Scientists suffocate Asian clam beds with rubber tarps | TahoeDailyTribune.com

Scientists suffocate Asian clam beds with rubber tarps

Matthew Renda
mrenda@tahoedailytribune.com

Annie Flanzraich / Tahoe Daily TribuneUC Davis scientists Marion Wittmann and Brant Allen emerge from the depths of Marla Bay to show some Asian clams they found while laying down bottom barriers.

ZEPHYR COVE, Nev. – Come all ye pioneers of clam killing.

In collaboration with a variety of environmental oversight agencies, Lake Tahoe scientists unveiled the first stage of an experiment designed to test the effectiveness of a nascent technique aimed at curtailing the population growth of a non-native freshwater mollusks.

A team of scientists, spearheaded by Geoffrey Schladow, director of the Tahoe Environmental Research Center, rolled out a series of 100-foot by 10-foot black bottom barriers and spread them over a half-acre portion of the bottom of Lake Tahoe in the general vicinity of the Round Hill Pines Beach and Marina, where Asian clam populations have become increasingly prevalent in recent years.

The bottom barriers are a 45 mil thick pond liner capable of depriving organisms of dissolved oxygen necessary for survival.

“The goal of this experiment is to determine whether it is feasible to control clams using impermeable bottom barriers,” Schladow said. “We need to know how to efficiently deploy and remove large areas of rubber sheeting, and when it is all done, we must know whether the clams recolonize the treated areas.”

Schladow said the experiment will also be important in assessing if the cost of implementing control measures is practical. The experiment is estimated to cost $648,000 to implement. In total, $1.4 million has been allocated for studies and scientific projects relating to the control of Asian clams. The majority of the money has been received from the Southern Nevada Public Land Management Act.

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Schladow said complete elimination of the species from Lake Tahoe is not likely and the experiment focuses more on the possibility of population control. Asian clam population has reached thousands per square yard in some portions of Lake Tahoe, particularly in the southeastern corner of the lake.

“Given the size of the lake and the Asian clam’s capacity for propagation, total elimination is not feasible,” said Schladow.

The experiment could have far-reaching implications if deemed successful by scientists come September, when the barriers are scheduled to be removed.

“Bottom barriers have been used in Tahoe to kill underwater plant species, but the scale of this project and the fact it relates to Asian clams makes it unique,” Schladow said.

A bevy of local and national media outlets witnessed the implementation of the experiment. The University of California, Davis deployed two research boats and a modestly sized barge. One research boat was used by three divers tasked with the installation of the bottom barriers while two scientists remained on the boat to oversee the mission.

The second boat accommodated the large media contingent.

The barge was equipped with a small portable crane operated by Research Engineer Bill Sluis, Research Engineer at UC Davis, and his team. Sluis began the mission by using the crane to pick up large rolls of black rubber and drop them into the water.

The rolls were then suspended underwater by flotation devices, while the three divers unroll the tarpaulin material. The divers then secured the barriers at the bottom before surfacing with examples of Asian clams both living and dead.

When alive the clams have a golden sheen, when dead they turn white and are visible from 30 feet or more from the bottom of the Lake.

Scientists will duplicate the experiment off the shore at Lakeside, meaning a full acre of the bottom of Lake Tahoe will be covered until September.

This video was filmed underwater Friday as UC Davis scientists rolled out the first layer of black rubber over Asian clam beds in Marla Bay.

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