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Longmont Monitoring Lakes and Ponds for Blue-green Algae

Post Date:08/23/2019 10:57 AM

Potentially harmful blue-green algae (cyanobacteria) blooms have been identified at Golden Ponds. 

While swimming, boating and wading are prohibited at Golden Ponds, fishing is allowed. Visitors should exercise caution while fishing and follow state recommendations to clean any caught fish thoroughly.  

Although visitors might be tempted to dip their toes or allow their pets to play in the water during this unseasonably hot weather, visitors and residents should exercise caution and keep children and pets out of the water in any areas where algae blooms are observed. 

Longmont staff has visually inspected Union Reservoir for potentially toxic algae, and found no evidence of a bloom.  Union Reservoir remains open for swimming, fishing and boating. 

Blue-green algae can produce toxins called cyanotoxins that can be harmful to humans and animals. These algae occur naturally in aquatic ecosystems and can appear rapidly in the summer in slow moving water such as lakes and ponds when the weather is hot.  Some species can produce cyanotoxins during algal blooms which can be harmful at elevated levels if ingested by dogs and humans or during wading or other recreational contact. The toxicity of a blue-green algae bloom is difficult to predict because a single species can have toxic and non-toxic strains, and toxic strains do not always produce toxins. The St. Vrain Creek, with its flowing water, is less susceptible to such blooms.

Union Reservoir is the only reservoir where swimming is allowed in the City of Longmont. Swimming in other bodies of water like those at Golden Ponds, Izaak Walton Nature Area, Jim Hamm Nature Area, Sandstone Ranch and others is never allowed. McIntosh Reservoir allows carry-on, non-motorized boats only. This includes canoes, kayaks, belly boats, sailboats and other small boats. Inner tubes are not allowed and swimming is prohibited at all times.

Many cities across the Front Range are finding blue-green algae in their lakes and ponds. The City of Longmont continues to monitor reports of blue-green algae and will provide additional notices if it is found. According to the Colorado Department of Public Health and Environment, harmful algae blooms often have the following characteristics: 

• May look like thick pea soup or spilled paint on the water's surface. 
• Can create a thick mat of foam along the shoreline.
• Usually are green or blue-green, although they can be brown, purple or white. 
• Sometimes are made up of small specks or blobs floating just at or below the water's surface 

Harmful algae blooms are NOT:
• Long, stringy bright green grass strands that feel either slimy or cottony.
• Mustard yellow (this probably is pollen).

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