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Look Out for Harmful Algal Blooms When Recreating this Summer

  • Rebecca Harbage
  • June 04 2024

HELENA—When recreating on Montana’s waterbodies, be on the lookout for harmful algal blooms (HABs) that can occur on Montana’s lakes and reservoirs. HABs can release toxins that can impact human and animal health. Report suspected HABs at HAB.mt.gov to help alert others and prevent illness.

How to identify a HAB:

  • A coloration or scum in the water that can look like spilled paint, pea soup, or grass clippings.
  • Often blue, green or red in color.

HABs can occur when certain water conditions (nutrient levels, sunlight and temperature) cause a rapid overgrowth of blue-green algae, also called cyanobacteria. Blue-green algae are native organisms and commonly occur at low, safe densities in Montana’s lakes, streams, and reservoirs. Blue-green algae are often confused with green algae since both can produce overgrowths (blooms) that can affect recreation, cause odor issues, and reduce oxygen in the water. However, green algae do not produce harmful toxins.

HABs can release harmful toxins in the water that may cause skin irritation, sicken humans and even kill pets or livestock if ingested. HABs do not always release toxins. Water sampling is the only way to determine if toxins are present.

When in doubt, stay out. Do not drink, swallow, or swim in water that shows signs of a HAB and keep kids, pets and livestock out. Direct contact, ingestion, or inhalation of the toxins may irritate the skin, eyes, nose, throat and respiratory system, or cause nausea, vomiting, diarrhea, headache, dizziness, muscle weakness or liver and kidney damage. If you suspect a HAB-related illness in a person or animal, call your health care provider or veterinarian immediately.

The Montana Department of Environmental Quality (DEQ) and Department of Public Health and Human Services (DPHHS) maintain a website where people can submit and view reports of suspected HABs at: HAB.mt.gov

Recreationalists may check the website and view the map of reported blooms, associated health advisories and information associated with reports. The site also has photos and information on how to identify a HAB. If you suspect a HAB, submit a report to HAB.mt.gov. State agencies will then work with the local jurisdiction to sample for the presence of toxins and monitor the incident. These reports are important for the health and safety of recreators and water users in the state, and they also help state agencies track where nutrient pollution may be an issue.

Nutrients like nitrogen and phosphorus fuel algae growth and potential HABs. Actions you can take to reduce nutrient pollution in Montana’s waters include:

  • Reduce your use of lawn or crop fertilizers.
  • Landscape with native plants that don’t need fertilizers.
  • If you live alongside a stream or lake, restore and protect native woody vegetation, plants, and grasses because they help filter pollution and stabilize land.
  • If your home relies on a septic system, have it regularly serviced and consider upgrading it to a higher-level treatment system.

DEQ will post confirmed HABs at HAB.mt.gov and on Facebook throughout the summer. Follow @MTDEQ for updates.

Tags: Water and Press Release