Zebra mussels found in Lake Mendota

A section of the UW Hoofers pier, pulled from Lake Mendota in early November, was coated in zebra mussels, an invasive species found in the lake last fall.

Image By: Adam Hinterthuer

Lake Mendota had once been the home for swimming, sailing and fishing, among many other recreational and scenic activities. But since the discovery of zebra mussels in the lake by a limnology lab last fall, the lake’s environment has shifted, resulting in changed food sources for fish and less attractive experiences for water activities at the Memorial Union terrace on a summer day.

Throughout the summer following the zebra mussel discovery, Lake Mendota had become completely invaded by the mussels, with amounts ranging from 10 zebra mussels per square meter to 60,000 in some areas of the lake, which has created an imbalanced ecosystem, resulting in many future changes to the lake’s ecology and aesthetics.

“[The lakes are] the heart of the community. Imagine Madison didn’t have these lakes. Imagine if [the lakes] were one big corn field. I mean, Madison wouldn’t be Madison. The lakes are what make this place special,” said Jake Vander Zanden, a professor at the Center for Limnology and expert on aquatic invasive species.

The zebra mussel population has not reached numbers to fully impact Lake Mendota’s ecosystem yet, so there is no certainty how the zebra mussel invasion will play out except to examine how previously documented zebra mussel invasions impacted other bodies of water.

These invasive species throw off the balance of the food system in lakes and rivers they infect because they are efficient and effective filter feeders, sucking up tiny plants and algae, which in turn, create clearer waters but eliminate food sources for zooplankton, or tiny crustaceans that small fish feed off of.

Zebra mussels will alter the quality and appearance of the water as they filter the water because they allow for blue-green algae to form when they disrupt the food chain of the water system.

“Blue-green algae blooms are in some cases toxic. It’s a special group of algae that create these really bad surface scums, and you say to yourself, ‘I would never swim in that in a million years because that looks like green paint,’ that’s blue-green algae blooms,” Vander Zanden said.

“These invasive species coming in is a huge disruption to the system,” Vander Zanden said, adding that the system will not be the same after zebra mussels fully establish.

The zebra mussel population is too high to be able to eradicate them at this point, Vander Zanden explained. The only option, according to Vander Zanden, would be to poison them, which would in turn, poison the entire lake.

Vander Zanden said that although many species currently thriving in Lake Mendota will suffer due to the zebra mussel invasion, there are several species of fish that will feed off of zebra mussels. Those species may being to thrive.

It doesn’t take much to spread zebra mussels from one body of water to another. Humans, mostly anglers, are the largest factor in their transportation, according to Vander Zanden. He added that it only takes a cup of water in the bottom of a boat or an unnoticed zebra mussel attached to a paddleboard to begin the infestation of an entire lake. People spreading zebra mussels through uncleaned boats and transferring water from infected water sources is what worries Vander Zanden the most.

Madison is a very populated area, with many visitors using the lakes every day, which means there is a high chance that residents and visitors will spread zebra mussels or their larva to other uncontaminated waters.

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