Aquatic invasive species are a primary concern near any body of water, and Lake Michigan and surrounding waterways are no exception. The U.S. Fish and Wildlife Service has identified a new aquatic plant as an invasive species, and one that is posing a threat to the upper Mississippi River area. 
From their news release
“It was speculated that any undiscovered plants would not survive the freezing temperatures of winter and would be eliminated. However, on July 26, 2012, a large infestation of nearly 10,000 plants was discovered in a secluded backwater bay. While the density of plants was alarming, even more troubling was the discovery of an additional plant, Parrot Feather also known as Brazilian water milfoil, among the water lettuce and hyacinth.  Parrot feather is even more aggressive than Eurasian water milfoil and can quickly fill-in an area and choke-out native species.”
Read the complete release at the link above, and find out more about common aquatic invasive plants at our aquatic nuisance species site.