Austin expands battle with harmful, pet-threatening algae to north shore of Lady Bird Lake

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.

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. 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.