Hazardous Algal Blooms
The cyanobacteria colonies have been blown by wind and current and are gathered into bands of "green paint"
While the blooms are often called "algae blooms" the organism is actually a bacteria called cyanobacteria. It can be red or greenish blue in color. A common name is "blue-green algae". Some species of cyanobacteria secrete powerful neurotoxins that have killed pets at American Lake when they drank the water. Without a lab test it is impossible to tell whether a bloom is toxic or not.
Non-hazardous algae blooms
This is filamentous green algae. It is a true plant, unlike blue-green algae which is a bacteria. It begins to grow on the bottom of the lake in March or April. It dies in May and begins to become detached from the bottom. It floats up to the surface in June where it eventually decays and sinks to the bottom or dries on the shore and blows away.
What to do if you suspect a hazardous algae bloom
To report a hazardous algae bloom in American Lake follow these steps:
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Observe the bloom and take note of its location and size.
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Contact the Pierce County Health Department at 253-798-6470.
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Provide details about the algae bloom, including any visible effects on water quality.
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Take photos if possible to assist with the report.
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Follow any additional instructions provided by health officials.
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Stay informed about local advisories regarding water safety.
Toxicity Reports from King County Water Lab Analysis
Date Location Toxicity
Aug 5, 2026 TCGC irrigation intake pipe, clear, no bloom no measurable toxins
Oct 15, 2026 Bloom west of Silcox Island pending