Boulder-area officials are warning residents to exercise caution at lakes and ponds this summer, to avoid toxic algal blooms that may appear in stagnant bodies of water as temperatures increase.
While the majority of algae found in lakes and ponds are not toxic, some algal blooms can contain cyanobacteria, which a Wednesday news release from Boulder and Boulder County said “can be harmful to dogs and humans at elevated levels.” Cyanobacteria growth can be a result of a number of things including warmer temperatures, stagnant waters and nutrient loading from fertilized lawns.
Swimming and wading in certain lakes such as Wonderland Lake in Boulder, where some algae already has been seen, has been prohibited, but the release urges residents to be aware of algal blooms in all stagnant bodies of water.
Philip Yates, a spokesperson for Boulder emphasized that residents should consider the warning beyond city limits as well, as last year there were reports up and down the Front Range.
“Blooms can appear rapidly in slow moving bodies such as ponds and lakes,” he said. “So, people need to be mindful. Not only in the city, but in other areas that they might recreate in.”
The release notes that neither the city nor county tests for cyanobacteria at lakes and ponds because the production of the toxins it can produce is highly variable. For example, harmful toxins can be detected at one point in time, and then not be detectable hours later.
The Colorado Department of Public Health and Environment described the cyanobacterial blooms, also called blue- green algae, as appearing similar to “thick pea soup or spilled bluish-green paint on the water’s surface and can also create a thick mat of foam along the shoreline.”
In contrast, algae that appear to be “long, stringy, bright green strands that appear either slimy or cottony, or are mustard yellow in color,” are generally not the harmful type of algae.
“People really do need to be mindful of making sure they keep their dogs and children out of water where they see algae,” Yates said.
