Boulder warns of possible algae blooms in nearby lakes, ponds
May 27—With temperatures heating up, the city of Boulder is reminding residents to be careful around city lakes and ponds because algae blooms may be present.
According to a news release from the city, at elevated levels some algae may produce toxins that are harmful to people and pets.
"Please remember to avoid contact with the water where algae are observed," the release states.
The Colorado Department of Public Health and Environment states that algae blooms occur naturally in aquatic ecosystems and can appear rapidly during hot weather. Blooms tend to appear in slow-moving water bodies such as lakes and ponds and may contain cyanobacteria, often referred to as blue-green algae.
While the majority of algae found in ponds and lakes during summer months are non-toxic, cyanobacteria can produce toxins that can be harmful to humans and dogs. Warmer temperatures, stagnant water and nitrogen and phosphorus or nutrient loading from fertilized lawns and other sources, facilitate algae and cyanobacteria growth, the release states.
Generally, the long, stringy, bright green strands that appear either slimy or cottony, or are mustard yellow in color, are not the harmful type of algae. Cyanobacteria blooms appear like thick, pea soup, create a thick mat of foam on the shoreline and look like spilled bluish-green paint on the water.
Swimming, wading, or boating is not allowed in city lakes and ponds. The city recommends dog owners practice caution at lakes and ponds where dogs are allowed to enter the water. Anglers should also exercise caution and follow state recommendations for cleaning caught fish.
According to the city, in previous years algae has been observed at Wonderland Lake in north Boulder. A recent research project suggests that the repeated presence of algae blooms in the lake is likely caused by phosphorus coming from fertilized lawns. High nutrients and high temperatures can lower oxygen in the lake and help contribute to fish kills.
Boulder does not test for cyanobacteria at lakes and ponds because the production of cyanotoxins can be highly variable. City officials recommend all residents use caution wherever algae may be present.
