Use caution if your local lake has a colorful coating

Reports of toxic blue-green algae blooms are beginning to surface east of the Cascades.

Blue-green algae can appear throughout the year in many Washington lakes and rivers, but it most often develops in summer and early fall when there's a wealth of warm, calm water and sunlight. While many blue-green blooms are non-toxic, some produce nerve or liver toxins.

Blue-green algae blooms typically resemble a thick mat of

bright green or blue-green paint. Testing can reveal toxicity.

(Photo: Potholes Reservoir, Grant County, 2018)

“Blue-green algae is very common, found in every lake in this state,” said Amanda Richardson, watershed implementation lead at the Department of Ecology’s eastern region office. “Certain types of blue-green algae can produce toxins under specific conditions, but those conditions are hard to pinpoint.”

The only way to determine whether toxins exist in the algae is through testing, conducted in Washington at the King County Environmental Lab.

Last week, the lab tested samples from Moses Lake and found microcystin toxin levels of 26 micrograms per liter, exceeding the Washington state recreational guidelines of six micrograms per liter. The Grant County Health District has since issued warnings that the lake is unsafe for people and pets.

Let’s get technical

Toxic blue-green algae is more formally known as cyanobacteria, as cyan means “blue-green.” It’s a type of bacteria that shares some of the same characteristics of plants and is found in waterbodies across the world.

As cyanobacteria cells die, toxins are released into surrounding waters. Some toxins, called microcystins, are very stable and can remain in the water for several days after the bloom has disappeared. Microcystin is found most often in the scum floating on top of the water.

While there’s no clear consensus on how to get rid of blue-green algae blooms, dumping vegetation – including grass clippings and uprooted plants – into waterbodies has been known to exacerbate growth. Heaps of vegetation also stop wind and water currents from mixing the water and breaking up algae blooms.

What to look for

Blue-green blooms typically sit on the surface and can often resemble a thick floating mat of bright green or blue-green paint. Wind can churn cyanobacteria into something resembling pea soup, and what’s near your beach one day can be carried across the lake the next.

Although blue-green blooms can create nuisance conditions and nasty water quality, most are not toxic. But as the adage cautions, “when in doubt, stay out.” If you see anything resembling the above, steer clear and keep children and animals away. People can develop skin rashes or become very ill after being in the water, and the toxins can kill pets and livestock, even if they’re exposed for a limited time.

Ingesting contaminated water is the easiest way to get sick, but exposure may also occur during recreational activities such as swimming and waterskiing, or by drinking or eating food contaminated with the toxin – including fish that hasn’t been cleaned well.

See something? Say something.

County health districts and state agencies like the Department of Ecology rely on the public to report when they see blue-green algae blooms in local waterbodies. If sampling results reveal toxins above the Washington Department of Health’s Recreational Guidance Levels, health districts will post signs at public access areas such as swim beaches and boat launches. They may also notify the public

The Grant County Health District is advising people to avoid

contact with Moses Lake, including recreational water

activities, due to a toxic blue-green algae bloom in the lake.

through press releases and social media.

Local jurisdictions, lake managers and Washington residents can report an algae bloom and sample it to test for potential toxins produced by algae. Visit the Washington State Toxic Algae website to learn how, and to access a database showing recent test results from across the state.

The Grant County Health District is now recruiting volunteers to help conduct the water testing this summer. Contact them at 509-766-7960 to learn more.

And wherever you live, consider participating in a nation-wide program called BloomWatch, which tracks cyanobacteria blooms using a smartphone with the help of the public.

Find even more information on blue-green algae at the Washington State Department of Health.