The quagga mussel is a freshwater species of mollusks that only grow to be the size of a dime, but they’re having outsized effects on the waters of Lake Mead. The mussels first appeared in the lake in 2007 and have since grown to numbers exceeding a trillion.

Lake Mead, Nevada.

Lake Mead, Nevada. Image by marcwings / CC BY 2.0

The shellfish form clusters that can clog boat and water system pipes, leading to millions of dollars’ worth of repair costs, and their excrement poisons lakewater and animals’ drinking supply. Quagga mussels are also voracious eaters, filtering out important phytoplankton and other particulates in the water, which disrupts the lake’s ecosystem. To combat the infestation, Hoover Dam officials have signed a deal to install UV light filters that kill quagga mussel larvae.

Scientists believe the quagga mussel came to the United States in the late ‘80s, housed in the ballast water discharged from ships from Eastern Europe, where the shellfish are prevalent. The animals now exist in all of the Great Lakes except Lake Superior, which lacks the calcium level to support the shellfish. Read more: lasvegassun.com