Harmful Algal Bloom Notifications occur when water quality test results indicate that high risk conditions exist for water recreators or there has been a confirmed report of symptoms of algal toxin exposure. Notifications expire at the end of the calendar year and apply to an entire lake/waterbody due to the likelihood that high risk conditions will persist or reoccur.
Mina Lake 7/25/2021
Lake Mitchell 7/25/2021
Lake Hendricks 8/17/2021
Lake Madison 8/17/2021
Lake Traverse 8/17/2021
Beaver Lake (Yankton County) 8/9/2021
Lake Herman 8/27/2021
Lake Poinsett 8/30/2021
A harmful algal bloom occurs when toxin producing algae grow excessively in a body of water. In South Dakota, HABs are typically produced by blue-green algae, a primitive photosynthetic algae also known as cyanobacteria. Blue-green algae are capable of producing toxins that can be harmful to people and fatal to pets and livestock. In South Dakota, harmful algal blooms typically occur during the warm summer months in nutrient enriched lakes and ponds.
South Dakota Harmful Algal Blooms Interactive
To see reports of algal blooms and results of HABs monitoring in South Dakota, browse the South Dakota Harmful Algal Blooms Interactive Map. Be aware that this map does not show current conditions of toxin producing algae or algal toxins (cyanotoxins) in the state and should not be used to determine whether waters are safe for recreation at the current moment. Reports of harmful algal blooms are indicated on the map with red symbols. New reports will be added as they are received from the public or other entities. The map also presents the sample results of 2019 toxin producing algae monitoring. In 2020, monitoring for algal toxins and toxin producing algae are occurring as part of the Statewide Lake Assessment and other DANR projects. Results will be added to the map as the data is available in the winter of 2020-2021. To see the results of chlorophyll-a testing, visit the DANR Water Quality Monitoring Access Portal and search for or click on your waterbody of interest.
What should I do if I see an algal bloom?
If you witness what you believe may be a harmful algal bloom, the first, and most important action you can take is to protect people, pets and livestock by ensuring they stay out of the water. When in doubt, stay out! It is impossible to tell if an algal bloom is producing toxins without testing for toxins, so the safest course of action is to exercise caution. If you would like to contact DANR to report a potential harmful algal bloom, email DENRINTERNET@state.sd.us or phone 1-800-438-3367.
What should I do if I'm exposed to a harmful algal bloom?
If a person or animal comes into contact with HABs impacted water, take the following actions to protect yourself, your children, your pets, or your livestock:
To learn more about harmful algal blooms in South Dakota and see pictures of algal blooms, scroll through our HABs storymap below or view it in fullscreen here.