Hundreds' discovered near Holy Island in August

By Chris Engle, LCA Freelance Writer

Photo by Kenneth Koski

SOUTH ARM TOWNSHIP -As Kenneth Koski recalls it, his routine snorkeling outing in early August turned surreal when he discovered that the whitish clumps of "dogwood tree fluff" surrounding him in 15 feet of water near Holy Island were living creatures. "I recognized that, whatever they were, they were alive and undulating," Koski said. Undulating, just like jellyfish. Hundreds of them.

But Koski, an experienced snorkeler and SCUBA diver who has spent 30 years exploring underwater worlds of both freshwater and saltwater environments, did not believe his eyes. After some time watching what he described as a silent, underwater ballet, Koski went to his South Arm home and consulted the Internet. What he learned completely altered his understanding of Lake Charlevoix.

Kenneth Koski on the bridge to Holy Island, near where he made his discovery. Photo by Chris Engle

On that day, Koski had come upon a bloom of Craspedacusta sowerbyi - freshwater jellyfish - each one less than an inch across but all with the same traits as their oceangoing cousins: transparent bell-shaped bodies, tentacles, and the telltale swimming motion likened to jellyfish.

The following weekend, Koski returned to the "back bay" area south of the Holy Island bridge with fellow snorkeler, Frank Quinn. Though the jellyfish were fewer in numbers, the men were able to photograph the creatures both in a lake environment and in baby food jars they used to momentarily capture the specimens.

The questions

For starters, C. sowerbyi is not harmful to humans. According to University of Pennsylvania, their stinging cells, called "nematocysts," are too small to pierce human skin, so it's still safe to swim here.

That said, C. sowerbyi is not native to Michigan, nor is it native to North America, where it's shown up in 45 states and in the Canadian provinces of Quebec and Ontario, according to the U.S. Geological Survey (USGS). The species was first found in Michigan in 1933, in the Huron River near Ann Arbor, and soon spread throughout the Great Lakes region.

The species is indigenous to China's Yangtze River valley and its likely their transportation to North America from Asia was an unintended result of the aquatic plant trade. It may have spread across the United States naturally (on waterfowl) or with the help of man (fish stockings). Todd Kalish, fisheries biologist with the Dept. of Natural Resources and Environment in Cadillac, said Koski's report of the jellyfish is the first he'd heard for Lake Charlevoix, but added "it's likely they've been in there for a while." Compared to zebra mussels, milfoil, sea lamprey, goby or other aquatic invasives, C. sowerbyi is generally considered harmless to its environment. Adult jellyfish, or medusa, feed on tiny plankton; while C. sowerbyi in the polyp stage are fixed to the bottom and have been reported to feed on bass larvae in laboratories.

Even so, Jordan River National Fish Hatchery biologist Roger Gordon is worried the jellyfish is "just another mouth to feed."

Photo by Kenneth Koski

"Until we know how that animal is going to fit in and not displace other species, it's always a concern," he said. "Native species are already being pushed, and whatever the jellyfish eat is energy not going into native fish."

Jellyfish "bloom" at a certain water temperature and are in the medusa stage for only a period of days or weeks. Blooms of freshwater jellyfish, like the one Koski came across, are considered by the USGS to be an indicator of good lake health - the canary in the mine shaft, so to speak.

Protection

Koski says the species deserves protection in Lake Charlevoix because it is a rare and "beautiful" spectacle, even for an experienced diver like himself. He wants people to know the jellyfish are fragile - about the same density as water - and reminds boaters the canal between Holy Island and the western shore of the South Arm is a no-wake zone.

"It's a number-one oddity for me," he said. "It's the first time I've experienced a freshwater jellyfish, and its rare you can find something non-indigenous and not be threatened by it. It's the only time I've been truly surprised by an underwater specimen in Lake Charlevoix, and I'd like to see more of them."