Yellowstone national park has the highest concentration of thermal features anywhere in the world, but it is far from a sterile place as far as living organisms are concerned — even in the hottest of the hot springs, “life has found a way”.
Bands of color in the hot pools reflect the types of microorganisms that live there. Clear blue or bluish green water in the center of the pool bubbles up just below boiling temperature, but cools rapidly toward the periphery, allowing various bacteria to colonize.
Two groups of microorganisms (Archaea and Bacteria) are the foundation of Yellowstone’s thermal ecosystems. By utilizing the chemical elements liberated by steam and boiling water from the rocky matrix, they build vast and deep mats of bacteria that encircle the hot pools, different species existing in different thermal gradients from just below boiling temperature to simply “hot” water.
Types of organisms found in the thermal strata around a hot pool can often be identified by the colors they produce.
Clear blue water with steam and bubbles arising from the surface indicates this pool is probably too hot to support life.
Blue-green (cyano)bacteria are some of the most heat tolerant organisms. The color of the water in the pool is actually a blend of blue reflected light that normally occurs in clear water and the yellow light reflected by the carotenoids pigments of the blue-green bacteria. Higher concentrations of the bacteria are growing next to the pool, giving it a more yellow color.
This is a much cooler pool, indicated by an orange ring of thermophilic bacteria surrounding organisms that reflect dark green to brown colored light. According to the chart above, we might expect organisms like algae, Protozoa, and fungi, rather than just bacteria here.
Ephydrid flies specialize on eating the bacterial and algal mats in the hot pools, although they too (especially their eggs) must be heat tolerant. These consumers in turn attract a variety of predators, like spiders and dragonflies, who must be mobile to escape sudden spurts of boiling water.
Half a dozen dragonflies met their demise at the edge of one hot pool. Perhaps wind blew them into the hot water. The substrate here is not sand or rock, but clumps of bacteria that have formed small columnar structures.
Sometimes the patterns formed by bacterial growth take on the form of familiar (to me at least) structures. This looks just like a huge capillary network, branching off an arteriole on the left.
Or how about this one — what do you see in this accumulation of bacterial growth at the edge of the hot water?
What am I?