Lake George and Lake Tahoe have more in common with one another than expensive second homes and classic wooden boats.

“Both are known for gorgeous scenery, excellent water quality and high biodiversity. Both are very important economically as well as ecologically,” said Sandra Nierzwicki-Bauer, the director of RPI’s Darrin Fresh Water Institute.

In August, scientists working on both lakes learned they also faced a common threat: Asian clam. The clams were first observed in Lake Tahoe in 2002 and since then have grown to densities as high as 3,000 per square meter in the southeast part of the lake, said Dr. Marion Wittmann, a scientist with the Tahoe Environmental Research Center of the University of California at Davis.

“Suddenly there were piles and piles of white clams on the lake bed,” said Wittmann. “That’s what shocked everyone.” Within ten years, they began replacing native clams and in the most heavily infested areas, they now constitute almost half of all the organisms dwelling in the lake sediment.

A Darrin Freshwater Institute researcher, Jeremy Farell, discovered a colony of Asian clams near a small beach in Lake George Village in mid-August. The colony may have established itself in Lake George as early as 2008, perhaps transported to the lake in a bait bucket, Nierzwicki-Bauer said.

Wittmann and other scientists at Lake Tahoe were contacted as soon as the Asian clam was discovered in Lake George, said Nierzwicki-Bauer. “The experience, knowledge and information that the folks at Tahoe shared with us was invaluable,” she said. “Because of that, we were able to mount a rapid response effort within a few days of the discovery in Lake George.

Two Lake Tahoe scientists, Wittmann and Dr. Sudeep Chandra of the University of Nevada, Reno, came to Lake George on September 25 to help strengthen the collaborative effort.

“We were hopeful that we could impart information that would be useful,” said Wittmann. “Like a transfer of technology, this visit is a transfer of information.”
The scientists said they came to Lake George not only to impart information, but to receive it.

Lake Tahoe is threatened with Eurasian milfoil, Zebra mussels and other invasives that Lake George has already seen, said Wittmann, and the scientists hoped to learn from the Darrin Fresh Water Institute’s research and conservation work.

On Monday, they led seminars for RPI students participating in the Darrin Fresh Water Institute’s Semester of Study on Lake George on the Asian clam and other invasive species and later met with representatives from the organizations and agencies developing plans to combat the Asian clam invasion.

Asian clams are known for their ability to aggressively outcompete native invertebrate species thanks to their high rates of filtration, metabolism, reproduction, and tolerance to a wide range of habitats, Wittmann told the students.
The clams are also associated with the growth of algae, which may be stimulated by the nutrients in its waste, Wittmann said.

“That’s a real danger here, especially in the four acre area in Lake George Village where we believe the infestation is localized,” said Nierzwicki-Bauer.

Other ill-effects associated with the Asian clam include its tendency to ease the introduction of other invasive species, said Sudeep Chandra. “The dead shells become a substrate for invasive mussels.” The shells also produce calcium, which alters the water chemistry to the advantage of the mussels, according to Chandra said. “All the progress that’s made in protecting water quality can be compromised by one invasive.”

Wittmann and Chandra also discussed the methods they have used to control the spread of Asian clams in Lake Tahoe. Benthic barriers, laid on top of clam beds to reduce oxygen, have been the most efficient and cost-effective way of killing Asian clams. After experimenting with mats of different fabrics, the Tahoe scientists chose one of rubber.

Earlier this summer, divers put 10-feet wide and 100-feet long rubber mats across clam-infested areas of lake Tahoe to determine whether the rubber mats will be effective when used on a large scale.

On the Monday of the Tahoe scientists’ visit, the Lake George group agreed to launch a pilot project to test four types of mat, including one made from rubber. Although mats of other types were found to be ineffective on Lake Tahoe, they may work in Lake George, said Sudeep Chandra.

The possibility that they might serve the groups’ purposes makes the experiment worthwhile, since rubber mats will be expensive, said Peter Bauer, the executive director of The Fund for Lake George.

The mats of other fabrics have already been purchased, having been used for killing milfoil in Lake George and Lake Luzerne, according to Bauer who said the pilot project is expected to cost as much as $36,000.

According to Nierzwicki-Bauer, the results of the project will help the groups plan a control and eradication strategy that will be implemented next spring. “Here on Lake George, you have a chance to control the spread of the Asian clam, because it was detected early,” said Marion Wittmann.

Photo: Algae associated with Asian clams. Courtesy UC Davis

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