A Pleistocene Survivor
The waters around Antelope Island host one of Earth's most resilient creatures, the brine shrimp Artemia franciscana. This small crustacean, reaching only about half an inch in length, is an important species in the Great Salt Lake's unique ecosystem. The lake itself is a remnant of the massive Ice Age waterbody known as Lake Bonneville, which began to recede around 13,000 years ago as the climate warmed. Trapped in the increasingly saline water, the brine shrimp population adapted and evolved in isolation. Today, they thrive in salinity levels ranging from about 3% to 33%, conditions far too harsh for any fish to survive.
Artemia franciscana has a flexible reproductive strategy. When environmental conditions are favorable, with stable temperatures and abundant food like algae and bacteria, females give birth to live young called nauplii. However, when conditions become stressful—such as rising salinity or dropping temperatures in the fall—the females switch to producing dormant embryos encased in a hard shell. These tiny capsules, known as cysts, are the key to the species' incredible durability. The adult shrimp typically die off in the winter, leaving the cysts to repopulate the lake when spring arrives.
Cysts Built for Extremes
The brine shrimp cyst is a biological engineering. Measuring just 200 to 300 micrometers in diameter, each cyst contains an embryo in a state of suspended animation called cryptobiosis. In this dormant state, the embryo can withstand conditions that would be instantly lethal to most other life forms. The hard outer shell protects it from complete desiccation, and the embryo can survive exposure to temperatures over 100°C (212°F) and near absolute zero. The cysts are so tough that they were even taken on Apollo missions to study the effects of cosmic radiation.
This resilience makes the brine shrimp a important part of a global industry. The Great Salt Lake provides approximately 45% of the world's supply of brine shrimp cysts. These cysts are harvested, dried, and shipped internationally, primarily as a high-quality food source for fish and prawn aquaculture. The cysts can be stored for years and hatched on demand, providing a convenient live feed. Back in the Great Salt Lake, these same cysts are the primary food source for millions of migratory birds. Over one million eared grebes, for example, stop at the lake each fall and can consume up to 30,000 brine shrimp per day.