Harsh Habitat: The Endangered Desert Pupfish

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Several previous posts have discussed the ecological importance of the Salton Sea, particularly its effect on migratory birds. However, the Salton Sea is also home to a much less obvious endangered species, the tiny desert pupfish. Desert pupfish, which are less than 3” long fully grown, are an unusual species due to their incredible tolerance for extreme water conditions. The desert pupfish can survive at salinities of up to 70 g/L—more than double the salt concentration of seawater.[1] This has historically allowed the desert pupfish to live in saline lakes, rivers, and marshes throughout the deserts of California, Arizona, Colorado, Nevada, and Mexico.

Desert Pupfish, Cyprinodon macularius, John Rinne

The Science of Salt

Millions of years ago, dinosaurs walked the Earth and the Salton Trough was at the bottom of the ocean. The Salton Trough was part of the Gulf of California until four million years ago when sediment from the Colorado River built up and closed the gap.¹ Today, there are 150 miles between the Salton Sea and the Gulf of California, but evidence of their former connection can be found in the soil.

The land around the Salton Sea is composed of minerals of marine origin; many of these minerals are salts. A salt is a compound made up of positively (cation) and negatively (anion) charged ions. Sodium chloride, known as table salt, is the primary salt in the ocean and it dissolves readily in water to form a sodium cation and a chlorine anion. Other chemical components of seawater include magnesium, calcium, and potassium cations and sulfate anions. The Salton Sea has many of the ions of seawater in addition to phosphate and nitrate nutrients from fertilizers that are flushed into the Sea.² Together, the total dissolved salt content of a body of water is called salinity.