Asian clam-killing project: The mats are up, but results aren’t in on $648,000 experiment |

Asian clam-killing project: The mats are up, but results aren’t in on $648,000 experiment

Matthew Renda
Sierra Sun
Sun File Photo The Asian clam. Researchers have found a connection between the invasive clam and algae bloom in Lake Tahoe, and are concerned increased calcium levels created by the clams could provide a foothold for other invasive species.
Jonah M. Kessel | Jonah M. Kessel / Tahoe Daily Tr

LAKE TAHOE and#8212; Tahoe scientists say it’s too early to determine whether a pioneering aquatic invasive species control experiment can be declared a success as they await results from sediment samples collected at the site.

Last week, Marion Wittmann and Brant Allen, certified divers and research scientists with University of California, Davis, Tahoe Environmental Research Center, dove to the bottom of the lake to remove two separate 100-foot by 10-foot black bottom barriers installed in early July to test the effectiveness of their ability to kill Asian clams and#8212; an invasive species many scientists say could pave the way for other more harmful invaders like zebra and quagga mussels.

and#8220;Going by visual inspection, there were dead clams, so the barriers did have an effect,and#8221; Wittmann said. and#8220;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.and#8221;

Wittmann and Allen used PONAR and#8212; a jaw-like apparatus used to collect sediment samples from the bottom of lakes and#8212; to garner material for UNR lab researchers to process.

and#8220;A lot of the animals are too small to see with the naked eye,and#8221; Wittmann said. and#8220;Also, many of the Asian clams and other native species are buried in the sediment, so the samples may contain live animals.and#8221;

Wittmann said she anticipates the timeline for solidified results to be and#8220;about a month.and#8221;

On Friday, July 9, Wittmann and Allen installed two large swathes of bottom barriers on separate half-acre plots on the bottom of Lake Tahoe.

The two locations and#8212; one in Marla Bay near Zephyr Cove and the other near Stateline and#8212; were selected due to a high concentration of Asian clams.

Bottom barriers are a 45-millimeter thick pond liner capable of depriving organisms of dissolved oxygen necessary for survival.

and#8220;The goal of this experiment is to determine whether it is feasible to control clams using impermeable bottom barriers,and#8221; said Geoffrey Schladow, director of TERC, during the installation process in July.

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 its southeastern corner.

Schladow noted bottom barriers have been used to kill underwater plant species, but the scale of the project and its relation to Asian clams rendered the experiment unique.

The estimated cost of the experiment is $648,000. 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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