Invasive zebra mussels have taken another step in their spread across Central Texas and now have a presence in Lake Austin, Texas Parks and Wildlife Department officials said Thursday.
Officials with the department and the Lower Colorado River Authority said scientists had been on the lookout for the small, striped mussels since an established, breeding population was discovered upstream at Lake Travis in June.
While Lake Travis has been classified as “infested” by the mussels — which can clog public-water intakes, damage boats and litter beach and lake beds with razor-sharp shells — Lake Austin has only been classified as “positive” for the species, which means that the mussels or their larvae have been detected more than one time.
Monica McGarrity, the wildlife department’s aquatic invasive species team leader, said authorities found a single zebra mussel larva near Tom Miller Dam and then a few small adult specimens attached to flotation devices and a barge near the Walsh Boat Landing on Aug. 9.
“The mussels we’ve found in Lake Austin at this point are roughly a half of an inch in size,” McGarrity said. “They are small, triangular mussels. They have a keel or a ridge on them that makes it so they’ll stand up, essentially, on a flat surface. That’s one way that you can tell them apart from native mussels or Asian clams.”
Greg Cummings, a wildlife department fisheries biologist, was with the group that found the mussels on Aug. 9.
“We were expecting mussels to be here at some point because Travis is right above Austin,” Cummings said. “We were not quite expecting that we would just find them near Tom Miller (Dam). That is a slight indicator that it was probably brought here by a boat, rather than traveled downstream through Mansfield Dam” from Lake Travis.
Cummings said there is still a chance that more of the mussels could be found in other parts of the reservoir.
Liz Johnston, environmental program coordinator with Austin’s Watershed Protection Department, said the mussels could threaten Lady Bird Lake as well, but it is unclear whether they will be able to spread and multiply in the same way that they have in lakes across the state.
“These systems are more (river) systems, so it is harder for the larvae to attach when water is moving,” she said. “Also, in other areas, lower, shallower reservoirs have not been infested as much. That’s probably related to temperature, so it’s going to be interesting to see what happens to Lady Bird Lake.”
McGarrity said the mussels could already be in Lady Bird Lake, but none have been found yet.
“It will require monitoring to see how the population develops, because these are really unique systems,” McGarrity said. “Unlike our really big reservoirs that have really cool temperature and depths, these do get hotter in a lot of areas, and they do have periodic drawdowns that can help pull the mussel populations back.”
The first zebra mussels arrived in Texas on Lake Texoma in 2009, about two decades after they were first found in the United States between Lake Huron and Lake Erie in the late 1980s.
Slowly, the species has crept its way through 10 more Texas lakes, including Canyon Lake, Lake Belton, Lewisville Lake, Eagle Mountain Lake and Lake Bridgeport.
Populations of zebra mussels have led to costly repairs in other states.
A 2009 report by the Idaho Aquatic Nuisance Species Task Force showed that zebra mussels clogging pipes in the Great Lakes cost the power industry more than $3 billion from 1993 through 1999.
The area of Lake Austin where the latest batch of mussels were found sits close to Austin Water intake systems, but Mehrdad Morabbi, operations manager for water treatment facilities, said Austin is in a better position to handle a potential outbreak of the species than other cities.
“We have actually installed a chemical feed system at Water Plant 4,” near Lake Travis, Morabbi said. “We did that during construction, so that chemical feed system will be able to feed a liquid chemical into the pipeline at the tunnel and keep that portion free of any colonies.”
He said there are two other main water treatment plants that don’t currently have that chemical feed system installed. Authorities expect to use divers to conduct more frequent inspection of those facilities and to clean them if necessary.
As scientists continue to monitor the lake, they are asking anyone who takes a personal watercraft onto the lake — whether a boat, kayak, paddle board or any other equipment — to completely clean, drain and dry the equipment before taking it onto another body of water.