Page 5 - Impact Fall 2024

On the water front: invasive lake species
Gretchen Hansen, assistant professor in the
Department of Fisheries, Wildlife and Conservation
Biology, is combatting invasive species like spiny water
fleas and zebra mussels that threaten Minnesota’s lakes.
These tiny invaders dramatically alter ecosystems by
disrupting the food chain, impacting species like walleye
and yellow perch.
Spiny water fleas, part of the zooplankton community,
consume native water fleas, depriving young fish
of a major food source. Zebra mussels filter out
phytoplankton, further depleting the food supply. “They
can quickly clear an entire small lake,” Hansen says,
underlining their effects on fish growth and survival.
Hansen’s research also shows how zebra mussels
increase water clarity, which hurts walleye by removing
their competitive advantage in low-light conditions. She’s
investigating the long-term effects on walleye survival and
how zebra mussels contribute to the production of toxic
methylmercury.
Hansen is also involved in early detection efforts,
including using environmental DNA (eDNA) sampling.
She highlights the role of citizen volunteers in aiding
detection: “Volunteers collectively did about as well
as the professionals,” Hansen notes, emphasizing the
importance of community involvement in protecting
Minnesota’s lakes.
Taking a stand for trees: rebuffing the emerald
ash borer
In Robert Blanchette’s lab, researchers are developing
treatments to combat the emerald ash borer (EAB), a pest
threatening Minnesota’s ash trees. “There are at least a
billion ash trees in Minnesota. We have to use everything
we can to stop this insect,” says Blanchette, emphasizing
the scale of the challenge.
Blanchette, a professor in the Department of Plant
Pathology, and his team are using biological methods,
such as fungi, to combat EAB without the need for costly
tree removal. Graduate student Colin Peters is testing
fungal species that infect adult borers, aiming to disrupt
their life cycle and reduce the impact on Minnesota’s
forests, particularly black ash trees significant to
Indigenous cultures.
Other efforts include research into “associational
protection,” which may preserve urban ash trees
by treating only a subset. Blanchette’s team is also
collaborating with the Minnesota Department of
Agriculture to prevent invasive fungi from spreading in the
state, focusing on early detection in nurseries and efforts
to protect Minnesota's conifers. “It’s taken the University’s
expertise to put together projects so we can control
invasive species before they cause enormous damage to
our natural resources,” he says.
 Scan for the full story or visit
z.umn.edu/impact-invasives.