Blue-green algae poisoning (or cyanobacterial toxicosis) occurs when dogs drink or swim in water contaminated by an algal bloom. Algal blooms are an overgrowth of cyanobacteria that can produce numerous types of toxins (specifically, cyanotoxins). The two most serious types of cyanotoxins (called microcystin and anatoxin), can cause liver or neurologic injury. Shock, liver failure, respiratory arrest and even death can occur.  

Algal blooms can be found in stagnant water, especially during warm weather spells or after periods with a noticeable lack of rain. They may appear as either blue-green or red-brown colored blooms, mats, foam or scum on the water. The water may also smell of rotting plant material.  

Lady Bird Lake experienced a harmful algae bloom in 2019, which sickened and killed several dogs. There have been harmful algae blooms on Lady Bird Lake every year since then. We have also detected harmful algae on Lake Austin.

Website to keep close at hand, when traveling with your furry family.

Current Status

Routine Monitoring (Updated 3/10/23): Blue-green algae is present at Red Bud Isle on Lady Bird Lake and at Jessica Hollis Park on Lake Austin. The blue-green algae is mixed in with lots of green algae. We have not tested the algae. Please assume it may be toxic and avoid it.


The dashboards display data from routine monitoring and sampling. They are temporarily unavailable during the winter and spring. Routine sampling will resume as summer approaches.

Incident-Based Sampling Results

  • “Barking Springs” on July 11, 2022: Dihydroanatoxin-A was detected in an algae sample. “Barking Springs” is the spillway area directly downstream of Barton Springs Pool. No toxins detected in water samples. More info in this news release: City of Austin Confirms Harmful Algae is Present at ‘Barking Springs.’
  • Barton Springs Pool on July 28, 2022: Trace amounts of Anatoxin-a were detected in water samples from the shallow end. The amount was below the World Health Organization’s thresholds for drinking water for infants and toddlers. The toxin was not found in subsequent testing. Separate algae samples were not collected. More info in this Memo to Mayor and Council about Monitoring in Barton Springs Pool.

Caution: Enter Water at Your Own Risk

There is always some level of risk in a natural water body. In addition to algae, bacteria, parasites and other dangers may be present.

People and Pets

  • Do not drink water directly from natural water bodies.
  • Avoid contact with algae.
  • Rinse skin or animal fur after contact with water.
  • Do not allow dogs to lick their fur prior to rinsing.

Do Not Enter a Natural Water Body If:

  • Water is warm or stagnant or you see scum, film or algae.
  • There has been rain in the past three days.
  • There are lots of dogs present.


  •       Avoid drinking from or walking and swimming in water that has visible algal blooms, scum, foam on the surface or that has an odor.  
  •       Check local advisories for warnings before visiting a particular body of water.  
  •       Remove stagnant water (plant containers, birdbaths, fountains, etc.) to prevent blue-green algae growth around the home.  
  •       If you think your pet may have been exposed to an algal bloom, rinse their fur with fresh water and bring them to a veterinary hospital immediately. 

Clinical signs 

The clinical signs for cyanobacteria toxicosis will vary depending on the specific toxins in the water. The two most dangerous toxins affect the nervous system and the liver.  

Clinical signs can develop rapidly or over several hours, and may include any of the following: 

  •       Vomiting 
  •       Diarrhea 
  •       Weakness 
  •       Pale gums 
  •       Collapse  
  •       Drooling 
  •       Muscle tremors 
  •       Difficulty breathing 
  •       Muscle rigidity  
  •       Paralysis 
  •       Seizures  
  •       Sudden death 


An initial diagnosis is made based on the presenting clinical signs and any history of exposure to water that may have contained an algal bloom. Water may be tested for cyanobacteria toxins to confirm a diagnosis. Your veterinarian will recommend blood work to look for signs of organ injury. They may also test for blood clotting abnormalities if the liver is damaged. 


Initiating treatment as early as possible after exposure to blue-green algae is critical. There is no specific antidote for cyanotoxins, and treatment involves intensive, supportive care for patients experiencing shock or respiratory arrest.  

Treatments may include: 

  •       IV fluids 
  •       Oxygen 
  •       Anti-seizure medication  
  •       Electrolytes and glucose  
  •       Blood products (e.g., whole blood or fresh frozen plasma) 

Additional treatments may include anti-nausea medications, antibiotics, liver supplements, muscle relaxants and atropine. Your veterinarian will monitor blood work during treatment and adjust medications as necessary.  

Decontamination of patients exposed to blue-green algae may not be performed because patients are usually in critical condition by the time they arrive at the hospital. If the patient is stable early after exposure, decontaminating may include bathing, inducing a patient to vomit, stomach pumping (gastric lavage), activated charcoal or a medication called cholestyramine. Activated charcoal may not be as effective for microcystins (liver cyanotoxin). 

Symptoms and Reporting Suspected Illness

If you, a family member or pet have sudden, unexplained symptoms after swimming, contact your medical provider, veterinarian or the Texas Poison Control Center at 1-800-222-1222. Please also let us know by completing our form:

You can find information on symptoms on the Centers for Disease Control and Prevention’s website, Illness and Symptoms: Cyanobacteria in Fresh Water




Algae Monitoring Sites