‘New, exotic’ freshwater jellyfish spotted in Alabama lake: What are they?

Several Alabama residents have reported finding freshwater jellyfish in a local lake — raising questions about the origin of the unusual creatures.

“Every year when the water starts to drop we hear of people seeing these cool little freshwater jellies at the lake,” said Lake Martin Life in an Oct. 22 Facebook post.

According to the Alabama Department of Conservation and Natural Resources (Outdoor Alabama), the jellyfish are sometimes seen in “high quality static waters” in the state.

The post had over 600 comments, with many people perplexed about not having previously seen the jellyfish.

“Did freshwater jellyfish just come into existence,” one person asked on the post.

“I was shocked. I didn’t know we had jellyfish,” commented another person. “They are mesmerizing.”

What are freshwater jellyfish?

Craspedacusta sowerbii are the only known species of freshwater jellyfish, according to the National Park Service.

The small jellies — no bigger than a quarter — originated in the Yangtze River in China but have been seen in North America since the 1900s, experts said. However, not much is known about the species.

“Some are important indicators of water quality, and their presence, abundance, and diversity reflect the overall condition of the water body,” the NPS said.

According to the United States Geological Survey, the jellyfish can be found across the United States, especially in the Northeast region. They were first observed in Alabama in 1995, records show.

Claire Kozal, a graduate student at Eastern Michigan University who studies freshwater jellyfish, told McClatchy News the creatures have populated quickly. In Michigan, freshwater jellies were first spotted in 1933, and now they’re in 236 bodies of water throughout the state, she said.

“That’s kind of a crazy number, if you think about it,” Kozal said. “Even in just less than 100 years, they’re in just so many freshwater bodies.”

Researchers aren’t exactly sure how the creatures are being transported, but they think a primary reason is through aquatic plant spread.

In the state, freshwater jellyfish can be observed in both the medusa, or moving, stage and the polyp or hydroid, or fixed, stage, according to Outdoor Alabama.

The medusa stage happens in the late summer through fall, the agency said.

“The only time where you’re going to see the actual Medusas of the jellyfish, or the jellyfish that people usually think of, is going to be from usually around late August through November,” Kozal said. “Usually by that point, people aren’t really looking in the water or swimming at that point.”

Are they dangerous?

While most jellyfish stings are not dangerous, there are some species of jellyfish that can be deadly.

According to Outdoor Alabama, freshwater jellyfish are not one of those species.

Though the jellyfish do sting, it is not strong enough to impact — or be felt by — humans, the agency said.

At this time researchers aren’t concerned with how quickly the jellyfish are spreading, Kozal said.

“It’s just kind of a new, exotic species, but there’s not an exact harm that can be measured at this point,” she said.