How zebra mussels will change Austin lakes (and maybe Barton Springs) forever

The invasive zebra mussel has been moving south for years, leaving destruction in its wake. Now, it’s in Lake Travis, and it will soon make its way downstream, changing the look, feel and maybe even the taste of Austin’s lakes forever.

At first glance, the mussels don’t look very threatening. They’re about the size of a nickel, with brown and yellow stripes. But in large enough numbers they wreak havoc.

You can sometimes find “thousands per square meter,” according to Robert McMahon, a mussel researcher at the University of Texas at Arlington.

“They’re literally filtering the water over in a lake,” he said. “Depending on how dense it is, they might turn over all the water in a lake every week.”

That robs other small creatures of food. The creatures that eat those creatures then go hungry, and so on.

“It’s going to be a top-to-bottom change in the whole ecosystem,” said Liz Johnston, an environmental program coordinator with the city.

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Going Clear

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One of the more visible effects will be in water clarity.

“That’s what they’ve seen in northern lakes,” Johnston said. “It may look beautiful to people because it’ll be crystal clear and you’ll think, ‘This is beautiful clean water,’ when really it’s not the way it’s supposed to be.”

That clarity allows sunlight to reach deeper into the lake. That could encourage more plant growth, including invasive hydrilla and algae blooms that sometimes make our drinking water taste funny.

“If there’s a really bad bloom and the water’s clearer, it may actually make the lake bluish green at times,” Johnston said.

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Shells That Cut And Clog

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The arrival of zebra mussels might mean no more walking barefoot in or near waterways.

“They live quickly and die quickly,” Johnston said. “All of the shells will get deposited on the banks. They’re very sharp to walk on. … It will make any beaches along our reservoirs not pleasant to walk on barefoot.”

The mussels also clog water-intake pipes. In other places, utilities have spent millions of dollars dealing with them.

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Lake Becomes Contagious

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“If you have a boat in the water, they like to attach to hard surfaces,” Johnston said.

“On Lady Bird Lake, we don’t have a lot of motor boats, but we do have people coming in and out on their standup paddle boards and kayaks that could potentially be transferred into other systems.”

That means, from now on, anyone who brings a boat to Austin’s lakes should wash it and let it dry, or risk spreading the mussels.

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Barton Springs At Risk

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It seems inevitable that Lake Austin and Lady Bird Lake, which are downstream from Lake Travis, will host the zebra mussels soon. Walter E. Long Lake is fed by the same water, so it’s a safe bet the mussels will get there, too.

And, Johnston said, Barton Springs might even be at risk.

“Catfish could potentially disperse them upstream,” she says. “I’m also concerned about people who swim downstream of Lady Bird Lake at ‘Barking Springs.’ The larva could be attached to them. If they decide they want to go dip in the Barton Springs pool immediately, they could also transfer it there.”

The relatively nutrient-poor waters of Barton Springs may help protect it from the invaders, though, she said.

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Nothing Can Be Done

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Here’s the kicker: There’s no way to safely get rid of zebra mussels.

Looking for some good news?

Not every lake makes an ideal home for them, so it’s possible they won’t proliferate in Austin to the point where they cause maximum harm.

The thing is, we won’t know until they’re here – and that should be any day now.

This story was produced as part of the Austin Monitor’s reporting partnership with KUT. Phto by Jorge Sanhueza-Lyon/KUT.

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