Lake Ouachita, Home to Freshwater Jellyfish and Sponges

Lake Ouachita is known for having a population of freshwater jellyfish. These jellyfish are non-stinging and are a rare sight in many freshwater lakes. They are small, often ranging from the size of a penny to about the size of a quarter. While they do have stingers, which they use to incapacitate their prey, they are too small to penetrate human skin.

The jellyfish are most commonly spotted in the warmer months, particularly in August and September, when the water is warm and the jellyfish are most active. They are easy to spot because they give off a whitish or greenish hue, depending on the sunlight. The jellyfish will be floating or swimming gently just below the surface of the water. Often they will surface in large numbers called “blooms”. Sunny days are especially good for spotting jellyfish. They can be seen at depth and floating on the surface from the middle of the lake to the shoreline.

They thrive in the clean, clear waters of Lake Ouachita, which allows them to reproduce in larger numbers. The presence of the freshwater jellyfish indicates a healthy water condition because the adult jellyfish can only exist within the pollution-free zone of pH 6.5 – 7. They consume macroinvertebrates and zooplankton found in the warm waters this time of the year.

Lake Ouachita is also home to freshwater sponges. In Arkansas, only seven species (all Demospongiae) of freshwater sponges have been documented. It was not until 1936 that the first report of a freshwater sponge was documented in Arkansas. Later, in 1951, two additional species were reported. In 1977, five species were reported, and in 2005, three species of sponges were reported. The particular species reported from Lake Ouachita is unknown.

Freshwater sponges typically attach to rocks and trees beneath the water. They are usually a light tan or green color. Some can grow as large as saucers, so don’t be surprised if you don’t run across one or two while swimming, diving, or snorkeling at the lake.