Invasive species may be key to understanding death of hundreds of loonsby Dan Kraker, Minnesota Public Radio
DULUTH, Minn. — Spring is in the air, with daylight savings taking effect on Sunday, and loons will begin their migration back to the north woods in less than a month.
Loons, of course, are a cultural and natural icon, not only in Minnesota but across the Great Lakes states. But last fall, nearly 900 loons died while migrating south across Lake Michigan, probably more. And it's likely at least some were from Minnesota.
Scientists are not sure what killed the loons, but they suspect that invasive species may be to blame.
In October, Lynette Grimes was hiking toward Lake Michigan at Sleeping Bear Dunes National Lakeshore, outside Traverse City, Mich. The 52-year-old from the nearby town of Benzonia has walked the beaches there for years. But she wasn't prepared for what she saw. ...
The scientists offered an idea about what might have happened: Invasive zebra and quagga mussels filter the water so it's incredibly clear, allowing an algae called cladophora to grow in huge amounts. Big storms churn up the algae, which settles to the lake bottom and rots. That creates an environment without any oxygen, an ideal home for bacteria that produces a deadly toxin called Type E botulism. That botulism is ingested by invertebrates, tiny worms and freshwater shrimp. And then it works its way up the food chain. They are eaten by fish, including the invasive round goby, which are then eaten by diving birds like loons. ...
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Image: J.M. Kosciw