Harmful Algal Blooms (HABs)
A HAB is an overgrowth of, cyanobacteria (blue-green algae) in surface water. Cyanobacteria are
microscopic organisms found in all types of water. They are more like bacteria than plants, but
because they live in water and use sunlight to create food (photosynthesis) they are often called
"blue-green algae." Cyanobacteria are important to freshwater ecosystems because they make oxygen as
a by-product of photosynthesis, and they are a food source for other organisms.
An Advisory means a blue-green algae bloom is present in portions of the waterbody. The blue-green algae may be
harmful to humans and pets. To reduce the risk of illness:
- Do not swim, waterski, or tube if the water looks like spilled green paint or pea soup.
- Avoid swallowing water and watch small children and pets who may ingest water.
- Rinse off with clean water after swimming.
- Stay away from areas of scum when boating.
A Warning means a blue-green algae bloom is present over a significant portion of the lake and excessive microcystin levels have been measured.
- Avoid contact with the water.
- Individuals should not take part in contact recreational activities (e.g., swimming, water skiing, kayaking and paddle boarding).
- Do not allow pets in the water.
Active Harmful Algal Bloom Advisories/Warnings:
Current List of Lakes in Table Format
Current Harmful Algal Bloom Map
The Harmful in Harmful Algal Bloom
Under certain environmental conditions, cyanobacteria can multiply quickly and form a bloom. Some
species of cyanobacteria produce cyanotoxins that are released when the cells die and rupture. The
toxins can cause harm to people, wildlife, livestock, pets and aquatic life. Almost every year in North
Dakota, a few cases of pet and livestock deaths occur due to drinking water with HABs.
Additional effects of HABs include:
- Blocking sunlight needed for other aquatic organisms
- Raising treatment costs for public water supply systems and industries
- Depleting dissolved oxygen as the algae dies off, resulting in fish kills
Specific human health effects are:
- Allergic-like reactions
- Skin rashes
- Eye irritation
- Respiratory irritation
- Neurological effects
What Grows Algae?
- Excess nutrients (phosphorus and nitrogen)
- Warm water temperatures
- Slow-moving water
The major source of food for algae is nutrients that enter North Dakota lakes from:
- Fertilizers (fields and yards)
- Livestock and pet waste
- Septic systems
The Source of the Problem
Once a waterbody has an excess of nutrients, the problem cannot be fixed overnight. Nutrients must be
removed mechanically and/or allowed to be reduced naturally through internal cycling, while limiting the
sources of nutrients in the watershed. Several North Dakota lakes have hypolimnetic drawdown systems
that remove nutrient-rich water from the bottom of the lake. These systems can be effective at removing
nutrients, but they do not address the nutrient sources.
What Can You Do?
Everyone plays a part in feeding the algae, from how you fertilize your lawn to the timing of fertilizing
a 160-acre field, to whether or not you pick up your pet's waste, to the proper management of livestock
waste. Tips to reduce nutrients from entering runoff to our surface waters:
- Sample the soil in your yard before you fertilize.
- Leave your grass clippings on the lawn - they give nitrogen back to the lawn.
- If you do need to fertilize, use only the recommended amount of product and keep it off sidewalks
and other hard surfaces.
- Use field soil samples to calculate a nutrient budget for your crops.
- Complete a comprehensive nutrient management plan for your farm.
- Sample manure before applying it to the soil to ensure it is applied at the correct agronomic rate.