Algae samples taken from Lady Bird Lake on July 13 have tested positive for the harmful toxins that killed five dogs in 2019.

According to data provided by the city of Austin on its website, samples from algae floating in the water near Red Bud Isle and Festival Beach tested by University of Texas researchers both have the toxins present.

The city is also monitoring algae samples at the mouth of Barton Creek and Auditorium Shores every week.

While algae mats in those areas have not yet tested positive for the toxins, a spokesperson from the Watershed Protection Department algae can move around the body of water and recommended dog owners do not allow their pets to swim in or drink from Lady Bird Lake.

The city has set up an online testing dashboard to provide information to residents, which provides an updated risk level that is currently high. Last summer, after reports of the toxic algae killing dogs, the city shut down Red Bud Isle, a popular off-leash dog spot, from August to November.


Hot, dry weather fosters an environment that allows algae to grow, according to researchers. Dogs who are exposed to the potentially fatal algae by licking it from their fur can exhibit a number of serious symptoms, including excessive drooling, foaming at the mouth, blood in urine and respiratory paralysis.

The algae’s risk to humans is currently low, according to the city. People have not been allowed to swim in Lady Bird Lake since 1964.