FILE – In this Thursday, Jan. 5, 2006 file photo, a bighead carp, front, a species of the Asian carp, swims in a new exhibit that highlights plants and animals that eat or compete with Great Lakes native species, at Chicago's Shedd Aquarium. Illinois environmental officials will dump a toxic chemical into a nearly 6-mile stretch of the Chicago Sanitary and Ship Canal Wednesday, Dec. 2, 2009 to keep the voracious Asian carp from entering the Great Lakes while an electrical barrier is turned off for maintenance. (AP Photo/M. Spencer Green, File)

(AP) — Fears that giant, voracious species of carp will get into the Great Lakes and wipe out other fish have led to rising demands that the government close the waterway connecting the lakes to the Mississippi River – an unprecedented step that could disrupt the movement of millions of tons of iron ore, coal, grain and other goods.

The dispute could become an epic clash of competing interests: commerce, environmentalists and fishermen.

Michigan Gov. Jennifer Granholm and five environmental groups threatened on Wednesday to sue the U.S. Army Corps of Engineers to force it to temporarily shut three shipping locks near Chicago because of evidence that may have breached the electrical barrier that is supposed to hold them back from the lakes.

The environmental groups went further than the governor and said the Great Lakes and the Mississippi should be permanently separated to avert what Granholm called "."

Col. Vincent Quarles, commander of the Corps' Chicago district, said the agency is considering all options but would not close the locks without first studying the possible effects.

Environmentalists fear that the fish, which consume up to 40 percent of their body weight daily in plankton, could starve out smaller and less aggressive competitors and cause the collapse of the $7 billion-a-year Great Lakes sport and industry.

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