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Prevention Holding Line Against Zebra Mussels, But Bill Causes Concern

In the battle to keep invasive species like zebra mussels out of Texas waters, no news is good news. That’s how state scientists are describing the status of several northeast Texas lakes.  




Zebra mussels damage water treatment systems, cost local governments millions of dollars and can make lake waters unsafe for humans.


But after years of new infestations, scientists at the Texas Parks and Wildlife Department say no new lakes in northeast Texas are testing positive. 


"In the northern part of the state, we have not documented or found any new infestations of zebra mussels," says Brian Van Zee,  director of fisheries management offices for the department.  


“A lot of boaters are becoming more and more aware of the need for them to clean, drain and dry and to help prevent and slow their spread. So I hope the fact that we're not seeing a lot of new infestations -- particularly in the northern part of the state -- I hope that's a good indication that boaters are doing what we're asking."


Texas has been reminding boaters for years to clean, dry and drain boats every time they leave a body of water. The wildlife department is set to ramp that campaign up this summer as boaters return to lakes.


The campaign is aimed at voluntary cooperation. But it’s also a Class C misdemeanor to transfer invasive species in Texas.  




The reason the state takes the threat so seriously is because zebra mussels cannot be safely removed from lakes. Prevention is key to any policy against the species.  


"You're talking about maybe thousands of individuals per square meter," says Robert McMahan, an expert on invasive species and professor emeritus of biology at the University of Texas at Arlington. 


"They literally cover the bottom, settle on top of each other, they attach with these pugnacious threads to hard surfaces. Then they attach to each other. And they filter algae and bacteria out of the water. 


"So, the whole ecology of the lake can change. And sometimes bad things happen when you reduce normal algae from the lake. Sometimes what happens is then you get what they call cyanobacteria -- blue-green algae -- which is poisonous. And then you can't recreate in the water." 


Barges started carrying the mussels from Eurasia in the 1980s all the way to North America. They invaded the Great Lakes region and started moving south along the Mississippi river. The species began their journey into Texas at Lake Texoma in 2009. That makes north Texas particularly vulnerable. And for an area with limited water resources, the threat up here is that much more serious.  


“These things can get into raw water piping systems … it slows the rate at which water flows. And then it gets more costly to pump the water. Plus the mussels to die periodically. And then if it's potable water system, all that dead flesh goes down into the treatment plant and that does not make for good-tasking water.


"So, the big concern at least in the north Texas region had been primarily among water treatment plants, about what infestations would mean."


Costly Threat to Water Supply


The infestation of Lake Texoma has already cost Dallas-area taxpayers several hundreds of millions of dollars. That’s because the agency responsible for supplying water to north Texas cities like Richardson and Plano was forced to take its pumps offline once the species was discovered in Lake Texoma.  


“We were faced with building a $300-million pipeline from Texoma into our Wiley facilities to prevent the spread of zebra mussels into Lake Lavon, which is one of our major water sources," says Janet Rummel, a spokeswoman for the North Texas Municipal Water District. "And this occurred at a time in which we were faced with extreme drought. And it basically cut off access to a third of our water supply at a time that we desperately needed that water." 


That pipeline was required because of a federal law called the Lacey Act that prohibits importing invasive species across state lines. The law impacted the water after surveying determined that part of the NTMWD's pump station crossed into Oklahoma territory.  


With that experience, it’s easy to understand why the water district is backing proposed legislation by Sen. Ted Cruz to weaken federal regulations on transporting invasive species. 


The Public Water Supply Invasive Species Compliance Act of 2017 would legalize movement of infested water across states so long as the destination is already infested with the same thing.  


"We serve 10 counties. So, any regulatory hurdle that can be cleared from that perspective is a good thing," Rummel says.  


"However, that being said, we are strong proponents of the awareness campaign that the state spearheads to follow state law and prevent the transport of zebra mussels from area lakes." 


Science-Policy Tradeoff


State scientists say the district has done exemplary work on controlling the mussels on its own. But they fear that weakening regulations against invasive species could slow the state’s progress overall.   


“I understand it but, man, you’ve really got to be careful," says Rafe Brock, a district fisheries biologist for the DFW area who was not familiar with Cruz' legislation. He said biologists generally tend to oppose mixing noxious water sources together even if both are contaminated. 


"Some of our data shows now that they're invested really bad for a first couple of years and then that population starts decreasing. If it starts decreasing, then their likelihood of spreading from one boat leaving out is theoretically lower also. 


"Well, if you keep pumping a contaminated organism then the numbers are always going to be high. Or potentially high. And thus that risk is always elevated and never decreases, naturally." 


Brock says water policy has to be a tradeoff between science and the economy. He acknowledges that there aren't simple solutions. 


“They have different interests. And we don’t measure those interests. So, I understand there's got to be a negotiation. Just from my past experience any time you loosen something like that up, the cows just get out. And how do you round them up and put them back in?"  


In 2014, Lavon Lake tested positive for zebra mussels but they haven’t started reproducing there yet. 


Trace evidence of the mussels has been found in Lake Ray Hubbard, Lake Tawakoni and Lake Fork. But those lakes are not yet classified as infested. 


To the east, Cooper Lake, Pat Mayse Lake, Lake Cyprus Spring and Lake Bob Sandlin remain free of zebra mussels.  


Elsewhere in Texas, four new lakes have been affected since last year. 


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