Toxins detected in algae in Lake Austin, Lady Bird Lake

The City of Austin says that low levels of dihydroanatoxin have been detected in an algae sample taken in mid-March from Lake Austin near Mansfield Dam.

Trace levels were also detected in two algae samples from Lady Bird Lake.

The city says that dihydroanatoxin is the same toxin that LCRA detected in other Highland Lakes in March2019 was the first year on record when toxic blue-green algae sickened and killed several dogs that played in the water at Lady Bird Lake. The following summer, another toxic algae bloom was detected there.

Cyanobacteria, or blue-green algae, are the source of the toxin and the city says this type of algae can be found in waterways in Central Texas throughout the year. The algae are more prevalent in warmer, more stagnant water, and more likely to produce toxins under these conditions.


This year however the first report of harmful algae followed a February freeze, this time at Lake Travis. Test results have since detected toxins emitted by blue-green algae at Inks Lake, Lake Marble Falls, and 10 locations on Lake Travis. Due to this, the Watershed Protection Department says it plans to reevaluate its monitoring program.

Dogs appear particularly vulnerable to dihydroanatoxin in algae mats, says the city, so dog owners are advised to not allow their dogs to ingest or touch algae in any area lakes, creeks, or water bodies. If owners allow their dogs in the water, it is at their own risk. It may help to rinse dogs after contact with water bodies to help prevent them from licking algae off their fur.

Dog owners are advised to take their pets to a veterinarian immediately if their dogs become sick after swimming in Lady Bird Lake and report the illness to 3-1-1.


Symptoms of exposure may include:

  • Excessive drooling, vomiting, and diarrhea
  • Foaming at the mouth
  • Jaundice and hepatomegaly
  • Blood in urine or dark urine
  • Stumbling
  • Loss of appetite
  • Photosensitization in recovering animals
  • Abdominal tenderness
  • Progression of muscle twitches
  • Respiratory paralysis

At this time, the risk to humans appears low and people may continue to boat and fish, following COVID-19 safety measures. However, people are advised to avoid handling algae, says the city. Swimming has been banned in Lady Bird Lake since 1964.