A modified clay called lanthanum-modified bentonite will be applied into Lady Bird Lake for the fourth year in a row to address toxic algae blooms in the water.

The overview

A harmful algae bloom occurred in Lady Bird Lake in 2019 and caused the death of five dogs. Ever since, officials have seen harmful algae in the lake.

Every summer for four years experts have sprayed a modified clay into the lake as part of a five-year pilot program. The program will cost the city $1.5 million.

The clay material reduces the amount of phosphorus in the lake, a key nutrient that cyanobacteria, or blue-green algae, needs to bloom. It will be applied starting June 3 to different parts of the lake throughout the summer.

A closer look

Algae thrives in warm weather, which Austinites are no strangers to, but is only harmful when it produces toxins.

Neurotoxins found in algae, such as anatoxin-A and saxitoxin, can cause symptoms in people including drowsiness, numbness and burning. Blue-green algae can also contain cylindrospermopsin, which can cause vomiting, fever and diarrhea, according to the Centers for Disease Control and Prevention.

Officials recommend:
  • Avoiding contact with algae
  • Not drinking from Lady Bird Lake
  • Rinsing off after contact with lake
  • Prohibiting dogs from licking fur after contact with the lake
Managing the impact

As a pilot program, the effectiveness of the clay is being monitored, and the program will expand based on results.

A reduction of harmful algae has been seen at Red Bud Isle after June applications of the clay. However, watershed protection officials have noted that algae returns by the following June.

Officials have noted the application of the clay east of I-35 in the lake hasn’t had any effect, likely due to new sediments from upstream bringing in more nutrients.

What residents should know

Lady Bird Lake meets Texas' recreational standards, and activities, such as paddleboarding and kayaking, are safe. Due to a city ordinance, however, swimming in Lady Bird Lake is prohibited.

The toxins have been confined to the mats of algae on Lady Bird Lake and haven’t been released into the water, so the lake has not yet needed to be closed to recreation, Austin officials said.

If a person has sudden, unexplainable symptoms after contact with algae, contact a medical provider or the Texas Poison Control Center. If a pet has sudden symptoms, contact a veterinarian. Incidents of exposure are encouraged to be reported to the Austin Watershed Protection Department.

For more information on harmful algae blooms, visit www.austintexas.gov/algae.