This blogpost was written by Annika Simonson, a senior at Olympus High School who plans to study bioengineering.
If you’ve ever looked into the shallows of Great Salt Lake, you may have noticed knobby, reef-like formations just below the surface. These are microbialites—living structures built by dense communities of microorganisms. Though they might look like simple rocks, they’re critical to brine flies, brine shrimp, and the millions of migratory birds that depend on the lake. As Great Salt Lake continues to shrink, the fate of these microbialites will determine whether the lake’s food web survives.
Photo by Utah Geological Survey
Microbes such as the salt-loving halophilic archaea and the alga Dunaliella salina form dense blooms in Great Salt Lake. Brine shrimp graze on these free-floating microbes, while brine fly larvae feed directly on microbialites—living structures built by microbial communities. In turn, shrimp and fly larvae provide a crucial food source for millions of migratory birds. Without these microbes, the lake’s entire food web would collapse. Great Salt Lake is one of the most vital migratory bird stopovers in the Western Hemisphere, and the survival of countless birds depends on the health of these tiny organisms.
Microbes do more than support the food web—they also recycle key elements, such as carbon, nitrogen, and sulfur, keeping the lake in balance. Dunaliella salina, a green algae, is a carbon producer in the lake, which helps regulate the environment. Halobacterium species, part of the archaea group, use special light-driven proteins to make energy in salty, oxygen-limited zones. Heterotrophic bacteria decompose dead organisms, releasing carbon dioxide and nutrients back into the water and helping keep it clean.
Nitrogen-cycling microbes convert atmospheric nitrogen into ammonia, a form other organisms can use, while also releasing ammonia as they decompose proteins in dead matter. Sulfur-cycling microbes detoxify water and recycle sulfur compounds, producing the familiar “rotten egg” smell. These processes prevent waste from building up and keep nutrients moving through the lake.
In addition to recycling nutrients, microbes have a visible impact on the lake’s appearance. One of the most noticeable things microbes do is change the lake’s color. The lake can turn pink, red, and orange from the pigments that the microbes produce. Some microbes use these colors to protect the algae from UV radiation and salt stress, while others use them to produce energy from sunlight in salty, low-oxygen conditions. Colors are most commonly seen on the north arm of the lake, which has a higher salinity than the south arm. These colors, while beautiful, also serve as a signal of just how active and alive the microbial community truly is.
But as Great Salt Lake shrinks, microbialites are in serious danger. Vast stretches of these living reefs have been left uncovered, exposed to air and sunlight that quickly kill them. Even if water returns, the dead microbialites cannot come back to life, and new ones take years to form. Without microbialites, brine flies lose their main food source, and the ripple effects move up the entire food web.
The survival of microbialites is directly tied to the survival of Great Salt Lake. If the lake continues to decline and salinity rises beyond what microbes can tolerate, the food web will collapse—from brine shrimp and flies all the way up to the millions of birds that migrate here each year. Protecting microbialites is not just about saving strange reef-like structures; it’s about saving the future of Great Salt Lake.
