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Harmful Algal Blooms: Recreation

Algal blooms occur most frequently in nutrient-rich waters during hot, calm weather. Many lakes and reservoirs in Utah are subject to these conditions during the late summer and early fall. Toxic blooms in recreational waters can cause illness in humans and kill livestock and pets that drink the water.

The “algae” in an algal bloom are actually photosynthesizing bacteria called cyanobacteria. They can cause illness in humans, pets, waterfowl, and other animals that come in contact with them.

Because natural surface waters contain bacteria, algae, viruses, and other pathogens that if consumed may pose health risks, you should not drink untreated water in recreational areas.

Can water containing harmful algal blooms be used for recreational activities?

Because it is very difficult to tell when toxins are being produced from an algal bloom, we recommend that you do not recreate in or on water that has a greenish layer of scum or a floating mat. You are much more likely to experience adverse health effects if you swim, wade, waterski, jet-ski, or windsurf in or on water containing an algal bloom.

What should I do to protect my pet?

Animals are usually eager to swim in or drink lake water. They may experience skin irritation if they swim in water with an algal bloom, but they are more likely to have a severe reaction, even death, from drinking or eating cyanobacteria or licking it off their fur. Keep pets away from waters with algal blooms and any surrounding shorelines that contain accumulated algal scum.

Is it safe to let my children or pets swim in ponds?

By design, many farm ponds, golf course ponds, and stormwater detention ponds are constructed to trap nutrients, eroded soil, and other debris. By doing so, they prevent these materials from reaching nearby lakes, ponds, and streams. But because more nutrients may be available and because these types of ponds are generally more shallow and warm, it is possible for them to experience more frequent harmful algal blooms that may produce toxins. Again, a common sense approach is recommended for such ponds: if a scum layer or floating mat is present or the water looks like pea soup or green or blue paint, do not let your children or pets swim in it.

Can I eat fish from water containing harmful algal blooms?

Fish caught in affected waters pose unknown health risks. Exercise caution when considering whether to eat fish caught in areas where major algal blooms occur. If you choose to eat them, remove all fat, skin, and organs before cooking because toxins are more likely to collect in these tissues. Also, ensure to rinse the prepared fish in clean water prior to cooking.

How can I protect myself when I am camping or recreating at a lake with a bloom? 

Don’t go into the water and keep children and pets away. Never drink or cook with water from an algal bloom. If you come in contact with the water, wash off thoroughly with soap and another source of water if available.

Can I treat toxins in the water to make it safe to drink? 

No. Personal water filtration devices for camping or hiking have not been proven to be effective. Boiling water will not remove the toxins; in fact, it will concentrate them and increase the water’s toxicity.

For more information, visit: Wisconsin Department of Natural Resources, the New York Department of Environmental Conservation, Oregon Health Authority, Washington Department of Ecology, and the U.S. Environmental Protection Agency.