Some of the most destructive invasive species come in small packages. Few come smaller than the spiny water flea, a tiny crustacean with a long, spiked “tail.”

“Spinies” and the more famous zebra mussels change lake ecosystems far out of proportion to their size. At the University of Minnesota Twin Cities, Gretchen Hansen is untangling the web of biological and chemical impacts that these and other aquatic invasive species weave.

“A lot of our research focuses on documenting impacts while also identifying places that are more sensitive or more resilient,” says Hansen, an assistant professor in the Department of Fisheries, Wildlife and Conservation Biology. “We also study climate change and how lakes and fish respond.”

Spinies are part of the zooplankton—tiny animals that drift around with tiny plants called phytoplankton. So are native water fleas, which are eaten by many young fish and, unfortunately, spinies. Spinies afflict lakes large and small, including Lake Mendota in Madison, Wisconsin, and Minnesota’s Lake Mille Lacs.