Center for Limnology grad student Jake Walsh and UW-Madison undergrad Carly Broshat use plankton nets to take samples of Daphnia pulicaria and spiny water flea in Lake Mendota. — Photo: Bryce Richter/UW-Madison

‘Eco’ impact of invasives on Great Lakes underestimated

New research from Wisconsin suggests the negative economic and ecological impacts of invasives in the Great Lakes is dramatically underestimated.

The study from researchers at the University of Wisconsin-Madison found just one non-native species in one inland lake triggered $80 million to $163 million in damages.

“Our study indicates that previous attempts to put a price tag on invasive species impacts haven't come close to the true cost," says Jake Walsh of the UW Center for Limnology and the lead author on the report recently published in the Proceedings of the National Academy of Sciences.

He says the study also might inform the conversation about costs and benefits of the Great Lakes shipping industry. For decades, oceangoing ships have brought tons of cargo and pumped tens of millions of dollars into the Great Lakes economy each year. But the man-made connection between the Great Lakes and the Atlantic Ocean has brought in more than 180 non-native species.

Most studies, Walsh says, have focused only on invasive species that live in the five Great Lakes and looked at direct costs of managing them — like the $20 million spent each year to poison invasive sea lamprey.

Walsh and his colleagues examined “secondary invasions” — places where invasive species have moved since their introduction to the Great Lakes.

For example, the researchers observed that since at least 2009, Madison’s Lake Mendota has been invaded by a voracious zooplankton — the spiny water flea — from Russian lakes. The invader made its way to the Great Lakes in the ballast water of oceangoing cargo ships, moved inland in boats or bait buckets and now feasts on a vital native species of zooplankton, Daphnia pulicaria.

Daphnia would eat huge amounts of algae, creating clear water. Now, however, the spiny water flea is consuming the lake’s daphnia before the daphnia can consume the algae.

Since the spiny water flea's invasion, water quality in Lake Mendota has plummeted and algal blooms are on the rise. — Photo: Steve Carpenter

Since the spiny water flea's invasion, water quality in Lake Mendota has plummeted and algal blooms are on the rise. — Photo: Steve Carpenter

Acting against invasive species

An AmeriCorps team is working with the River Revitalization Foundation through April 22 to remove invasive species from along the Milwaukee River.

An AmeriCorps National Civilian Community Corps team of nine people, dispatched from the North Central Region campus in Vinton, Iowa, is helping the RRF clear Japanese knotweed, garlic mustard, reed canary grass and common buckthorn in three locations along the river.

The crew is using herbicide, chainsaws, handsaws, loppers, wood chippers and brushcutters.

“I am very excited to be serving with the River Revitalization Foundation,” said AmeriCorps member Patricia Peacock of Henrietta, Texas. “It is a great organization. I love learning interesting things about invasive species.”

Interested in environmental activities? Throughout April, WiG will announce Earth Day events and other environmental events at

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