Aquatic Intruder Muscles Its Way In

Brian Nearing
October 7, 2014
 

A watery intruder gained little new territory in Lake George this summer, possibly because last year's harsh winter kept water cold enough to kill many Asian clams, according to a report issued last week by the Lake George Park Commission.

But there was a warning note: invasive clams that breed quickly and can foul beaches with their sharp-edged shells are now established on both sides of iconic Million Dollar Beach, although still at low levels — for now.

Summertime bathers at the village's popular beach likely did not realize that the invaders were there because live clams bury themselves in the sandy bottom, said Dave Wick, executive director of the Lake George Park Commission, on Tuesday.


Established on the western edge of Million Dollar Beach two years ago, the unwanted clams were discovered last month on the eastern edge, said Wick. Both colonies are relatively small, and didn't pose an inconvenience to bathers. But the clams will continue to breed, accumulate and die off, at which point layers of razor-sharp shells could start to blanket the lake bottom.

Thriving in sunlit, shallow, sandy lake bottoms, the tiny mollusks pose a major threat to the lake's legendary clear water, which drives vibrant tourism, boating and recreational fishing industries. Large clam colonies also can foul beach water because their excretions fuel massive algae blooms.

Clams have already caused some of those problems in Lake Tahoe, on the California-Nevada border, where beds now cover several hundred acres.

“So the good news on the clams is, there are still no impairments to Lake George overall,” said Wick. “We are still not at a density where we are seeing an impact.”

Last month, more than 25,000 samples from 200 locations around the lake were taken by commission staff members and volunteers during the third annual survey to track the progress of the invasive clam, which showed up in the lake in 2010.

A few miles to the northwest, at a sandy delta where English Brook enters Lake George, an infestation of clams was found that Wick called “shocking” — as many as 600 clams per square meter, the highest density ever found In the lake.

Anything above 1,000 can become a problem, said Wick. At Million Dollar Beach, per-meter levels are 20 clams or fewer.

Over the last three years, divers have been laying down weighted plastic mats atop clam colonies in English Brook and other places to smother the mollusks, which draw oxygen from the water. Wick said the clam numbers at the brook rebounded much more quickly than expected.

That costly matting effort likely won't be repeated this year, said Wick, so money can be devoted instead to research at Darrin Freshwater Institute in Bolton Landing into how clams reproduce and migrate in a bid to design better control methods.

Institute Director Sandra Nierzwicki-Bauer said research is examining the frequency and timing of the clam's reproduction, as well as how clams migrate from place to place, either through human assistance — like on boat anchors — or natural means such as drift and current.

That information could help in the design of better methods to inhibit or slow the spread of clams, she said. Any effort to stop the reproduction of the clams seems unlikely, as the creatures are hermaphroditic — meaning they contain both male and female parts — and don't need partners to reproduce.

Mother Nature helped protect the lake last winter, when sustained frigid temperatures kept the water temperature cold, which in turn caused the deaths of many clams in existing infested areas.

Those areas are predominantly in the southern section of the lake at Norowal Marina, Shelving Rock, Basin Bay, Boon Bay, Middleworth Bay, Diamond Cove, Sandy Bay, Paulist Fathers and Lake George Village.

Nierzwicki-Bauer said that research from McGill University in Montreal indicates that clams die when lake water temperature drops to 36 degrees or less for more than two months, which happened last winter in Lake George.

“We cannot count on winter to save us,” said Walt Lender, executive director of the Lake George Association. “We need this research to better understand how the clams reproduce and move, so we can design better control methods.”

Added Eric Siy, director of the Fund for Lake George, “Our only protection is going to come from prevention. These clams are very prolific and they can certainly spread again.”

He said the clam infestation shows the importance of the lake's invasive control program, which went into effect this year for boats that launch into the lake.

This season, more than 19,000 boats have been inspected, said Siy, with about 1,250 boats suspected of carrying invasives cleaned with a high-pressure wash. Inspectors found invasives including 100 instances of Eurasian milfoil, 23 instances of zebra mussels, 13 instances of curly leaf pondweed, two cases of Asian clams, seven cases of water chestnuts, and two cases of snails.

Read the full article on TimesUnion.com

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