DDPHE Blog: What You Need to Know About Blue-green Algae

DDPHE Blog: What You Need to Know About Blue-green Algae

Published on August 15, 2024

Summer heat means algae blooms in our front range lakes. While DDPHE never recommends swimming, wading, or playing in Denver's lakes and streams, here's what residents should know as they enjoy their time in nature this season.

Algae is a natural part of our lake environments. Blue-green algae, also known as cyanobacteria, are microscopic organisms that naturally occur in Denver's lakes. Under warm, nutrient-rich conditions, they can grow rapidly and produce toxins harmful to both people and pets. DDPHE actively monitors Denver's bodies of water for signs of blue-green algae and tests for levels of toxicity to post warning signs in affected areas.

Recognizing Blue-Green Algae Blooms

DDPHE recommends Denver residents and visitors to avoid contact with water affected by blue-green algae blooms. These algae blooms can vary in appearance, but they often look like pea soup or green paint on the water's surface and can range in color from blue-green to reddish-brown. Sometimes, blooms form scums or mats that can be mistaken for paint spills. If you notice water that looks suspicious, it is best to avoid contact with the water.

Local bodies of water currently experiencing toxic blue-green algae blooms include:

• Duck Lake

Lakes experiencing potential or light blue-green algae blooms include:

• Ferril (big lake in City Park)
• Garfield
• Green Valley Ranch
• Harvey
• Rocky Mountain (had been significant earlier this summer, but has been managed)
• Sloans

Lakes that have been experiencing additional algae blooms include:

• Ferril
• Garfield
• Harvey
• Smith

Health Risks Associated with Blue-Green Algae

Not all blue-green algae are harmful, but some species can produce toxins that are dangerous to humans, pets, and wildlife. These toxins can cause a range ofsymptomsin humanslikeskin rashes, eye irritation, vomiting, diarrhea, seizures, or breathing problems.

Pets thatingestcontaminated water can suffer from severe poisoning. Symptoms include vomiting, diarrhea, weakness, and seizures. In pets, especially dogs, ingestion of contaminated water can lead to severe illness or death.DDPHE regularly tests Denver's waterways for toxic algae in the summertime.

What to Do If You Are Exposed

If you or your pets come into contact with water suspected to be contaminated with blue-green algae:

• Rinse off immediately: Wash the affected area with clean, fresh water.
• Monitor for symptoms: If symptoms such as skin irritation, gastrointestinal distress, or respiratory issues occur, contact a healthcare provider or veterinarian promptly.

What You Can Do

Blue-green algae blooms are a result of excessive amounts of nutrients along with other factors. By limiting the amount of nutrients in our storm water, we can all help lessen severity of blue-green algae in our lakes. If you fertilize your lawn, select products without phosphorus.

When you apply fertilizers, do everything you can to avoid over applying product to hard services. This includes sidewalks, driveways, and especially streets and gutters. Just a little phosphorus will go a long way towards supporting algal growth that our lakes and ponds receive from storm runoff.

Understanding blue-green algae and the risks they pose is crucial for protecting health and safe recreation. By staying aware and informed, we can reduce the impact of toxic algal blooms and ensure our bodies of water remain safe for everyone. For more information and updates on water quality and blue-green algae monitoring, please follow guidance from DDPHE's Water Quality Program.

Tagged as:

• Public Health & Environment