Quagga Mussels — Worse Than Zebra Mussels and Maybe Headed Your Way

March 24, 2021
Invasive quagga and zebra mussels are spreading around the United States, threatening waterways. Image: U.S. Geological  Survey. Click to enlarge.

TipSheet: Quagga Mussels — Worse Than Zebra Mussels and Maybe Headed Your Way

By Joseph A. Davis

Invasive quagga mussels may be coming to mess up a lake or stream near you. People need to know about these pests and how to avoid spreading them.

Boaters, fishers and even pet owners have a role to play in making things better or worse. Water and electric utilities may be big victims — and pass costs on to their ratepayers.

Quagga mussels are believed to have originated in the Ukrainian portion of the Black Sea. They only started invading U.S. water bodies in the late 1980s. Oceangoing vessels coming into the Great Lakes via the St. Lawrence Seaway are thought to have carried their larvae in ballast water discharged into the Great Lakes. The mussels are small, usually less than an inch in size.

The latest news flash came when quaggas turned up in a commercial moss ball product sold for aquariums.


Why it matters

America’s lakes and streams are precious to us in many ways. The Great Lakes, where invasive quagga mussels were first found in the United States, contain more than one-fifth of the world’s liquid fresh surface water and are thus a crucial resource in a world where water is becoming scarce. But now quagga mussels are invading other river systems and major lakes in many parts of the country.


Like zebra mussels, quagga mussels

can colonize and befoul water intakes

for both utilities and industries.


Quagga mussels are easily confused with invasive zebra mussels — but arguably much worse. Like zebra mussels, they can colonize and befoul water intakes for both utilities and industries. It is expensive to remove them, which becomes necessary maintenance. The two species are actually related (both are in the genus dreissena). While zebra mussels were first to invade the Great Lakes, quagga mussels have now become dominant.

Quagga mussels are worse than zebra mussels in that they can alter the entire chemistry of a water ecosystem. Quagga mussels are such prolific filter feeders, removing plankton, that they make the water unnaturally clear. This encourages various plants and phytoplankton to flourish at greater depths. 

Initially, filter-feeding quaggas remove large amounts of phosphorus from water, storing it in their bodies. (Phosphorus in many waters is a pollutant, because it nourishes algae. When algae become excessive, they die and decompose, a process that depletes the oxygen in the water, killing fish.) But then when the mussels die, that phosphorus is released again, causing a spike in pollution.


The backstory

Quagga and zebra mussels were already expanding into Europe from their narrow Black Sea range in the 1940s. After the St. Lawrence Seaway opened in 1959, large ocean-going vessels began to ply the Great Lakes. Efforts to keep them from discharging ballast water in the lakes were not altogether successful — bringing various invasive species to the lakes. 

At first, the zebra mussels were perceived to be the biggest nuisance. It took time not only for the mussels to spread, but also for the problem to be understood. It also took time to realize how many government and private actors would be needed to slow the spread. 

Government response took considerably longer. By now, various state, provincial and federal agencies (including government bodies devoted to protecting the Great Lakes, most notably the International Joint Commission) have been fighting the mussels for years.

But quagga mussels have themselves expanded well beyond the Great Lakes — into continental-scale water systems like the Mississippi and Colorado basins. There are now quaggas in the huge southwestern U.S. reservoir, Lake Mead.  

Mussels colonize by adhering to both bottom sand and hard surfaces. These may include breakwaters, docks and buoys — but also the hulls of recreational boats. When those recreational boats are moved from lake to lake, mussels can be transplanted as well.

So, key among the agencies fighting quagga and zebra mussels are state agencies that regulate boating, fishing and boating facilities. These agencies may run boat inspection and cleaning programs (which are essential to prevent spread).


Story ideas

  • Are there quagga or zebra mussels in waters near you? Who uses these waters? How did the mussels get there?
  • Visit local docks, marinas and boat ramps, and talk to the people running or using them. Do the mussels bother them? What are they doing to prevent spread?
  • Talk to local electric utilities about the effect of mussels on their cooling water intakes and other plant infrastructure. Do the mussels get into the pipes? How much maintenance is needed? And at what cost?
  • Talk to drinking water utilities about any effect mussels may have on their intakes and plants.
  • Talk to local, state and federal agencies in your area about what they are doing to control any mussel infestations.


Reporting resources

Joseph A. Davis is a freelance writer/editor in Washington, D.C. who has been writing about the environment since 1976. He writes SEJournal Online's TipSheet, Reporter's Toolbox and Issue Backgrounder, as well as compiling SEJ's weekday news headlines service EJToday. Davis also directs SEJ's Freedom of Information Project and writes the WatchDog opinion column and WatchDog Alert.

* From the weekly news magazine SEJournal Online, Vol. 6, No. 12. Content from each new issue of SEJournal Online is available to the public via the SEJournal Online main page. Subscribe to the e-newsletter here. And see past issues of the SEJournal archived here.

SEJ Publication Types: