A troubling mix of soaring summer temperatures and near-static flow in Lady Bird Lake has city of Austin scientists worried again about a bloom of toxin-producing blue-green algae that can be deadly to pets frolicking in the water.
Last summer, the city began treating 22 acres near Red Bud Isle, upstream on Lady Bird Lake, with a claylike substance called Phoslock to slow or stop the growth of the algae. This year, the city’s Watershed Protection Department is expanding its use of Phoslock to the north shore of the lake in East Austin, from Interstate 35 to the lagoon by the Festival Beach boat ramp.
Watershed Protection will apply 30,000 pounds of Phoslock at each location Monday and Tuesday and will reapply Phoslock at Red Bud Isle on Wednesday. A second round of treatment is set for later in the summer. The cost for all the treatments, testing and lab work is $300,000, city officials said.
Why is blue-green algae a problem?
An algae sample taken from Red Bud Isle on May 30 indicated the presence of dihydroanatoxin, a previously detected, potent neurotoxin, Watershed Protection officials said.
“Some species of cyanobacteria, also called blue-green algae, can produce various toxins under the right conditions,” the Watershed Protection Department said in a statement last week. “When this occurs, it is called a harmful algae bloom or proliferation.”
The toxins not only can make people sick; they also can be deadly to pets. In 2019, several dogs died after swimming in Lady Bird Lake during a harmful algae bloom.
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If you plan to wade into the water with your dog anyway, make sure you do so in flowing, cooler waters that are less likely to allow the toxin-producing algae to thrive. Most cyanobacteria species, like the blue-green algae, grow and reproduce when water temperatures are above 65 degrees.
The city of Austin says pet owners should take their dogs to a veterinarian immediately if they become sick after swimming.
Symptoms of algae poisoning in dogs can pop up minutes to hours after they are exposed to algae or after they’ve ingested tainted water. Watch for excessive drooling, vomiting or diarrhea, foaming at the mouth, jaundice or an enlarged liver, blood in their urine or dark urine, stumbling, loss of appetite, abdominal tenderness, progression of muscle twitches or respiratory paralysis.
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Humans may experience different health issues, including a rash, irritation, swelling, sores, a fever, headache, eye irritation, or gastrointestinal, neurological, ear or respiratory issues.
Because other dangers, such as bacteria and parasites, may also be present, rinse after swimming in natural waterways and keep dogs from licking their fur before rinsing, city officials said.
How does Phoslock work?
Phoslock, which looks looks like gray cat litter, is mixed with water to form a material that binds to phosphorus and denies the blue-green algae a primary source of nutrients, thus slowing the spread of the algae.
When Watershed Protection applied Phoslock near Red Bud Isle last year, the department saw a 40% reduction in phosphorus available to the algae. Sediment testing last month “showed that the reduction in available phosphorus had persisted over nine months,” officials said.
“During treatments, boaters should avoid the treatment area and keep plenty of distance from the barge applying the Phoslock,” department officials said. “The barge will be spraying a gray slurry into the lake that will temporarily cloud the water.”
City officials said Phoslock “is safe for humans, the environment and wildlife, and will settle to the bottom in a few hours.”