They quietly invaded the Great Lakes a few years ago aboard ships and have rapidly multiplied into swarms that now threaten to choke off the water supply and squeeze out rival aquatic life nationwide.
It has the ring of a sci-fi matinee, but it is real - the thumbnail-size invader called the zebra mussel. The first of these shellfish were unwanted imports from Europe, dumped with the ballast of visiting freighters. They have a penchant for clinging with an iron grip to just about anything, and their multiplication rate puts guppies to shame.They attach themselves to smooth surfaces, such as the inside of intake pipes carrying water from the Great Lakes to homes, power plants and industry. The shells accumulate by the millions, clogging the pipes and restricting the water flow.
Now it seems even nuclear power plants are feeling the pinch.
Nuclear plants draw less water than coal-fired plants, but they pose a much greater risk. The mussels reproduce in the submerged intake pipes that send water to replenish the nuclear plants' critical cooling systems.
Experts note that nuclear plants have elaborate contingency plans to avert possible disasters, and the mussels are not now threatening to cause a meltdown. But the buildup of the pesky shells nevertheless requires action to prevent clogged pipes that could shut down a plant.
Some plant operators are working against time as they join other industries in seeking a way to curb the foreign interlopers.
"These (power) plants are up against a wall. They've got to do something and they've got to do it fast," Ohio State University biologist Fred Snyder told our associate Dan Njegomir.
Lake Erie is infested with zebra mussels, and the Perry nuclear plant near Cleveland draws water from the lake. The plant is one of several that is seeking permits to fight the mussels with chemicals in the water. Another method is to blow the mussels off with high-pressure water guns.
"We're still new at this," a Perry plant engineer told us. "We're seeing a definite threat and we're figuring out how we can deal with it."
As the relentless mussels proliferate, they are botching up everything from sport fishing to city water supplies. Some mussel watchers predict they could infest lakes and rivers all over America by the end of the decade.
That should serve notice to the nuclear power industry to start planning for a mussel ambush that has already hit the Great Lakes.
"It may be (Ohio's) problem now," Snyder told us, "but before long it will be a problem across the country."