|Ijams September canoe group|
The first Ijams guided canoe trip open to the public on Ijams Quarry Lake turned up an oddity, ghostly aquatic apparitions.
I expected we'd see herons and turtles, which we did, but I didn't believe we'd find the rare freshwater jellyfish that pop up occasionally. The medusa's appearance is sporadic and unpredictable from year to year.
Freshwater jellyfish (Craspedacusta sowerbyi) are not native to North America. They first appeared in a greenhouse aquarium in Washington D.C. in 1907. Since then, they've slowly spread across the country and are usually found in calm, freshwater reservoirs, impoundments, gravel pits and old quarries. Ninety years after they were collected in the nation's capital, the jellies first appeared—or were first documented—in Mead's Quarry Lake in 1997. (Retired TVA biologist Bob Terry, husband of Ijams educator Jean Terry, identified them from collected samples.)
Generally, the small jellies appear in their medusa stage during the heat of summer. This is why I didn't expect we'd find them in mid-September on a cool morning. Lynn Keffer, a canoeist in our group, was the first to see one undulating just below the water's surface, virtually transparent and as wispy as morning fog. About the size of a penny, the jellies are clear to slightly milky white. Walter Cromer, another paddler in our group, quickly became attuned at spotting them swimming around our canoes.
They look like water bubbles, bobbing up and down underwater; one of the most ephemeral lifeforms I've ever written about.