It’s not unusual for people to destroy the ecological balance of a lake – whether by oil slick, milfoil or bulldozer.

But in a new pilot project, scientists from the state, the University of Maine and Colby College are planning to kill hundreds, perhaps thousands of fish, in hopes of restoring the natural balance of East Pond, one of the Belgrade chain of lakes in western Maine.

For seven of the past 10 years, East Pond has bloomed green with algae. Hundreds of thousands of organisms have covered the water’s surface, discouraging swimmers and worrying local property owners, said Richard Seaman, vice president of the local lake association.

“A couple years ago, it was a very serious pea-soup condition,” he said Friday.

If algae blooms are allowed to grow unchecked, they can sap the oxygen that fish and other organisms need to survive – speeding up a natural process known as eutrophication and over many years transforming a vibrant lake into a sterile one.

Camp owners have come together to fight the most common cause of algae blooms – phosphorus and other nutrients that can make their way into lakes from sewage systems, lawn fertilizer and household detergents.

Most lake associations have been battling nutrient-laden runoff for decades. Indeed, the East Pond has already taken countless precautions and is continuing its efforts – but it hasn’t been enough, Seaman said.

So this summer, researchers are investigating whether a process known as bio-manipulation can re-establish the natural food web.

Scientists believe the algae are blooming because the tiny creatures that feed on algae – a type of zooplankton commonly known as water fleas – are themselves being eaten by a prolific population of white perch.

In a balanced system, the zooplankton would graze on the algae, keeping its population under control, explained researcher Katherine Webster, who is an assistant professor in the biological sciences department at the University of Maine.

“They’re very effective grazers. We call them the cows of lakes,” Webster said.

But young white perch eat zooplankton, and East Pond has a lot of perch. Scientists are currently taking samples to determine the exact population, but estimates place it at around 165,000 fish, Seaman said.

A perch’s fertility is legendary. A fish can live as long as 10 years, and females can release a quarter of a million eggs annually, said John Boland, a fisheries biologist with the Maine Department of Inland Fisheries and Wildlife.

This type of bio-manipulation has been successfully used in Europe and in the midwestern United States, but never in New England, Webster said.

Over the next year, researchers will be studying sediment cores, water samples and even the pumped-out contents of fish stomachs to develop a detailed picture of East Pond’s food web.

Researchers from Colby will launch a pontoon boat armed with an array of environmental monitoring equipment to look at the role of such factors as cloud cover, wind, temperature and humidity.

“I think we’re going to learn a lot about the lake and the way it works as time goes on,” said Melissa Evers, an environmental specialist with DEP who also happens to have a home on East Pond.

If the data back up scientists’ suspicions, perch removal would likely start in 2006.

Already, there is some anecdotal data to suggest that removing the perch can make a huge difference.

At Sabattus Pond in Lewiston, once one of the most algae-clogged in the state, waters became clear after pike, a non-native predator fish, were illegally introduced and began feeding on the perch, Evers said.

Of course, introducing predators to East Pond is not an option – non-native fish introductions are illegal because they cause innumerable biological problems – but researchers believe that killing the perch directly could have the same result.

It’s doubtful that biologists could ever completely remove perch from the lake. However, Webster said she believes that with ongoing perch control programs, the population can remain low enough to keep the water clear.

State fisheries managers have few concerns about the project. Perch aren’t a popular game fish, and it’s unknown whether the fish – which were historically found in some Maine lakes but not in others – are even native to East Pond, Boland said.

The department will stay in touch with the researchers, monitoring any impact, good or bad, that the project has on populations of large and small-mouth bass, fish that while non-native, are well-established and popular with fishermen.

If the biomanipulation works, the process could be used in other ponds in New England, as long as local communities tackle their own nutrient pollution and show the same enthusiasm for the projects as those at East Pond, Webster said.

“The more we get into the project, the more exciting it becomes. Potentially, we’re dealing with something much larger than East Pond,” Seaman agreed.