Vernal Pools and Fairy Shrimp

One of the interesting micro ecosystems here at Enchanted Rock are the Vernal Pools up the rock itself. A Vernal Pool is a shallow depression that fills with water after rain.  Most of the pools will only hold water for a few days, but the deeper ones will stay full for several weeks.

Vernal Pool on Enchanted Rock

The deepest Vernal Pools host a tiny crustacean known as Fairy Shrimp. They are similar to Brine Shrimp or "Sea Monkeys" that we might have seen as children. The Fairy Shrimp have a very short life cycle, and their eggs persist in dried out pools for months. The eggs lay in the bottom of dried out Vernal Pools until it rains, at which time they hatch. The shrimp grow quickly and reproduce, laying eggs before the pools dry up. Fairy Shrimp are slow-moving and tasty, and they can't successfully exist in water with fish or other predators. Hence their need for short-lived Vernal Pools.

Vernal Pool with Fairy Shrimp

The Fairy Shrimp can blend into the bottom of the pools. Can you find the three Fairy Shrimp in the photo below?  They look like tiny gray tadpoles.

Fairy Shrimp

Here they are circled.

Fairy Shrimp - circled

Check back for another blog that will discuss life at the Vernal Pools.

Mark