Tahoe’s petite pest

People call pest-removal companies every day to rid their homes and yards of small creatures that have become a nuisance. Gophers tear up manicured lawns and cockroaches skitter along floors spreading germs. Most people are unaware that Emerald Bay at Lake Tahoe has a similar but much larger problem.

Corbicula fluminea, more commonly known as the Asiatic clam, appeared in Lake Tahoe around 2002. While small, these aquatic mollusks can self-fertilize and release 2,000 juveniles per day, amounting to over 100,000 in a lifetime. Their numbers increased exponentially in Emerald Bay and now these tiny clams are a big problem.

“Typically, when a non-native species is introduced, the native species begin to die… When the clams appeared, they basically overtook the native [Tahoe] species,” said Geoffrey Schladow, director of the UC Davis Tahoe Environmental Research Center.

The repercussions of introducing a non-native species on an established food web of an ecosystem can be significant. Historically, many species have become endangered this way. In addition to the effect on the native flora and fauna, it has an impact on the aesthetic value of the lake, a process known as biofouling.

“Residents complained about how the lake looked. Usually Tahoe has clear water and nice, white, sandy beaches but they did not look like that anymore …The [clams] take in particles …and they [excrete] nutrients that help green algae grow, making the water in Emerald Bay look green … People are worried [that] the tourist economy, which is huge at Lake Tahoe, might suffer,” Schladow said.

The UC Davis Tahoe Environmental Research Center aims to prevent any long-term impact by eliminating the population of Asiatic clams using rubber mats. In 2010, the rubber barrier was tested, along with a suction method, and the barrier killed more than 90 percent of the clams.

“The rubber mats are each about 100 feet long … [The researchers] will lay down a bed of [organic material] and put the rubber mat over it. The decomposition from the [material] will cause a decrease in oxygen and the clams will suffocate,” said Chris Wheaton, an undergraduate in civil and environmental engineering who is involved in the project.

The rubber mats are made by undergraduate students Civil and Environmental Engineering. They work on unrolling each pre-cut rubber mat and installing grommets along the sides to allow researchers to tie the mats down.

“We [also] make holes, or ports, in the mats so that divers can go down and collect water samples,” said Brandon Wang, a civil and environmental engineering undergraduate.

Schladow expressed confidence in the success of the project, and hoped to use it in other areas affected by the Asiatic clams. However, there is a disadvantage to the rubber mat treatment.

“The treatment will kill some of the native species along with the [Asiatic clams], but what we have found is that the native species can survive much longer than the non-native one,” Schladow said. “Once the [Asiatic clams] are eliminated, the native species will re-populate.”

The Asiatic clam is currently found in 38 states, and many different lake communities around the country are trying to find solutions to the biofouling. In some places, the larvae of the clams are drawn into water intake pipes and clog raw-water service pipes, firefighting equipment and condenser tubes, costing millions of dollars a year to remove. Researchers hope that with the success of the project, these issues will be resolved and put these pests to rest.

NICOLE NOGA can be reached at science@theeaggie.org.