They're called Asian clams and they're not native to the lake. They breed rapidly and could adversely affect Tahoe's ecological balance and established food chain.
The U.C. Davis Tahoe Environmental Research Center is trying to fight the problem by laying a rubber tarp on the bottom of the lake with the hopes of suffocating the clams.
"What's interesting though is the rate at which they would start to re-colonize in this treated area. If the Asian clam comes back right away, than it hasn't been a success. But what we are hoping is that they won't come back at least for many years and then we will start to get colonization by native species," says Gregory Schladow, the research center director.
The Asian clam fosters the growth of bright green algae which makes the water cloudy and less blue.