Blue-green Lake: The King County warns of toxic blue-green algae in Green Lake

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Green Lake is known for its beautiful waters and the luscious landscape surrounding it, but aside from the reeds and fall-colored trees, there are also hazardous warning signs for toxic algae.

The warning signs warn of toxic blue-green algae that has been found in the lake. Visitors are advised to keep themselves and their pets away from the water. 

But this kind of algae isn’t new to Green Lake. In fact, algae is one of the oldest forms of life on the planet, and their color might be the reason why Green Lake was given its name in the first place.

The official name of the blue-green algae is cyanobacteria, a form of bacteria, not algae. It can be found in pretty much any sweetwater lake and isn’t always toxic as not all species of Cyanobacteria can produce toxins. 

There are essentially three ways that those toxins can get into a person’s system and harm them. The first, most concerning one would be actually drinking the water. Though this is usually unlikely to happen to adults, since they usually can see when algae is present in the water and don’t tend to drink it. Ingestion of cyanobacteria is more dangerous and prevalent among children. 

“The major concern is small kids who maybe aren’t aware, and certainly pets,” Chris Knutson, water quality planner with King County, said.

That is why owners are encouraged to not let their pets, usually dogs, swim in waters with cyanobacteria present. They tend to get a higher dose than people because they will get the bacteria on their coat and usually lick it off and ingest it that way. 

Another way to get affected by cyanobacteria is through inhalation. 

“Say you’re water skiing, even just breathing around the lake on a really windy day, if you had a really high toxicity of it, people could experience irritation and inflammation in the lungs, your sinuses,” Knutson said. 

Lastly, getting the toxins of cyanobacteria in contact with your skin can cause allergy-like symptoms, like rashes, redness of the skin, and itching. 

“There are many different species that can create toxins and there are some that don’t produce toxins,” Knutson said. “Some of them can create multiple different toxins, some of them can create maybe only one of the toxins.” 

The two major toxins that cyanobacteria can produce are anatoxin-a and microcystin.

Microcystin is a liver toxin that, when ingested, can cause vomiting and liver damage, and in some cases even chronic issues such as liver cancer. 

The other toxin that cyanobacteria produces is the anatoxin-a, an acute central nervous system toxin. Anatoxin-a can cause slurred speech, stumbling, vomiting, and even paralysis, and other than microcystin, it can have effects on people after just a single exposure. 

While cyanobacteria doesn’t always produce toxins, the danger is that it is impossible to tell whether or not they do at any given point. 

 “There is no way to tell toxicity by looking at an algae bloom,” Knutson said. ”You have to have it analyzed at a lab to get those results.”

But luckily, there are resources for our residents to keep up with toxic blooms all throughout Washington. The Northwest Toxic Algae website, for example, is a site where lab outcomes of samples that have been taken from lakes statewide are constantly posted and updated. The samples can be taken by anyone, sent into the King County environmental lab, where they are analyzed and reported. 

Over the years there was an increase of reported toxic algae blooms, according to Knutson. While that might have to do with the fact that awareness of such blooms has only increased in recent years and some blooms might have gone unnoticed or unreported before, it might also be because of a change in climate, as cyanobacteria thrives in warm waters, ideally of 24 degrees Celsius or around 75 degrees Fahrenheit. 

“We certainly are seeing it more and more around our region,” Knutson said. “A combination of warmer summers, longer growing seasons, it’s getting warmer earlier in the year and staying warmer later in the year.” 

But aside from warmer and longer summers, they have other natural advantages towards other algae or plants that might not create toxins. 

Many species of cyanobacteria have the ability to absorb nitrogen out of the atmosphere around them. The two main nutrients that they require to live are nitrogen and phosphorus, so if they are in an environment with sufficient phosphorus but not enough nitrogen in the water, they can make use of the nitrogen in the atmosphere. 

“They also have the ability to regulate their buoyancy, so they can move up and down in the water column,” Knutson said. “They can sink down to the bottom, where they collect the nutrients. They can get their nutrients there, and then they can buoy themselves up [to a better temperature and lighted area].”

Due to these advantages, cyanotoxins have over other water plants or algae, they have been growing more and more within Washington’s lakes. There are lifeguards in the designated beach areas who know how to identify the algae, so when they are on duty it is safe to actually swim there.

“We’ll keep the swim beaches open because we have eyes on it, all day long,” Knutson said.

Still, King County recommends to not access the lake outside the cleared areas, not to paddleboard, not to swim out, and not to let your dogs swim in the lake, because even the experts can’t always tell the exact location of the cyanobacteria, as it tends to move around in the water. 

Reach contributing writer Lilli Trompke at science@dailyuw.com. Twitter: @LilliTrompke

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