Efforts made to control population of invasive clam in California

Scientists in California’s Lake Tahoe are running a pioneering marine invasive species control experiment on the Asian clam. They anticipate the results in about a month.

Certified divers and research scientists from the University of California, Davis, Tahoe Environmental Research Centre (TERC) Marion Wittmann and Brant Allen recently dove to remove two separate 100-ft by 10-ft black bottom barriers the bottom of the lake installed in July to gauge how effectively they can kill the invasive Asian clams, reports Matthew Renda for North Lake Tahoe Bonanza.

Researchers installing Bottom barrier deployment
to control Asian clam populations in Lake Tahoe. (TERC, UC Davis)

“Going by visual inspection, there were dead clams, so the barriers did have an effect,” Wittmann said. “However, workers (at the University of Nevada, Reno) are currently processing the samples, and until we get the results, we can’t truly know if the experiment was a success.”

Wittmann and Allen used a device called PONAR to collect sediment samples from lake bottoms for lab analysis.

“A lot of the animals are too small to see with the naked eye,” Wittmann said. “Also, many of the Asian clams and other native species are buried in the sediment, so the samples may contain live animals.”

The Asian clam was first seen in Lake Tahoe in 2002, and is found in waters in 38 US states. Originally a species of freshwater, it has also gone to the brackish San Francisco Bay; scientists blame the moves on the species’ significant powers of adaptation.

The clam expels high levels of nitrogen and phosphorus which provoke algal blooms. The clams also deprive native species of key nutrients and food sources by filtering high volumes of water.

Scientific studies, moreover, predict that the clams’ production of high levels of calcium could provide a hospitable environment for the introduction of quagga and zebra mussels – highly hazardous invasive species, as they could devastate the economy and ecosystem of water bodies.

Studies show that zebra and quagga mussels could survive in Tahoe, if perhaps not reproduce; the presence of Asian clams would facilitate the plague.

Back in July, Wittmann and Allen installed two large bottom barriers on separate half-ac plots on Lake Tahoe’s bottom. The 45-mm bottom barriers are thick pond liners that can deprive organisms of dissolved oxygen which they need to survive.

Lake Tahoe Species Introduction Timeline. (Graph: TERC, UC Davis)

“The goal of this experiment is to determine whether it is feasible to control clams using impermeable bottom barriers,” declared Geoffrey Schladow, director of TERC.

He said that because complete elimination of the species from the lake is not probable, the experiment concentrates on possible population control.

The experiment is estimated to cost USD 648,000; although USD 1.4 million has been assigned for studies and scientific projects to control Asian clams.

By Natalia Real