Harmful algae bloom at Lake Anna

by | Jun 30, 2023 | Health & Wellness

The Rappahannock Area Health District says the Upper section of Pamunkey Branch of Lake Anna in Orange and Spotsylvania counties is experiencing a harmful algae bloom (HAB). The public is advised to avoid contact with this specific area of the lake until algae concentrations return to acceptable levels. Some harmful algae, called cyanobacteria, can cause skin rash and gastrointestinal illnesses, such as upset stomach, nausea, vomiting and diarrhea. The area to avoid can be seen on an interactive Harmful Algal Bloom map. A status report containing the updated advisory areas may be viewed at Lake Anna HAB Status Report 6.29.23.

The section of the lake currently under a swimming advisory due to unsafe levels of cyanobacteria:

  • Upper Pamunkey BranchFrom the upper inundated waters of Pamunkey Branch to Runnymede Park

Cyanobacteria have the potential to produce toxins. People and pets are advised to avoid swimming, windsurfing and stand-up-paddle-boarding, as well as other activities that pose a risk of ingesting water. Activities such as boating may continue with proper precaution in advisory areas. Follow-up monitoring above Route 208 on the lake is planned (weather permitting) for the third week of July.

Lake Anna State Park beach as well as six other sites had acceptable cyanobacteria densities and do not require a swimming advisory. Results from several of these sites detected toxins, but all were at acceptable levels.

Algae blooms can occur when warm water and nutrients combine to make conditions favorable for algae growth. Most algae species are harmless, however, some species may produce irritating compounds or toxins. Avoid discolored water or scums that are green or bluish-green because they are more likely to contain toxins.

To prevent illness, people should:

  • Avoid contact with any area of the lake where water is green or an advisory sign is posted,


  • Do not allow children or pets to drink from natural bodies of water.
  • Keep children and pets out of the areas experiencing a harmful algae bloom and quickly wash them off with plenty of fresh, clean water after coming into contact with algae scum or bloom water.
  • Seek medical/veterinarian care if you or your animals experience symptoms after swimming in or near an algal bloom.
  • Properly clean fish by removing skin and discarding all internal organs, and cooking fish to the proper temperature to ensure fish fillets are safe to eat.
  • Contact the Harmful Algal Bloom Hotline at 1-888-238-6154 if you suspect you experienced health-related effects following exposure to a bloom.
  • Visit www.SwimHealthyVA.com to learn more about harmful algae blooms or to report an algae bloom or fish kill.

The Virginia Department of Health (VDH) and the Virginia Harmful Algal Bloom Task Force, which includes the VDH, the Virginia Department of Environmental Quality, and the Old Dominion University Phytoplankton Laboratory, will continue to monitor water quality in the lake. In general, advisories will be lifted following two consecutive test results with acceptable levels for algal cell counts and/or toxin concentration.

The Harmful Algal Bloom map is updated to reflect the HAB advisory status of Lake Anna. The recent advisory extent is summarized in the Lake Anna HAB Status Report 6.29.23. For more information visit www.SwimHealthyVA.com.

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