Have you ever felt unwell or like you had an allergic reaction after swimming in a pond? Well, the culprit could be blue-green algae, which thrives during warm weather in bodies of water experiencing eutrophication. Blooms of blue-green algae grow quickly and can produce cyanobacteria, which is toxic to humans and can even be fatal for pets.
With various long-term forecasts predicting that October temperatures will be higher than average, these algae risks, typically confined to the summer months, could extend into autumn. While blue-green algae occurs naturally in Colorado waters, historically it’s grown in small quantities.
In bodies of water tainted by excess agricultural fertilizer, nitrogen-based de-icing agents or even livestock and pet waste the algae can experience a bloom. Algal blooms are rapid growth spurts that affect the appearance, smell and composition of bodies of water. Health and environmental science professionals refer to these as “harmful algal blooms” (HABs). There is a higher chance of HABs being found in ponds, lakes and slow-moving tributaries near some farms, roads and dog parks.
Algal blooms often give water an opaque appearance with a pea-green tint. However, some blooms grow below the surface of water and may not be visible.
For people, exposure to toxic algae presents symptoms similar to allergies or common colds, and can include rashes or skin irritations, fatigue, fever, headache, sore throat or digestive problems. These issues are generally non-lethal, but anyone who suspects they’ve been in contact with toxic algae should shower or rinse with fresh water as soon as possible. It is recommended that people experiencing persistent or severe symptoms contact a healthcare provider.
Blue-green algae can be deadly to pets, who are also more likely to enter contaminated water.
It is even more risky if the animal drinks the affected water. Symptoms range from mild to serious. Minor symptoms may include drooling, low energy and loss of appetite; but they can be as severe as diarrhea, vomiting, stumbling and tremors.
If a pet comes into contact with HABs contaminated water, they should be removed from the water as quickly as possible. Owners should prevent the animal from licking their paws or fur until they’ve been thoroughly rinsed with clean water. If visible strands or chunks of algae are attached to their fur or skin, it should be picked or combed out. If a pet shows any symptoms, it’s advisable to contact a veterinarian immediately. It’s possible for animals to die within hours of exposure.
The Colorado Department of Public Health and Environment (CDPHE) asks residents to help prevent algal blooms and to report contaminated water. Practices which help decrease the likelihood of HABs include picking up and properly disposing of pet waste and minimizing use of chemical fertilizers and de-icers with urea or nitrogen-based ingredients.
Property owners can also take precautions by establishing native-flora buffer zones between gardens or agricultural land and nearby bodies of water, like ditches or ponds. The plants can strengthen soil, provide habitat for native birds and pollinators, mitigate mosquitoes and absorb excess nutrients from fertilizers. Suitable native plants in the Western U.S. include saltgrass, shrubby cinquefoil (popular for its small yellow blossoms), chokecherry shrubs, swamp verbena, columbines and butterfly milkweed.
CDPHE maintains a dashboard of recently reported algal blooms, safe water and potentially risky water. Because the only certain way to check for algal toxicity is to test for it, the department asks the community to report suspected toxic algae and to avoid entering suspicious water. Of 74 tracked bodies of water, 60 were reported safe, 11 with suggested caution due to blooms without detected toxins, three with verified toxic blooms and one as a third-party unverified report. Of those, Vega Reservoir between Rifle and Colbran was ranked as “caution” as of press time. Other potentially dangerous waters are further from the Roaring Fork Valley.
Readers can learn more about blue-green algae at cdphe.colorado.gov/toxic-algae