an unyielding grip

Summer after summer, Pat Rooney looked out at this revered North Woods lake, hoping the tea-colored waters that lured so many anglers also provided a magical barrier against a creature that might destroy it.

Zebra mussels already were fouling some of the biggest and best known waters in Minnesota, and were spreading throughout neighboring Cass Lake, a popular swimming, boating and fishing lake near Bemidji. While the larvae had appeared in “Lake Winnie,” scuba divers repeatedly failed to find evidence of adult shells – the surest sign of infestation.

http://www.startribune.com/how-the-scourge-of-zebra-mussels-spread-across-minnesota/423913703/