Information on the Harmful Algae Bloom – Lake Anna

Orange, Louisa, and Spotsylvania Counties, VA

VDH Advisories Last Updated September 29, 2018

Click HERE for the updated press release.

*NEW* For information on blooms in the Dominion Virginia Power Waste Heat Treatment Facility lagoons (WHTF, private property) please visit the Dominion Energy website at: Sampling locations identified by Dominion Energy are noted on the VDH HAB Map with purple dots (private lake).

Algae are microorganisms which are naturally occurring in fresh and brackish waters and some species have the potential to produce toxins when they accumulate at high numbers. A bloom becomes visible at high numbers and may form a scum that looks like spilled paint or mat on the water surface which may appear green, bluish-green, or reddish-brown in fresh water. Blooms can become harmful when they produce a toxin, which if ingested may affect the nervous system or the liver. Some toxins may also cause skin irritation such as a rash, tingling, or numbness. In the environment, algae blooms may cause fish kills or wildlife mortality. Algae blooms may be indicative of water pollution, such as nutrients from discharges or non-point source runoff from agriculture or residential fertilizer applications, but may also occur naturally.

A summary of the current advisories are below. Scroll down to see the current advisories in the HAB Map.

WARNING: “No-Swimming” Advisory Areas (red dots in HAB Map): 

Potentially harmful algae species detected in eight areas are at levels that present a moderate to high risk for human health effects. Coves, shallow areas, and shorelines in these areas are likely to have scum present. VDH is issuing or continuing a human health advisory for these areas and the public should avoid swimming in these vicinities:

  • Upper Pamunkey Branch east of Rt. 522 bridge (38.14309, -77.91724)
  • Upper-Middle Pamunkey Branch at Simms Point/Harris Lane (38.13942, -77.89372)
  • Lower-Middle Pamunkey Branch at Rt. 719 “Dillard’s Bridge” (38.13505, -77.8661)
  • Lower Pamunkey Branch at Lake Anna State Park Beach (112324, -77.833099)
  • Upper North Anna Branch near Goldmine Creek and “the Sandbar” (38.11517,-77.93754)
  • Middle North Anna Branch at Rt. 719 Bridge (38.11063, -77.88568)
  • Lower North Anna Branch near Rose Valley Island (38.10347, -77.85698)
  • Fisherman’s Cove (38.0474, -77.74151)

Activities such as swimming, wading, skiing, tubing, and stand-up paddle-boarding are not advised in the above locations while the bloom is ongoing.

Children and dogs are particularly vulnerable to cyanobacteria toxins (if present) and should avoid contact with the water in above areas.

ATTENTION: “Harmful Algae Detected – Be Aware of Blooms” In These Areas (orange dots in HAB Map):

Potentially harmful algae species detected in two areas are at levels that present a low to moderate risk for human health effects. VDH is notifying the public of the bloom in these areas but current levels do not warrant a “no swimming” advisory. Be aware of the bloom as water conditions may change quickly in these areas. Avoid contact with the water if scums appear on the water surface in these vicinities:

  • Upper-Middle North Anna Branch at Rt. 522 Bridge (38.11607, -77.91367)
  • Christopher Creek Branch north of Rt. 522 Bridge (38.10049, -77.89427); based on 9/5 samples – continued advisory

Above is an example of a sign which you might see which signifies there have been harmful algae detected at levels of concern in the above areas.


When algae are below levels which could pose a health risk for two consecutive weeks of sampling, the advisories will be downgraded or lifted.


In prior sampling events, Low Densities of Potentially Harmful Cyanobacteria – No Health Advisory Issued In these Areas (yellow dots in HAB Map):

Low concentrations of cyanobacteria were found in the following locations. These levels should not pose a human health risk. The public should be aware of the bloom in up-lake areas because water conditions may change quickly. Coves, shallow areas, and shorelines in these areas have the potential to have scum due to proximity to other bloom areas. Avoid contact with the water should scums appear in these vicinities:

  • Thurman Islands – Lake Anna (GPS 38.06581, -77.76877)
  • Cocktail Islands – Lake Anna (GPS 38.05536, -77.7751)

In prior sampling events, locations where there were no potentially harmful Cyanobacteria detected (grey dots in HAB Map):

  • Contrary Creek at Rt. 652 – Lake Anna (GPS 38.063112, -77.83194)
  • Sturgeon Creek near mouth of Joeys Creek – Lake Anna (GPS 38.07911, -77.78778)
  • Dukes Creek near confluence with Lake Anna (GPS 38.05181, -77.74914)
  • Lake Anna – mid-lake near 2nd berm of Lake Anna Power Station (GPS 38.03103, -77.7378)
  • Valentine Cove – Lake Anna (GPS 38.02169, -77.71211)
  • Lake Anna at Rt. 208 Bridge (GPS 38.08578, -77.81385)


The next round of algae monitoring for Lake Anna is currently being planned – check back for an update soon. Unfortunately, the Virginia HAB Task Force does not have the capacity to respond to every scum report in Lake Anna. When in doubt, stay out!

If you would like to submit your scum observations to the online HAB report, VDH will include your scum report in the HAB map so the public is aware of locations where scum has been sighted. LOOK for the “blue dots” on the HAB map for crowd-sourced scum reports!

Double-click on the map in the area of Lake Anna (north-west of Richmond) to zoom in- Expand the map [ ]  and click on dots to review sample results for each site. The color legend for the HAB Map is below.

Summary of the Harmful Algal Bloom Investigation to-date…

The bloom was first detected Aug. 7th by the Department of Environmental Quality (DEQ). DEQ reported to the Virginia Department of Health (VDH) there appeared to be an algae bloom in the upper Pamunkey and North Anna Branches of Lake Anna during the monthly sampling run. Preliminary field algal toxin test conducted by DEQ suggested that toxin was being produced in the upper North Anna Branch.

Additional samples were collected by DEQ on Aug. 15 and analyzed by the Old Dominion Phytoplankton (ODU) Lab. The upper Pamunkey Branch of Lake Anna at Simms Point/Harris Lane had cyanobateria present at concentrations below the threshold for a recreational advisory (<20,000 cells/mL). The upper North Anna Branch at Red House Point/Woodberry Farm Rd. and  the Middle Pamunkey Branch at Belmont Rd. Rt. 719 “Dillards Bridge”, had multiple cyanobacteria species present at total toxigenic cell count ranges between 20,000 -100,000 cells/mL. Microcystin and Cylindrospermopsin concentrations were below detectable limits. These levels posed a moderate concern for human health risk requiring notification of the public (recreational use is not restricted at this level). The middle North Anna Branch of Lake Anna at Belmont Rd. Rt.719 “Holladay Bridge”, had multiple cyanobacteria species present at total toxigenic cell counts above 100,000 cells/mL. Toxin concentration was just above the detectable limit for Microcystin (0.35ppb, detectable limit 0.15 ppb) and the Cylindrospermopsin concentration was below detectable limits. These levels posed a moderate to high human health risk requiring notification of the public and a recommendation to avoid swimming in the vicinity.

Samples collected by DEQ on Aug. 21st indicated that harmful algae concentrations increased from prior samples collected  in the Pamunkey and North Anna Branches of Lake Anna on 8/15. DCR collected samples at the state park beach on 8/23, which indicated there were toxigenc cyanobacteria present but below levels which should pose a health concern.

Samples collected on 9/5 are indicated that while there was scum in areas of the Lake south of Route 208, cyanobacteria densities were low in addition to toxin levels. The majority of the “No-Swimming Advisories”  were  downgraded to the mid-level advisory for the Pamunkey and North Anna Branches of the Lake.  The Upper Pamunkey and Upper North Anna Branches, in addition to Fisherman’s Cove are remained under a “no-swimming” advisory.

Samples collected on 9/25, resulted in nearly all sites of the Pamunkey and North Anna Branches – including the lower sites – being upgraded to ‘no-swimming advisories’. This is likely in response to heavy rains from Florence and continuation of warm temperatures. Lake Anna State Park beach is also under a ‘no-swimming’ advisory, where sampling until 9/25, indicated low levels of cyanobacteria.  Two sites which had lower concentrations of cyanobacteria than previously sampled include Fisherman’s Cove (8,600 cells/mL) and North Anna Branch near Goldmine Creek and the Sandbar (24,000 cells/mL). These sites remain as ‘no-swimming’ advisory areas because 2 consecutive samples below thresholds are necessary to downgrade or lift the current advisory.

Scum on the water surface of Fisherman’s Cove 8/25/18   (photo credit R. Saunders) 


Photo of Microcystis aeruginosa; dominant cyanobacteria from 8/28/18 sample taken at Fisherman’s Cove  (photo credit ODU Phytoplankton Analysis Laboratory)

The next round of algae monitoring for Lake Anna is scheduled for late September, depending on weather.

Information about Lake Anna…                                                                                               

Picture is of Lake Anna State Park Beach 8/23/18 courtesy of DCR staff             

The 9,600-acre lake is a popular recreational and vacation destination. Lake Anna State Park, which features a swimming beach and boat ramp, is located at the confluence of the Pamunkey and North Anna Branches of Lake Anna. Several marinas and a campground are also along the shores of the Lake.

There have been multiple complaints of a bloom in the ‘hot side’ of Lake Anna, which is privately owned and not publicly accessible. Complaints in these areas will be forwarded to Dominion Virginia Power biological staff to investigate. If you would like to submit a HAB report online for blooms/fish kills on the ‘hot side’ VDH will forward your complaint to Dominion Virginia Energy.

The lake is very large and water quality has the potential to be very different from one area to the next. Officials can only speak to the results which have been collected at each site. The recommendations are based on cyanobacteria concentrations at the time of collection. The public is encouraged to be aware of algae blooms while on the lake when in areas which have not been sampled and to watch for areas where there is a color change or where there appears to be a scum or film present. In addition, all natural bodies of water contain viruses, protozoans, and bacteria which may pose health risks, especially following rain events. The VDH advises the public to avoid swimming after rain events.

Harvesting fish from an algae bloom providing the fillets are properly cleaned and cooked, and the organs and skin are discarded, should not pose a health risk. 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 Environmental Quality (VDEQ), VDH, and Old Dominion University (ODU), and the Department of Conservation and Recreation (DCR) will conduct additional testing at the end of September, weather permitting. The tests assess the presence and abundance of harmful algae species in addition to evaluating potential toxins the algae may produce and health risks associated with them. When algae are below levels which could pose a health risk for two consecutive weeks of sampling, the advisories will be lifted. Results of analyses will be posted on the Algal Bloom map at


Looking for signage or other resources?  Visit the

Virtual HAB Toolkit

for brochures, signage, and other helpful materials.


  • Be aware of algae blooms and stay safe while recreating by following these practices:

    • Do not let children, pets, or livestock get into or drink water from natural waterbodies.
    • Avoid direct contact with water that has unusual color or where blue-green bacteria have been identified. This means no swimming, wading, paddling, diving, or water-skiing in affected waters.
    • If skin is exposed to algae bloom water, wash off with fresh water. Use rubber gloves if contact with affected waters is unavoidable.
    • If you or pets are exposed to a bloom and are experiencing health effects, consult your local health care provider/veterinarian.
    • It is considered safe to consume properly cooked fish fillets cleaned from fish caught in waters with an algae bloom. Discard the carcass and guts and thoroughly wash skin and surfaces that come into contact with the fish.
    • Report health effects which are believed to be a result of exposure to an algae bloom on the HAB Hotline at 888-238-6154.
    • Review the algae bloom map for sites where you should be aware of blooms and where to avoid swimming.
    • Report algae blooms and fish kills using the online HAB report form at


The Virginia HAB Task Force has conducted surveillance and response of fresh and marine waterbodies for nearly 20 years within the Commonwealth in recreational waters, shellfish growing areas, and drinking water sources. To learn more about HABs, to review frequently asked questions, and for printable brochures or other materials and information, please visit