ENVIRONMENT : Little Mussel Is a Big Worry in Great Lakes

There’s bad news for anyone who works or plays around fresh water: The zebra mussels that arrived from Europe as uninvited guests in the late 1980s are spreading fast and may one day be found across two-thirds of the United States and much of southern Canada.

Experts who study lakes have estimated the cost of slowing their progress at $5 billion over the next 10 years; even after that money is spent, no one is expected to have found a way to halt them.

“When we first started talking about this, people thought there was some kind of giant clam that was invading the Great Lakes,” recalls Chris Brousseau, zebra mussel program coordinator at the Ontario Ministry of Natural Resources. Though the mussels are small, and even pretty, the problems they are causing are stupendous.

The trouble stems from the mussels’ impressive fertility and their tendency to encrust and despoil every underwater object, living or inanimate, that they encounter. Thanks to hard threads that they alone possess among freshwater mollusks, zebra mussels can even stick to Teflon.

At power plants, municipal pumping stations, oil refineries and other water-using facilities, zebra mussels move in and build up on the insides of water intake pipes. (So clogged do the pipes become in so little time that some Great Lakes mayors fear they may run short of drinking and firefighting water this summer.)

At marinas it’s much the same thing: Zebra mussels infest the cooling water intakes of boats and start growing, blocking the pipes in a matter of weeks.

In Lake Erie, where natural gas producers use buoys to mark the sites of their underwater wellheads, zebra mussels are moving aboard in such vast numbers that their weight drags floats under. Zebra mussels think fishnets are the cat’s meow, and researchers have also found half-starved clams with as many as 15,000 young zebra mussels on their shells.

The zebra mussel lives mainly on phytoplankton, the simple, microscopic plants that make up the lowest rung of the Great Lakes’ food chain. As millions of mussels gobble up the phytoplankton, the lakes take on a lovely new clarity--but traditional, lake-dwelling animals and fish also are being deprived of food.

The zebra mussel is thought to have reached North America in a load of ballast water that an unknown ship carried from Europe. When the mussel arrived in the Great Lakes, it wasted not a moment. In a single year, it colonized all of Lake Erie, where experts have turned up samples of as many as 1 million baby zebra mussels per cubic meter of water--the highest population density ever seen.

From Lake Erie, it has been just a hop to Lake Ontario, the St. Lawrence River and beyond. Experts say it is just a matter of time before it reaches the Mississippi and other river systems, and perhaps even inland farmers’ irrigation works.

North American industrial water users haven’t had the time--or the tremendous amount of money needed--to sink whole new intakes in sand, as was done in Europe to combat the threat. So they are experimenting, with scant success, with various lesser mussel stoppers.

Some hope for relief in ultraviolet light or ozone treatments, while others are developing microscopically fine filters for water intakes. Some research has focused on blasting the mussels with intolerable sound frequencies. Water authorities have been chlorinating mussels away with some success, but chlorine can produce a cancer-causing substance when combined with organic matter.

Ontario Hydro, one of the largest electric utilities in North America and a major Great Lakes water user, has found that the most effective means of coping with the mussel invasion is sending divers down to its water intakes to scrape the mussels off like so much old paint.

Invading Mollusk Scientific name: Dreissena polymorphia Origin: Caspian Sea Habitat: Freshwater lakes, rivers History: About 200 years ago, zebra mussels began moving up the Volga River from the Caspian Sea, attaching themselves to the hulls of boats. Prolific breeders, they spread throughout Europe. In 1988, the mussels were discovered in the Great Lakes of North America. About 1 1/2 inches long, with a life span of three to four years, the zebra mussels produce 30,000 eggs a year. The problem: Zebra mussels attach themselves to almost any surface. Within a short time they can clog water intakes of plants or boats, sink navigation buoys or destroy fishnets with their combined weight, and kill other marine life. The estimated cost just to slow their progress in the Great Lakes is $5 billion over 10 years.