Zebra Mussels Threaten the Trinity River and North Texas Water Supplies

UPDATE: Since this article was posted in June 2013 there have been significant developments with zebra mussels in Texas.  Zebra mussels have now been found in Lakes Belton, Bridgeport, Lavon, Lewisville, and Ray Roberts since initially being found in Lake Texoma in 2009.  Texas Parks and Wildlife Commission recently approved expansion of rules to 30 counties in Texas to drain boats, in addition to 17 counties with the rules already in place.  To find out which counties and the specifics of the rules, visit the Texas Parks and Wildlife website.  There may be a solution on the horizon however.  A researcher in New York has discovered a bacteria that can kill zebra mussels.  Commercial development of the bacteria for large scale is currently underway and its effectiveness in large lakes remains to be seen, but there is great hope. Read more in this New York Times article.

Zebra Mussel - Photo by Amy Benson, U.S. Geological Survey

Recent reports of invasive zebra mussels (Dreissena polymorpha) in North Texas lakes has many different natural resource agencies and water utilities scrambling to find solutions to keep them from spreading to other water bodies in Texas.

What Are Zebra Mussels?

Zebra mussels are small (~1 inch) mollusks that are named for the striped pattern on their shell and feed by filtering microscopic organisms out of the water. Native to Eastern Europe, they made their way to North America by shipping vessels and were first discovered in the Great Lakes region in 1988.  Since then they have spread rapidly (see maps below) as females can produce 30,000 to 1 million microscopic eggs per year. 
 

1990 Zebra Mussel Distribution - National Atlas

2010 Zebra Mussel Distribution - National Atlas

Why Are Zebra Mussels a Problem?
 
Zebra mussels attach to any hard surfaces, such as rocks, boat propellers, docks, water intake pipes, and even other aquatic animals (see photo below).  The major problem with zebra mussels is their ability to reproduce rapidly which allows them to outcompete native mollusks.  They can filter one liter of water per day, and combined with their strong attachment capability, can devastate aquatic ecosystems by removing large amounts of phytoplankton that is a critical part of the food chain that ultimately impacts sport fish species and occupies space that is needed for aquatic vegetation to establish.  Significant economic impacts also occur as zebra mussels can clog water intake pipes, destroy boat propellers and motors, damage docks and corrode other hard surfaces that are in the water.     

Zebra mussels attached to native mollusk. Photo by Corey Raimond.

What Does This Mean For North Texas?

Zebra mussels are already having a profound impact on the Trinity River as these invasive bivalves have been found in two Trinity basin lakes (Ray Roberts and Lewisville) after Lake Texoma was the first lake in Texas to discover them.  Lake Texoma provides 28% of the water supply for North Texas Municipal Water District (NTMWD), which supplies water to 1.6 million people cities north of Dallas, such as McKinney and Frisco. NTMWD was pumping water from Texoma to Lake Lavon near Wylie for distribution to customers until zebra mussels were discovered in Texoma in 2009 and NTMWD shut down that pipeline for fear of introducing zebra mussels into Lake Lavon.

To avoid contaminating Lake Lavon, NTMWD is building a $300 million pipeline from Texoma directly to the Wylie Wastewater Treatment Plant, which has driven up the cost of water bills by approximately 14%.  Many experts believe this is just the beginning of problems related to the zebra mussel invasion in Texas.   

Stopping the Spread

Even though officials in Virginia were able to eliminate a population of zebra mussels in the 12 acre Millbrook Quarry with potassium chloride, this would be impossible to do in the much larger Texas lakes without effectively destroying the lake itself.  With no practical ways to get rid of established populations, stopping the spread of zebra mussels is the best bet.


Media campaigns are being directed at boaters to clean, drain, and dry their boats after they get out of the lake.  That's because the microscopic zebra mussel larvae can attach to boats and other gear that was in the water and live outside of water for up to two weeks. In fact, if you are in a lake known to have zebra mussels in it, IT IS THE LAW to CLEAN, DRAIN, and DRY your boat in order to prevent spreading zebra mussels to other lakes.  Even if you unknowingly transport mussel larvae, you could face a class C misdemeanor with fines up to $500 for first time offenses, with steeper rates and possibly jail time after that.

You can help prevent the spread by removing vegetation, mud and other objects from your boat after you pull it out of the water, draining water from all parts of your boat, and allowing the boat to dry for up to 2 weeks before putting it back into water.  If you can't wait 2 weeks, use high-pressure sprayer with soapy water at 140 degrees to remove zebra mussel larvae.

Please do your part to stop this invasive creature, because as the saying goes, "Hello Zebra Mussels, Goodbye Texas Lakes."




U.S. Geological Survey. [2013]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [6/24/2013].