Invasive species are no strangers to Wisconsin waters. Zebra mussels, round gobies, and aquatic plants like Eurasian water milfoil have taken root in many places, disrupting food chains and threatening native species.
The quagga mussel poses a threat, too.
They’ve now been found in a popular and large Wisconsin inland lake — Geneva Lake.
Last week, a DNR team began investigating the quagga mussel’s prevalence and its long-term impact.
At the public boat launch in Williams Bay, DNR aquatic invasive species biologist Patrick Siwula layered up for a breezy morning. He and a couple of colleagues loaded equipment onto the DNR’s “no-frills” 20-foot flat-bottom workboat.
The purpose of the mission: to learn more about the invasive quagga mussels in Geneva Lake.
“We want to answer some big-picture questions today, like are these at various depths, are they present in deep areas only, shallow only. Are they co-occurring with zebra mussels?” Siwula says.
Here’s the backstory: both zebra and quagga mussels don’t belong here. They’re native to faraway waters, including the Caspian Sea. The mussels made their way into the Great Lakes unintentionally—aboard commercial cargo ships’ discharged ballast water.
“Zebra mussels came into the Great Lakes in the 1980s,” Siwula says.
And about 10 years later, they hitchhiked into inland lakes. For Geneva, the year was 1995.
As for quagga mussels, which are bigger and unlike their cousin, the zebra mussel, that has one flat side—kind of a D-shape—if you place them on their side, they’ll sit flat. "Quagga mussels are curved on all sides,” Siwula says.
Quaggas moved into the Great Lakes in the 1990s. “And we haven’t seen them move inland, at least documented, until now,” he says.
Siwula’s team would be checking for quagga mussels on metal plates.
“They’re called Hester-Dendy—a fancy term for a series of plates that you can hang off a pier or other structures in the lake. The larval zebra or quagga mussels attach to the hard surface and start growing. Then beyond that, some of the stuff we’re going to do today involves a ponar unit,” Siwula says.
Picture one of those grabber machines at an arcade—you try to grab the coolest stuffed animal. In this case, “We lower it to the bottom and it takes a scoop of whatever is on the bottom—sometimes it’s sand, sometimes it’s plants. And obviously, if there are mussels present, we would capture those as well,” Siwula says.
Zebra mussels have already disrupted Geneva Lake’s ecosystem, gobbling up a portion of the foundation of its food chain. Siwula says time—and monitoring—will tell what the addition of the quaggas will mean.
“They’re both filter-feeding organisms, eating the smaller things in the water column—micronutrients, zooplankton, phytoplankton—making them less available for larval fish, insects, and other parts of the food web. Do they compete with each other? Can they grow where zebra mussels are not?” Siwula says.
In other systems, quagga mussels have survived in deeper, colder waters. At its deepest, Geneva Lake is 135 feet.
There’s no stopping quagga mussels here now.
“Once introduced to a water body, there’s currently no control method available on a large enough scale. It’s either cost-prohibitive or the chemicals that would be required are highly toxic to everything else,” Siwula says.
But several organizations have been and continue to look out for Geneva Lake’s health.
Recent UW-Madison graduate Henry Huss interned for one of them over the summer, the Geneva Lake Environmental Agency. In fact, Huss—who grew up on the lake—was the person who spotted the quagga mussels just steps away from this boat launch.
“What we were really doing was looking at the snails and stumbled across a couple of shells that looked out of the ordinary. I’ve been on this lake long enough to know I hadn’t seen that before,” Huss says.
Karen Yancey is the executive director of the Geneva Lakes Conservancy.
“Because it was the first inland lake known to have quagga mussels, I realized that we were going to have to change the way we manage the lake to minimize the damage,” she says.
The conservancy is spearheading a comprehensive lake management plan that will update a 2008 version.
It likely will try to strike a delicate balance. Geneva Lake is a highly popular tourist and boating destination, key drivers of the local economy.
But when it comes to environmental impacts, Yancey says, “All of the invasive species in the lake have been brought in by boats that have been in other lakes and brought them here.”
The conservancy and other partners initiated a Clean Boats, Clean Waters program.
“But we took that a step further, educating property owners around the lake on the importance of clean boats and making sure they’re cleaning out their ballast and other things that have clung to their boats from use in other lakes,” she says.
Yancey says they’ll continue to build on those programs, and she’s counting on the new comprehensive management plan to lead to even greater collaboration among Geneva Lake organizations.
The plan will outline everything from how tributaries—there are 50 that feed into the lake—are impacting its quality, to the density of development and the importance of environmental corridors around the lake.
Yancey says the plan will also look at influences outside the watershed.
“Part of our new management plan is going to call for communication to tourists and visitors to tell them why it’s important that they also help us keep the lake’s water clean for the future,” she says
As for last week’s DNR exploratory survey, biologist Patrick Siwula’s team found quagga mussels, including at depths of 40 feet. They are “co-occurring” with zebra mussels in shallower waters. Based on the quaggas’ size, Siwula suspects they’ve been in Geneva Lake for “multiple years” but have gone undetected until now.
Siwula hopes news of this invasion can help prevent the spread of quagga mussels to more Wisconsin inland lakes.
State law requires boaters to clean, drain and dry their vessels when they move out of a lake.
