Update Sunday 10 p.m.: Three more lakes in Colorado have tested positive for blue-green algae:

• Wonderland Lake, Thunderbird Lake in Boulder
• Quincy Reservoir in Aurora
• Sloan’s Lake in Denver
• Pikeview Reservoir and Prospect Lake in Colorado Springs

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Colorado Parks and Wildlife is warning the public of algae blooms in the state’s lakes and reservoirs. The majority of algae blooms occur in late summer.

Most algae is harmless and an important part of the aquatic food chain. However, lakes with high nutrients are more susceptible to blue-green algae, which is the specific type of algae capable of producing deadly toxins. Blue-green algae is responsible for the recent death of five dogs in North Carolina, Georgia and Texas.

Parks and Wildlife warns humans and their animals to stay out of the water if they appear to have excess algae. Algae feeds on nitrogen and phosphorous, which is present in fertilizers and dog excrement. The agency urged people to help keep algae away by using phosphorous-free fertilizers and picking up after their dogs.