The testing in the area comes after a dog died following swimming in Barking Springs on July 10, a section of Barton Creek next to Barton Springs Pool. On July 22, the department detected potent neurotoxin dihydroanatoxin A in an algae sample from Barking Springs and ruled ingesting toxic algae as the dog’s likely cause of death.
As Barking Springs is next to the spillway at Barton Springs Pool, the department took algae samples from both the deep and shallow ends of the city-owned pool July 15 and Aug. 1. All but one algae sample from the pool came back clean; a July 15 sample from the shallower side of the pool detected trace amounts of anatoxin A at 0.029 µg/L July 28.
In an Aug. 4 letter to Mayor Steve Adler and Austin City Council, Katie Coyne, environmental officer and assistant director for the watershed department, said these levels are “far below levels of concern,” according to the World Health Organization.
The World Health Organization’s guidance threshold for anatoxin A is 30 µg/L for adults and 6 µg/L for children and infants in drinking water and 60µg/L for recreational waters.
“Given that the toxin level detected was so low, far below drinking standards for infants according to the World Health Organization, there is not a reason for concern, and swimmers should continue to follow normal guidelines for swimming in natural water,” a watershed department spokesperson said.
As toxic algae is most commonly found in warm, stagnant bodies of water, the department is collaborating with Austin Public Health to study the dynamics of toxic algae in Austin’s springs. An Austin Public Health spokesperson said the study “will inform our recommendations for future monitoring efforts.”
The Austin Parks and Recreation Department, which owns Barton Springs Pool, will “follow public safety and health guidance from partner agencies,” a watershed department spokesperson said.
As for Barking Springs, the watershed department recommended people avoid swimming in the area due to high bacteria levels. The high E. coli levels are likely from the presence of many dogs at Barking Springs, said Stephanie Lott, public information specialist for the department.
“As far as algae is concerned, people and their dogs should avoid the stagnant areas with algae and avoid handling or ingesting the algae,” a watershed department spokesperson said.
Because toxins have been detected in the algae and not the water at Barking Springs, contamination can only come from ingesting the algae, putting pets more at risk than humans. Pets may be exposed from drinking the water or ingesting or licking algae from their fur, according to the department.
The department is warning that harmful algae may be found in any body of water at any time. Warm, stagnant, scum- or algae-filled water should be avoided as well as water where it has rained in the last three days or areas where many dogs are present, the department said.
"When swimming in natural bodies of water, it’s always important to make sure you’re not drinking the water and you’re rinsing off after swimming, regardless of whether harmful algae is present,” a watershed protection department spokesperson said.