Life at the Limits: Earth, Mars, and Beyond

an educator workshop and fieldtrip

Mono Lake Ecosystems

Reported by: Julie D. Clift, C. Johnson, Mike Marchiondo, Barbara Reng, Brenda A. Wolpa

Driving east from Yosemite National Park, one can see Mono Lake, located in the Long Valley Caldera. Runoff from the Sierra Nevada range fills this 40,000-acre briny, highly alkaline body of water that has no outlet.

Mono Lake is one of the oldest lakes in North America, and may be more than 760,000 years old. Lake deposits cover volcanic deposits of that age, and more lake deposits may be present below the volcanic layers. Over time, the size of the lake has fluctuated greatly in this high desert environment.

Vista View of Mono Lake and Negit Island.

Figure 1. Vista View of Mono Lake and Negit Island.

Chemistry. Temperature, salinity and pH measurements were taken along the shoreline near Navy Beach.

Sample site

Temperature (° C)

Salinity (%)


Shore sample




Freshwater Spring sample




Although the temperature of the water is 23°C, freshwater springs enter the lake at a much lower temperature, 13.8°C.

The reason Mono Lake is so salty is due its placement in the Sierra Nevada Mountain Basin. The factors influencing the salinity of the lake include:

    • Water flows into the lake but not out;
    • Freshwater streams and underwater springs bring dissolved salts and other minerals into the lake;
    • Evaporation is very high, concentrating the salts.

The high concentrations of carbonates make Mono Lake quite alkaline. Because of this, it tastes bitter and feels slippery. Some of the carbonates are deposited in the tufa towers that presently are forming on the lake floor. The alkali flies that inhabit the lake environments actually deposit calcium as a waste product! In addition, occasional volcanic eruptions and the resultant ash have added considerably to the chemical mix;

Sampling the temperature in a freshwater spring.

Figure 2. Sampling the Temperature in a Freshwater Spring.
Note the ”murkiness” of the water where it mixes with the lake water near the dark opening.
This was interpreted to reflect the difference in salinity between the spring water and the lake water.

To make Mono Lake water in your classroom, mix into one quart of freshwater:

Is there any wonder fish can't live in this water? At such high saline levels, Mono Lake is about two times (sometimes more!) as salty as the ocean.

Food Chain. Mono Lake abounds with life. Within its waters are trillions of brine shrimp and the shoreline is covered with billions of black alkali flies. Both organisms feed on microscopic green algae and, in turn, serve as the food source for more than 100 species of birds. Many birds visit the lake each spring and summer along their migratory paths.

Sample of green species of brine shrimp
Sample of brown species of brine shrimp

Figures 3 and 4. A sample of the green (left) and brown (right) species of brine shrimp commonly found in
Mono Lake. Alkali flies are a vital link in the Mono Lakes food chain.

A California gull

Figure 5. A California gull is a common species of bird inhabiting the waters of Mono Lake.

The alkali fly was an important food source for the native Kutzadika people. In their native tongue, "Kutzadika" means "fly-eater." The pupal stage of the alkali fly is rich in fat and protein, with 12-20 calories per larval casing.

Microbial Mat. Along the beach, one can find microbial mats that grow 4–5 centimeters thick. These exist due to the lack of "ecological toothbrushes" that would normally scrape away these microbes from the surrounding sand and rock. The succession of organisms in the mats consist of oygenetic, photosynthetic organisms near the surface, underlying layers of purple organisms that use infrared radiation, and the bottom layer sulfate-producing microbes. Sulfate reducers react with iron to produce a visible black coating that is iron sulfide.

A core sample of the microbial mat found along the marshy shoreline of Mono Lake.A core sample of the microbial mat found along the marshy shoreline of Mono Lake.

Figures 6 and 7. A core sample of the microbial mat found along the marshy shoreline
of Mono Lake is shown. These microbes live in this location, where larger organisms cannot prey upon them.


Studying the extremophiles in the high saline conditions of Mono Lake may be helpful in our exploration and understanding of past life on Mars or current life in the ocean depths on Jupiter's moon Europa. Astronomers believe that Europa's hidden ocean water has a high mineral content.

For more information, resources, and links about Mono Lake, please visit the Mono Lake Committee Web site:



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