(WBIR - Knoxville) Just a stone's throw from Downtown Knoxville, the deep waters of an old rock quarry are now home to thousands of transparent alien invaders.
A bloom of freshwater jellyfish have inundated Meads Quarry Lake in South Knoxville.
"I have several friends that think I'm making this all up," said Stephen Lyn Bales, senior naturalist at Ijams Nature Center. "They tease me about freshwater jellyfish. They are real and they're right here. You just need good timing to find them."
Bales probed the 25 acre lake in a canoe, scanning the surface of the water for a species usually associated with the salty sea.
"To the scientific community, they are called Craspedacusta sowerbii. That's their Latin name. But to the rest of the world, they're 'freshwater jellyfish.' It is the only species of freshwater jellyfish in the entire world," said Bales. "Right now the water is warming up and they're coming to the surface to reproduce."
After a few minutes of searching, Bales bumped into a full bloom of the jellyfish along the steep cliffs of Meads Quarry and captured a few in a clear plastic container. Blasting bright beams of light through the glass revealed all of the seemingly clear water's algae, sediment, and a tangle of translucent tentacles on the tiny creatures.
"The jellyfish are tiny. They're about the size of a penny and they're transparent. They can have up to 300 tentacles that can sting. But they only sting zoo-plankton, tiny little animals in the water. Those are the kind of things we studied in high school biology looking through a microscope," said Bales.
While the jellyfish feed on microscopic creatures, Bales said there is no need for people to fear an excruciating freshwater sting.
"That's usually the first question, 'Will they sting me?' They cannot sting our skin. They don't have enough venom in their tentacles to hurt us to penetrate our flesh. So you can literally pick one up if they get close enough to the surface."
Freshwater jellyfish are native to China and first arrived in the United States around 1907. One theory is the jellyfish polyps were attached to water lilies imported from Asia. For the last century, they've spread to new bodies of water with help from our feathered friends.
"They think they've jumped around the country riding on the legs and feet of ducks and water birds. Now they're in pretty much all of the lower 48 states in North America. They first appeared in this lake [Meads Quarry] in 1997," said Bales. "They can pop up anywhere, which is one of the reasons they're so interesting."
Freshwater jellyfish really thrive in calm waters, such as reservoirs, ponds, and quarries. While the animals are widespread, there is a reason so many people have never seen one. They only look like a jellyfish for a few weeks of their lives.
"It's about a two-year life cycle. Most of their lives, they're in another form. They're down at the bottom, little polyps that are like transparent gelatin and in the shape of a bowling pin that is hollow. Those little polyps have tentacles around a hole at the top of their heads and they feed on the same things they do as an adult. The polyps can clone and reproduce asexually into other polyps down at the bottom. As the polyps grow, it can also develop that classic jellyfish Medusa stage that people recognize. That's their adult stage. It's a lot like a butterfly's final stage of life," said Bales.
And when the water temperature heats up, so does the underwater undulation of jellyfish as they reproduce.
"Boys and girls find each other. She lays eggs and the eggs float to the bottom. And pretty shortly after that, as the temperatures eventually drops, all of the adult Medusas die. Then the cycle repeats with the eggs on the bottom."
Bales says jellyfish are sensitive to pollution, so the large bloom in Meads Quarry is a good sign the water is clean. The stagnant water will serve as a ripe location for eggs take hold and transform 80 feet below, repeating the cycle of life until their next late-summer surge to the surface.
"I think you should care because it simply shows the marvel of life on Earth," said Bales. "Even here at an old industrial site that was heavily used and then treated as an illegal dump site for years, nature can reclaim this place and even attract these incredibly wonderful tiny little creatures called freshwater jellyfish."
As the quarry gives live to something between the solid rocks and the flowing fluids, Bales tells people to take advantage of the opportunity to interact with a joyful jelly.
"These are the most fascinating creatures I can imagine. Just enjoy them," said Bales. "You can rent paddle-boards, canoes, and kayaks out here from River Sports. Paddle out here and see them for yourself. They're 99 percent water and so ephemeral, so you never know when the next chance you'll have to see them. I have not seen them for two years, so I'm excited. It's like seeing old friends again," said Bales.
Bales is writing a book for UT Press called Ephemeral by Nature. Bales said the topic of freshwater jellyfish will be one of the keystone chapters of his book.
While the freshwater jellyfish are generally unable to injure human skin, a Tennessee Wildlife Resources Agency website says there has been one reported case of the creatures temporarily paralyzing a man's vocal cords after he intentionally ate the creatures.
The jellyfish generally do not live long in aquariums. The water must be replenished frequently to prolong their life. Because the typical jellyfish appearance occurs at the end of the animal's life cycle, the creatures inevitably die.
