City officials say two separate samples of algae near Red Bud Isle have tested positive for traces of a neurotoxin, but samples in other parts of Lady Bird Lake were found to be "harmless."
Three dogs died recently after swimming in Lady Bird Lake.
The city says the dangerous blue-green algae appears to be confined to that area, which has been closed since Wednesday. Officials say they haven't found the toxic algae at eight other locations on Lady Bird Lake – as well as at the Walsh Boat Ramp on Lake Austin and downstream of Longhorn Dam – but they still urge people and pets to avoid direct contact with the water as a precaution.
"Be aware the algae can move and because there may be potentially harmful algae in other areas of the lake, people should continue to minimize their exposure to the water and avoid all contact with algae," the city said in a statement.
The neurotoxin in the blue-green algae can cause respiratory paralysis and death, the city said, and owners should monitor their pets for the following symptoms, if they've been exposed to water containing the algae:
- Excessive drooling, vomiting, diarrhea
- Foaming at the mouth
- Jaundice, hepatomegaly
- Blood in urine or dark urine
- Loss of appetite
- Photosensitization in recovering animals
- Abdominal tenderness
- Progression of muscle twitches
- Respiratory paralysis
Austin Public Health has not seen any emergency room admittances that would suggest humans have been affected by exposure to the algae.
The city says it's working on a plan to test Lady Bird Lake for toxic algae, and that it's taken samples at Barton Creek, as well.