The Virginia Department of Health has reported a harmful algae bloom advisory for Lake Anna.
The 13,000-acre man-made lake — in Spotsylvania, Orange and Louisa counties —cools the Dominion Virginia Energy North Anna nuclear power plant, but also is surrounded by homes and used by boaters and swimmers.
The algae blooms are cyanobacteria, and the health department says it can cause skin rashes, upset stomach, nausea, vomiting and diarrhea.
The department issued the advisory on Tuesday. An online map shows the areas with the harmful algae blooms, in the North Anna and Pamunkey branches of the lake.
The department said samples collected on July 10 showed the harmful algae blooms in the middle and lower branches of the North Anna branches as well as the middle and upper branches of the Pamunkey.
The warning advises people to “avoid contact with the lake in these areas until algae concentrations return to acceptable levels.” The warning also advises keeping pets out of the affected spots in the lake.
Algae blooms typically happen in hot weather, which mixes warm water with nutrients that allow the algae to grow, according to the health department.
The health department and the Virginia Harmful Algal Bloom task force monitor the lake water quality monthly.
The lake had algae and other problems last year.
First, the lake was hit by E. coli. Then, algae blooms appeared in August, prompting a warning from the health department for people to avoid five areas of the lake.
To see the areas of the lake affected by the advisory, visit www.vdh.virginia.gov/environmental-epidemiology/harmful-algal-blooms-habs/algal-bloom-surveillance-map.