Invasive species in lakes Mendota, Monona, Waubesa - WKOW 27: Madison, WI Breaking News, Weather and Sports

Invasive species in lakes Mendota, Monona, Waubesa


MADISON (WKOW) -- They're not known for being pristine. Madison's lakes and the presence of algae go hand in hand.

Yet when UW limnology professor Jake Vander Zanden and his students cast a net into Lake Mendota's University Bay ten days ago, they got quite a surprise.

"They handed it to me, I looked at it, and something didn't look right," said Vander Zanden on Monday.

He held up a vial of what they found. It contained samples of the spiny water flea.

"Soon it was apparent that the lake was infested with spiny water flea," he said.

That's a concern to people like Vander Zanden. The water fleas feed on the small creatures that eat algae.

"If they become very abundant, I would say abundant enough to reduce the levels of those other plankton, I would expect to see reduced water clarity, more algae."

The small, sharp crustaceans are native to Europe. It's believed cargo ships brought them to the Great Lakes in the 1980's. It's thought from there, they've latched onto small boats, where they wound up here.

This discovery happens as state lawmakers this year followed Dane County's lead, and banned phosphorous fertilizers.

Another bill would ban dishwashing detergents with phosphates. The policies are meant to decrease the amount of algae and weeds in the lakes.

Of those policies, Vander Zanden said they're "not futile, but this is working against those."

This small and sharp water creature could cloud the plans to clear up Dane County's lakes.

"Now we have an invaded lake, we need to make sure that the Madison chain doesn't become source for infesting other water with this nasty critter."

So how concerned are lake experts about this? The Department of Natural Resources has already started its own study of Wisconsin lakes. That group of students at UW-Madison will start a similar study this fall.


What they do know is that since that invasive species was found in Lake Mendota, it has since been found in lakes Monona and Waubesa.

Studies of the spiny water flea in other lakes in North America have shown different results on whether or not it increases the algae load.

Email Carl Agnelly at

Follow Carl Agnelly on Twitter.

Read Carl's Good to be Green blog.


MADISON (WKOW) -- The Department of Natural Resources and a team of UW-Madison students are set to begin separate studies of lakes in southern Wisconsin following the discovery of a new invasive species.

On September 11, a team of limnology students cast a net into Lake Mendota's University Bay and pulled out spiny water fleas.  The discovery was a shock to limnology professor Jake Vander Zanden.  The invasive species had earlier only been seen in Lake Michigan and portions of Ontario, Canada.

The spiny water flea is a small crustacean that feasts on zooplankton in the lakes.  Because zooplanton normally eat algae, there's now concern that the presence of the water flea will worsen the Madzooplankton' notorious algae blooms.

Vander Zanden said since the discovery two weeks ago, the species has also been detected in lakes Monona and Waubesa.

Carl Agnelly is looking into the implications this discovery will have on boaters, as well as policies already in place that were designed to decrease the algae load.

Email Carl Agnelly at

Follow Carl Agnelly on Twitter.

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