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Second Wave Of Blue-Green Algae Crops Up At Red Bud Isle

Toxic algae found at Red Bud Isle
Jorge Sanhueza-Lyon
Toxic blue-green algae is blamed for the deaths of a handful of dogs.

Blooms of blue-green algae on Lady Bird Lake persist, city officials said Wednesday.

After a brief decline in the neurotoxin-laden algae at Red Bud Isle, the Austin Watershed Department says, another swath of algae is covering as much as a quarter of the surface.

The blue-green algae, also known as cyanobacteria, produce toxins blamed for the deaths of a handful of dogs that swam in Lady Bird Lake. The city continues to caution owners not to allow pets to come in contact with the algae, which can cause paralysis and death. 

The city closed off Red Bud Isle in August and began testing at additional sites on Lady Bird Lake, including along Auditorium Shores, at the boat ramp at Lake Austin and downstream from Longhorn Dam.

RELATED | Here's What You Need To Know About The Toxic Algae Blooms On Lady Bird Lake

The city says owners should let pets swim at the Barton Springs spillway, known as Barking Springs, at their own risk, as cyanobacteria previously has been detected downstream toward Lady Bird Lake.

Scientists collecting samples found a new bloom of algae at Red Bud on Tuesday that "appears similar to the type that produced toxins in August," the city said. The algae and toxin levels had dwindled a few weeks ago, but now the algae have returned and have covered 20% to 25% of the surface. The city says it's awaiting more test results.

Red Bud Isle is still closed.

Currently, the city says it has no means to eliminate the bacteria, as using chemicals could harm ecosystems in Lady Bird Lake. The algae will naturally die off as temperatures drop or as rains increase the flow of water in the lake. 

Officials say the algae can cause paralysis and respiratory failure in dogs. Owners should monitor pets if they have ingested the water and take them to the vet if they exhibit these symptoms:

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

The city says the algae could potentially be harmful to humans, too. Boating and paddleboarding are allowed on the lake – at people's own risk. As always, swimming is not allowed in Lady Bird Lake.

The algae stems from a handful of environmental factors, including consistently warm temperatures, an increase in runoff from human waste upstream and even zebra mussels, which filter the water and allow the blooms to thrive. It's become more common in the United States and will likely continue to be a problem as Austin sees more triple-digit days.

Andrew Weber is a general assignment reporter for KUT, focusing on criminal justice, policing, courts and homelessness in Austin and Travis County. Got a tip? You can email him at Follow him on Twitter @England_Weber.
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