Harmful algal blooms occur when normally occurring cyanobacteria in the water multiply quickly to form visible colonies or blooms. These blooms sometimes produce potent cyanotoxins that pose serious health risks to humans and animals.

Although most algal blooms are not toxic, some types of cyanobacteria produce nerve or liver toxins. Toxicity is hard to predict in part because a single species of algae can have both toxic and non-toxic strains, and a bloom that tests non-toxic one day can be toxic the next.

Note: The HABs monitoring season ended on October 31, 2019. Warning Advisories are being removed from waterbodies. The Utah Department of Health and local health departments have determined that the health risk from HABs from primary contact recreation drops with the onset of colder temperatures.

The close of the monitoring season and removal of advisories doesn’t mean HABs are no longer present. HABs can persist throughout the fall and winter and can pose a potential threat to humans and pets. It’s important to recognize the signs of a bloom and take appropriate precautions. Recreators are advised to stay out of the water and avoid any contact with water or scum if they suspect a harmful algal bloom. Hunters and fishers should clean waterfowl and fish well and discard all guts.