Local waters might seem clearer to the naked eye, but the reason behind it could disrupt the food chain and eventually the fish supply.
Zebra mussels, which are spreading throughout the Chain O’ Lakes and the Fox River, filter through a liter of plankton-filled water a day each as they go, said Pat Charlebois, aquatic invasive specialist with the Illinois Natural History Survey and the Illinois-Indiana Sea Grant program.
But those plankton, which fog the water, are needed to serve as the base of the food chain.
“[Zebra mussels] are bad,” Charlebois said. “Because they’re removing particles from the water, some people think the water becomes clearer. Lake Michigan is clearer now, but that is because there’s no food.”
The mussels, named for their brown and cream stripes, are about the size of a nickel and have become more prevalent in inland lakes over the past three to four years, said Mike Adam, senior biologist with the Lake County Department of Health.
They stick to boats with cementlike strength, which is how they spread between bodies of water.
“They’re all over,” said Algonquin resident Phyllis Walters, the McHenry County recorder of deeds. “I’ve been on the river for many, many years, and I’ve never seen anything like this.”
Don Ericson, owner of Ericson Marine in Algonquin, said he noticed their prevalence last fall.
“It’s getting worse and worse, and [they’re] clogging up the water intakes of the boats, especially those that are just sitting in the water,” he said.
The mussels can be hard to remove from boats or equipment, usually requiring a high-pressure wash or even a manual scraping to get them off.
“They’re really coarse,” Ericson said. “You could hurt your hand badly if you scrape your arm on them.”
Charlebois said the shells are very thin, making them easy to break. They then become sharp enough to cut people, which can lead to problems for swimmers stepping on boat ladders or bottoms of rivers or lakes.
One way to prevent their spread is for boaters to clean out their watercraft and let them dry for five days when transferring between bodies of water, Adam said.
“What we’re trying to do is educate people,” he said. “There’s no natural way to get rid of them at this point.”
The mussels originated in the Caspian and Black seas and traveled to the Great Lakes through ships. Once they reached Lake Michigan, local boaters transferred them inland.
“There’s still a lot of unknowns about the long-term impact zebra mussels have on different lakes,” Adam said.
In Lake Michigan, which has had zebra mussels for about a decade, there has been a decline in the shrimplike Diporeia, which many fish eat, said Kristin TePas, with the Illinois Natural History Survey and the Illinois-Indiana Sea Grant program. She added that it’s unclear whether it’s directly related to the zebra mussels at this point.
Charlebois said some companies are working on control methods, but so far the only products that work also kill surrounding plants and animals.
“[For now] we ask people to take precautions,” she said. “And to not spread them.”