Toxic green slime has taken over the lakes of America. Again.

Algae bloom on Wisconsin’s Lake Tainter. (Photo by Peg McAloon.)

It’s a haunting remake of a 50-year-old tale: The Green Slime that Coated the Midwest. And this rehashed horror story is no work of fiction.

Like the classic film they may have inspired, the toxic blooms of blue-green algae that coated and stunk up the Great Lakes from the 1950s to the 1970s have returned to the region with a vengeance.

The blooms of decades past were fueled largely by decrepit sewage systems that spewed nutrient-rich human waste into the world’s largest body of fresh surface water. The modern remake, by contrast, is the handiwork of corporate agriculture.

Heavy rainfall in the farming region last spring and summer washed vast volumes of agricultural pollution into rivers and lakes, where it fueled poisonous blooms that sickened and disgusted residents and tourists and killed family pets.

Midwesterners describe some of last year’s blooms, particularly those in Lake Erie, as the worst in recent memory. And this year — despite much less rainfall washing into the lakes — is shaping up to be nearly as bad.

“It looked like green mud covering the entire lake,” said Rick Unger, president of the Lake Erie Charter Boat Association and one of 800 charter captains who makes a living from the lake, where shallow waters foster abundant fish and other wildlife. “It makes me sick thinking about it, and I’m sure my customers don’t want to come back.”

As the single-celled creatures that form the algae blooms grow, rot, and die, they poison the water, prevent needed light from reaching aquatic plants, and consume much of a lake’s oxygen.

Unger said the Lake Erie bloom was so “dense and thick” that it slowed down his motor, which spins two feet beneath the water’s surface. It was also so big it seemed to go on forever.

“I went 14 miles straight north out of Cleveland and never got out of it,” Unger added.

Large corn and soy farms are mostly to blame, scientists and activists say, because they rely heavily on large quantities of phosphorous- and nitrogen-rich fertilizer that leach into the lakes, where they feed toxic blooms of cladophora and other nasty algae species. Manure from factory farms only adds to the nutrient load.

Farmers retort by pointing out that many households are also wasteful when it comes to the use of lawn fertilizers, which enter the lakes through storm-water drains.

This year, parts of Lake Michigan have been home to foul thickets of blue-green algae throughout the summer, and a bloom was confirmed last month near the western shorelines of the normally pristine Lake Superior following heavy rainfall.

Health warnings have been issued in 20 states, with residents and visitors cautioned that potent toxins are lurking in the fetid waters.