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City discusses the future of Austin waterways in the face of zebra mussel infestation

Tuesday, August 8, 2017 by Jessi Devenyns

The city needs to batten down the hatches and get ready for the zebra mussel invasion, according to Liz Johnston, environmental program coordinator for the Watershed Protection Department. On Wednesday, Johnston brought the Environmental Commission up to speed on the forecasted consequences of the new zebra mussel population found in the waters of Lake Travis.

Based on what has been seen in other states nationwide, Johnston said that in the near future Austinites can expect city water intake pipes clogging, beaches being overrun with shells, hydrilla and Eurasian watermilfoil plant populations growing, and an overall alteration in Central Texas water ecology with the expansion of the mussel population.

Furthermore, the Watershed Protection Department does not expect these ecology changes to be isolated to Lake Travis. “We expect them to always go downstream,” Johnston told the commissioners. That means that soon zebra mussels may be found in Lake Austin and Lady Bird Lake, and they may even find their way into Barton Springs Pool.

In response to the collective concern the commissioners expressed at the potential of this invasive species making its home in one of the city’s largest public pools, Johnston said, “There is protection for Barton Springs, but it’s not 100 percent safe.”

At this time, there is no fail-proof prevention method available. Nevertheless, the city recommends for everyone who uses a boat to continue to clean, drain and dry it after use. Unfortunately, since zebra mussels can live out of the water for up to a week or two, unless hot water is used to wash the boat, there is no guarantee that they will be removed from the vehicle successfully.

When questioned if there would be hot water spigots available to boaters on the docks, Johnston responded, “It would be up to (boaters) to take boats through a car wash or wash them down with vinegar.”

However, it wasn’t all bad news. In addition to populations of zebra mussels expanding throughout Austin waters, so too are six species of native mussels.

Commissioner Mary Ann Neely inquired as to the importance of such emphasis on these bivalves saying, “I know we support all life, but what is the benefit of mussels for water quality?”

Johnston acknowledged that these organisms are indeed mysterious, but said that “they’re basically like free ecosystem services” and not something to be overlooked.

In conjunction with her report on zebra mussels, Johnston presented the department’s initial findings on the effects of drawdowns on native mussel populations.

Since the 1950s, Austin has utilized drawdowns as a lake management tool. However, the frequency of these drawdowns has varied over the years. Most recently, the city drew down its lakes in the beginning of 2017, but before that, there had been a six-year break in drawdowns due to the prolonged drought that Central Texas experienced.

In 2011, the Watershed Protection Department conducted a study to see how many mussels lived in the city’s waterways. The department canvassed sites from Ullrich Water Treatment Plant to Fritz Hughes Park and only found 153 individuals from two species, with none north of Commons Ford Park.

When the department repeated the study this year, it discovered four more species and many more individuals at all sites.

“After six years the populations appear to have recovered,” Johnston said. “We don’t know how (zebra mussels will) affect native mussels in the future, but it probably won’t be good.”

The Watershed Protection Department plans to bring back a policy guideline on lake drawdowns to the Environmental Commission before any formal decision is made on the lake management for next year.

The Texas Comptroller’s office, too, is taking the changing mussel populations seriously and has launched a study on freshwater mussels of the Colorado, Guadalupe and Brazos river basins. There are currently 12 species under review, with three species from Central Texas currently in candidacy for listing as endangered and one – the false spike mussel – already petitioned for a listing on the federal endangerment list.

Photo courtesy of the U.S. Fish and Wildlife Service.

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