat trout and rainbow trout ancestry also exists. They form part of the diet of bears and humans.
More than sixty mammal species inhabit Yellowstone, from the familiar bison and bears to groundsquirrels. Others include ten species of bats, eight species of hoofed mammals, five species of rabbits, hares, and pikas, five species of shrews, beavers, mice, squirrels, two species of weasels, wolverines, skunks, otters, minks, beavers, badgers, fox, lynx, bobcats, cougars and coyotes.
Habitats within the ecosystem affect where species live. Mammals seen in forests include the following: bears, elk, coyotes, wolves, bobcats, lynx, fisher, martin, mink (near rivers), weasels, wolverines, mule deer, white-tail deer, porcupines, voles, red squirrels, northern flying squirrels, gold-mantled ground squirrels, yellow pine chipmunks, uinta chipmunks, least chipmunks, and snowshoe hares. Meadows are home to: bears, coyotes, wolves, foxes, bobcats, shrews, gophers, voles, mountain goats, and elk. Grasslands are home to: coyotes, mule deer and white-tail deer. Mammals living in shrub lands include desert cottontail and mountain cottontail. Cougars prefer mountains and rocky areas. Bighorn sheep also like mountains, and rocky slopes. Bats roost in trees, caves, sheltered places, and buildings. Water voles, moose, and beavers are found in or near rivers and ponds.
The two species of bears in Yellowstone are the grizzly and black bears. Bears are omnivores, eating both plants and animals. Fish, small rodents, elk, bison, insects, roots, tubers, grasses, berries and pine nuts form most of their diet.
Gray wolves are carnivores, eating elk, field mice and caribou. Wolves were introduced to Yellowstone to control the elk population, which was believed to be overgrazing the aspen trees.
Ungulates such as bighorn sheep, elk, and deer eat grasses and other plants, converting the sugar made by the plants from sunlight into muscles, organs, and fat, which provide nutrition for animals such as wolves, cougars, and bears. When the animals who have eaten other creatures die they return their molecules to the soil as part of the never-ending cycle of life in Yellowstone.
Humans constantly have an impact upon the ecosystem, making decisions as to which species should inhabit the land and to what extent. Introduction of wolves and hunting bison are two examples. The U.S. National Park Service will continue to monitor this ecosystem with the goal of maintaining its delicate balance.