Keatons Lake Update 8/28/26:
Algal toxin samples collected on 08/20/2026 have been received.
The toxins anatoxin-a, cylindrospermopsin, microsystins/nodularins, and saxitoxin were all sampled. For every toxin sampled, the results were very low and well under the thresholds of concern listed by the Virginia Department of Health and World Health Organization.
This set of results concludes the response for the Keatons Lake algae bloom and the lake is open and returned to regular status. LOWA will now return to baseline weekly algae sampling in Keatons Lake.
Keatons Lake Update 8/26/26:
Keatons Lake Swim Advisory is LIFTED. Keatons Lake is OPEN for all water recreation.
Second post-treatment cyanobacteria samples taken on 08/20/2026 algae sample results = PTOX average of less than 40 cells/ml.
The Keatons Lake algal community is no longer dominated by cyanobacteria and has shifted back to non-harmful green algae being the current dominant algae group in Keatons Lake.
Algal toxin samples were also collected 08/20/2026 but have not yet been received. The toxin results will be reported when they are received and analyzed.
With two consecutive sets of cyanobacteria cell counts below the threshold of concern, Keatons Lake is open and lake users may make the decision to wait for the toxin results or resume use of the lake now.
The sampling schedule will return to the regular once per week algae cell count testing in Keatons Lake through the end of the season.
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Keatons Lake HAB Notice 8/20/26: Status has been downgraded to a SWIM ADVISORY due to Harmful Algal Bloom (HAB) Conditions.
People may resume recreational activities such as boating or kayaking on Keatons Lake. All people and pets should use caution and avoid contact with water or any activity that could lead to ingesting water.
Residents choosing to use the lake during this period must do so at their own risk. Anyone who comes in contact with the water should promptly rinse with clean water. Anyone experiencing signs of illness after water contact should seek appropriate medical attention.
8/12/26 TREATMENT UPDATE:Algaecide Treatment was applied successfully on Wednesday, August 12
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Pre-treatment samples were collected in the morning on 08/12/2026.
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Algae treatment was successfully applied on 08/12/2026
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Post-treatment samples were collected on 08/17/2026
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Pre-treatment 08/12/2026 sample results = PTOX average of 37,000 cells/ml
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Post-treatment 08/17/2026 sample results = PTOX average of less than 40 cells/ml
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Initial toxin samples indicated toxin concentration was well below the level of concern.
NEXT STEPS:
Water Quality Testing: Staff will take more follow-up samples. If consecutive sets of testing results are below concerning thresholds, the last warning level will be lifted, and the lake will return to normal status.
Continued Monitoring: Water sampling will continue throughout the response process until results indicate it is safe to lift the lake closure or any advisory conditions.
To learn more about our testing and what we are learning, go to the following link:
Algae Science at Lake of the Woods
We will continue to keep the community informed as we monitor progress and await post-treatment results
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