Blue-Green Algae Bloom Response for Beach Operators and Staff

Operator Action Steps

These instructions are for beach operators and staff to help protect patrons from potentially harmful blue-green algae blooms.

  • Monitor beach areas for blue-green algae.
  • Contact the local health department if blue-green algae is suspected.
  • Close swim area and post signs to prohibit wading and swimming if suspicious algae is in the swim area.
  • Post advisory signs if blooms are observed outside of the swim area.
  • Inform staff when suspicious blooms are present, when the swimming area is closed, and when advisories are in effect.
  • Report symptoms of blue-green algae exposure to the local health department.

What is blue-green algae?

Blue-green algae (cyanobacteria) are microscopic organisms that occur naturally in lakes, streams and oceans. Under certain conditions they can form dense blooms that discolor the water or produce floating scums.

Why is blue-green algae a concern?

Some blue-green algae can produce toxins, some do not. However, exposure to any blue-green algae can cause health effects in people and animals when water with dense blooms is contacted or swallowed or when airborne droplets are inhaled.

How do I recognize blue-green algae?

It could be a blue-green algae bloom if the water is blue-green, green, yellow, brown, red, has a paint-like appearance, or there is scum on the water surface.

pictures of blue-green algae blooms

What do beach operators and staff need to know?

  • People and animals should avoid contact with blooms because blue-green algae exposure can cause health effects.
  • Beaches should be monitored for blooms.
  • Blooms can appear and disappear rapidly, even in under an hour. Staff should be trained to identify blooms and take action to prevent people from being exposed.
  • Inform staff and beach patrons when suspicious blooms are present, when the swimming area is closed, and when blue-green algae advisories are in effect.

What should beach operators and staff do if they suspect a blue-green algae bloom?

Contact the local health department immediately if you suspect a bloom anywhere on a waterbody with a regulated bathing beach. Health department staff will help confirm that the bloom is blue-green algae and provide signs to post to help prevent exposure.

  • If the bloom is within the swimming area

    Prohibit wading, swimming, diving and any water contact activities in the swimming area. Post beach closure and advisory signs at the beach and other shoreline access areas.

  • If the bloom is outside the swimming area

    Advisory signs should be posted to inform beach patrons to protect themselves and their animals from contact with blooms. Staff should monitor the location of the bloom and if it moves into the swim area, water contact activities should be prohibited and a beach closure sign should be posted.

pictures of warning signs

When can the swim area be re-opened?

The local health department will provide guidance for reopening a beach. After the bloom is gone from the swimming area, a water sample from the swimming area must be collected. Wading, swimming and other water contact activities can resume if the results show that the water is clear of blooms and toxin levels are below a level of concern. Most blue-green algae blooms go away naturally, and can come and go in a short time period.

What are the health effects from blue-green algae bloom exposure?

Potential health effects include irritation of the skin, eyes, nose, throat and respiratory tract. Swallowing water with blue-green algae blooms or toxins can also cause nausea, diarrhea and vomiting. Ingesting water with high levels of blue-green algae toxins over long time periods has also been associated with effects on the liver and nervous system.

Low levels of blue-green algae (where there is no visible bloom) are not expected to cause health effects in most people who are exposed during recreational contact. However, some people could be more sensitive and might experience mild symptoms such as skin, eye or throat irritation or allergic reactions.

What should someone do after being exposed to blue-green algae blooms?

  • Rinse off with clean water immediately.
  • Consider medical attention for symptoms such as nausea, vomiting or diarrhea; skin, eye or throat irritation, allergic reactions or breathing difficulties.
  • Report symptoms that may be related to blue-green algae to the local health department as soon as possible.

Where can I get more information?

Please Note

Some documents on this page are saved in the Portable Document Format (PDF). If it's not already on your computer, you'll need to download the latest free version of Adobe Reader.