By Lasca Randels
WARSAW — Zebra mussels are small freshwater shellfish, typically the size of a fingernail once they reach adulthood.
But despite their diminutive size, they can cause a significant amount of damage — and once they invade a lake, it’s virtually impossible to get rid of them.
Studies have shown a spike in toxic blue-green algae in some lakes that have been infested with zebra mussels. In addition, pipes, power plants and boats can become clogged by zebra mussels, which cluster together on hard surfaces in water.
Zebra mussels also create a hazard with their sharp shells when they cover seawalls, ladders and pier posts.
Zebra mussels were originally native to lakes in Russia and the Ukraine; however, they were unwittingly brought to the United States and other countries via ballast water that was discharged from ships.
They were initially discovered in the Great Lakes in 1988 and by 1990, zebra mussels were found in all five Great Lakes.
The invasive species spreads quickly and damages lake infrastructure, ecology and recreation. They spread in part when they are transferred to new lakes while attached to boats.
The Lilly Center for Lakes & Streams, which conducts research on the freshwater lakes and streams in Kosciusko County, performed a study on the species last summer.
Between May and August 2019, the Lilly Center for Lakes & Streams installed PVC multi-tiered samplers on piers across 14 major lakes in Kosciusko County.
Of those 14 lakes, 12 have been infested with zebra mussels. Tippecanoe Lake had the highest total, with 75,754 zebra mussels found on one sampler.
Two lakes, Yellow Creek and Beaver Dam, showed no indication of the species.
As far as ways to get rid of zebra mussels in lakes already infested — or at the very least control the zebra mussel population — there’s no easy solution.
Using a chemical control agent to kill zebra mussels could result in harm to other aquatic life or lead to diminished water quality.
Because zebra mussels are “filter feeders,” that consume microscopic organisms, such as algae, in the water, removing algae could result in the reduction of zebra mussels; however, this method would also reduce other organisms that rely on algae.
Several species of fish are known to eat zebra mussels, including the pumpkinseed sunfish, freshwater drum, river redhorse, river carpsucker and smallmouth buffalo.
Dr. Nate Bosch, director of the Lilly Center, addressed this option.
“We do have pumpkinseed sunfish in our lakes and also redear sunfish (also known as the sun perch) as zebra mussel eaters. We have thought of the potential solution with these fish potentially helping control the zebra mussel populations,” Bosch said. “The first step, however, is to establish the baseline zebra mussel populations in our lakes before we would potentially work with the DNR on strategically managing fish populations.”
De-watering of lakes to lower lake levels in an attempt to expose zebra mussels to freezing air temperatures is a method that has been tried in some areas. Individual zebra mussels die within 15 hours when exposed to temperatures of 29 degrees, although clustered mussels are able to survive freezing temps for longer periods of time.
“Zebra mussels can overwinter in our lakes in deeper water that does not freeze,” Bosch said. “The ice layer, often with snow on the top, creates an insulating layer that allows the water beneath to stay unfrozen and allows zebra mussels to survive.”
Until a viable solution is discovered, stopping the spread of zebra mussels to lakes that have not yet been infested is vital.
Because zebra mussels cling to the motors of boats, boat owners should follow specific procedures after removing their boats from lakes.
Boat owners should inspect their boat, trailer and any equipment that has been in contact with water. Bilge water should be drained and all compartments should be opened. The boat, as well as all equipment, should be washed in warm, soapy water. The boat and trailer, as well as any equipment, should be allowed to dry for at least five days before placing the boat into another body of water.
For more information on the Lilly Center for Lakes & Streams, visit lakes.grace.edu.