Delighting environmentalists, a Freeport marina is believed to be the first on Long Island to stop using copper paint on the bottom of boats that can leach into local waters.

Dante Grover, owner of Al Grover's High & Dry Marina, said the roughly 500 boats there are now being painted with an environmentally friendly alternative.

The switch began in March, he said, and most of the vessels have already been repainted.

"When you know there's an alternative that's not harmful to the environment, then why continue to do something that is harmful? You would be acting out of ignorance," Grover said.

Water-quality activists hope other Island marinas -- and tens of thousands of boat owners -- follow suit.

"It's a huge step," said Rob Weltner, president of Operation SPLASH, a Freeport-based nonprofit that cleans up local waters and is pushing the change in boat bottom paint. "I hope it will be like the shot heard 'round the world."

The move comes amid growing concern nationwide over impacts on marine life from the copper chemical in the antifouling paint, cuprous oxide.

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Weltner has met with marina owners and the New York Marine Trades Association to inform them of more environmentally friendly alternatives.

For years, environmental groups have warned of the dangers of cuprous oxide in boat paint. The chemical deters marine creatures, such as barnacles, from attaching to hulls, but it also leaches into the water, studies have found.

Studies show traces of the copper left in the water accumulate and harm the nervous systems and gills of fish. It also kills algae, a main source of food for other marine life.

Conrad Kreuter, owner of Moriches Inlet Marine, said about half his customers now request the eco-friendly boat paint he offers. "Copper-based paint does no good to marinas," he said. "The difference is in the price, but I expect in time most people will be using it."

But Susan Shingledecker, vice president of the BoatUS Foundation for Boating Safety and Clean Water, said alternatives to copper paint don't appear to be as effective based on the feedback the group has received.

"For boats stored in high-salinity warm waters that are used infrequently, many of the copper-free coatings are just not performing well," she said."It is important that there remain antifouling solutions that are effective, affordable and readily available."

There are 93,026 registered powerboats in Nassau and Suffolk counties, according to state figures,and the Island boasts more than 100 marinas.

The vast majority of local boat owners use copper bottom paint, Grover believes.

Use of copper paint grew among boaters after the toxin tributyltin was outlawed more than two decades ago. But studies found that the leaching copper paint was also harmful.

In 2011, Washington became the first state to ban copper paint; California is proposing similar action.

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Grover believes only a New York State ban will spur boaters to change their ways.

"They're creatures of habit," he said. "If you want to be on the cutting edge of any industry, you have to embrace the change."

Grover, whose marina spends about $60,000 a year on bottom paint, estimates the alternative he uses costs about 15 percent more.

But some boaters are wary of trying a product that may not work as well.

"If someone has a big boat and he doesn't use copper paint, his boat would be gone after a year," said Doug Mooney, 42, of Amityville, who restores boats at a local shop. "You have to have the copper."Richard Reese, 45, of Babylon, said the copper additive allows him to repaint his boat only once a year.

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"This is the stuff they told me to buy at the store; they said it was the best," he said. " . . . I never really thought it was doing much damage."

Weltner said boat owners simply need more information on the issue. "We just want people to know there are alternatives out there," he said.