Zebra mussels are turning up in Lake George

Lab tests had indicated that some quirk of the water inhibited growth

April 23, 2000|By New York Times News Service

LAKE GEORGE, N.Y. -- A year and a half ago, it looked as if Lake George, a blue jewel in the green Adirondacks, had dodged a biological bullet -- the zebra mussel, an invasive European mollusk that is clogging pipes, crowding local aquatic life and turning beaches into toe-slicing shell heaps from Michigan to the Hudson River.

Scientists had found microscopic mussel larvae in the water, probably imported in the bilges of boats. But lab tests showed that some quirk of Lake George chemistry -- probably a lack of calcium -- seemed to keep them from maturing and reproducing. No adult mussels could be found anywhere in the 32-mile-long lake.

Now, though, shoreside communities again face the prospect of an invasion that could eventually choke drinking-water pumps, foul outboard motors and deter tourists.

Thousands found

Thousands of mature mussels have been found in the south end of the lake. Scientists say the mussels seem to be confined to a 60-foot-wide band of water along 250 feet of shoreline. But once mussels appear in a body of water, even one where conditions are not ideal, they eventually seem to adapt and multiply rapidly, said Sandra Nierzwicki-Bauer, the director of the Darrin Fresh Water Institute of Rensselaer Polytechnic Institute in Troy, N.Y., and a biologist who has spent years studying the mussels.

Divers from Rensselaer and from a Lake George diving group recently began systematically pulling the mussels from the affected area, in the village of Lake George, which is packed with fishing boats in the summer. The mussels, which the divers are pulling up by hand, are thought by scientists to move from lake to lake mainly by hitchhiking on boats.

"To the best of our ability, the goal is to remove as many as we're able to find," Nierzwicki-Bauer said.

She added that the discovery of the mussels left her "a little red-faced," because 1998 lab tests appeared to show that the lake was safe from invasion. "It seems like every time someone says zebra mussels won't be able to exist in some particular body of water," she said, "the next thing you know, they're there."

The hope, Nierzwicki-Bauer said, is to cull the colony before the lake water warms to 55 degrees or so, the prime breeding temperature.

If the effort fails, the mussels may take hold and -- as they have done in so many other waters -- multiply rapidly, coat the shallows in a thick mat, suck oxygen from the water and filter out plankton that would be food for local species.

Discovered in December

The mussels were discovered in December by two divers from Bateaux Below, a nonprofit group whose members survey the lake's dozens of 18th-century shipwrecks. The divers had been on the lookout for mussels for fear that they might engulf and destroy the wrecks, many of which are rare vessels from the French and Indian War.

The divers, Bob Benway and Joseph Zarzynski, were cleaning up sunken litter at the south end of the lake, in an annual volunteer program.

Groping on the bottom in near-freezing, chest-deep water, Benway hauled up a brown beer bottle and saw two dark, thumbnail-size shells attached. "I'd been trained to recognize them," he said, "and there was no doubt."

At first, he said, he hoped that it was a fluke, a bottle that had been tossed from the shore or a boat. But quickly they determined otherwise.

The men called state conservation officials and the institute at Rensselaer, and soon a broader survey of the lake bottom was under way.

Nierzwicki-Bauer said individual mussels were scattered on the bottom, but, here and there were clusters of dozens, particularly where there was some smooth or hard surface. "They really seem to love garbage, plastic cups, Frito bags and so forth," she said.

She said it immediately became clear that this was a functioning, reproducing colony. "Since we found them in different sizes, from fairly large to small, the only conclusion was that not all of those were transported to the lake," she said. "Some of them had reproduced there."

A prime question was why. If the lake is generally not alkaline enough or sufficiently rich in calcium to support the mussels, she said, why were they growing at this spot?

Tests of water in the area and in streams and culverts along the shore may have found the answer, Nierzwicki-Bauer said. The water flowing into the lake from one culvert contains calcium at a concentration that is four times higher than the average for the lake waters, she said. The culvert empties into the lake just a few yards north of where the mussels were found, she said, and a weak current runs south along that shore.

Nierzwicki-Bauer said it was possible that the culvert had unusually high calcium levels because it disgorged both ground water, which is naturally high in calcium, and storm runoff, which can carry de-icing chemicals that contain much calcium.

The scientists and some local officials concerned about the mussels have begun discussing whether it makes sense to divert or treat the culvert water. But for now, Nierzwicki-Bauer said, "the first order of business is to get the mussels out of the lake."

Nierzwicki-Bauer and other biologists said it remains to be seen whether the removal effort would be enough to keep the mussels in check or whether they would slowly adapt to the hostile lake conditions and find a way to spread.

Several mussel experts were not very optimistic. "Once something like this gets out in open waters in the open environment, it's almost impossible to stop," said Amy Benson, a fisheries biologist at a Gainesville, Fla., office of the U.S. Geological Survey, which tracks zebra mussels and other invasive species.

She said Lake George might soon have to be added to a list that includes hundreds of lakes and rivers in 20 states. "They're there to stay, I imagine," Benson said.

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