Toxic blue-green algae confirmed at Prospect Lake in Colorado Springs

 Photo courtesy: City of Colorado Springs
Photo courtesy: City of Colorado Springs (KKTV)
Published: Jun. 15, 2020 at 5:06 PM MDT
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A popular Colorado Springs lake is closed over the return of toxic algae.

On Monday, the city announced the confirmation of blue-green algae in Prospect Lake at Memorial Park. The lake was closed a week ago after a visual inspection.

“Our region has again been experiencing hot, dry weather, creating conditions similar to what we experienced prior to the 2019 algae bloom in Prospect Lake,” said Erik Rodriguez, health, safety and environmental specialist with the Parks, Recreation and Cultural Services Department.

The lake is expected to be tested weekly until the algae bloom clears up.

Prospect Lake was closed for 12 weeks in the late summer and early fall of 2019 due to blue-green algae. Since that time, parks staff have taken proactive measures, including the application of an enzyme-based, non-pesticide treatment that consumes the biomass at the bottom of the lake and helps oxygenate the water. The first two treatments were applied on May 26 and June 11. Additionally, more water will be added to the lake, which will increase the oxygen level and help dilute the toxin.

During the closure, the following activities are prohibited:

swimming, bathing, paddle boarding, tubing, water skiing and non-motorized boating of any kind. No pets are allowed. The use of permitted motorized boats is encouraged as this activity can help aerate the water. Fishing areas will remain open, though anglers are urged to clean fish well and remove


What is harmful algae?

Blue-green algae are a type of bacteria common in lakes throughout Colorado. When conditions are right, blue-green algae multiplies quickly. Those conditions include sustained hot weather, stagnant water, and polluted stormwater runoff.

These conditions result in too much nitrogen, potassium and phosphorus in the water. This causes the harmful bacteria to grow faster than the ecosystem can handle. The increased bacteria harm water quality, decrease the amount of oxygen available to animals living in the water, and can produce a toxin that is harmful to humans and pets.

Blue-green algae are self-limiting, naturally-occurring bacteria, which means it eventually phases itself out of bodies of water.