The Pamunkey and North Anna Branches of Lake Anna in Orange, Louisa and Spotsylvania counties are experiencing a harmful algae bloom. The public is advised to avoid contact with the lake in some areas 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.
On Aug. 21, follow-up tests were collected at sites sampled previously on Aug. 15 (with the exception of Upper North Anna Branch) and included two new sites (1) Lower North Anna Branch and (2) Lower Pamunkey at Lake Anna State Park Beach.
The results of Aug. 21 samples indicate that concentrations of potentially harmful algae species exceed safe swimming concentrations in the vicinity of the upper North Anna Branch of Lake Anna at Zachary Taylor Highway (Rt. 522 bridge) and middle North Anna Branch at Barnes Point near Belmont Road (Rt. 719; “Holladay Bridge”); also the upper Pamunkey Branch at Simms Point/Harris Lane, in addition to the middle Pamunkey Branch in the vicinity of Belmont Road (Rt. 719 bridge; “Dillards Bridge”). In the vicinity of these areas, people and pets are advised to avoid swimming, windsurfing and stand-up-paddle-boarding as well as other activities which pose a risk of ingesting water or exposure to skin. The levels detected in this section of the lake present a moderate to high-risk for human health effects.
Additional tests also indicate lower concentrations of potentially harmful algae were present in the upper North Anna Branch of Lake Anna near Red House Point (Rt. 621 and Woodberry Farm Road, based on samples collected Aug. 15), and on Aug. 21, the lower North Anna Branch in the vicinity of Rose Valley Island. The levels detected in these areas present a low risk for human health effects but conditions may be favorable to cyanobacterial growth.
Samples collected on Aug. 23 at Lake Anna State Park Beach were at low concentrations that are not expected to pose a health risk.
Most algae species are harmless; however some species may produce irritating compounds or toxins. Multiple species of cyanobacteria capable of producing several toxins were detected in the Aug. 15 and Aug. 21 samples. Samples screened for two toxins collected Aug. 15 and Aug. 21 were below levels which may pose a health risk, however the concentration of potentially harmful algae species indicate that toxins may be present or may develop in the area. Advisory signs have been posted at areas such as marinas and campgrounds in the area. Locations where blooms were sampled mid-lake on these branches are not conducive to signage.
Algae blooms can occur when warm water and nutrients combine to make conditions favorable for algae growth. These conditions have occurred recently with the significantly warmer temperatures and sunny weather, which occurred after high amounts of rainfall over the last month. Discolored water or scums that are green or blueish-green should be avoided as they are more likely to contain toxins.
Properly cleaned fish fillets which are cooked to proper temperature are considered safe to eat; providing the fish is skinned and all internal organs are discarded. There is some research that suggests waterbodies with long-term, recurrent toxic algae blooms can result in algal toxin accumulation in the fillet of fish; however, toxins have not been detected above safe swimming levels in Lake Anna.
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. Additional samples will be collected the week of Sept. 5. The advisories will be lifted following a minimum of two consecutive weeks of acceptable levels for algal cell counts and/or toxin concentration. For more information on acceptable algae levels, see the Virginia Department of Health Recreational Advisory Guidance for Microcystin/Microcystis at www.SwimHealthyVA.com.
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 fresh water after coming into contact with algae.
- If you or your animals experience symptoms after swimming in or near an algal bloom, seek medical/veterinarian care.
- 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 www.SwimHealthyVA.com.
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