AUSTIN (KXAN) — The City of Austin’s Watershed Protection Department said it saw a lot of green algae Monday on Lady Bird Lake, but warned there might be blue-green algae mixed in.

While the department said it had not yet tested the algae, people should assume the algae might be toxic and avoid it.

According to the city, a harmful algae bloom occurs when Cyanobacteria, also called blue-green algae, produces toxins.

“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,” the city said.

In addition to Lady Bird Lake, the city also advised avoiding algae on Lake Austin as well.

Watershed Protection’s routine algae sampling has been focused on the traditional algae growth seasons of summer and fall and is paused during winter and spring to allow staff time to process data and adjust methods accordingly, according to the city.

As for drinking water, the city said Austin Water regularly tests algae levels on Lake Austin and Lake Travis near their intake pipes and has not seen levels of concern for drinking water.

According to the city, blue-green algae is often mixed in with other types of algae, and the city said it was treating specific areas of Lady Bird Lake to lower the nutrient levels in the lake to help reduce the amount of harmful algae.

More information on blue-green algae is available on the City of Austin website.