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
At the University of Minnesota Duluth, Donn Branstrator, a professor in the Swenson College of Science and Engineering, has done foundational work on spiny water fleas, their impacts, and what spreads them. And Valerie Brady, a senior research associate and aquatic ecologist in UMD’s Natural Resources Research Institute (NRRI), led a study that showed how they get caught on fishing lines and tackle. (see accompanying video).
NRRI also sponsors projects that include:
- A thorough testing of boat landing self service cleaning stations to find the best techniques for removing aquatic invasive species from the insides of boats; and
- Testing international ship ballast tank treatment technologies to better understand how well they actually kill the hitchhiking critters. Testing is done in a lab near the Duluth-Superior harbor and on ships moving between ports.
- Musseling in on native species
- Zebra mussels are famous for clogging pipes, encrusting equipment, and carpeting shoreline lake bottoms with their razor-sharp shells. But figuring out how they affect species like walleye is complicated, due to their wide-reaching effects on lake ecosystems. Hansen is at the forefront of discovering those effects and their repercussions.
- Much of zebra mussels’ mischief stems from their prodigious ability to filter and clear water. “They can quickly clear an entire small lake,” Hansen observes.
- They do it largely by sucking in and eating phytoplankton, a major food source for native water fleas and other zooplankton.
- “These changes lower on the food chain can cascade up to fish,” Hansen notes. “A few years ago, we published a study showing that young walleye and yellow perch grow more slowly and reach smaller sizes at the end of the year when spiny water fleas or zebra mussels are present.”
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