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Use caution. Harmful algae bloom warning for areas of Lake Anna

The Virginia Department of Health has issued a harmful algae bloom advisory for the North Anna Upper and Middle Branches in addition to the Upper Pamunkey Branch of Lake Anna. The impacted areas include Orange, Louisa and Spotsylvania.

The public is advised to avoid contact with the lake in this area until algae concentrations return to acceptable levels.

The State Health Department says 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 map at

A  VDH advisory says samples collected July 13 in the North Anna Upper and Middle Branches and in the Upper Pamunkey Branch below Rt. 522, indicated swimming advisories were necessary due to unsafe levels of cyanobacteria densities.   The sample collected at the Upper Pamunkey Branch at Simms Point/Harris Lane, indicated cyanobacteria densities were at acceptable levels. The advisory said two samples with cyanobacteria densities and cyanotoxin concentrations collected at least 10 days apart are necessary to lift the advisory, therefore the advisory remains in place.

Cyanotoxins were detected at each of these sites, but were well below safe swimming levels. 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.

Follow-up monitoring above Rt. 208 on the lake are planned in two weeks.

The sections of the lake currently under advisory:

Pamunkey Branch (Rt. 522 site added, Branch remains under advisory)

  • Upper – From the upper inundated waters of the Pamunkey arm of the lake downstream to just above the confluence with Terry’s Run (does not include Terry’s Run).
  • Upper – From the upper inundated waters of the North Anna arm of the lake downstream to the Rt. 522 Bridge.
  • Middle – From the Rt. 522 Bridge downstream to the Lumsden Flats/Rose Valley Cove.

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

The State Health Department says to avoid illness…

  • 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.
  • If you or your animals experience symptoms after swimming in or near an algal bloom, seek medical/veterinarian care.
  • To ensure fish fillets are safe to eat, properly clean fish by removing skin and discarding all internal organs, and cooking fish to the proper temperature.
  • If you suspect you experienced health-related effects following exposure to a bloom, contact the Virginia Harmful Algal Bloom Hotline at 1-888-238-6154.
  • To learn more about harmful algae blooms or to report an algae bloom or fish kill visit

The Virginia Department of Health and the Virginia Harmful Algal Bloom Task Force, which includes the Virginia Department of Health, Virginia Department of Environmental Quality, and the Old Dominion Phytoplankton lab, 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. An advisory may be lifted or maintained at the discretion of the health department. For example, after one test an advisory may be lifted if results are within safe levels for swimming if other information indicates exposure or human health risk is low.

A status report is updated to reflect the HAB advisory status of Lake Anna under routine monitoring online at “Lake Anna Status Fact Sheet.”

For more information visit

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