Quagga mussels wreak havoc in Lake Mead

At the bottom of Lake Mead lie trillions of invaders — tiny quagga mussels that clog pipes, damage boats and transform freshwater ecosystems into toxic bogs.

The invasive mollusks first appeared in the lake in 2007 and since have colonized by the trillions. In 2012, UNLV researchers estimated there were more than 1.5 trillion adult quagga mussels in Lake Mead and 320 trillion microscopic baby mussels.

The dime-sized shellfish form massive clusters and can almost entirely halt water flow through plumbing or intake pipes. They cause millions of dollars of damage to boats and water systems, and disrupt native ecosystems, threatening sport fisheries. Not only that, their excrement poisons the lake’s water and animals.

What are quagga mussels?

Quagga mussels are a freshwater species of bivalve mollusks that grow to be the size of a dime. They are relatives of clams and oysters, with sharp, triangular shells.

In North America, they remain confined to rivers, lakes and reservoirs because they can’t tolerate extremely salty water.

The depth at which quagga mussels live depends on the temperature of the water. In some places, they have been known to live as deep as 450 feet.

Where did they come from?

The first sighting of quagga mussels in the United States was in 1988 in Lake Saint Clair, Mich.

The mussels are native to the Caspian, Black and Azov seas of Eastern Europe. Scientists believe they were introduced stateside in 1986 through ballast water discharged from ocean-going ships.

The species now is prominent in all of the Great Lakes except Lake Superior, which has too little calcium to support their formation. Scientists estimate there now are about 500 million pounds of quagga mussels in Lake Michigan, four times the amount of prey fish in the lake.

Quagga mussels also have invaded the Mississippi River, the Colorado River, the California Aqueduct and the vast majority of North America’s freshwater sources.

Why are quagga mussels harmful?

Quagga mussels are prodigious water filters and remove massive amounts of phytoplankton and other particulates from water bodies. (1) That significantly increases the water transparency, which starts a major domino effect.

With more light shining (2) through the water, aquatic plants are unable to grow, and the animals that feed on them are left without food. (3) The added sunlight, along with the fact that the mussels trap phosphorus on the lake bottom, makes the water a perfect breeding ground for algae, which is equally harmful to the ecosystem.

Quagga mussels also naturally collect organic pollutants in their tissues. When fish feed on them, the poisons are ingested and passed up through the food chain. Finally, the mussels take in pollutants, such as mercury and polychlorinated biphenyls (PCBs), and excrete them in concentrated pellets. The pellets get eaten by bottom-feeding fish, causing the toxins to be passed onto the fish and even birds of prey.

Why are there so many of them?

Quagga mussels reproduce at an alarming rate. A fully mature female can produce up to 1 million eggs per year.

Once quagga mussels have been established in a water body, there is no economically feasible way to eradicate them.

They are spread through human activity. Because they attach to hard surfaces and can survive out of water, infestations occur when adult mussels hitch rides on watercraft or other items. Microscopic larvae also can be transported in bilges, ballast water, live wells, thru-hull fittings or any other equipment that holds water. Larvae have been found on nonwatercraft objects that simply came in contact with mussel-infested water.

What is being done?

Hoover Dam officials spend $900,000 a year on equipment and research to prevent quagga mussels from blocking pipes at the dam. Officials signed a 10-year, long-term plan to install tailbay pumps that filter water flowing through the dam and UV light solution filters that kill quagga mussel larvae.

Leonard Willet, Bureau of Reclamation quagga mussel task manager for the lower Colorado River region, said the equipment should be fully installed by 2018 or 2019.

“It’s not getting better or worse,” Willet said. “They are just plugging everything. The unfortunate part is there are chemicals that can be added to solve the problem, but that kills everything, including the fish, so it’s not practical.”

Although the number of quagga mussels in Lake Mead may decrease, it’s highly unlikely the problem will be solved, Willet said. For now, his main concern is keeping the pipes unblocked, and with the plan in place, he believes that will happen.

Are quagga mussels edible?

Technically, yes. Most clams and mussels are safe for human consumption. But they taste lousy, and officials recommend against eating them because of the toxins, pollutants and microorganisms that accumulate in their bodies.

You can help curb the spread of mussels

Quagga mussels latch onto anything they find — bungee cords, dive gear, flip-flops and lobsters, but especially boats, which carry them between bodies of water and enable their spread. To try to curb the invasion, UNLV researchers created a simple three-step process to decontaminate watercraft from mussels.

1. Clean: If your boat was in the lake only for a day or two, a simple hosing down with tap water usually will do the trick. If the boat was in the lake for longer, pressure wash it with water that’s 140 degrees Fahrenheit or hotter. It is not recommended to use chemicals or bleach because they can harm the water.

2. Drain: Boats store water in plenty of unseen places, such as the circulation system, barge or ballast. Be sure to drain each completely.

3. Dry: Allow your boat to dry for two or three days before using it in another body of water. This will kill any remaining quagga mussels. Research has shown that microscopic baby mussels can live up to 27 days in wet or moist conditions

Sources: UNLV, National Park Service, U.S. Geological Survey